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Network Working Group C. Monia
Request for Comments: 4172 Consultant
Category: Standards Track R. Mullendore
McDATA
F. Travostino
Nortel
W. Jeong
Troika Networks
M. Edwards
Adaptec (UK) Ltd.
September 2005
iFCP - A Protocol for Internet Fibre Channel Storage Networking
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document specifies an architecture and a gateway-to-gateway
protocol for the implementation of fibre channel fabric functionality
over an IP network. This functionality is provided through TCP
protocols for fibre channel frame transport and the distributed
fabric services specified by the fibre channel standards. The
architecture enables internetworking of fibre channel devices through
gateway-accessed regions with the fault isolation properties of
autonomous systems and the scalability of the IP network.
Table of Contents
1. Introduction.................................................. 4
1.1. Conventions used in This Document....................... 4
1.1.1. Data Structures Internal to an Implementation... 4
1.2. Purpose of This Document................................ 4
2. iFCP Introduction............................................. 4
2.1. Definitions............................................. 5
3. Fibre Channel Communication Concepts.......................... 7
3.1. The Fibre Channel Network............................... 8
Monia, et al. Standards Track [Page 1]
RFC 4172 Internet Fibre Channel Networking September 2005
3.2. Fibre Channel Network Topologies........................ 9
3.2.1. Switched Fibre Channel Fabrics.................. 11
3.2.2. Mixed Fibre Channel Fabric...................... 12
3.3. Fibre Channel Layers and Link Services.................. 12
3.3.1. Fabric-Supplied Link Services................... 13
3.4. Fibre Channel Nodes..................................... 14
3.5. Fibre Channel Device Discovery.......................... 14
3.6. Fibre Channel Information Elements...................... 15
3.7. Fibre Channel Frame Format.............................. 15
3.7.1. N_PORT Address Model............................ 16
3.8. Fibre Channel Transport Services........................ 17
3.9. Login Processes......................................... 18
4. The iFCP Network Model........................................ 18
4.1. iFCP Transport Services................................. 21
4.1.1. Fibre Channel Transport Services Supported by
iFCP............................................ 21
4.2. iFCP Device Discovery and Configuration Management...... 21
4.3. iFCP Fabric Properties.................................. 22
4.3.1. Address Transparency............................ 22
4.3.2. Configuration Scalability....................... 23
4.3.3. Fault Tolerance................................. 23
4.4. The iFCP N_PORT Address Model........................... 24
4.5. Operation in Address Transparent Mode................... 25
4.5.1. Transparent Mode Domain ID Management........... 26
4.5.2. Incompatibility with Address Translation Mode... 26
4.6. Operation in Address Translation Mode................... 27
4.6.1. Inbound Frame Address Translation............... 28
4.6.2. Incompatibility with Address Transparent Mode... 29
5. iFCP Protocol................................................. 29
5.1. Overview ............................................... 29
5.1.1. iFCP Transport Services......................... 29
5.1.2. iFCP Support for Link Services.................. 30
5.2. TCP Stream Transport of iFCP Frames..................... 30
5.2.1. iFCP Session Model.............................. 30
5.2.2. iFCP Session Management......................... 31
5.2.3. Terminating iFCP Sessions....................... 39
5.3. Fibre Channel Frame Encapsulation....................... 40
5.3.1. Encapsulation Header Format..................... 41
5.3.2. SOF and EOF Delimiter Fields.................... 44
5.3.3. Frame Encapsulation............................. 45
5.3.4. Frame De-encapsulation.......................... 46
6. TCP Session Control Messages.................................. 47
6.1. Connection Bind (CBIND)................................. 50
6.2. Unbind Connection (UNBIND).............................. 52
6.3. LTEST -- Test Connection Liveness....................... 54
7. Fibre Channel Link Services................................... 55
7.1. Special Link Service Messages........................... 56
7.2. Link Services Requiring Payload Address Translation..... 58
Monia, et al. Standards Track [Page 2]
RFC 4172 Internet Fibre Channel Networking September 2005
7.3. Fibre Channel Link Services Processed by iFCP........... 61
7.3.1. Special Extended Link Services.................. 63
7.3.2. Special FC-4 Link Services...................... 83
7.4. FLOGI Service Parameters Supported by an iFCP Gateway... 84
8. iFCP Error Detection.......................................... 86
8.1. Overview................................................ 86
8.2. Stale Frame Prevention.................................. 86
8.2.1. Enforcing R_A_TOV Limits........................ 86
9. Fabric Services Supported by an iFCP Implementation........... 88
9.1. F_PORT Server........................................... 88
9.2. Fabric Controller....................................... 89
9.3. Directory/Name Server................................... 89
9.4. Broadcast Server........................................ 89
9.4.1. Establishing the Broadcast Configuration........ 90
9.4.2. Broadcast Session Management.................... 91
9.4.3. Standby Global Broadcast Server................. 91
10. iFCP Security................................................. 91
10.1. Overview................................................ 91
10.2. iFCP Security Threats and Scope......................... 92
10.2.1. Context......................................... 92
10.2.2. Security Threats................................ 92
10.2.3. Interoperability with Security Gateways......... 93
10.2.4. Authentication.................................. 93
10.2.5. Confidentiality................................. 93
10.2.6. Rekeying........................................ 93
10.2.7. Authorization................................... 94
10.2.8. Policy Control.................................. 94
10.2.9. iSNS Role....................................... 94
10.3. iFCP Security Design.................................... 94
10.3.1. Enabling Technologies........................... 94
10.3.2. Use of IKE and IPsec............................ 96
10.3.3. Signatures and Certificate-Based Authentication. 98
10.4. iSNS and iFCP Security.................................. 99
10.5. Use of iSNS to Distribute Security Policy............... 99
10.6. Minimal Security Policy for an iFCP Gateway............. 99
11. Quality of Service Considerations.............................100
11.1. Minimal Requirements....................................100
11.2. High Assurance..........................................100
12. IANA Considerations...........................................101
13. Normative References..........................................101
14. Informative References........................................103
Appendix A. iFCP Support for Fibre Channel Link Services.........105
A.1. Basic Link Services.....................................105
A.2. Pass-Through Link Services..............................105
A.3. Special Link Services...................................107
Appendix B. Supporting the Fibre Channel Loop Topology...........108
B.1. Remote Control of a Public Loop.........................108
Acknowledgements..................................................109
Monia, et al. Standards Track [Page 3]
RFC 4172 Internet Fibre Channel Networking September 2005
1. Introduction
1.1. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, RFC 2119
[RFC2119].
Unless specified otherwise, numeric quantities are given as decimal
values.
All diagrams that portray bit and byte ordering, including the
depiction of structures defined by fibre channel standards, adhere to
the IETF conventions whereby bit 0 is the most significant bit and
the first addressable byte is in the upper left corner. This IETF
convention differs from that used for INCITS T11 fibre channel
standards, in which bit 0 is the least significant bit.
1.1.1. Data Structures Internal to an Implementation
To facilitate the specification of required behavior, this document
may define and refer to internal data structures within an iFCP
implementation. Such structures are intended for explanatory
purposes only and need not be instantiated within an implementation
as described in this specification.
1.2. Purpose of This Document
This is a standards-track document that specifies a protocol for the
implementation of fibre channel transport services on a TCP/IP
network. Some portions of this document contain material from
standards controlled by INCITS T10 and T11. This material is
included here for informational purposes only. The authoritative
information is given in the appropriate NCITS standards document.
The authoritative portions of this document specify the mapping of
standards-compliant fibre channel protocol implementations to TCP/IP.
This mapping includes sections of this document that describe the
"iFCP Protocol" (see Section 5).
2. iFCP Introduction
iFCP is a gateway-to-gateway protocol that provides fibre channel
fabric services to fibre channel devices over a TCP/IP network. iFCP
uses TCP to provide congestion control, error detection, and
recovery. iFCP's primary objective is to allow interconnection and
Monia, et al. Standards Track [Page 4]
RFC 4172 Internet Fibre Channel Networking September 2005
networking of existing fibre channel devices at wire speeds over an
IP network.
The protocol and method of frame address translation described in
this document permit the attachment of fibre channel storage devices
to an IP-based fabric by means of transparent gateways.
The protocol achieves this transparency by allowing normal fibre
channel frame traffic to pass through the gateway directly, with
provisions, where necessary, for intercepting and emulating the
fabric services required by a fibre channel device.
2.1. Definitions
Terms needed to describe the concepts presented in this document are
presented here.
Address-translation mode -- A mode of gateway operation in which the
scope of N_PORT fabric addresses, for locally attached devices,
are local to the iFCP gateway region in which the devices reside.
Address-transparent mode -- A mode of gateway operation in which the
scope of N_PORT fabric addresses, for all fibre channel devices,
are unique to the bounded iFCP fabric to which the gateway
belongs.
Bounded iFCP Fabric -- The union of two or more gateway regions
configured to interoperate in address-transparent mode.
DOMAIN_ID -- The value contained in the high-order byte of a 24-bit
N_PORT fibre channel address.
F_PORT -- The interface used by an N_PORT to access fibre channel
switched-fabric functionality.
Fabric -- From [FC-FS]: "The entity that interconnects N_PORTs
attached to it and is capable of routing frames by using only the
address information in the fibre channel frame."
Fabric Port -- The interface through which an N_PORT accesses a fibre
channel fabric. The type of fabric port depends on the fibre
channel fabric topology. In this specification, all fabric port
interfaces are considered functionally equivalent.
FC-2 -- The fibre channel transport services layer, described in
[FC-FS].
Monia, et al. Standards Track [Page 5]
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FC-4 -- The fibre channel mapping of an upper-layer protocol, such as
[FCP-2], the fibre channel to SCSI mapping.
Fibre Channel Device -- An entity implementing the functionality
accessed through an FC-4 application protocol.
Fibre Channel Network -- A native fibre channel fabric and all
attached fibre channel nodes.
Fibre Channel Node -- A collection of one or more N_PORTs controlled
by a level above the FC-2 layer. A node is attached to a fibre
channel fabric by means of the N_PORT interface, described in
[FC-FS].
Gateway Region -- The portion of an iFCP fabric accessed through an
iFCP gateway by a remotely attached N_PORT. Fibre channel devices
in the region consist of all those locally attached to the
gateway.
iFCP -- The protocol discussed in this document.
iFCP Frame -- A fibre channel frame encapsulated in accordance with
the FC Frame Encapsulation Specification [ENCAP] and this
specification.
iFCP Portal -- An entity representing the point at which a logical or
physical iFCP device is attached to the IP network. The network
address of the iFCP portal consists of the IP address and TCP port
number to which a request is sent when the TCP connection is
created for an iFCP session (see Section 5.2.1).
iFCP Session -- An association comprised of a pair of N_PORTs and a
TCP connection that carries traffic between them. An iFCP session
may be created as the result of a PLOGI fibre channel login
operation.
iSNS -- The server functionality and IP protocol that provide storage
name services in an iFCP network. Fibre channel name services are
implemented by an iSNS name server, as described in [ISNS].
Locally Attached Device -- With respect to a gateway, a fibre channel
device accessed through the fibre channel fabric to which the
gateway is attached.
Logical iFCP Device -- The abstraction representing a single fibre
channel device as it appears on an iFCP network.
Monia, et al. Standards Track [Page 6]
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N_PORT -- An iFCP or fibre channel entity representing the interface
to fibre channel device functionality. This interface implements
the fibre channel N_PORT semantics, specified in [FC-FS]. Fibre
channel defines several variants of this interface that depend on
the fibre channel fabric topology. As used in this document, the
term applies equally to all variants.
N_PORT Alias -- The N_PORT address assigned by a gateway to
represent a remote N_PORT accessed via the iFCP protocol.
N_PORT fabric address -- The address of an N_PORT within the fibre
channel fabric.
N_PORT ID -- The address of a locally attached N_PORT within a
gateway region. N_PORT IDs are assigned in accordance with the
fibre channel rules for address assignment, specified in [FC-FS].
N_PORT Network Address -- The address of an N_PORT in the iFCP
fabric. This address consists of the IP address and TCP port
number of the iFCP Portal and the N_PORT ID of the locally
attached fibre channel device.
Port Login (PLOGI) -- The fibre channel Extended Link Service (ELS)
that establishes an iFCP session through the exchange of
identification and operation parameters between an originating
N_PORT and a responding N_PORT.
Remotely Attached Device -- With respect to a gateway, a fibre
channel device accessed from the gateway by means of the iFCP
protocol.
Unbounded iFCP Fabric -- The union of two or more gateway regions
configured to interoperate in address-translation mode.
3. Fibre Channel Communication Concepts
Fibre channel is a frame-based, serial technology designed for peer-
to-peer communication between devices at gigabit speeds and with low
overhead and latency.
This section contains a discussion of the fibre channel concepts that
form the basis for the iFCP network architecture and protocol
described in this document. Readers familiar with this material may
skip to Section 4.
Monia, et al. Standards Track [Page 7]
RFC 4172 Internet Fibre Channel Networking September 2005
Material presented in this section is drawn from the following T11
specifications:
-- The Fibre Channel Framing and Signaling Interface, [FC-FS]
-- Fibre Channel Switch Fabric -2, [FC-SW2]
-- Fibre Channel Generic Services, [FC-GS3]
-- Fibre Channel Fabric Loop Attachment, [FC-FLA]
The reader will find an in-depth treatment of the technology in
[KEMCMP] and [KEMALP].
3.1. The Fibre Channel Network
The fundamental entity in fibre channel is the fibre channel network.
Unlike a layered network architecture, a fibre channel network is
largely specified by functional elements and the interfaces between
them. As shown in Figure 1, these consist, in part, of the
following:
a) N_PORTs -- The end points for fibre channel traffic. In the FC
standards, N_PORT interfaces have several variants, depending on
the topology of the fabric to which they are attached. As used in
this specification, the term applies to any one of the variants.
b) FC Devices -- The fibre channel devices to which the N_PORTs
provide access.
c) Fabric Ports -- The interfaces within a fibre channel network that
provide attachment for an N_PORT. The types of fabric port depend
on the fabric topology and are discussed in Section 3.2.
d) The network infrastructure for carrying frame traffic between
N_PORTs.
e) Within a switched or mixed fabric (see Section 3.2), a set of
auxiliary servers, including a name server for device discovery
and network address resolution. The types of service depend on
the network topology.
Monia, et al. Standards Track [Page 8]
RFC 4172 Internet Fibre Channel Networking September 2005
+--------+ +--------+ +--------+ +--------+
| FC | | FC | | FC | | FC |
| Device | | Device |<-------->| Device | | Device |
|........| |........| |........| |........|
| N_PORT | | N_PORT | | N_PORT | | N_PORT |
+---+----+ +----+---+ +----+---+ +----+---+
| | | |
+---+----+ +----+---+ +----+---+ +----+---+
| Fabric | | Fabric | | Fabric | | Fabric |
| Port | | Port | | Port | | Port |
+========+===+========+==========+========+==+========+
| Fabric |
| & |
| Fabric Services |
+-----------------------------------------------------+
Figure 1. A Fibre Channel Network
The following sections describe fibre channel network topologies and
give an overview of the fibre channel communications model.
3.2. Fibre Channel Network Topologies
The principal fibre channel network topologies consist of the
following:
a) Arbitrated Loop -- A series of N_PORTs connected together in
daisy-chain fashion. In [FC-FS], loop-connected N_PORTs are
referred to as NL_PORTs. Data transmission between NL_PORTs
requires arbitration for control of the loop in a manner similar
to that of a token ring network.
b) Switched Fabric -- A network consisting of switching elements, as
described in Section 3.2.1.
c) Mixed Fabric -- A network consisting of switches and "fabric-
attached" loops. A description can be found in [FC-FLA]. A
loop-attached N_PORT (NL_PORT) is connected to the loop through an
L_PORT and accesses the fabric by way of an FL_PORT.
Monia, et al. Standards Track [Page 9]
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Depending on the topology, the N_PORT and its means of network
attachment may be one of the following:
FC Network
Topology Network Interface N_PORT Variant
--------------- ----------------- --------------
Loop L_PORT NL_PORT
Switched F_PORT N_PORT
Mixed FL_PORT via L_PORT NL_PORT
F_PORT N_PORT
The differences in each N_PORT variant and its corresponding fabric
port are confined to the interactions between them. To an external
N_PORT, all fabric ports are transparent, and all remote N_PORTs are
functionally identical.
Monia, et al. Standards Track [Page 10]
RFC 4172 Internet Fibre Channel Networking September 2005
3.2.1. Switched Fibre Channel Fabrics
An example of a multi-switch fibre channel fabric is shown in Figure
2.
+----------+ +----------+
| FC | | FC |
| Device | | Device |
|..........| |..........|
| N_PORT |<........>| N_PORT |
+----+-----+ +-----+----+
| |
+----+-----+ +-----+----+
| F_PORT | | F_PORT |
==========+==========+==========+==========+==============
| FC | | FC |
| Switch | | Switch |
+----------+ +----------+ Fibre Channel
|Inter- | |Inter- | Fabric
|Switch | |Switch |
|Interface | |Interface |
+-----+----+ +-----+----+
| |
| |
+-----+----+----------+-----+----+
|Inter- | |Inter- |
|Switch | |Switch |
|Interface | |Interface |
+----------+ +----------+
| FC Switch |
| |
+--------------------------------+
Figure 2. Multi-Switch Fibre Channel Fabric
The interface between switch elements is either a proprietary
interface or the standards-compliant E_PORT interface, which is
described by the FC-SW2 specification, [FC-SW2].
Monia, et al. Standards Track [Page 11]
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3.2.2. Mixed Fibre Channel Fabric
A mixed fabric contains one or more arbitrated loops connected to a
switched fabric as shown in Figure 3.
+----------+ +----------+ +---------+
| FC | | FC | | FC |
| Device | | Device | | Device |
|..........| FC |..........| |.........|
| N_PORT |<........>| NL_PORT +---+ NL_PORT |
+----+-----+ Traffic +-----+----+ +----+----+
| | FC Loop |
+----+-----+ +-----+----+ |
| F_PORT | | FL_PORT +--------+
| | | |
==========+==========+==========+==========+==============
| FC | | FC |
| Switch | | Switch |
+----------+ +----------+
|Inter- | |Inter- |
|Switch | |Switch |
|Interface | |Interface |
+-----+----+ +-----+----+
| |
| |
+-----+----+----------+-----+----+
|Inter- | |Inter- |
|Switch | |Switch |
|Interface | |Interface |
+----------+ +----------+
| FC Switch |
| |
+--------------------------------+
Figure 3. Mixed Fibre Channel Fabric
As noted previously, the protocol for communications between peer
N_PORTs is independent of the fabric topology, N_PORT variant, and
type of fabric port to which an N_PORT is attached.
3.3. Fibre Channel Layers and Link Services
A fibre channel consists of the following layers:
FC-0 -- The interface to the physical media.
FC-1 -- The encoding and decoding of data and out-of-band physical
link control information for transmission over the physical media.
Monia, et al. Standards Track [Page 12]
RFC 4172 Internet Fibre Channel Networking September 2005
FC-2 -- The transfer of frames, sequences, and Exchanges
comprising protocol information units.
FC-3 -- Common Services.
FC-4 -- Application protocols such as the fibre channel protocol
for SCSI (FCP).
In addition to the layers defined above, a fibre channel defines a
set of auxiliary operations, some of which are implemented within the
transport layer fabric, called link services. These are required in
order to manage the fibre channel environment, establish
communications with other devices, retrieve error information,
perform error recovery, and provide other similar services. Some
link services are executed by the N_PORT. Others are implemented
internally within the fabric. These internal services are described
in the next section.
3.3.1. Fabric-Supplied Link Services
Servers that are internal to a switched fabric handle certain classes
of Link Service requests and service-specific commands. The servers
appear as N_PORTs located at the 'well-known' N_PORT fabric addresses
specified in [FC-FS]. Service requests use the standard fibre
channel mechanisms for N_PORT-to-N_PORT communications.
All switched fabrics must provide the following services:
Fabric F_PORT server -- Services N_PORT requests to access the
fabric for communications.
Fabric Controller -- Provides state change information to inform
other FC devices when an N_PORT exits or enters the fabric (see
Section 3.5).
Directory/Name Server - Allows N_PORTs to register information in
a database, retrieve information about other N_PORTs, and to
discover other devices as described in Section 3.5.
A switched fabric may also implement the following optional services:
Broadcast Address/Server -- Transmits single-frame, class 3
sequences to all N_PORTs.
Time Server -- Intended for the management of fabric-wide
expiration timers or elapsed time values; not intended for precise
time synchronization.
Monia, et al. Standards Track [Page 13]
RFC 4172 Internet Fibre Channel Networking September 2005
Management Server - Collects and reports management information,
such as link usage, error statistics, link quality, and similar
items.
Quality of Service Facilitator - Performs fabric-wide bandwidth
and latency management.
3.4. Fibre Channel Nodes
A fibre channel node has one or more fabric-attached N_PORTs. The
node and its N_PORTs have the following associated identifiers:
a) A worldwide-unique identifier for the node.
b) A worldwide-unique identifier for each N_PORT associated with the
node.
c) For each N_PORT attached to a fabric, a 24-bit fabric-unique
address with the properties defined in Section 3.7.1. The fabric
address is the address to which frames are sent.
Each worldwide-unique identifier is a 64-bit binary quantity with the
format defined in [FC-FS].
3.5. Fibre Channel Device Discovery
In a switched or mixed fabric, fibre channel devices and changes in
the device configuration may be discovered by means of services
provided by the fibre channel Name Server and Fabric Controller.
The Name Server provides registration and query services that allow a
fibre channel device to register its presence on the fabric and to
discover the existence of other devices. For example, one type of
query obtains the fabric address of an N_PORT from its 64-bit
worldwide-unique name. The full set of supported fibre channel name
server queries is specified in [FC-GS3].
The Fabric Controller complements the static discovery capabilities
provided by the Name Server through a service that dynamically alerts
a fibre channel device whenever an N_PORT is added or removed from
the configuration. A fibre channel device receives these
notifications by subscribing to the service as specified in [FC-FS].
Monia, et al. Standards Track [Page 14]
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3.6. Fibre Channel Information Elements
The fundamental element of information in fibre channel is the frame.
A frame consists of a fixed header and up to 2112 bytes of payload
with the structure described in Section 3.7. The maximum frame size
that may be transmitted between a pair of fibre channel devices is
negotiable up to the payload limit, based on the size of the frame
buffers in each fibre channel device and the path maximum
transmission unit (MTU) supported by the fabric.
Operations involving the transfer of information between N_PORT pairs
are performed through 'Exchanges'. In an Exchange, information is
transferred in one or more ordered series of frames, referred to as
Sequences.
Within this framework, an upper layer protocol is defined in terms of
transactions carried by Exchanges. In turn, each transaction
consists of protocol information units, each of which is carried by
an individual Sequence within an Exchange.
3.7. Fibre Channel Frame Format
A fibre channel frame consists of a header, payload and 32-bit CRC
bracketed by SOF and EOF delimiters. The header contains the control
information necessary to route frames between N_PORTs and manage
Exchanges and Sequences. The following diagram gives a schematic
view of the frame.
Monia, et al. Standards Track [Page 15]
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Bit 0 31
+-----------------------------+
Word 0 | Start-of-frame Delimiter |
+-----+-----------------------+<----+
| | Destination N_PORT | |
1 | | Fabric Address (D_ID) | |
| | (24 bits) | |
+-----+-----------------------+ 24-byte
| | Source N_PORT | Frame
2 | | Fabric Address (S_ID) | Header
| | (24 bits) | |
+-----+-----------------------+ |
3 | Control information for | |
. | frame type, Exchange | |
. | management, IU | |
. | segmentation and | |
6 | re-assembly | |
+-----------------------------+<----+
7 | |
. | Frame payload |
. | (0 - 2112 bytes) |
. | |
. | |
. | |
+-----------------------------+
. | CRC |
+-----------------------------+
n | End-of-Frame Delimiter |
+-----------------------------+
Figure 4. Fibre Channel Frame Format
The source and destination N_PORT fabric addresses embedded in the
S_ID and D_ID fields represent the physical addresses of originating
and receiving N_PORTs, respectively.
3.7.1. N_PORT Address Model
N_PORT fabric addresses are 24-bit values with the following format,
defined by the fibre channel specification [FC-FS]:
Bit 0 7 8 15 16 23
+-----------+------------+----------+
| Domain ID | Area ID | Port ID |
+-----------+------------+----------+
Figure 5. Fibre Channel Address Format
Monia, et al. Standards Track [Page 16]
RFC 4172 Internet Fibre Channel Networking September 2005
A fibre channel device acquires an address when it logs into the
fabric. Such addresses are volatile and subject to change based on
modifications in the fabric configuration.
In a fibre channel fabric, each switch element has a unique Domain ID
assigned by the principal switch. The value of the Domain ID ranges
from 1 to 239 (0xEF). Each switch element, in turn, administers a
block of addresses divided into area and port IDs. An N_PORT
connected to an F_PORT receives a unique fabric address, consisting
of the switch's Domain ID concatenated with switch-assigned area and
port IDs.
A loop-attached NL_PORT (see Figure 3) obtains the Port ID component
of its address during the loop initialization process described in
[FC-AL2]. The area and domain IDs are supplied by the fabric when
the fabric login (FLOGI) is executed.
3.8. Fibre Channel Transport Services
N_PORTs communicate by means of the following classes of service,
which are specified in the fibre channel standard ([FC-FS]):
Class 1 - A dedicated physical circuit connecting two N_PORTs.
Class 2 - A frame-multiplexed connection with end-to-end flow
control and delivery confirmation.
Class 3 - A frame-multiplexed connection with no provisions for
end-to-end flow control or delivery confirmation.
Class 4 -- A connection-oriented service, based on a virtual
circuit model, providing confirmed delivery with bandwidth and
latency guarantees.
Class 6 -- A reliable multicast service derived from class 1.
Classes 2 and 3 are the predominant services supported by deployed
fibre channel storage and clustering systems.
Class 3 service is similar to UDP or IP datagram service. Fibre
channel storage devices using this class of service rely on the ULP
implementation to detect and recover from transient device and
transport errors.
For class 2 and class 3 service, the fibre channel fabric is not
required to provide in-order delivery of frames unless it is
explicitly requested by the frame originator (and supported by the
fabric). If ordered delivery is not in effect, it is the
Monia, et al. Standards Track [Page 17]
RFC 4172 Internet Fibre Channel Networking September 2005
responsibility of the frame recipient to reconstruct the order in
which frames were sent, based on information in the frame header.
3.9. Login Processes
The Login processes are FC-2 operations that allow an N_PORT to
establish the operating environment necessary to communicate with the
fabric, other N_PORTs, and ULP implementations accessed via the
N_PORT. Three login operations are supported:
a) Fabric Login (FLOGI) -- An operation whereby the N_PORT registers
its presence on the fabric, obtains fabric parameters, such as
classes of service supported, and receives its N_PORT address,
b) Port Login (PLOGI) -- An operation by which an N_PORT establishes
communication with another N_PORT.
c) Process Login (PRLOGI) -- An operation that establishes the
process-to-process communications associated with a specific FC-4
ULP, such as FCP-2, the fibre channel SCSI mapping.
Since N_PORT addresses are volatile, an N_PORT originating a login
(PLOGI) operation executes a Name Server query to discover the fibre
channel address of the remote device. A common query type involves
use of the worldwide-unique name of an N_PORT to obtain the 24-bit
N_PORT fibre channel address to which the PLOGI request is sent.
4. The iFCP Network Model
The iFCP protocol enables the implementation of fibre channel fabric
functionality on an IP network in which IP components and technology
replace the fibre channel switching and routing infrastructure
described in Section 3.2.
The example of Figure 6 shows a fibre channel network with attached
devices. Each device accesses the network through an N_PORT
connected to an interface whose behavior is specified in [FC-FS] or
[FC-AL2]. In this case, the N_PORT represents any of the variants
described in Section 3.2. The interface to the fabric may be an
L_PORT, F_PORT, or FL_PORT.
Within the fibre channel device domain, addressable entities consist
of other N_PORTs and fibre channel devices internal to the network
that perform the fabric services defined in [FC-GS3].
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Fibre Channel Network
+--------+ +--------+
| FC | | FC |
| Device | | Device |
|........| FC |........| Fibre Channel
| N_PORT |<......>| N_PORT | Device Domain
+---+----+ Traffic+----+---+ ^
| | |
+---+----+ +----+---+ |
| Fabric | | Fabric | |
| Port | | Port | |
==========+========+========+========+==============
| FC Network & | |
| Fabric Services | v
| | Fibre Channel
+--------------------------+ Network Domain
Figure 6. A Fibre Channel Network
Gateway Region Gateway Region
+--------+ +--------+ +--------+ +--------+
| FC | | FC | | FC | | FC |
| Device | | Device | | Device | | Device | Fibre
|........| |........| FC |........| |........| Channel
| N_PORT | | N_PORT |<.........>| N_PORT | | N_PORT | Device
+---+----+ +---+----+ Traffic +----+---+ +----+---+ Domain
| | | | ^
+---+----+ +---+----+ +----+---+ +----+---+ |
| F_PORT | | F_PORT | | F_PORT | | F_PORT | |
=+========+==+========+===========+========+==+========+==========
| iFCP Layer |<--------->| iFCP Layer | |
|....................| ^ |....................| |
| iFCP Portal | | | iFCP Portal | v
+--------+-----------+ | +----------+---------+ IP
iFCP|Gateway Control iFCP|Gateway Network
| Data |
| |
| |
|<------Encapsulated Frames------->|
| +------------------+ |
| | | |
+------+ IP Network +--------+
| |
+------------------+
Figure 7. An iFCP Fabric Example
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One example of an equivalent iFCP fabric is shown in Figure 7. The
fabric consists of two gateway regions, each accessed by a single
iFCP gateway.
Each gateway contains two standards-compliant F_PORTs and an iFCP
Portal for attachment to the IP network. Fibre channel devices in
the region are those locally connected to the iFCP fabric through the
gateway fabric ports.
Looking into the fabric port, the gateway appears as a fibre channel
switch element. At this interface, remote N_PORTs are presented as
fabric-attached devices. Conversely, on the IP network side, the
gateway presents each locally connected N_PORT as a logical fibre
channel device.
Extrapolating to the general case, each gateway region behaves like
an autonomous system whose configuration is invisible to the IP
network and other gateway regions. Consequently, in addition to the
F_PORT shown in the example, a gateway implementation may
transparently support the following fibre channel interfaces:
Inter-Switch Link -- A fibre channel switch-to-switch interface
used to access a region containing fibre channel switch elements.
An implementation may support the E_PORT defined by [FC-SW2] or
one of the proprietary interfaces provided by various fibre
channel switch vendors. In this case, the gateway acts as a
border switch connecting the gateway region to the IP network.
FL_PORT -- An interface that provides fabric access for loop-
attached fibre channel devices, as specified in [FC-FLA].
L_PORT -- An interface through which a gateway may emulate the
fibre channel loop environment specified in [FC-AL2]. As
discussed in appendix B, the gateway presents remotely accessed
N_PORTS as loop-attached devices.
The manner in which these interfaces are provided by a gateway is
implementation specific and therefore beyond the scope of this
document.
Although each region is connected to the IP network through one
gateway, a region may incorporate multiple gateways for added
performance and fault tolerance if the following conditions are met:
a) The gateways MUST coordinate the assignment of N_PORT IDs and
aliases so that each N_PORT has one and only one address.
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b) All iFCP traffic between a given remote and local N_PORT pair MUST
flow through the same iFCP session (see Section 5.2.1). However,
iFCP sessions to a given remotely attached N_PORT need not
traverse the same gateway.
Coordinating address assignments and managing the flow of traffic is
implementation specific and outside the scope of this specification.
4.1. iFCP Transport Services
N_PORT to N_PORT communications that traverse a TCP/IP network
require the intervention of the iFCP layer within the gateway. This
consists of the following operations:
a) Execution of the frame-addressing and -mapping functions described
in Section 4.4.
b) Encapsulation of fibre channel frames for injection into the
TCP/IP network and de-encapsulation of fibre channel frames
received from the TCP/IP network.
c) Establishment of an iFCP session in response to a PLOGI directed
to a remote device.
Section 4.4 discusses the iFCP frame-addressing mechanism and the way
that it is used to achieve communications transparency between
N_PORTs.
4.1.1. Fibre Channel Transport Services Supported by iFCP
An iFCP fabric supports Class 2 and Class 3 fibre channel transport
services, as specified in [FC-FS]. An iFCP fabric does not support
Class 4, Class 6, or Class 1 (dedicated connection) service. An
N_PORT discovers the classes of transport services supported by the
fabric during fabric login.
4.2. iFCP Device Discovery and Configuration Management
An iFCP implementation performs device discovery and iFCP fabric
management through the Internet Storage Name Service defined in
[ISNS]. Access to an iSNS server is required to perform the
following functions:
a) Emulate the services provided by the fibre channel name server
described in Section 3.3.1, including a mechanism for
asynchronously notifying an N_PORT of changes in the iFCP fabric
configuration.
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b) Aggregate gateways into iFCP fabrics for interoperation.
c) Segment an iFCP fabric into fibre channel zones through the
definition and management of device discovery scopes, referred to
as 'discovery domains'.
d) Store and distribute security policies, as described in Section
10.2.9.
e) Implementation of the fibre channel broadcast mechanism.
4.3. iFCP Fabric Properties
A collection of iFCP gateways may be configured for interoperation as
either a bounded or an unbounded iFCP fabric.
Gateways in a bounded iFCP fabric operate in address transparent
mode, as described in Section 4.5. In this mode, the scope of a
fibre channel N_PORT address is fabric-wide and is derived from
domain IDs issued by the iSNS server from a common pool. As
discussed in Section 4.3.2, the maximum number of domain IDs allowed
by the fibre channel limits the configuration of a bounded iFCP
fabric.
Gateways in an unbounded iFCP fabric operate in address translation
mode as described in Section 4.6. In this mode, the scope of an
N_PORT address is local to a gateway region. For fibre channel
traffic between regions, the translation of frame-embedded N_PORT
addresses is performed by the gateway. As discussed below, the
number of switch elements and gateways in an unbounded iFCP fabric
may exceed the limits of a conventional fibre channel fabric.
All iFCP gateways MUST support unbounded iFCP fabrics. Support for
bounded iFCP fabrics is OPTIONAL.
The decision to support bounded iFCP fabrics in a gateway
implementation depends on the address transparency, configuration
scalability, and fault tolerance considerations given in the
following sections.
4.3.1. Address Transparency
Although iFCP gateways in an unbounded fabric will convert N_PORT
addresses in the frame header and payload of standard link service
messages, a gateway cannot convert such addresses in the payload of
vendor- or user-specific fibre channel frame traffic.
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Consequently, although both bounded and unbounded iFCP fabrics
support standards-compliant FC-4 protocol implementations and link
services used by mainstream fibre channel applications, a bounded
iFCP fabric may also support vendor- or user-specific protocol and
link service implementations that carry N_PORT IDs in the frame
payload.
4.3.2. Configuration Scalability
The scalability limits of a bounded fabric configuration are a
consequence of the fibre channel address allocation policy discussed
in Section 3.7.1. As noted, a bounded iFCP fabric using this address
allocation scheme is limited to a combined total of 239 gateways and
fibre channel switch elements. As the system expands, the network
may grow to include many switch elements and gateways, each of which
controls a small number of devices. In this case, the limitation in
switch and gateway count may become a barrier to extending and fully
integrating the storage network.
Since N_PORT fibre channel addresses in an unbounded iFCP fabric are
not fabric-wide, the limits imposed by fibre channel address
allocation only apply within the gateway region. Across regions, the
number of iFCP gateways, fibre channel devices, and switch elements
that may be internetworked are not constrained by these limits. In
exchange for improved scalability, however, implementations must
consider the incremental overhead of address conversion, as well as
the address transparency issues discussed in Section 4.3.1.
4.3.3. Fault Tolerance
In a bounded iFCP fabric, address reassignment caused by a fault or
reconfiguration, such as the addition of a new gateway region, may
cascade to other regions, causing fabric-wide disruption as new
N_PORT addresses are assigned. Furthermore, before a new gateway can
be merged into the fabric, its iSNS server must be slaved to the iSNS
server in the bounded fabric to centralize the issuance of domain
IDs. In an unbounded iFCP fabric, coordinating the iSNS databases
requires only that the iSNS servers exchange client attributes with
one another.
A bounded iFCP fabric also has an increased dependency on the
availability of the iSNS server, which must act as the central
address assignment authority. If connectivity with the server is
lost, new DOMAIN_ID values cannot be automatically allocated as
gateways and fibre channel switch elements are added.
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4.4. The iFCP N_PORT Address Model
This section discusses iFCP extensions to the fibre channel
addressing model of Section 3.7.1, which are required for the
transparent routing of frames between locally and remotely attached
N_PORTs.
In the iFCP protocol, an N_PORT is represented by the following
addresses:
a) A 24-bit N_PORT ID. The fibre channel N_PORT address of a locally
attached device. Depending on the gateway addressing mode, the
scope is local either to a region or to a bounded iFCP fabric. In
either mode, communications between N_PORTs in the same gateway
region use the N_PORT ID.
b) A 24-bit N_PORT alias. The fibre channel N_PORT address assigned
by each gateway operating in address translation mode to identify
a remotely attached N_PORT. Frame traffic is intercepted by an
iFCP gateway and directed to a remotely attached N_PORT by means
of the N_PORT alias. The address assigned by each gateway is
unique within the scope of the gateway region.
c) An N_PORT network address. A tuple consisting of the gateway IP
address, TCP port number, and N_PORT ID. The N_PORT network
address identifies the source and destination N_PORTs for fibre
channel traffic on the IP network.
To provide transparent communications between a remote and local
N_PORT, a gateway MUST maintain an iFCP session descriptor (see
Section 5.2.2.2) reflecting the association between the fibre channel
address representing the remote N_PORT and the remote device's N_PORT
network address. To establish this association, the iFCP gateway
assigns and manages fibre channel N_PORT fabric addresses as
described in the following paragraphs.
In an iFCP fabric, the iFCP gateway performs the address assignment
and frame routing functions of an FC switch element. Unlike an FC
switch, however, an iFCP gateway must also direct frames to external
devices attached to remote gateways on the IP network.
In order to be transparent to FC devices, the gateway must deliver
such frames using only the 24-bit destination address in the frame
header. By exploiting its control of address allocation and access
to frame traffic entering or leaving the gateway region, the gateway
is able to achieve the necessary transparency.
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N_PORT addresses within a gateway region may be allocated in one of
two ways:
a) Address Translation Mode - A mode of N_PORT address assignment in
which the scope of an N_PORT fibre channel address is unique to
the gateway region. The address of a remote device is represented
in that gateway region by its gateway-assigned N_PORT alias.
b) Address Transparent Mode - A mode of N_PORT address assignment in
which the scope of an N_PORT fibre channel address is unique
across the set of gateway regions comprising a bounded iFCP
fabric.
In address transparent mode, gateways within a bounded fabric
cooperate in the assignment of addresses to locally attached N_PORTs.
Each gateway in control of a region is responsible for obtaining and
distributing unique domain IDs from the address assignment authority,
as described in Section 4.5.1. Consequently, within the scope of a
bounded fabric, the address of each N_PORT is unique. For that
reason, gateway-assigned aliases are not required for representing
remote N_PORTs.
All iFCP implementations MUST support operations in address
translation mode. Implementation of address transparent mode is
OPTIONAL but, of course, must be provided if bounded iFCP fabric
configurations are to be supported.
The mode of gateway operation is settable in an implementation-
specific manner. The implementation MUST NOT:
a) allow the mode to be changed after the gateway begins processing
fibre channel frame traffic,
b) permit operation in more than one mode at a time, or
c) establish an iFCP session with a gateway that is not in the same
mode.
4.5. Operation in Address Transparent Mode
The following considerations and requirements apply to this mode of
operation:
a) iFCP gateways in address transparent mode will not interoperate
with iFCP gateways that are not in address transparent mode.
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b) When interoperating with locally attached fibre channel switch
elements, each iFCP gateway MUST assume control of DOMAIN_ID
assignments in accordance with the appropriate fibre channel
standard or vendor-specific protocol specification. As described
in Section 4.5.1, DOMAIN_ID values that are assigned to FC
switches internal to the gateway region must be issued by the iSNS
server.
c) When operating in address transparent Mode, fibre channel address
translation SHALL NOT take place.
When operating in address transparent mode, however, the gateway MUST
establish and maintain the context of each iFCP session in accordance
with Section 5.2.2.
4.5.1. Transparent Mode Domain ID Management
As described in Section 4.5, each gateway and fibre channel switch in
a bounded iFCP fabric has a unique domain ID. In a gateway region
containing fibre channel switch elements, each element obtains a
domain ID by querying the principal switch as described in [FC-SW2]
-- in this case, the iFCP gateway itself. The gateway, in turn,
obtains domain IDs on demand from the iSNS name server acting as the
central address allocation authority. In effect, the iSNS server
assumes the role of principal switch for the bounded fabric. In that
case, the iSNS database contains:
a) The definition for one or more bounded iFCP fabrics, and
b) For each bounded fabric, a worldwide-unique name identifying each
gateway in the fabric. A gateway in address transparent mode MUST
reside in one, and only one, bounded fabric.
As the Principal Switch within the gateway region, an iFCP gateway in
address transparent mode SHALL obtain domain IDs for use in the
gateway region by issuing the appropriate iSNS query, using its
worldwide name.
4.5.2. Incompatibility with Address Translation Mode
Except for the session control frames specified in Section 6, iFCP
gateways in address transparent mode SHALL NOT originate or accept
frames that do not have the TRP bit set to one in the iFCP flags
field of the encapsulation header (see Section 5.3.1). The iFCP
gateway SHALL immediately terminate all iFCP sessions with the iFCP
gateway from which it receives such frames.
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4.6. Operation in Address Translation Mode
This section describes the process for managing the assignment of
addresses within a gateway region that is part of an unbounded iFCP
fabric, including the modification of FC frame addresses embedded in
the frame header for frames sent and received from remotely attached
N_PORTs.
As described in Section 4.4, the scope of N_PORT addresses in this
mode is local to the gateway region. A principal switch within the
gateway region, possibly the iFCP gateway itself, oversees the
assignment of such addresses, in accordance with the rules specified
in [FC-FS] and [FC-FLA].
The assignment of N_PORT addresses to locally attached devices is
controlled by the switch element to which the device is connected.
The assignment of N_PORT addresses for remotely attached devices is
controlled by the gateway by which the remote device is accessed. In
this case, the gateway MUST assign a locally significant N_PORT alias
to be used in place of the N_PORT ID assigned by the remote gateway.
The N_PORT alias is assigned during device discovery, as described in
Section 5.2.2.1.
To perform address conversion and to enable the appropriate routing,
the gateway MUST establish an iFCP session and generate the
information required to map each N_PORT alias to the appropriate
TCP/IP connection context and N_PORT ID of the remotely accessed
N_PORT. These mappings are created and updated by means specified in
Section 5.2.2.2. As described in that section, the required mapping
information is represented by the iFCP session descriptor reproduced
in Figure 8.
+-----------------------+
|TCP Connection Context |
+-----------------------+
| Local N_PORT ID |
+-----------------------+
| Remote N_PORT ID |
+-----------------------+
| Remote N_PORT Alias |
+-----------------------+
Figure 8. iFCP Session Descriptor (from Section 5.2.2.2)
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Except for frames comprising special link service messages (see
Section 7.2), outbound frames are encapsulated and sent without
modification. Address translation is deferred until receipt from the
IP network, as specified in Section 4.6.1.
4.6.1. Inbound Frame Address Translation
For inbound frames received from the IP network, the receiving
gateway SHALL reference the session descriptor to fill in the D_ID
field with the destination N_PORT ID and the S_ID field with the
N_PORT alias it assigned. The translation process for inbound frames
is shown in Figure 9.
Network Format of Inbound Frame
+--------------------------------------------+ iFCP
| FC Encapsulation Header | Session
+--------------------------------------------+ Descriptor
| SOF Delimiter Word | |
+========+===================================+ V
| | D_ID Field | +--------+-----+
+--------+-----------------------------------+ | Lookup source|
| | S_ID Field | | N_PORT Alias |
+--------+-----------------------------------+ | and |
| Control Information, Payload, | | destination |
| and FC CRC | | N_PORT ID |
| | +--------+-----+
| | |
| | |
+============================================+ |
| EOF Delimiter Word | |
+--------------------------------------------+ |
|
|
Frame after Address Translation and De-encapsulation |
+--------+-----------------------------------+ |
| | Destination N_PORT ID |<-------------+
+--------+-----------------------------------+ |
| | Source N_PORT Alias |<-------------+
+--------+-----------------------------------+
| |
| Control information, Payload, |
| and FC CRC |
+--------------------------------------------+
Figure 9. Inbound Frame Address Translation
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The receiving gateway SHALL consider the contents of the S_ID and
D_ID fields to be undefined when received. After replacing these
fields, the gateway MUST recalculate the FC CRC.
4.6.2. Incompatibility with Address Transparent Mode
iFCP gateways in address translation mode SHALL NOT originate or
accept frames that have the TRP bit set to one in the iFCP flags
field of the encapsulation header. The iFCP gateway SHALL
immediately abort all iFCP sessions with the iFCP gateway from which
it receives frames such as those described in Section 5.2.3.
5. iFCP Protocol
5.1. Overview
5.1.1. iFCP Transport Services
The main function of the iFCP protocol layer is to transport fibre
channel frame images between locally and remotely attached N_PORTs.
When transporting frames to a remote N_PORT, the iFCP layer
encapsulates and routes the fibre channel frames comprising each
fibre channel Information Unit via a predetermined TCP connection for
transport across the IP network.
When receiving fibre channel frame images from the IP network, the
iFCP layer de-encapsulates and delivers each frame to the appropriate
N_PORT.
The iFCP layer processes the following types of traffic:
a) FC-4 frame images associated with a fibre channel application
protocol.
b) FC-2 frames comprising fibre channel link service requests and
responses.
c) Fibre channel broadcast frames.
d) iFCP control messages required to set up, manage, or terminate an
iFCP session.
For FC-4 N_PORT traffic and most FC-2 messages, the iFCP layer never
interprets the contents of the frame payload.
iFCP does interpret and process iFCP control messages and certain
link service messages, as described in Section 5.1.2.
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5.1.2. iFCP Support for Link Services
iFCP must intervene in the processing of those fibre channel link
service messages that contain N_PORT addresses in the message payload
or that require other special handling, such as an N_PORT login
request (PLOGI).
In the former case, an iFCP gateway operating in address translation
mode MUST supplement the payload with additional information that
enables the receiving gateway to convert such embedded N_PORT
addresses to its frame of reference.
For out bound fibre channel frames comprising such a link service,
the iFCP layer creates the supplemental information based on frame
content, modifies the frame payload, and then transmits the resulting
fibre channel frame with supplemental data through the appropriate
TCP connection.
For incoming iFCP frames containing supplemented fibre channel link
service frames, iFCP must interpret the frame, including any
supplemental information, modify the frame content, and forward the
resulting frame to the destination N_PORT for further processing.
Section 7.1 describes the processing of these link service messages
in detail.
5.2. TCP Stream Transport of iFCP Frames
5.2.1. iFCP Session Model
An iFCP session consists of the pair of N_PORTs comprising the
session endpoints joined by a single TCP/IP connection. No more than
one iFCP session SHALL exist between a given pair of N_PORTs.
An N_PORT is identified by its network address, consisting of:
a) the N_PORT ID assigned by the gateway to which the N_PORT is
locally attached, and
b) the iFCP Portal address, consisting of its IP address and TCP port
number.
Because only one iFCP session may exist between a pair of N_PORTs,
the iFCP session is uniquely identified by the network addresses of
the session end points.
TCP connections that may be used for iFCP sessions between pairs of
iFCP portals are either "bound" or "unbound". An unbound connection
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is a TCP connection that is not actively supporting an iFCP session.
A gateway implementation MAY establish a pool of unbound connections
to reduce the session setup time. Such pre-existing TCP connections
between iFCP Portals remain unbound and uncommitted until allocated
to an iFCP session through a CBIND message (see Section 6.1).
When the iFCP layer creates an iFCP session, it may select an
existing unbound TCP connection or establish a new TCP connection and
send the CBIND message down that TCP connection. This allocates the
TCP connection to that iFCP session.
5.2.2. iFCP Session Management
This section describes the protocols and data structures required to
establish and terminate an iFCP session.
5.2.2.1. The Remote N_PORT Descriptor
In order to establish an iFCP session, an iFCP gateway MUST maintain
information allowing it to locate a remotely attached N_PORT. For
explanatory purposes, such information is assumed to reside in a
descriptor with the format shown in Figure 10.
+--------------------------------+
| N_PORT Worldwide Unique Name |
+--------------------------------+
| iFCP Portal Address |
+--------------------------------+
| N_PORT ID of Remote N_PORT |
+--------------------------------+
| N_PORT Alias |
+--------------------------------+
Figure 10. Remote N_PORT Descriptor
Each descriptor aggregates the following information about a remotely
attached N_PORT:
N_PORT Worldwide Unique Name -- 64-bit N_PORT worldwide name as
specified in [FC-FS]. A Remote N_PORT descriptor is uniquely
identified by this parameter.
iFCP Portal Address -- The IP address and TCP port number
referenced when creation of the TCP connection associated with an
iFCP session is requested.
N_PORT ID -- N_PORT fibre channel address assigned to the remote
device by the remote iFCP gateway.
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N_PORT Alias -- N_PORT fibre channel address assigned to the
remote device by the 'local' iFCP gateway when it operates in
address translation mode.
An iFCP gateway SHALL have one and only one descriptor for each
remote N_PORT it accesses. If a descriptor does not exist, one SHALL
be created using the information returned by an iSNS name server
query. Such queries may result from:
a) a fibre channel Name Server request originated by a locally
attached N_PORT (see Sections 3.5 and 9.3), or
b) a CBIND request received from a remote fibre channel device (see
Section 5.2.2.2).
When creating a descriptor in response to an incoming CBIND request,
the iFCP gateway SHALL perform an iSNS name server query using the
worldwide port name of the remote N_PORT in the SOURCE N_PORT NAME
field within the CBIND payload. The descriptor SHALL be filled in
using the query results.
After creating the descriptor, a gateway operating in address
translation mode SHALL create and add the 24-bit N_PORT alias.
5.2.2.1.1. Updating a Remote N_PORT Descriptor
A Remote N_PORT descriptor SHALL only be updated as the result of an
iSNS query to obtain information for the specified worldwide port
name or from information returned by an iSNS state change
notification. Following such an update, a new N_PORT alias SHALL NOT
be assigned.
Before such an update, the contents of a descriptor may have become
stale because of an event that invalidated or triggered a change in
the N_PORT network address of the remote device, such as a fabric
reconfiguration or the device's removal or replacement.
A collateral effect of such an event is that a fibre channel device
that has been added or whose N_PORT ID has changed will have no
active N_PORT logins. Consequently, FC-4 traffic directed to such an
N_PORT, because of a stale descriptor, will be rejected or discarded.
Once the originating N_PORT learns of the reconfiguration, usually
through the name server state change notification mechanism,
information returned in the notification or the subsequent name
server lookup needed to reestablish the iFCP session will
automatically purge such stale data from the gateway.
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5.2.2.1.2. Deleting a Remote N_PORT Descriptor
Deleting a remote N_PORT descriptor is equivalent to freeing up the
corresponding N_PORT alias for reuse. Consequently, the descriptor
MUST NOT be deleted while there are any iFCP sessions that reference
the remote N_PORT.
Descriptors eligible for deletion should be removed based on a last
in, first out policy.
5.2.2.2. Creating an iFCP Session
An iFCP session may be in one of the following states:
OPEN -- The session state in which fibre channel frame images
may be sent and received.
OPEN PENDING -- The session state after a gateway has issued a
CBIND request but no response has yet been received. No fibre
channel frames may be sent.
The session may be initiated in response to a PLOGI ELS (see Section
7.3.1.7) or for any other implementation-specific reason.
The gateway SHALL create the iFCP session as follows:
a) Locate the remote N_PORT descriptor corresponding to the session
end point. If the session is created in order to forward a fibre
channel frame, then the session endpoint may be obtained by
referencing the remote N_PORT alias contained in the frame header
D_ID field. If no descriptor exists, an iFCP session SHALL NOT be
created.
b) Allocate a TCP connection to the gateway to which the remote
N_PORT is locally attached. An implementation may use an existing
connection in the Unbound state, or a new connection may be
created and placed in the Unbound state.
When a connection is created, the IP address and TCP Port number
SHALL be obtained by referencing the remote N_PORT descriptor as
specified in Section 5.2.2.1.
c) If the TCP connection cannot be allocated or cannot be created due
to limited resources, the gateway SHALL terminate session
creation.
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d) If the TCP connection is aborted for any reason before the iFCP
session enters the OPEN state, the gateway SHALL respond in
accordance with Section 5.2.3 and MAY terminate the attempt to
create a session or MAY try to establish the TCP connection again.
e) The gateway SHALL then issue a CBIND session control message (see
Section 6.1) and place the session in the OPEN PENDING state.
f) If a CBIND response is returned with a status other than "Success"
or "iFCP session already exists", the session SHALL be terminated,
and the TCP connection returned to the Unbound state.
g) A CBIND STATUS of "iFCP session already exists" indicates that the
remote gateway has concurrently initiated a CBIND request to
create an iFCP session between the same pair of N_PORTs. A
gateway receiving such a response SHALL terminate this attempt and
process the incoming CBIND request in accordance with Section
5.2.2.3.
h) In response to a CBIND STATUS of "Success", the gateway SHALL
place the session in the OPEN state.
Once the session is placed in the OPEN state, an iFCP session
descriptor SHALL be created, containing the information shown in
Figure 11:
+-----------------------+
|TCP Connection Context |
+-----------------------+
| Local N_PORT ID |
+-----------------------+
| Remote N_PORT ID |
+-----------------------+
| Remote N_PORT Alias |
+-----------------------+
Figure 11. iFCP Session Descriptor
TCP Connection Context -- Information required to identify the TCP
connection associated with the iFCP session.
Local N_PORT ID -- N_PORT ID of the locally attached fibre
channel device.
Remote N_PORT ID -- N_PORT ID assigned to the remote device by the
remote gateway.
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Remote N_PORT Alias -- Alias assigned to the remote N_PORT by the
local gateway when it operates in address translation mode. If in
this mode, the gateway SHALL copy this parameter from the Remote
N_PORT descriptor. Otherwise, it is not filled in.
5.2.2.3. Responding to a CBIND Request
The gateway receiving a CBIND request SHALL respond as follows:
a) If the receiver has a duplicate iFCP session in the OPEN PENDING
state, then the receiving gateway SHALL compare the Source N_PORT
Name in the incoming CBIND payload with the Destination N_PORT
Name.
b) If the Source N_PORT Name is greater, the receiver SHALL issue a
CBIND response of "Success" and SHALL place the session in the
OPEN state.
c) If the Source N_PORT Name is less, the receiver shall issue a
CBIND RESPONSE of Failed - N_PORT session already exists. The
state of the receiver-initiated iFCP session SHALL BE unchanged.
d) If there is no duplicate iFCP session in the OPEN PENDING state,
the receiving gateway SHALL issue a CBIND response. If a status
of Success is returned, the receiving gateway SHALL create the
iFCP session and place it in the OPEN state. An iFCP session
descriptor SHALL be created as described in Section 5.2.2.2.
e) If a remote N_PORT descriptor does not exist, one SHALL be created
and filled in as described in Section 5.2.2.1.
5.2.2.4. Monitoring iFCP Connectivity
During extended periods of inactivity, an iFCP session may be
terminated due to a hardware failure within the gateway or through
loss of TCP/IP connectivity. The latter may occur when the session
traverses a stateful intermediate device, such as a NA(P)T box or
firewall, that detects and purges connections it believes are unused.
To test session liveness, expedite the detection of connectivity
failures, and avoid spontaneous connection termination, an iFCP
gateway may maintain a low level of session activity and monitor the
session by requesting that the remote gateway periodically transmit
the LTEST message described in Section 6.3. All iFCP gateways SHALL
support liveness testing as described in this specification.
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A gateway requests the LTEST heartbeat by specifying a non-zero value
for the LIVENESS TEST INTERVAL in the CBIND request or response
message as described in Section 6.1. If both gateways seek to
monitor liveness, each must set the LIVENESS TEST INTERVAL in the
CBIND request or response.
Upon receiving such a request, the gateway providing the heartbeat
SHALL transmit LTEST messages at the specified interval. The first
message SHALL be sent as soon as the iFCP session enters the OPEN
state. LTEST messages SHALL NOT be sent when the iFCP session is not
in the OPEN state.
An iFCP session SHALL be terminated as described in Section 5.2.3 if:
a) the contents of the LTEST message are incorrect, or
b) an LTEST message is not received within twice the specified
interval or the iFCP session has been quiescent for longer than
twice the specified interval.
The gateway to receive the LTEST message SHALL measure the interval
for the first expected LTEST message from when the session is placed
in the OPEN state. Thereafter, the interval SHALL be measured
relative to the last LTEST message received.
To maximize liveness test coverage, LTEST messages SHOULD flow
through all the gateway components used to enter and retrieve fibre
channel frames from the IP network, including the mechanisms for
encapsulating and de-encapsulating fibre channel frames.
In addition to monitoring a session, information in the LTEST message
encapsulation header may also be used to compute an estimate of
network propagation delay, as described in Section 8.2.1. However,
the propagation delay limit SHALL NOT be enforced for LTEST traffic.
5.2.2.5. Use of TCP Features and Settings
This section describes ground rules for the use of TCP features in an
iFCP session. The core TCP protocol is defined in [RFC793]. TCP
implementation requirements and guidelines are specified in
[RFC1122].
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+-----------+------------+--------------+------------+------------+
| Feature | Applicable | RFC | Peer-Wise | Requirement|
| | RFCs | Status | Agreement | Level |
| | | | Required? | |
+===========+============+==============+============+============+
| Keep Alive| [RFC1122] | None | No | Should not |
| |(discussion)| | | use |
+-----------+------------+--------------+------------+------------+
| Tiny | [RFC896] | Standard | No | Should not |
| Segment | | | | use |
| Avoidance | | | | |
| (Nagle) | | | | |
+-----------+------------+--------------+------------+------------+
| Window | [RFC1323] | Proposed | No | Should use |
| Scale | | Standard | | |
+-----------+------------+--------------+------------+------------+
| Wrapped | [RFC1323] | Proposed | No | SHOULD use |
| Sequence | | Standard | | |
| Protection| | | | |
| (PAWS) | | | | |
+-----------+------------+--------------+------------+------------+
Table 1. Usage of Optional TCP Features
The following sections describe these options in greater detail.
5.2.2.5.1. Keep Alive
Keep Alive speeds the detection and cleanup of dysfunctional TCP
connections by sending traffic when a connection would otherwise be
idle. The issues are discussed in [RFC1122].
In order to test the device more comprehensively, fibre channel
applications, such as storage, may implement an equivalent keep alive
function at the FC-4 level. Alternatively, periodic liveness test
messages may be issued as described in Section 5.2.2.4. Because of
these more comprehensive end-to-end mechanisms and the considerations
described in [RFC1122], keep alive at the transport layer should not
be implemented.
5.2.2.5.2. 'Tiny' Segment Avoidance (Nagle)
The Nagle algorithm described in [RFC896] is designed to avoid the
overhead of small segments by delaying transmission in order to
agglomerate transfer requests into a large segment. In iFCP, such
small transfers often contain I/O requests. The transmission delay
of the Nagle algorithm may decrease I/O throughput. Therefore, the
Nagle algorithm should not be used.
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5.2.2.5.3. Window Scale
Window scaling, as specified in [RFC1323], allows full use of links
with large bandwidth - delay products and should be supported by an
iFCP implementation.
5.2.2.5.4. Wrapped Sequence Protection (PAWS)
TCP segments are identified with 32-bit sequence numbers. In
networks with large bandwidth - delay products, it is possible for
more than one TCP segment with the same sequence number to be in
flight. In iFCP, receipt of such a sequence out of order may cause
out-of-order frame delivery or data corruption. Consequently, this
feature SHOULD be supported as described in [RFC1323].
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5.2.3. Terminating iFCP Sessions
iFCP sessions SHALL be terminated in response to one of the events in
Table 2:
+-------------------------------------------+---------------------+
| Event | iFCP Sessions |
| | to Terminate |
+===========================================+=====================+
| PLOGI terminated with LS_RJT response | Peer N_PORT |
+-------------------------------------------+---------------------+
| State change notification indicating | All iFCP Sessions |
| N_PORT removal or reconfiguration. | from the |
| | reconfigured N_PORT |
+-------------------------------------------+---------------------+
| LOGO ACC response from peer N_PORT | Peer N_PORT |
+-------------------------------------------+---------------------+
| ACC response to LOGO ELS sent to F_PORT | All iFCP sessions |
| server (D_ID = 0xFF-FF-FE) (fabric | from the originating|
| logout) | N_PORT |
+-------------------------------------------+---------------------+
| Implicit N_PORT LOGO as defined in | All iFCP sessions |
| [FC-FS] | from the N_PORT |
| | logged out |
+-------------------------------------------+---------------------+
| LTEST Message Error (see Section 5.2.2.4) | Peer N_PORT |
+-------------------------------------------+---------------------+
| Non fatal encapsulation error as | Peer N_PORT |
| specified in Section 5.3.3 | |
+-------------------------------------------+---------------------+
| Failure of the TCP connection associated | Peer N_PORT |
| with the iFCP session | |
+-------------------------------------------+---------------------+
| Receipt of an UNBIND session control | Peer N_PORT |
| message | |
+-------------------------------------------+---------------------+
| Gateway enters the Unsynchronized state | All iFCP sessions |
| (see Section 8.2.1) | |
+-------------------------------------------+---------------------+
| Gateway detects incorrect address mode | All iFCP sessions |
| to peer gateway(see Section 4.6.2) | with peer gateway |
+-------------------------------------------+---------------------+
Table 2. Session Termination Events
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If a session is being terminated due to an incorrect address mode
with the peer gateway, the TCP connection SHALL be aborted by means
of a connection reset (RST) without performing an UNBIND. Otherwise,
if the TCP connection is still open following the event, the gateway
SHALL shut down the connection as follows:
a) Stop sending fibre channel frames over the TCP connection.
b) Discard all incoming traffic, except for an UNBIND session control
message.
c) If an UNBIND message is received at any time, return a response in
accordance with Section 6.2.
d) If session termination was not triggered by an UNBIND message,
issue the UNBIND session control message, as described in Section
6.2.
e) If the UNBIND message completes with a status of Success, the TCP
connection MAY remain open at the discretion of either gateway and
may be kept in a pool of unbound connections in order to speed up
the creation of a new iFCP session.
If the UNBIND fails for any reason, the TCP connection MUST be
terminated. In this case, the connection SHOULD be aborted with a
connection reset (RST).
For each terminated session, the session descriptor SHALL be deleted.
If a session was terminated by an event other than an implicit LOGO
or a LOGO ACC response, the gateway shall issue a LOGO to the locally
attached N_PORT on behalf of the remote N_PORT.
To recover resources, either gateway may spontaneously close an
unbound TCP connection at any time. If a gateway terminates a
connection with a TCP close operation, the peer gateway MUST respond
by executing a TCP close.
5.3. Fibre Channel Frame Encapsulation
This section describes the iFCP encapsulation of fibre channel
frames. The encapsulation complies with the common encapsulation
format defined in [ENCAP], portions of which are included here for
convenience.
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The format of an encapsulated frame is shown below:
+--------------------+
| Header |
+--------------------+-----+
| SOF | f |
+--------------------+ F r |
| FC frame content | C a |
+--------------------+ m |
| EOF | e |
+--------------------+-----+
Figure 12. Encapsulation Format
The encapsulation consists of a 7-word header, an SOF delimiter word,
the FC frame (including the fibre channel CRC), and an EOF delimiter
word. The header and delimiter formats are described in the
following sections.
5.3.1. Encapsulation Header Format
W|------------------------------Bit------------------------------|
o| |
r| 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3|
d|0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1|
+---------------+---------------+---------------+---------------+
0| Protocol# | Version | -Protocol# | -Version |
+---------------+---------------+---------------+---------------+
1| Reserved (must be zero) |
+---------------+---------------+---------------+---------------+
2| LS_COMMAND_ACC| iFCP Flags | SOF | EOF |
+-----------+---+---------------+-----------+---+---------------+
3| Flags | Frame Length | -Flags | -Frame Length |
+-----------+-------------------+-----------+-------------------+
4| Time Stamp [integer] |
+---------------------------------------------------------------+
5| Time Stamp [fraction] |
+---------------------------------------------------------------+
6| CRC |
+---------------------------------------------------------------+
Figure 13. Encapsulation Header Format
Common Encapsulation Fields:
Protocol# IANA-assigned protocol number identifying the
protocol using the encapsulation. For iFCP, the
value assigned by [ENCAP] is 2.
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Version Encapsulation version, as specified in [ENCAP].
-Protocol# Ones complement of the Protocol#.
-Version Ones complement of the version.
Flags Encapsulation flags (see 5.3.1.1).
Frame Length Contains the length of the entire FC
Encapsulated frame, including the FC
Encapsulation Header and the FC frame (including
SOF and EOF words) in units of 32-bit words.
-Flags Ones complement of the Flags field.
-Frame Length Ones complement of the Frame Length field.
Time Stamp [integer] Integer component of the frame time stamp, as
specified in [ENCAP].
Time Stamp Fractional component of the time stamp,
[fraction] as specified in [ENCAP].
CRC Header CRC. MUST be valid for iFCP.
The time stamp fields are used to enforce the limit on the lifetime
of a fibre channel frame as described in Section 8.2.1.
iFCP-Specific Fields:
LS_COMMAND_ACC For a special link service ACC response to be
processed by iFCP, the LS_COMMAND_ACC field
SHALL contain a copy of bits 0 through 7 of the
LS_COMMAND to which the ACC applies. Otherwise,
the LS_COMMAND_ACC field SHALL be set to zero.
iFCP Flags iFCP-specific flags (see below).
SOF Copy of the SOF delimiter encoding (see Section
5.3.2).
EOF Copy of the EOF delimiter encoding (see Section
5.3.2).
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The iFCP flags word has the following format:
|------------------------Bit----------------------------|
| |
| 8 9 10 11 12 13 14 15 |
+------+------+------+------+------+------+------+------+
| Reserved | SES | TRP | SPC |
+------+------+------+------+------+------+------+------+
Figure 14. iFCP Flags Word
iFCP Flags:
SES 1 = Session control frame (TRP and SPC MUST be 0)
TRP 1 = Address transparent mode enabled
0 = Address translation mode enabled
SPC 1 = Frame is part of a link service message requiring
special processing by iFCP prior to forwarding to the
destination N_PORT.
5.3.1.1. Common Encapsulation Flags
The iFCP usage of the common encapsulation flags defined in [ENCAP]
is shown in Figure 15:
|------------------------Bit--------------------------|
| |
| 0 1 2 3 4 5 |
+--------------------------------------------+--------+
| Reserved | CRCV |
+--------------------------------------------+--------+
Figure 15. iFCP Common Encapsulation Flags
For iFCP, the CRC field MUST be valid, and CRCV MUST be set to one.
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5.3.2. SOF and EOF Delimiter Fields
The format of the delimiter fields is shown below.
W|------------------------------Bit------------------------------|
o| |
r| 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 3 3|
d|0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1|
+---------------+---------------+---------------+---------------+
0| SOF | SOF | -SOF | -SOF |
+---------------+---------------+---------------+---------------+
1| |
+----- FC frame content -----+
| |
+---------------+---------------+---------------+---------------+
n| EOF | EOF | -EOF | -EOF |
+---------------+---------------+---------------+---------------+
Figure 16. FC Frame Encapsulation Format
SOF (bits 0-7 and bits 8-15 in word 0): iFCP uses the following
subset of the SOF fields specified in [ENCAP]. For convenience,
these are reproduced in Table 3. The authoritative encodings should
be obtained from [ENCAP].
+-------+----------+
| FC | |
| SOF | SOF Code |
+-------+----------+
| SOFi2 | 0x2D |
| SOFn2 | 0x35 |
| SOFi3 | 0x2E |
| SOFn3 | 0x36 |
+-------+----------+
Table 3. Translation of FC SOF Values to SOF Field Contents
-SOF (bits 16-23 and 24-31 in word 0): The -SOF fields contain the
ones complement the value in the SOF fields.
EOF (bits 0-7 and 8-15 in word n): iFCP uses the following subset of
EOF fields specified in [ENCAP]. For convenience, these are
reproduced in Table 4. The authoritative encodings should be
obtained from [ENCAP].
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+-------+----------+
| FC | |
| EOF | EOF Code |
+-------+----------+
| EOFn | 0x41 |
| EOFt | 0x42 |
+-------+----------+
Table 4. Translation of FC EOF Values to EOF Field Contents
-EOF (bits 16-23 and 24-31 in word n): The -EOF fields contain the
ones complement the value in the EOF fields.
iFCP implementations SHALL place a copy of the SOF and EOF delimiter
codes in the appropriate header fields.
5.3.3. Frame Encapsulation
A fibre channel Frame to be encapsulated MUST first be validated as
described in [FC-FS]. Any frames received from a locally attached
fibre channel device that do not pass the validity tests in [FC-FS]
SHALL be discarded by the gateway.
If the frame is a PLOGI ELS, the creation of an iFCP session, as
described in Section 7.3.1.7, may precede encapsulation. Once the
session has been created, frame encapsulation SHALL proceed as
follows.
The S_ID and D_ID fields in the frame header SHALL be referenced to
look up the iFCP session descriptor (see Section 5.2.2.2). If no
iFCP session descriptor exists, the frame SHALL be discarded.
Frame types submitted for encapsulation and forwarding on the IP
network SHALL have one of the SOF delimiters in Table 3 and an EOF
delimiter from Table 4. Other valid frame types MUST be processed
internally by the gateway as specified in the appropriate fibre
channel specification.
If operating in address translation mode and processing a special
link service message requiring the inclusion of supplemental data,
the gateway SHALL format the frame payload and add the supplemental
information specified in Section 7.1. The gateway SHALL then
calculate a new FC CRC on the reformatted frame.
Otherwise, the frame contents SHALL NOT be modified and the gateway
MAY encapsulate and transmit the frame image without recalculating
the FC CRC.
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The frame originator MUST then create and fill in the header and the
SOF and EOF delimiter words, as specified in Sections 5.3.1 and
5.3.2.
5.3.4. Frame De-encapsulation
The receiving gateway SHALL perform de-encapsulation as follows:
Upon receiving the encapsulated frame, the gateway SHALL check the
header CRC. If the header CRC is valid, the receiving gateway SHALL
check the iFCP flags field. If one of the error conditions in Table
5 is detected, the gateway SHALL handle the error as specified in
Section 5.2.3.
+------------------------------+-------------------------+
| Condition | Error Type |
+==============================+=========================+
| Header CRC Invalid | Encapsulation error |
+------------------------------+-------------------------+
| SES = 1, TRP or SPC not 0 | Encapsulation error |
+------------------------------+-------------------------+
| SES = 0, TRP set incorrectly | Incorrect address mode |
+------------------------------+-------------------------+
Table 5. Encapsulation Header Errors
The receiving gateway SHALL then verify the frame propagation delay
as described in Section 8.2.1. If the propagation delay is too long,
the frame SHALL be discarded. Otherwise, the gateway SHALL check the
SOF and EOF in the encapsulation header. A frame SHALL be discarded
if it has an SOF code that is not in Table 3 or an EOF code that is
not in Table 4.
The gateway SHALL then de-encapsulate the frame as follows:
a) Check the FC CRC and discard the frame if the CRC is invalid.
b) If operating in address translation mode, replace the S_ID field
with the N_PORT alias of the frame originator, and the D_ID with
the N_PORT ID, of the frame recipient. Both parameters SHALL be
obtained from the iFCP session descriptor.
c) If processing a special link service message, replace the frame
with a copy whose payload has been modified as specified in
Section 7.1.
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The de-encapsulated frame SHALL then be forwarded to the N_PORT
specified in the D_ID field. If the frame contents have been
modified by the receiving gateway, a new FC CRC SHALL be calculated.
6. TCP Session Control Messages
TCP session control messages are used to create and manage an iFCP
session as described in Section 5.2.2. They are passed between peer
iFCP Portals and are only processed within the iFCP layer.
The message format is based on the fibre channel extended link
service message template shown below.
Word
0<--Bits-->7 8<---------------Bits------------------------>31
+------------+------------------------------------------------+
0| R_CTL | D_ID [0x00 00 00] |
|[Req = 0x22]| [Destination of extended link Service request] |
|[Rep = 0x23]| |
+------------+------------------------------------------------+
1| CS_CTL | S_ID [0x00 00 00] |
| [0x0] | [Source of extended link service request] |
+------------+------------------------------------------------+
2|TYPE [0x1] | F_CTL [0] |
+------------+------------------+-----------------------------+
3|SEQ_ID | DF_CTL [0x00] | SEQ_CNT [0x00] |
|[0x0] | | |
+------------+------------------+-----------------------------+
4| OX_ID [0x0000] | RX_ID_[0x0000] |
+-------------------------------+-----------------------------+
5| Parameter |
| [ 00 00 00 00 ] |
+-------------------------------------------------------------+
6| LS_COMMAND |
| [Session Control Command Code] |
+-------------------------------------------------------------+
7| |
.| Additional Session Control Parameters |
.| ( if any ) |
n| |
+=============================================================+
n| Fibre Channel CRC |
+| |
1+=============================================================+
Figure 17. Format of Session Control Message
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The LS_COMMAND value for the response remains the same as that used
for the request.
The session control frame is terminated with a fibre channel CRC.
The frame SHALL be encapsulated and de-encapsulated according to the
rules specified in Section 5.3.
The encapsulation header for the link Service frame carrying a
session control message SHALL be set as follows:
Encapsulation Header Fields:
LS_COMMAND_ACC 0
iFCP Flags SES = 1
TRP = 0
INT = 0
SOF code SOFi3 encoding (0x2E)
EOF code EOFt encoding (0x42)
The encapsulation time stamp words SHALL be set as described for each
message type.
The SOF and EOF delimiter words SHALL be set based on the SOF and EOF
codes specified above.
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Table 6 lists the values assigned to byte 0 of the LS_COMMAND field
for iFCP session control messages.
+--------------+-------------------------+----------+-------------+
| LS_COMMAND | Function | Mnemonic | iFCP |
| field, byte 0| | | Support |
+--------------+-------------------------+----------+-------------+
| 0xE0 | Connection Bind | CBIND | REQUIRED |
+--------------+-------------------------+----------+-------------+
| 0xE4 | Unbind Connection | UNBIND | REQUIRED |
+--------------+-------------------------+----------+-------------+
| 0xE5 | Test Connection Liveness| LTEST | REQUIRED |
+--------------+-------------------------+----------+-------------+
| 0x01-0x7F | Vendor-Specific | | |
+--------------+-------------------------+----------+-------------+
| 0x00 | Reserved -- Unassignable| | |
+--------------+-------------------------+----------+-------------+
| All other | Reserved | | |
| values | | | |
+--------------+-------------------------+----------+-------------+
Table 6. Session Control LS_COMMAND Field, Byte 0 Values
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6.1. Connection Bind (CBIND)
As described in Section 5.2.2.2, the CBIND message and response are
used to bind an N_PORT login to a specific TCP connection and
establish an iFCP session. In the CBIND request message, the source
and destination N_PORTs are identified by their worldwide port names.
The time stamp words in the encapsulation header SHALL be set to zero
in the request and response message frames.
The following shows the format of the CBIND request.
+------+------------+------------+-----------+----------+
| Word | Byte 0 | Byte 1 | Byte 2 | Byte 3 |
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0xE0 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | LIVENESS TEST INTERVAL | Addr Mode | iFCP Ver |
| | (Seconds) | | |
+------+-------------------------+-----------+----------+
| 2 | USER INFO |
+------+------------+------------+-----------+----------+
| 3 | |
+------+ SOURCE N_PORT NAME |
| 4 | |
+------+------------------------------------------------+
| 5 | |
+------+ DESTINATION N_PORT NAME |
| 6 | |
+------+------------------------------------------------+
Addr Mode: The addressing mode of the originating
gateway. 0 = Address Translation mode;
1 = Address Transparent mode.
iFCP Ver: iFCP version number. SHALL be set to 1.
LIVENESS TEST If non-zero, requests that the receiving
INTERVAL: gateway transmit an LTEST message at the
specified interval in seconds. If set to
zero, LTEST messages SHALL NOT be sent.
USER INFO: Contains any data desired by the requestor.
This information MUST be echoed by the
recipient in the CBIND response message.
SOURCE N_PORT NAME: The Worldwide Port Name (WWPN) of the N_PORT
locally attached to the gateway originating
the CBIND request.
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DESTINATION N_PORT The Worldwide Port Name (WWPN) of the
NAME: N_PORT locally attached to the gateway
receiving the CBIND request.
The following shows the format of the CBIND response.
+------+------------+------------+-----------+----------+
| Word | Byte 0 | Byte 1 | Byte 2 | Byte 3 |
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0xE0 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | LIVENESS TEST INTERVAL | Addr Mode | iFCP Ver |
| | (Seconds) | | |
+------+-------------------------+-----------+----------+
| 2 | USER INFO |
+------+------------+------------+-----------+----------+
| 3 | |
+------+ SOURCE N_PORT NAME |
| 4 | |
+------+------------------------------------------------+
| 5 | |
+------+ DESTINATION N_PORT NAME |
| 6 | |
+------+-------------------------+----------------------+
| 7 | Reserved | CBIND Status |
+------+-------------------------+----------------------+
| 8 | Reserved | CONNECTION HANDLE |
+------+-------------------------+----------------------+
Total Length = 36
Addr Mode: The address translation mode of the
responding gateway. 0 = Address
Translation mode, 1 = Address Transparent
mode.
iFCP Ver: iFCP version number. Shall be set to 1.
LIVENESS TEST If non-zero, requests that the gateway
INTERVAL: receiving the CBIND RESPONSE transmit an
LTEST message at the specified interval in
seconds. If zero, LTEST messages SHALL NOT
be sent.
USER INFO: Echoes the value received in the USER INFO
field of the CBIND request message.
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SOURCE N_PORT NAME: Contains the Worldwide Port Name (WWPN) of
the N_PORT locally attached to the gateway
issuing the CBIND request.
DESTINATION N_PORT Contains the Worldwide Port Name (WWPN) of
NAME: the N_PORT locally attached to the gateway
issuing the CBIND response.
CBIND STATUS: Indicates success or failure of the CBIND
request. CBIND values are shown below.
CONNECTION HANDLE: Contains a value assigned by the gateway to
identify the connection. The connection
handle is required when the UNBIND
request is issued.
CBIND Status Description
------------ -----------
0 Success
1 - 15 Reserved
16 Failed - Unspecified Reason
17 Failed - No such device
18 Failed - iFCP session already exists
19 Failed - Lack of resources
20 Failed - Incompatible address translation mode
21 Failed - Incorrect protocol version number
22 Failed - Gateway not Synchronized (see Section
8.2)
Others Reserved
6.2. Unbind Connection (UNBIND)
UNBIND is used to terminate an iFCP session and disassociate the TCP
connection as described in Section 5.2.3.
The UNBIND message is transmitted over the connection that is to be
unbound. The time stamp words in the encapsulation header shall be
set to zero in the request and response message frames.
Monia, et al. Standards Track [Page 52]
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The following is the format of the UNBIND request message.
+------+------------+------------+-----------+----------+
| Word | Byte 0 | Byte 1 | Byte 2 | Byte 3 |
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0xE4 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | USER INFO |
+------+------------+------------+-----------+----------+
| 2 | Reserved | CONNECTION HANDLE |
+------+------------+------------+----------------------+
| 3 | Reserved |
+------+------------+------------+-----------+----------+
| 4 | Reserved |
+------+------------+------------+-----------+----------+
USER INFO Contains any data desired by the requestor.
This information MUST be echoed by the
recipient in the UNBIND response message.
CONNECTION HANDLE: Contains the gateway-assigned value from
the CBIND request.
The following shows the format of the UNBIND response message.
+------+------------+------------+-----------+----------+
| Word | Byte 0 | Byte 1 | Byte 2 | Byte 3 |
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0xE4 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | USER INFO |
+------+------------+------------+-----------+----------+
| 2 | Reserved | CONNECTION HANDLE |
+------+------------+------------+-----------+----------+
| 3 | Reserved |
+------+------------+------------+-----------+----------+
| 4 | Reserved |
+------+------------+------------+-----------+----------+
| 5 | Reserved | UNBIND STATUS |
+------+------------+------------+-----------+----------+
USER INFO Echoes the value received in the USER INFO
field of the UNBIND request message.
CONNECTION HANDLE: Echoes the CONNECTION HANDLE specified in
the UNBIND request message.
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UNBIND STATUS: Indicates the success or failure of the
UNBIND request as follows:
Unbind Status Description
------------- -----------
0 Successful - No other status
1 - 15 Reserved
16 Failed - Unspecified Reason
18 Failed - Connection ID Invalid
Others Reserved
6.3. LTEST -- Test Connection Liveness
The LTEST message is sent at the interval specified in the CBIND
request or response payload. The LTEST encapsulation time stamp
SHALL be set as described in Section 8.2.1 and may be used by the
receiver to compute an estimate of propagation delay. However, the
propagation delay limit SHALL NOT be enforced.
+------+------------+------------+-----------+----------+
| Word | Byte 0 | Byte 1 | Byte 2 | Byte 3 |
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0xE5 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | LIVENESS TEST INTERVAL | Reserved |
| | (Seconds) | |
+------+-------------------------+----------------------+
| 2 | COUNT |
+------+------------+------------+-----------+----------+
| 3 | |
+------+ SOURCE N_PORT NAME |
| 4 | |
+------+------------------------------------------------+
| 5 | |
+------+ DESTINATION N_PORT NAME |
| 6 | |
+------+------------------------------------------------+
LIVENESS TEST Copy of the LIVENESS TEST INTERVAL
INTERVAL: specified in the CBIND request or reply
message.
COUNT: Monotonically increasing value, initialized
to 0 and incremented by one for each
successive LTEST message.
Monia, et al. Standards Track [Page 54]
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SOURCE N_PORT NAME: Contains a copy of the SOURCE N_PORT NAME
specified in the CBIND request.
DESTINATION N_PORT Contains a copy of the DESTINATION N_PORT
NAME: NAME specified in the CBIND request.
7. Fibre Channel Link Services
Link services provide a set of fibre channel functions that allow a
port to send control information or request another port to perform a
specific control function.
There are three types of link services:
a) Basic
b) Extended
c) ULP-specific (FC-4)
Each link service message (request and reply) is carried by a fibre
channel sequence and can be segmented into multiple frames.
The iFCP layer is responsible for transporting link service messages
across the IP network. This includes mapping link service messages
appropriately from the domain of the fibre channel transport to that
of the IP network. This process may require special processing and
the inclusion of supplemental data by the iFCP layer.
Each link service MUST be processed according to one of the following
rules:
a) Pass-through - The link service message and reply MUST be
delivered to the receiving N_PORT by the iFCP protocol layer
without altering the message payload. The link service message
and reply are not processed by the iFCP protocol layer.
b) Special - Applies to a link service reply or request requiring
the intervention of the iFCP layer before forwarding to the
destination N_PORT. Such messages may contain fibre channel
addresses in the payload or may require other special processing.
c) Rejected - When issued by a locally attached N_PORT, the specified
link service request MUST be rejected by the iFCP gateway. The
gateway SHALL return an LS_RJT response with a Reason Code of 0x0B
(Command Not Supported), and a Reason Code Explanation of 0x0 (No
Additional Explanation).
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This section describes the processing for special link services,
including the manner in which supplemental data is added to the
message payload.
Appendix A enumerates all link services and the iFCP processing
policy that applies to each.
7.1. Special Link Service Messages
Special link service messages require the intervention of the iFCP
layer before forwarding to the destination N_PORT. Such intervention
is required in order to:
a) service any link service message that requires special handling,
such as a PLOGI, and
b) service any link service message that has an N_PORT address in the
payload in address translation mode only .
Unless the link service description specifies otherwise, support for
each special link service is MANDATORY.
Such messages SHALL be transmitted in a fibre channel frame with the
format shown in Figure 18 for extended link services or Figure 19 for
FC-4 link services.
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Word
0<---Bit-->7 8<-------------------------------------------->31
+------------+------------------------------------------------+
0| R_CTL | D_ID |
|[Req = 0x22]|[Destination of extended link Service request] |
|[Rep = 0x23]| |
+------------+------------------------------------------------+
1| CS_CTL | S_ID |
| | [Source of extended link service request] |
+------------+------------------------------------------------+
2| TYPE | F_CTL |
| [0x01] | |
+------------+------------------+-----------------------------+
3| SEQ_ID | DF_CTL | SEQ_CNT |
+------------+------------------+-----------------------------+
4| OX_ID | RX_ID |
+-------------------------------+-----------------------------+
5| Parameter |
| [ 00 00 00 00 ] |
+-------------------------------------------------------------+
6| LS_COMMAND |
| [Extended Link Service Command Code] |
+-------------==----------------------------------------------+
7| |
.| Additional Service Request Parameters |
.| ( if any ) |
n| |
+-------------------------------------------------------------+
Figure 18. Format of an Extended Link Service Frame
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Word
0<---Bit-->7 8<-------------------------------------------->31
+------------+------------------------------------------------+
0| R_CTL | D_ID |
|[Req = 0x32]| [Destination of FC-4 link Service request] |
|[Rep = 0x33]| |
+------------+------------------------------------------------+
1| CS_CTL | S_ID |
| | [Source of FC-4 link service request] |
+------------+------------------------------------------------+
2| TYPE | F_CTL |
| (FC-4 | |
| specific) | |
+------------+------------------+-----------------------------+
3| SEQ_ID | DF_CTL | SEQ_CNT |
+------------+------------------+-----------------------------+
4| OX_ID | RX_ID |
+-------------------------------+-----------------------------+
5| Parameter |
| [ 00 00 00 00 ] |
+-------------------------------------------------------------+
6| LS_COMMAND |
| [FC-4 Link Service Command Code] |
+-------------------------------------------------------------+
7| |
.| Additional Service Request Parameters |
.| ( if any ) |
n| |
+-------------------------------------------------------------+
Figure 19. Format of an FC-4 Link Service Frame
7.2. Link Services Requiring Payload Address Translation
This section describes the handling for link service frames
containing N_PORT addresses in the frame payload. Such addresses
SHALL only be translated when the gateway is operating in address
translation mode. When operating in address transparent mode, these
addresses SHALL NOT be translated, and such link service messages
SHALL NOT be sent as special frames unless other processing by the
iFCP layer is required.
Supplemental data includes information required by the receiving
gateway to convert an N_PORT address in the payload to an N_PORT
address in the receiving gateway's address space. The following
rules define the manner in which such supplemental data shall be
packaged and referenced.
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For an N_PORT address field, the gateway originating the frame MUST
set the value in the payload to identify the address translation type
as follows:
0x00 00 01 - The gateway receiving the frame from the IP network
MUST replace the contents of the field with the N_PORT alias of
the frame originator. This translation type MUST be used when the
address to be converted is that of the source N_PORT.
0x00 00 02 - The gateway receiving the frame from the IP network
MUST replace the contents of the field with the N_PORT ID of the
destination N_PORT. This translation type MUST be used when the
address to be converted is that of the destination N_PORT
0x00 00 03 - The gateway receiving the frame from the IP network
MUST reference the specified supplemental data to set the field
contents. The supplemental information is the 64-bit worldwide
identifier of the N_PORT, as set forth in the fibre channel
specification [FC-FS]. If not otherwise part of the link service
payload, this information MUST be appended in accordance with the
applicable link service description. Unless specified otherwise,
this translation type SHALL NOT be used if the address to be
converted corresponds to that of the frame originator or
recipient.
Since fibre channel addressing rules prohibit the assignment of
fabric addresses with a domain ID of 0, the above codes will never
correspond to valid N_PORT fabric IDs.
If the sending gateway cannot obtain the worldwide identifier of an
N_PORT, the gateway SHALL terminate the request with an LS_RJT
message as described in [FC-FS]. The Reason Code SHALL be set to
0x07 (protocol error), and the Reason Explanation SHALL be set to
0x1F (Invalid N_PORT identifier).
Supplemental data is sent with the link service request or ACC frames
in one of the following ways:
a) By appending the necessary data to the end of the link service
frame.
b) By extending the sequence with additional frames.
In the first case, a new frame SHALL be created whose length includes
the supplemental data. The procedure for extending the link service
sequence with additional frames is dependent on the link service
type.
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For each field requiring address translation, the receiving gateway
SHALL reference the translation type encoded in the field and replace
it with the N_PORT address as shown in Table 7.
+------------------+------------------------------------+
| Translation | N_PORT Translation |
| Type Code | |
+------------------+------------------------------------+
| 0x00 00 01 | Replace field contents with N_PORT |
| | alias of frame originator. |
+------------------+------------------------------------+
| 0x00 00 02 | Replace field contents with N_PORT |
| | ID of frame recipient. |
+------------------+------------------------------------+
| | Lookup N_PORT via iSNS query. |
| | If locally attached, replace with |
| 0x00 00 03 | N_PORT ID. |
| | If remotely attached, replace with |
| | N_PORT alias from remote N_PORT. |
| | descriptor (see Section 5.2.2.1). |
+------------------+------------------------------------+
Table 7. Link Service Address Translation
For translation type 3, the receiving gateway SHALL obtain the
information needed to fill in the field in the link service frame
payload by converting the specified N_PORT worldwide identifier to a
gateway IP address and N_PORT ID. This information MUST be obtained
through an iSNS name server query. If the query is unsuccessful, the
gateway SHALL terminate the request with an LS_RJT response message
as described in [FC-FS]. The Reason Code SHALL be set to 0x07
(protocol error), and the Reason Explanation SHALL be set to 0x1F
(Invalid N_PORT identifier).
After applying the supplemental data, the receiving gateway SHALL
forward the resulting link service frames to the destination N_PORT
with the supplemental information removed.
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7.3. Fibre Channel Link Services Processed by iFCP
The following Extended and FC-4 Link Service Messages must receive
special processing.
Extended Link Service LS_COMMAND Mnemonic
Messages ---------- --------
----------------------
Abort Exchange 0x06 00 00 00 ABTX
Discover Address 0x52 00 00 00 ADISC
Discover Address Accept 0x02 00 00 00 ADISC ACC
FC Address Resolution 0x55 00 00 00 FARP-REPLY
Protocol Reply
FC Address Resolution 0x54 00 00 00 FARP-REQ
Protocol Request
Logout 0x05 00 00 00 LOGO
Port Login 0x30 00 00 00 PLOGI
Read Exchange Concise 0x13 00 00 00 REC
Read Exchange Concise 0x02 00 00 00 REC ACC
Accept
Read Exchange Status Block 0x08 00 00 00 RES
Read Exchange Status Block 0x02 00 00 00 RES ACC
Accept
Read Link Error Status 0x0F 00 00 00 RLS
Block
Read Sequence Status Block 0x09 00 00 00 RSS
Reinstate Recovery 0x12 00 00 00 RRQ
Qualifier
Request Sequence 0x0A 00 00 00 RSI
Initiative
Scan Remote Loop 0x7B 00 00 00 SRL
Third Party Process Logout 0x24 00 00 00 TPRLO
Third Party Process Logout 0x02 00 00 00 TPRLO ACC
Accept
FC-4 Link Service Messages LS_COMMAND Mnemonic
-------------------------- ---------- --------
FCP Read Exchange Concise 0x13 00 00 00 FCP REC
FCP Read Exchange Concise 0x02 00 00 00 FCP REC
Accept ACC
Each encapsulated fibre channel frame that is part of a special link
service MUST have the SPC bit set to one in the iFCP FLAGS field of
the encapsulation header, as specified in Section 5.3.1. If an ACC
link service response requires special processing, the responding
gateway SHALL place a copy of LS_COMMAND bits 0 through 7, from the
Monia, et al. Standards Track [Page 61]
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link service request frame, in the LS_COMMAND_ACC field of the ACC
encapsulation header. Supplemental data (if any) MUST be appended as
described in the following section.
The format of each special link service message, including
supplemental data, where applicable, is shown in the following
sections. Each description shows the basic format, as specified in
the applicable FC standard, followed by supplemental data as shown in
the example below.
+------+------------+------------+-----------+----------+
| Word | Bits 0-7 | Bits 8-15 | Bits 16-24|Bits 25-31|
+------+------------+------------+-----------+----------+
| 0 | LS_COMMAND |
+------+------------+------------+-----------+----------+
| 1 | |
| . | |
| . | Link Service Frame Payload |
| | |
| n | |
+======+============+============+===========+==========+
| n+1 | |
| . | Supplemental Data |
| . | (if any) |
| n+k | |
+======+================================================+
Figure 20. Special Link Service Frame Payload
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7.3.1. Special Extended Link Services
The following sections define extended link services for which
special processing is required.
7.3.1.1. Abort Exchange (ABTX)
ELS Format:
+------+------------+------------+-----------+----------+
| Word | Bits 0-7 | Bits 8-15 | Bits 16-24|Bits 25-31|
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x6 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | RRQ Status | Exchange Originator S_ID |
+------+------------+------------+-----------+----------+
| 2 | OX_ID of Tgt exchange | RX_ID of tgt exchange|
+------+------------+------------+-----------+----------+
| 3-10 | Optional association header (32 bytes |
+======+============+============+===========+==========+
Fields Requiring Translation Supplemental Data
Address Translation Type (see (type 3 only)
------------------- Section 7.2) ------------
-----------
Exchange Originator 1, 2 N/A
S_ID
Other Special Processing:
None.
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7.3.1.2. Discover Address (ADISC)
Format of ADISC ELS:
+------+------------+------------+-----------+----------+
| Word | Bits 0-7 | Bits 8-15 | Bits 16-24|Bits 25-31|
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x52 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | Reserved | Hard address of ELS Originator |
+------+------------+------------+-----------+----------+
| 2-3 | Port Name of Originator |
+------+------------+------------+-----------+----------+
| 4-5 | Node Name of originator |
+------+------------+------------+-----------+----------+
| 6 | Rsvd | N_PORT ID of ELS Originator |
+======+============+============+===========+==========+
Fields Requiring Translation Supplemental Data
Address Translation Type (see (type 3 only)
------------------- Section 7.2) -------------
------------
N_PORT ID of ELS 1 N/A
Originator
Other Special Processing:
The Hard Address of the ELS originator SHALL be set to 0.
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7.3.1.3. Discover Address Accept (ADISC ACC)
Format of ADISC ACC ELS:
+------+------------+------------+-----------+----------+
| Word | Bits 0-7 | Bits 8-15 | Bits 16-24|Bits 25-31|
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x20 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | Reserved | Hard address of ELS Originator |
+------+------------+------------+-----------+----------+
| 2-3 | Port Name of Originator |
+------+------------+------------+-----------+----------+
| 4-5 | Node Name of originator |
+------+------------+------------+-----------+----------+
| 6 | Rsvd | N_PORT ID of ELS Originator |
+======+============+============+===========+==========+
Fields Requiring Translation Supplemental Data
Address Translation Type (see (type 3 only)
------------------- Section 7.2) -------------
------------
N_PORT ID of ELS 1 N/A
Originator
Other Special Processing:
The Hard Address of the ELS originator SHALL be set to 0.
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7.3.1.4. FC Address Resolution Protocol Reply (FARP-REPLY)
The FARP-REPLY ELS is used in conjunction with the FARP-REQ ELS (see
Section 7.3.1.5) to perform the address resolution services required
by the FC-VI protocol [FC-VI] and the fibre channel mapping of IP and
ARP specified in RFC 2625 [RFC2625].
Format of FARP-REPLY ELS:
+------+------------+------------+-----------+----------+
| Word | Bits 0-7 | Bits 8-15 | Bits 16-24|Bits 25-31|
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x55 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | Match Addr | Requesting N_PORT Identifier |
| | Code Points| |
+------+------------+------------+-----------+----------+
| 2 | Responder | Responding N_PORT Identifier |
| | Action | |
+------+------------+------------+-----------+----------+
| 3-4 | Requesting N_PORT Port_Name |
+------+------------+------------+-----------+----------+
| 5-6 | Requesting N_PORT Node_Name |
+------+------------+------------+-----------+----------+
| 7-8 | Responding N_PORT Port_Name |
+------+------------+------------+-----------+----------+
| 9-10 | Responding N_PORT Node_Name |
+------+------------+------------+-----------+----------+
| 11-14| Requesting N_PORT IP Address |
+------+------------+------------+-----------+----------+
| 15-18| Responding N_PORT IP Address |
+======+============+============+===========+==========+
Fields Requiring Translation Supplemental Data
Address Translation Type (see (type 3 only)
------------------- Section 7.2) -----------------
------------
Requesting N_PORT 2 N/A
Identifier
Responding N_PORT 1 N/A
Identifier
Other Special Processing:
None.
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7.3.1.5. FC Address Resolution Protocol Request (FARP-REQ)
The FARP-REQ ELS is used in conjunction with the FC-VI protocol
[FC-VI] and IP-to-FC mapping of RFC 2625 [RFC2625] to perform IP and
FC address resolution in an FC fabric. The FARP-REQ ELS is usually
directed to the fabric broadcast server at well-known address
0xFF-FF-FF for retransmission to all attached N_PORTs.
Section 9.4 describes the iFCP implementation of FC broadcast server
functionality in an iFCP fabric.
Format of FARP_REQ ELS:
+------+------------+------------+-----------+----------+
| Word | Bits 0-7 | Bits 8-15 | Bits 16-24|Bits 25-31|
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x54 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | Match Addr | Requesting N_PORT Identifier |
| | Code Points| |
+------+------------+------------+-----------+----------+
| 2 | Responder | Responding N_PORT Identifier |
| | Action | |
+------+------------+------------+-----------+----------+
| 3-4 | Requesting N_PORT Port_Name |
+------+------------+------------+-----------+----------+
| 5-6 | Requesting N_PORT Node_Name |
+------+------------+------------+-----------+----------+
| 7-8 | Responding N_PORT Port_Name |
+------+------------+------------+-----------+----------+
| 9-10 | Responding N_PORT Node_Name |
+------+------------+------------+-----------+----------+
| 11-14| Requesting N_PORT IP Address |
+------+------------+------------+-----------+----------+
| 15-18| Responding N_PORT IP Address |
+======+============+============+===========+==========+
Fields Requiring Translation Supplemental Data
Address Translation Type (see (type 3 only)
------------------- Section 7.2) -----------------
-----------
Requesting N_PORT 3 Requesting N_PORT
Identifier Port Name
Responding N_PORT 3 Responding N_PORT
Identifier Port Name
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Other Special Processing:
None.
7.3.1.6. Logout (LOGO) and LOGO ACC
ELS Format:
+------+------------+------------+-----------+----------+
| Word | Bits 0-7 | Bits 8-15 | Bits 16-24|Bits 25-31|
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x5 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | Rsvd | N_PORT ID being logged out |
+------+------------+------------+-----------+----------+
| 2-3 | Port name of the LOGO originator (8 bytes) |
+======+============+============+===========+==========+
This ELS SHALL always be sent as a special ELS regardless of the
translation mode in effect.
Fields Requiring Translation Supplemental Data
Address Translation Type (see (type 3 only)
------------------- Section 7.2) ---------------
-----------
N_PORT ID Being 1 N/A
Logged Out
Other Special Processing:
See Section 5.2.3.
7.3.1.7. Port Login (PLOGI) and PLOGI ACC
A PLOGI ELS establishes fibre channel communications between two
N_PORTs and triggers the creation of an iFCP session if one does not
exist.
The PLOGI request and ACC response carry information identifying the
originating N_PORT, including a specification of its capabilities.
If the destination N_PORT accepts the login request, it sends an
Accept response (an ACC frame with PLOGI payload) specifying its
capabilities. This exchange establishes the operating environment
for the two N_PORTs.
Monia, et al. Standards Track [Page 68]
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The following figure is duplicated from [FC-FS], and shows the PLOGI
message format for both the request and Accept (ACC) response. An
N_PORT will reject a PLOGI request by transmitting an LS_RJT message
containing no payload.
+------+------------+------------+-----------+----------+
| Word | Bits 0-7 | Bits 8-15 | Bits 16-24|Bits 25-31|
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x3 | 0x00 | 0x00 | 0x00 |
| | Acc = 0x2 | | | |
+------+------------+------------+-----------+----------+
| 1-4 | Common Service Parameters |
+------+------------+------------+-----------+----------+
| 5-6 | N_PORT Name |
+------+------------+------------+-----------+----------+
| 7-8 | Node Name |
+------+------------+------------+-----------+----------+
| 9-12 | Class 1 Service Parameters |
+------+------------+------------+-----------+----------+
|13-17 | Class 2 Service Parameters |
+------+------------+------------+-----------+----------+
|18-21 | Class 3 Service Parameters |
+------+------------+------------+-----------+----------+
|22-25 | Class 4 Service Parameters |
+------+------------+------------+-----------+----------+
|26-29 | Vendor Version Level |
+======+============+============+===========+==========+
Figure 21. Format of PLOGI Request and ACC Payloads
Details of the above fields, including common and class-based service
parameters, can be found in [FC-FS].
Special Processing
As specified in Section 5.2.2.2, a PLOGI request addressed to a
remotely attached N_PORT MUST cause the creation of an iFCP
session if one does not exist. Otherwise, the PLOGI and PLOGI ACC
payloads MUST be passed through without modification to the
destination N_PORT using the existing iFCP session. In either
case, the SPC bit must be set in the frame encapsulation header as
specified in 5.3.3.
If the CBIND to create the iFCP session fails, the issuing gateway
SHALL terminate the PLOGI with an LS_RJT response. The Reason
Code and Reason Code Explanation SHALL be selected from Table 8
based on the CBIND failure status.
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+---------------+-------------------+---------------------+
| CBIND Failure | LS_RJT Reason | LS_RJT Reason Code |
| Status | Code | Explanation |
+===============+===================+=====================+
| Unspecified | Unable to Perform | No Additional |
| Reason (16) | Command Request | Explanation (0x00) |
| | (0x09) | |
+---------------+-------------------+---------------------+
| No Such | Unable to Perform | Invalid N_PORT |
| Device (17) | Command Request | Name (0x0D) |
| | (0x09) | |
+---------------+-------------------+---------------------+
| Lack of | Unable to Perform | Insufficient |
| Resources (19)| Command Request | Resources to Support|
| | (0x09) | Login (0x29) |
+---------------+-------------------+---------------------+
| Incompatible | Unable to Perform | No Additional |
| Address | Command Request | Explanation (0x00) |
| Translation | (0x09) | |
| Mode (20) | | |
+---------------+-------------------+---------------------+
| Incorrect iFCP| Unable to Perform | No Additional |
| Protocol | Command Request | Explanation (0x00) |
| version Number| (0x09) | |
| (21) | | |
+---------------+-------------------+---------------------+
| Gateway Not | Unable to Perform | No Additional |
| Synchronized | Command Request | Explanation (0x00) |
| (22) | (0x09) | |
+---------------+-------------------+---------------------+
Table 8. PLOGI LS_RJT Status for CBIND Failures
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7.3.1.8. Read Exchange Concise (REC)
Link Service Request Format:
+------+------------+------------+-----------+----------+
| Word | Bits 0-7 | Bits 8-15 |Bits 16-24 |Bits 25-31|
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x13 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | Rsvd | Exchange Originator S_ID |
+------+------------+------------+-----------+----------+
| 2 | OX_ID | RX_ID |
+======+============+============+===========+==========+
| 3-4 |Port Name of the Exchange Originator (8 bytes) |
| | (present only for translation type 3) |
+======+============+============+===========+==========+
Fields Requiring Translation Supplemental Data
Address Translation Type (see (type 3 only)
------------------- Section 7.2) -----------------
-----------
Exchange Originator 1, 2, or 3 Port Name of the
S_ID Exchange Originator
Other Special Processing:
None.
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7.3.1.9. Read Exchange Concise Accept (REC ACC)
Format of REC ACC Response:
+------+------------+------------+-----------+----------+
| Word | Bits 0-7 | Bits 8-15 |Bits 16-24 |Bits 25-31|
+------+------------+------------+-----------+----------+
| 0 | Acc = 0x02 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | OX_ID | RX_ID |
+------+------------+------------+-----------+----------+
| 2 | Rsvd | Originator Address Identifier |
+------+------------+------------+-----------+----------+
| 3 | Rsvd | Responder Address Identifier |
+------+------------+------------+-----------+----------+
| 4 | FC4VALUE (FC-4-Dependent Value) |
+------+------------+------------+-----------+----------+
| 5 | E_STAT (Exchange Status) |
+======+============+============+===========+==========+
| 6-7 |Port Name of the Exchange Originator (8 bytes) |
+======+============+============+===========+==========+
| 8-9 |Port Name of the Exchange Responder (8 bytes) |
+======+============+============+===========+==========+
Fields Requiring Translation Supplemental Data
Address Translation Type (see (type 3 only)
------------------- Section 7.2) ------------------
-----------
Originator Address 1, 2, or 3 Port Name of the
Identifier Exchange Originator
Responder Address 1, 2, or 3 Port Name of the
Identifier Exchange Responder
When supplemental data is required, the frame SHALL always be
extended by 4 words as shown above. If the translation type for the
Originator Address Identifier or the Responder Address Identifier is
1 or 2, the corresponding 8-byte port name SHALL be set to all zeros.
Other Special Processing:
None.
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7.3.1.10. Read Exchange Status Block (RES)
ELS Format:
+------+------------+------------+-----------+----------+
| Word | Bits 0-7 | Bits 8-15 | Bits 16-24|Bits 25-31|
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x13 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | Rsvd | Exchange Originator S_ID |
+------+------------+------------+-----------+----------+
| 2 | OX_ID | RX_ID |
+------+------------+------------+-----------+----------+
| 3-10 | Association Header (may be optionally req**d) |
+======+============+============+===========+==========+
| 11-12| Port Name of the Exchange Originator (8 bytes) |
+======+============+============+===========+==========+
Fields Requiring Translation Supplemental Data
Address Translation Type (see (type 3 only)
------------------- Section 7.2) ------------------
-----------
Exchange Originator 1, 2, or 3 Port Name of the
S_ID Exchange Originator
Other Special Processing:
None.
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7.3.1.11. Read Exchange Status Block Accept (RES ACC)
Format of ELS Accept Response:
+------+------------+------------+-----------+----------+
| Word | Bits 0-7 | Bits 8-15 | Bits 16-24|Bits 25-31|
+------+------------+------------+-----------+----------+
| 0 | Acc = 0x02 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | OX_ID | RX_ID |
+------+------------+------------+-----------+----------+
| 2 | Rsvd | Exchange Originator N_PORT ID |
+------+------------+------------+-----------+----------+
| 3 | Rsvd | Exchange Responder N_PORT ID |
+------+------------+------------+-----------+----------+
| 4 | Exchange Status Bits |
+------+------------+------------+-----------+----------+
| 5 | Reserved |
+------+------------+------------+-----------+----------+
| 6-n | Service Parameters and Sequence Statuses |
| | as described in [FC-FS] |
+======+============+============+===========+==========+
|n+1- | Port Name of the Exchange Originator (8 bytes) |
|n+2 | |
+======+============+============+===========+==========+
|n+3- | Port Name of the Exchange Responder (8 bytes) |
|n+4 | |
+======+============+============+===========+==========+
Fields Requiring Translation Supplemental Data
Address Translation Type (see (type 3 only)
------------------- Section 7.2) ------------------
-----------
Exchange Originator 1, 2, or 3 Port Name of the
N_PORT ID Exchange Originator
Exchange Responder 1, 2, or 3 Port Name of the
N_PORT ID Exchange Responder
When supplemental data is required, the ELS SHALL be extended by 4
words as shown above. If the translation type for the Exchange
Originator N_PORT ID or the Exchange Responder N_PORT ID is 1 or 2,
the corresponding 8-byte port name SHALL be set to all zeros.
Other Special Processing:
None.
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7.3.1.12. Read Link Error Status (RLS)
ELS Format:
+------+------------+------------+-----------+----------+
| Word | Bits 0-7 | Bits 8-15 | Bits 16-24|Bits 25-31|
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x0F | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | Rsvd | N_PORT Identifier |
+======+============+============+===========+==========+
| 2-3 | Port Name of the N_PORT (8 bytes) |
+======+============+============+===========+==========+
Fields Requiring Translation Supplemental Data
Address Translation Type (see (type 3 only)
------------------- Section 7.2) -----------------
-----------
N_PORT Identifier 1, 2, or 3 Port Name of the
N_PORT
Other Special Processing:
None.
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7.3.1.13. Read Sequence Status Block (RSS)
ELS Format:
+------+------------+------------+-----------+----------+
| Word | Bits 0-7 | Bits 8-15 | Bits 16-24|Bits 25-31|
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x09 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | SEQ_ID | Exchange Originator S_ID |
+------+------------+------------+-----------+----------+
| 2 | OX_ID | RX_ID |
+======+============+============+===========+==========+
| 3-4 |Port Name of the Exchange Originator (8 bytes) |
+======+============+============+===========+==========+
Fields Requiring Translation Supplemental Data
Address Translation Type (see (type 3 only)
------------------- Section 7.2) ------------------
-----------
Exchange Originator 1, 2, or 3 Port Name of the
S_ID Exchange Originator
Other Special Processing:
None.
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7.3.1.14. Reinstate Recovery Qualifier (RRQ)
ELS Format:
+------+------------+------------+-----------+----------+
| Word | Bits 0-7 | Bits 8-15 | Bits 16-24|Bits 25-31|
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x12 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | Rsvd | Exchange Originator S_ID |
+------+------------+------------+-----------+----------+
| 2 | OX_ID | RX_ID |
+------+------------+------------+-----------+----------+
| 3-10 | Association Header (may be optionally req**d) |
+======+============+============+===========+==========+
Fields Requiring Translation Supplemental Data
Address Translation Type (see (type 3 only)
------------------- Section 7.2) ------------------
-----------
Exchange Originator 1 or 2 N/A
S_ID
Other Special Processing:
None.
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7.3.1.15. Request Sequence Initiative (RSI)
ELS Format:
+------+------------+------------+-----------+----------+
| Word | Bits 0-7 | Bits 8-15 | Bits 16-24|Bits 25-31|
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x0A | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | Rsvd | Exchange Originator S_ID |
+------+------------+------------+-----------+----------+
| 2 | OX_ID | RX_ID |
+------+------------+------------+-----------+----------+
| 3-10 | Association Header (may be optionally req**d) |
+======+============+============+===========+==========+
Fields Requiring Translation Supplemental Data
Address Translation Type (see (type 3 only)
------------------- Section 7.2) ------------------
-----------
Exchange Originator 1 or 2 N/A
S_ID
Other Special Processing:
None.
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7.3.1.16. Scan Remote Loop (SRL)
SRL allows a remote loop to be scanned to detect changes in the
device configuration. Any changes will trigger a fibre channel state
change notification and subsequent update of the iSNS database.
ELS Format:
+------+------------+------------+-----------+----------+
| Word | Bits 0-7 | Bits 8-15 | Bits 16-24|Bits 25-31|
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x7B | Reserved |
+------+------------+------------+-----------+----------+
| 1 | Flag | Address Identifier of the FL_PORT |
| | | (see B.1) |
+======+============+============+===========+==========+
| 2-3 | Worldwide Name of the Remote FL_PORT |
+======+============+============+===========+==========+
Fields Requiring Translation Supplemental Data
Address Translation Type (see (type 3 only)
------------------- Section 7.2) ------------------
-----------
Address Identifier 3 Worldwide Name of
of the FL_PORT the Remote FL_PORT
Other Special Processing:
The D_ID field is the address of the Domain Controller associated
with the remote loop. The format of the Domain Controller address
is the hex 'FF FC' || Domain_ID, where Domain_ID is the gateway-
assigned alias representing the remote gateway or switch element
being queried. After translation by the remote gateway, the D_ID
identifies the gateway or switch element to be scanned within the
remote gateway region.
The FLAG field defines the scope of the SRL. If set to 0, all
loop port interfaces on the given switch element or gateway are
scanned. If set to one, the loop port interface on the gateway or
switch element to be scanned MUST be specified in bits 8 through
31.
If the Flag field is zero, the SRL request SHALL NOT be sent as a
special ELS.
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If the Domain_ID represents a remote switch or gateway and an iFCP
session to the remote Domain Controller does not exist, the
requesting gateway SHALL create the iFCP session.
7.3.1.17. Third Party Process Logout (TPRLO)
TPRLO provides a mechanism for an N_PORT (third party) to remove one
or more process login sessions that exist between the destination
N_PORT and other N_PORTs specified in the command. This command
includes one or more TPRLO LOGOUT PARAMETER PAGEs, each of which,
when combined with the destination N_PORT, identifies a process login
to be terminated by the command.
+--------+------------+--------------------+----------------------+
| Word | Bits 0-7 | Bits 8-15 | Bits 16 - 31 |
+--------+------------+--------------------+----------------------+
| 0 | Cmd = 0x24 | Page Length (0x10) | Payload Length |
+--------+------------+--------------------+----------------------+
| 1 | TPRLO Logout Parameter Page 0 |
+--------+--------------------------------------------------------+
| 5 | TPRLO Logout Parameter Page 1 |
+--------+--------------------------------------------------------+
....
+--------+--------------------------------------------------------+
|(4*n)+1 | TPRLO Logout Parameter Page n |
+--------+--------------------------------------------------------+
Figure 22. Format of TPRLO ELS
Each TPRLO parameter page contains parameters identifying one or more
image pairs and may be associated with a single FC-4 protocol type
that is common to all FC-4 protocol types between the specified image
pair or global to all specified image pairs. The format of a TPRLO
page requiring address translation is shown in Figure 23. Additional
information on TPRLO can be found in [FC-FS].
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+------+------------+------------+-----------+----------+
| Word | Bits 0-7 | Bits 8-15 | Bits 16-31 |
+------+------------+------------+-----------+----------+
| 0 | TYPE Code | TYPE CODE | |
| | or | EXTENSION | TPRLO Flags |
| | Common SVC | | |
| | Parameters | | |
+------+------------+------------+-----------+----------+
| 1 | Third Party Process Associator |
+------+------------+------------+-----------+----------+
| 2 | Responder Process Associator |
+------+------------+------------+-----------+----------+
| 3 | Reserved | Third Party Originator N_PORT ID |
+======+============+============+===========+==========+
| 4-5 | Worldwide Name of Third Party Originator |
| | N_PORT |
+------+------------------------------------------------+
Figure 23. Format of an Augmented TPRLO Parameter Page
The TPRLO flags that affect supplemented ELS processing are as
follows:
Bit 18: Third party Originator N_PORT Validity. When set to one,
this bit indicates that word 3, bits 8-31 (Third Party
Originator N_PORT ID), are meaningful.
Bit 19: Global Process logout. When set to one, this bit indicates
that all image pairs for all N_PORTs of the specified FC-4
protocol shall be invalidated. When the value of this bit
is one, only one logout parameter page is permitted in the
TPRLO payload.
If bit 18 has a value of zero and bit 19 has a value of one in the
TPRLO flags field, then the ELS SHALL NOT be sent as a special ELS.
Otherwise, the originating gateway SHALL process the ELS as follows:
a) The first word of the TPRLO payload SHALL NOT be modified.
b) Each TPRLO parameter page shall be extended by two words as shown
in Figure 23.
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c) If word 0, bit 18 (Third Party Originator N_PORT ID validity), in
the TPRLO flags field has a value of one, then the sender shall
place the worldwide port name of the fibre channel device's N_PORT
in the extension words. The N_PORT ID SHALL be set to 3.
Otherwise, the contents of the extension words and the Third Party
Originator N_PORT ID SHALL be set to zero.
d) The ELS originator SHALL set the SPC bit in the encapsulation
header of each augmented frame comprising the ELS (see Section
5.3.1).
e) If the ELS contains a single TPRLO parameter page, the originator
SHALL increase the frame length as necessary to include the
extended parameter page.
f) If the ELS to be augmented contains multiple TPRLO parameter
pages, the FC frames created to contain the augmented ELS payload
SHALL NOT exceed the maximum frame size that can be accepted by
the destination N_PORT.
Each fibre channel frame SHALL contain an integer number of
extended TPRLO parameter pages. The maximum number of extended
TPRLO parameter pages in a frame SHALL be limited to the number
that can be held without exceeding the above upper limit. New
frames resulting from the extension of the TPRLO pages to include
the supplemental data SHALL be created by extending the SEQ_CNT in
the fibre channel frame header. The SEQ_ID SHALL NOT be modified.
The gateway receiving the augmented TPRLO ELS SHALL generate ELS
frames to be sent to the destination N_PORT by copying word 0 of the
ELS payload and processing each augmented parameter page as follows:
a) If word 0, bit 18, has a value of one, create a parameter page by
copying words 0 through 2 of the augmented parameter page. The
Third Party Originator N_PORT ID in word 3 shall be generated by
referencing the supplemental data as described in Section 7.2.
b) If word 0, bit 18, has a value of zero, create a parameter page by
copying words 0 through 3 of the augmented parameter page.
The size of each frame to be sent to the destination N_PORT MUST NOT
exceed the maximum frame size that the destination N_PORT can accept.
The sequence identifier in each frame header SHALL be copied from the
augmented ELS, and the sequence count SHALL be monotonically
increasing.
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7.3.1.18. Third Party Logout Accept (TPRLO ACC)
The format of the TPRLO ACC frame is shown in Figure 24.
+--------+------------+--------------------+----------------------+
| Word | Bits 0-7 | Bits 8-15 | Bits 16 - 31 |
+--------+------------+--------------------+----------------------+
| 0 | Cmd = 0x2 | Page Length (0x10) | Payload Length |
+--------+------------+--------------------+----------------------+
| 1 | TPRLO Logout Parameter Page 0 |
+--------+--------------------------------------------------------+
| 5 | TPRLO Logout Parameter Page 1 |
+--------+--------------------------------------------------------+
....
+--------+--------------------------------------------------------+
|(4*n)+1 | TPRLO Logout Parameter Page n |
+--------+--------------------------------------------------------+
Figure 24. Format of TPRLO ACC ELS
The format of the parameter page and rules for parameter page
augmentation are as specified in Section 7.3.1.17.
7.3.2. Special FC-4 Link Services
The following sections define FC-4 link services for which special
processing is required.
7.3.2.1. FC-4 Link Services Defined by FCP
The format of FC-4 link service frames defined by FCP can be found in
[FCP-2].
7.3.2.1.1. FCP Read Exchange Concise (FCP REC)
The payload format for this link service is identical to the REC
extended link service specified in Section 7.3.1.8 and SHALL be
processed as described in that section. The FC-4 version will become
obsolete in [FCP-2]. However, in order to support devices
implemented against early revisions of FCP-2, an iFCP gateway MUST
support both versions.
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7.3.2.1.2. FCP Read Exchange Concise Accept (FCP REC ACC)
The payload format for this link service is identical to the REC ACC
extended link service specified in Section 7.3.1.9 and SHALL be
processed as described in that section. The FC-4 version will become
obsolete in [FCP-2]. However, in order to support devices
implemented against earlier revisions of FCP-2, an iFCP gateway MUST
support both versions.
7.4. FLOGI Service Parameters Supported by an iFCP Gateway
The FLOGI ELS is issued by an N_PORT that wishes to access the fabric
transport services.
The format of the FLOGI request and FLOGI ACC payloads are identical
to the PLOGI request and ACC payloads described in Section 7.3.1.7.
+------+------------+------------+-----------+----------+
| Word | Bits 0-7 | Bits 8-15 |Bits 16-24 |Bits 25-31|
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x4 | 0x00 | 0x00 | 0x00 |
| | Acc = 0x2 | | | |
+------+------------+------------+-----------+----------+
| 1-4 | Common Service Parameters |
+------+------------+------------+-----------+----------+
| 5-6 | N_PORT Name |
+------+------------+------------+-----------+----------+
| 7-8 | Node Name |
+------+------------+------------+-----------+----------+
| 9-12 | Class 1 Service Parameters |
+------+------------+------------+-----------+----------+
|13-17 | Class 2 Service Parameters |
+------+------------+------------+-----------+----------+
|18-21 | Class 3 Service Parameters |
+------+------------+------------+-----------+----------+
|22-25 | Class 4 Service Parameters |
+------+------------+------------+-----------+----------+
|26-29 | Vendor Version Level |
+======+============+============+===========+==========+
Figure 25. FLOGI Request and ACC Payload Format
A full description of each parameter is given in [FC-FS].
This section tabulates the protocol-dependent service parameters
supported by a fabric port attached to an iFCP gateway.
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The service parameters carried in the payload of an FLOGI extended
link service request MUST be set in accordance with Table 9.
+-----------------------------------------+---------------+
| | Fabric Login |
| Service Parameter | Class |
| +---+---+---+---+
| | 1 | 2 | 3 | 4 |
+-----------------------------------------+---+---+---+---+
| Class Validity | n | M | M | n |
+-----------------------------------------+---+---+---+---+
| Service Options | |
+-----------------------------------------+---+---+---+---+
| Intermix Mode | n | n | n | n |
+-----------------------------------------+---+---+---+---+
| Stacked Connect-Requests | n | n | n | n |
+-----------------------------------------+---+---+---+---+
| Sequential Delivery | n | M | M | n |
+-----------------------------------------+---+---+---+---+
| Dedicated Simplex | n | n | n | n |
+-----------------------------------------+---+---+---+---+
| Camp On | n | n | n | n |
+-----------------------------------------+---+---+---+---+
| Buffered Class 1 | n | n | n | n |
+-----------------------------------------+---+---+---+---+
| Priority | n | n | n | n |
+-----------------------------------------+---+---+---+---+
| Initiator/Recipient Control | |
+-----------------------------------------+---+---+---+---+
| Clock Synchronization ELS Capable | n | n | n | n |
+-----------------------------------------+---+---+---+---+
Table 9. FLOGI Service Parameter Settings
Notes:
1) "n" indicates a parameter or capability that is not supported
by the iFCP protocol.
2) "M" indicates an applicable parameter that MUST be supported by
an iFCP gateway.
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8. iFCP Error Detection
8.1. Overview
This section specifies provisions for error detection and recovery in
addition to those in [FC-FS], which continue to be available in the
iFCP network environment.
8.2. Stale Frame Prevention
Recovery from fibre channel protocol error conditions requires that
frames associated with a failed or aborted exchange drain from the
fabric before exchange resources can be safely reused.
Since a fibre channel fabric may not preserve frame order, there is
no deterministic way to purge such frames. Instead, the fabric
guarantees that frame the lifetime will not exceed a specific limit
(R_A_TOV).
R_A_TOV is defined in [FC-FS] as "the maximum transit time within a
fabric to guarantee that a lost frame will never emerge from the
fabric". For example, a value of 2 x R_A_TOV is the minimum time
that the originator of an ELS request or FC-4 link service request
must wait for the response to that request. The fibre channel
default value for R_A_TOV is 10 seconds.
An iFCP gateway SHALL actively enforce limits on R_A_TOV as described
in Section 8.2.1.
8.2.1. Enforcing R_A_TOV Limits
The R_A_TOV limit on frame lifetimes SHALL be enforced by means of
the time stamp in the encapsulation header (see Section 5.3.1) as
described in this section.
The budget for R_A_TOV SHOULD include allowances for the propagation
delay through the gateway regions of the sending and receiving
N_PORTs, plus the propagation delay through the IP network. This
latter component is referred to in this specification as IP_TOV.
IP_TOV should be set well below the value of R_A_TOV specified for
the iFCP fabric and should be stored in the iSNS server. IP_TOV
should be set to 50 percent of R_A_TOV.
The following paragraphs describe the requirements for synchronizing
gateway time bases and the rules for measuring and enforcing
propagation delay limits.
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The protocol for synchronizing a gateway time base is SNTP [RFC2030].
In order to ensure that all gateways are time aligned, a gateway
SHOULD obtain the address of an SNTP-compatible time server via an
iSNS query. If multiple time server addresses are returned by the
query, the servers must be synchronized and the gateway may use any
server in the list. Alternatively, the server may return a multicast
group address in support of operation in Anycast mode.
Implementation of Anycast mode is as specified in [RFC2030],
including the precautions defined in that document. Multicast mode
SHOULD NOT be used.
An SNTP server may use any one of the time reference sources listed
in [RFC2030]. The resolution of the time reference MUST be 125
milliseconds or better.
Stability of the SNTP server and gateway time bases should be 100 ppm
or better.
With regard to its time base, the gateway is in either the
Synchronized or Unsynchronized state.
When in the synchronized state, the gateway SHALL
a) set the time stamp field for each outgoing frame in accordance
with the gateway's internal time base;
b) check the time stamp field of each incoming frame, following
validation of the encapsulation header CRC, as described in
Section 5.3.4;
c) if the incoming frame has a time stamp of 0,0 and is not one of
the session control frames that require a 0,0 time stamp (see
Section 6), the frame SHALL be discarded;
d) if the incoming frame has a non-zero time stamp, the receiving
gateway SHALL compute the absolute value of the time in flight and
SHALL compare it against the value of IP_TOV specified for the IP
fabric;
e) if the result in step (d) exceeds IP_TOV, the encapsulated frame
shall be discarded. Otherwise, the frame shall be de-encapsulated
as described in Section 5.3.4.
A gateway SHALL enter the Synchronized state upon receiving a
successful response to an SNTP query.
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A gateway shall enter the Unsynchronized state:
a) upon power-up and before successful completion of an SNTP query,
and
b) whenever the gateway looses contact with the SNTP server, such
that the gateway's time base may no longer be in alignment with
that of the SNTP server. The criterion for determining loss of
contact is implementation specific.
Following loss of contact, it is recommended that the gateway enter
the Unsynchronized state when the estimated time base drift relative
to the SNTP reference is greater than ten percent of the IP_TOV
limit. (Assuming that all timers have an accuracy of 100 ppm and
IP_TOV equals 5 seconds, the maximum allowable loss of contact
duration would be about 42 minutes.)
As the result of a transition from the Synchronized to the
Unsynchronized state, a gateway MUST abort all iFCP sessions as
described in Section 5.2.3. While in the Unsynchronized state, a
gateway SHALL NOT permit the creation of new iFCP sessions.
9. Fabric Services Supported by an iFCP Implementation
An iFCP gateway implementation MUST support the following fabric
services:
N_PORT ID Value Description Section
--------------- ----------- -------
0xFF-FF-FE F_PORT Server 9.1
0xFF-FF-FD Fabric Controller 9.2
0xFF-FF-FC Directory/Name Server 9.3
In addition, an iFCP gateway MAY support the FC broadcast server
functionality described in Section 9.4.
9.1. F_PORT Server
The F_PORT server SHALL support the FLOGI ELS, as described in
Section 7.4, as well as the following ELSs specified in [FC-FS]:
a) Request for fabric service parameters (FDISC).
b) Request for the link error status (RLS).
c) Read Fabric Timeout Values (RTV).
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9.2. Fabric Controller
The Fabric Controller SHALL support the following ELSs as specified
in [FC-FS]:
a) State Change Notification (SCN).
b) Registered State Change Notification (RSCN).
c) State Change Registration (SCR).
9.3. Directory/Name Server
The Directory/Name server provides a registration service allowing an
N_PORT to record or query the database for information about other
N_PORTs. The services are defined in [FC-GS3]. The queries are
issued as FC-4 transactions using the FC-CT command transport
protocol specified in [FC-GS3].
In iFCP, each name server request MUST be translated to the
appropriate iSNS query defined in [ISNS]. The definitions of name
server objects are specified in [FC-GS3].
The name server SHALL support record and query operations for
directory subtype 0x02 (Name Server) and 0x03 (IP Address Server) and
MAY support the FC-4 specific services as defined in [FC-GS3].
9.4. Broadcast Server
Fibre channel frames are broadcast throughout the fabric by
addressing them to the fibre channel broadcast server at the well-
known fibre channel address 0xFF-FF-FF. The broadcast server then
replicates and delivers the frame to each attached N_PORT in all
zones to which the originating device belongs. Only class 3
(datagram) service is supported.
In an iFCP system, the fibre channel broadcast function is emulated
by means of a two-tier architecture comprising the following
elements:
a) A local broadcast server residing in each iFCP gateway. The local
server distributes broadcast traffic within the gateway region and
forwards outgoing broadcast traffic to a global server for
distribution throughout the iFCP fabric.
b) A global broadcast server that re-distributes broadcast traffic to
the local server in each participating gateway.
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c) An iSNS discovery domain defining the scope over which broadcast
traffic is propagated. The discovery domain is populated with a
global broadcast server and the set of local servers it supports.
The local and global broadcast servers are logical iFCP devices that
communicate using the iFCP protocol. The servers have an N_PORT
Network Address consisting of an iFCP portal address and an N_PORT ID
set to the well-known fibre channel address of the FC broadcast
server (0xFF-FF-FF).
As noted above, an N_PORT originates a broadcast by directing frame
traffic to the fibre channel broadcast server. The gateway-resident
local server distributes a copy of the frame locally and forwards a
copy to the global server for redistribution to the local servers on
other gateways. The global server MUST NOT echo a broadcast frame to
the originating local server.
9.4.1. Establishing the Broadcast Configuration
The broadcast configuration is managed with facilities provided by
the iSNS server by the following means:
a) An iSNS discovery domain is created and seeded with the network
address of the global broadcast server N_PORT. The global server
is identified as such by setting the appropriate N_PORT entity
attribute.
b) Using the management interface, each broadcast server is preset
with the identity of the broadcast domain.
During power up, each gateway SHALL invoke the iSNS service to
register its local broadcast server in the broadcast discovery
domain. After registration, the local server SHALL wait for the
global broadcast server to establish an iFCP session.
The global server SHALL register with the iSNS server as follows:
a) The server SHALL query the iSNS name server by attribute to obtain
the worldwide port name of the N_PORT pre-configured to provide
global broadcast services.
b) If the worldwide port name obtained above does not correspond to
that of the server issuing the query, the N_PORT SHALL NOT perform
global broadcast functions for N_PORTs in that discovery domain.
c) Otherwise, the global server N_PORT SHALL register with the
discovery domain and query the iSNS server to identify all
currently registered local servers.
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d) The global broadcast server SHALL initiate an iFCP session with
each local broadcast server in the domain. When a new local
server registers, the global server SHALL receive a state change
notification and respond by initiating an iFCP session with the
newly added server. The gateway SHALL obtain these notifications
using the iSNS provisions for lossless delivery.
Upon receiving the CBIND request to initiate the iFCP session, the
local server SHALL record the worldwide port name and N_PORT network
address of the global server.
9.4.2. Broadcast Session Management
After the initial broadcast session is established, the local or
global broadcast server MAY choose to manage the session in one of
the following ways, depending on resource requirements and the
anticipated level of broadcast traffic:
a) A server MAY keep the session open continuously. Since broadcast
sessions are often quiescent for long periods of time, the server
SHOULD monitor session connectivity as described in Section
5.2.2.4.
b) A server MAY open the broadcast session on demand only when
broadcast traffic is to be sent. If the session is reopened by
the global server, the local server SHALL replace the previously
recorded network address of the global broadcast server.
9.4.3. Standby Global Broadcast Server
An implementation may designate a local server to assume the duties
of the global broadcast server in the event of a failure. The local
server may use the LTEST message to determine whether the global
server is functioning and may assume control if it is not.
When assuming control, the standby server must register with the iSNS
server as the global broadcast server in place of the failed server
and must install itself in the broadcast discovery domain as
specified in steps c) and d) of Section 9.4.1.
10. iFCP Security
10.1. Overview
iFCP relies upon the IPSec protocol suite to provide data
confidentiality and authentication services, and it relies upon IKE
as the key management protocol. Section 10.2 describes the security
requirements arising from iFCP's operating environment, and Section
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10.3 describes the resulting design choices, their requirement
levels, and how they apply to the iFCP protocol.
Detailed considerations for use of IPsec and IKE with the iFCP
protocol can be found in [SECIPS].
10.2. iFCP Security Threats and Scope
10.2.1. Context
iFCP is a protocol designed for use by gateway devices deployed in
enterprise data centers. Such environments typically have security
gateways designed to provide network security through isolation from
public networks. Furthermore, iFCP data may have to traverse
security gateways in order to support SAN-to-SAN connectivity across
public networks.
10.2.2. Security Threats
Communicating iFCP gateways may be subjected to attacks, including
attempts by an adversary to:
a) acquire confidential data and identities by snooping data packets,
b) modify packets containing iFCP data and control messages,
c) inject new packets into the iFCP session,
d) hijack the TCP connection carrying the iFCP session,
e) launch denial-of-service attacks against the iFCP gateway,
f) disrupt the security negotiation process,
g) impersonate a legitimate security gateway, or
h) compromise communication with the iSNS server.
It is imperative to thwart these attacks, given that an iFCP gateway
is the last line of defense for a whole fibre channel island, which
may include several hosts and fibre channel switches. To do so, the
iFCP gateway must implement and may use confidentiality, data origin
authentication, integrity, and replay protection on a per-datagram
basis. The iFCP gateway must implement and may use bi-directional
authentication of the communication endpoints. Finally, it must
implement and may use a scalable approach to key management.
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10.2.3. Interoperability with Security Gateways
Enterprise data center networks are considered mission-critical
facilities that must be isolated and protected from all possible
security threats. Such networks are usually protected by security
gateways, which, at a minimum, provide a shield against denial-of-
service attacks. The iFCP security architecture is capable of
leveraging the protective services of the existing security
infrastructure, including firewall protection, NAT and NAPT services,
and IPSec VPN services available on existing security gateways.
Considerations regarding intervening NAT and NAPT boxes along the
iFCP-iSNS path can be found in [ISNS].
10.2.4. Authentication
iFCP is a peer-to-peer protocol. iFCP sessions may be initiated by
either peer gateway or both. Consequently, bi-directional
authentication of peer gateways must be provided in accordance with
the requirement levels specified in Section 10.3.1.
N_PORT identities used in the Port Login (PLOGI) process shall be
considered authenticated if the PLOGI request is received from the
remote gateway over a secure, IPSec-protected connection.
There is no requirement that the identities used in authentication be
kept confidential.
10.2.5. Confidentiality
iFCP traffic may traverse insecure public networks, and therefore
implementations must have per-packet encryption capabilities to
provide confidentiality in accordance with the requirements specified
in Section 10.3.1.
10.2.6. Rekeying
Due to the high data transfer rates and the amount of data involved,
an iFCP implementation must support the capability to rekey each
phase 2 security association in the time intervals dictated by
sequence number space exhaustion at a given link rate. In the
rekeying scenario described in [SECIPS], for example, rekeying events
happen as often as every 27.5 seconds at a 10 Gbps rate.
The iFCP gateway must provide the capability for forward secrecy in
the rekeying process.
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10.2.7. Authorization
Basic access control properties stem from the requirement that two
communicating iFCP gateways be known to one or more iSNS servers
before they can engage in iFCP exchanges. The optional use of
discovery domains [ISNS], Identity Payloads (e.g., ID_FQDNs), and
certificate-based authentication (e.g., with X509v3 certificates)
enables authorization schemas of increasing complexity. The
definition of such schemas (e.g., role-based access control) is
outside of the scope of this specification.
10.2.8. Policy Control
This specification allows any and all security mechanisms in an iFCP
gateway to be administratively disabled. Security policies MUST
have, at most, iFCP Portal resolution. Administrators may gain
control over security policies through an adequately secured
interaction with a management interface or with iSNS.
10.2.9. iSNS Role
iSNS [ISNS] is an invariant in all iFCP deployments. iFCP gateways
MUST use iSNS for discovery services and MAY use security policies
configured in the iSNS database as the basis for algorithm
negotiation in IKE. The iSNS specification defines mechanisms for
securing communication between an iFCP gateway and iSNS server(s).
Additionally, the specification indicates how elements of security
policy concerning individual iFCP sessions can be retrieved from iSNS
server(s).
10.3. iFCP Security Design
10.3.1. Enabling Technologies
Applicable technology from IPsec and IKE is defined in the following
suite of specifications:
[RFC2401] Security Architecture for the Internet Protocol
[RFC2402] IP Authentication Header
[RFC2404] The Use of HMAC-SHA-1-96 within ESP and AH
[RFC2405] The ESP DES-CBC Cipher Algorithm with Explicit IV
[RFC2406] IP Encapsulating Security Payload
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[RFC2407] The Internet IP Security Domain of Interpretation for
ISAKMP
[RFC2408] Internet Security Association and Key Management
Protocol (ISAKMP)
[RFC2409] The Internet Key Exchange (IKE)
[RFC2410] The NULL Encryption Algorithm and Its Use With IPSEC
[RFC2451] The ESP CBC-Mode Cipher Algorithms
[RFC2709] Security Model with Tunnel-mode IPsec for NAT Domains
The implementation of IPsec and IKE is required according to the
following guidelines.
Support for the IP Encapsulating Security Payload (ESP) [RFC2406] is
MANDATORY to implement. When ESP is used, per-packet data origin
authentication, integrity, and replay protection MUST be used.
For data origin authentication and integrity with ESP, HMAC with SHA1
[RFC2404] MUST be implemented, and the Advanced Encryption Standard
[AES] in CBC MAC mode with Extended Cipher Block Chaining SHOULD be
implemented in accordance with [AESCBC].
For confidentiality with ESP, 3DES in CBC mode [RFC2451] MUST be
implemented, and AES counter mode encryption [AESCTR] SHOULD be
implemented. NULL encryption MUST be supported as well, as defined
in [RFC2410]. DES in CBC mode SHOULD NOT be used due to its inherent
weakness. Since it is known to be crackable with modest computation
resources, it is inappropriate for use in any iFCP deployment
scenario.
A conforming iFCP protocol implementation MUST implement IPsec ESP
[RFC2406] in tunnel mode [RFC2401] and MAY implement IPsec ESP in
transport mode.
Regarding key management, iFCP implementations MUST support IKE
[RFC2409] for bi-directional peer authentication, negotiation of
security associations, and key management, using the IPsec DOI.
There is no requirement that the identities used in authentication be
kept confidential. Manual keying MUST NOT be used since it does not
provide the necessary keying support. According to [RFC2409], pre-
shared secret key authentication is MANDATORY to implement, whereas
certificate-based peer authentication using digital signatures MAY be
implemented (see Section 10.3.3 regarding the use of certificates).
[RFC2409] defines the following requirement levels for IKE Modes:
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Phase-1 Main Mode MUST be implemented.
Phase-1 Aggressive Mode SHOULD be implemented.
Phase-2 Quick Mode MUST be implemented.
Phase-2 Quick Mode with key exchange payload MUST be implemented.
With iFCP, Phase-1 Main Mode SHOULD NOT be used in conjunction with
pre-shared keys, due to Main Mode's vulnerability to man-in-the-
middle-attackers when group pre-shared keys are used. In this
scenario, Aggressive Mode SHOULD be used instead. Peer
authentication using the public key encryption methods outlined in
[RFC2409] SHOULD NOT be used.
The DOI [RFC2407] provides for several types of Identification
Payloads.
When used for iFCP, IKE Phase 1 exchanges MUST explicitly carry the
Identification Payload fields (IDii and IDir). Conforming iFCP
implementations MUST use ID_IPV4_ADDR, ID_IPV6_ADDR (if the protocol
stack supports IPv6), or ID_FQDN Identification Type values. The
ID_USER_FQDN, IP Subnet, IP Address Range, ID_DER_ASN1_DN,
ID_DER_ASN1_GN Identification Type values SHOULD NOT be used. The
ID_KEY_ID Identification Type values MUST NOT be used. As described
in [RFC2407], the port and protocol fields in the Identification
Payload MUST be set to zero or UDP port 500.
When used for iFCP, IKE Phase 2 exchanges MUST explicitly carry the
Identification Payload fields (IDci and IDcr). Conforming iFCP
implementations MUST use either ID_IPV4_ADDR or ID_IPV6_ADDR
Identification Type values (according to the version of IP
supported). Other Identification Type values MUST NOT be used. As
described in Section 5.2.2, the gateway creating the iFCP session
must query the iSNS server to determine the appropriate port on which
to initiate the associated TCP connection. Upon a successful IKE
Phase 2 exchange, the IKE responder enforces the negotiated selectors
on the IPsec SAs. Any subsequent iFCP session creation requires the
iFCP peer to query its iSNS server for access control (in accordance
with the session creation requirements specified in Section 5.2.2.1).
10.3.2. Use of IKE and IPsec
A conforming iFCP Portal is capable of establishing one or more IKE
Phase-1 Security Associations (SAs) to a peer iFCP Portal. A Phase-1
SA may be established when an iFCP Portal is initialized or may be
deferred until the first TCP connection with security requirements is
established.
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An IKE Phase-2 SA protects one or more TCP connections within the
same iFCP Portal. More specifically, the successful establishment of
an IKE Phase-2 SA results in the creation of two uni-directional
IPsec SAs fully qualified by the tuple <SPI, destination IP address,
ESP>.
These SAs protect the setup process of the underlying TCP connections
and all their subsequent TCP traffic. The number of TCP connections
in an IPsec SA, as well as the number of SAs, is practically driven
by security policy considerations (i.e., security services are
defined at the granularity of an IPsec SA only), QoS considerations
(e.g., multiple QoS classes within the same IPsec SA increase odds of
packet reordering, possibly falling outside the replay window), and
failure compartmentalization considerations. Each of the TCP
connections protected by an IPsec SA is either in the unbound state,
or bound to a specific iFCP session.
In summary, at any point in time:
-- there exist 0..M IKE Phase-1 SAs between peer iFCP portals,
-- each IKE Phase-1 SA has 0..N IKE Phase-2 SAs, and
-- each IKE Phase-2 SA protects 0..Z TCP connections.
The creation of an IKE Phase-2 SA may be triggered by a policy rule
supplied through a management interface or by iFCP Portal properties
registered with the iSNS server. Similarly, the use of a Key
Exchange payload in Quick Mode for perfect forward secrecy may be
dictated through a management interface or by an iFCP Portal policy
rule registered with the iSNS server.
If an iFCP implementation makes use of unbound TCP connections, and
such connections belong to an iFCP Portal with security requirements,
then the unbound connections MUST be protected by an SA at all times
just like bound connections.
Upon receipt of an IKE Phase-2 delete message, there is no
requirement to terminate the protected TCP connections or delete the
associated IKE Phase-1 SA. Since an IKE Phase-2 SA may be associated
with multiple TCP connections, terminating these connections might in
fact be inappropriate and untimely.
To minimize the number of active Phase-2 SAs, IKE Phase-2 delete
messages may be sent for Phase-2 SAs whose TCP connections have not
handled data traffic for a while. To minimize the use of SA
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resources while the associated TCP connections are idle, creation of
a new SA should be deferred until new data are to be sent over the
connections.
10.3.3. Signatures and Certificate-Based Authentication
Conforming iFCP implementations MAY support peer authentication via
digital signatures and certificates. When certificate authentication
is chosen within IKE, each iFCP gateway needs the certificate
credentials of each peer iFCP gateway in order to establish a
security association with that peer.
Certificate credentials used by iFCP gateways MUST be those of the
machine. Certificate credentials MAY be bound to the interface (IP
Address or FQDN) of the iFCP gateway used for the iFCP session, or to
the fabric WWN of the iFCP gateway itself. Since the value of a
machine certificate is inversely proportional to the ease with which
an attacker can obtain one under false pretenses, it is advisable
that the machine certificate enrollment process be strictly
controlled. For example, only administrators may have the ability to
enroll a machine with a machine certificate. User certificates
SHOULD NOT be used by iFCP gateways for establishment of SAs
protecting iFCP sessions.
If the gateway does not have the peer iFCP gateway's certificate
credentials, then it can obtain them:
a) by using the iSNS protocol to query for the peer gateway's
certificate(s) stored in a trusted iSNS server, or
b) through use of the ISAKMP Certificate Request Payload (CRP)
[RFC2408] to request the certificate(s) directly from the peer
iFCP gateway.
When certificate chains are long enough, IKE exchanges using UDP as
the underlying transport may yield IP fragments, which are known to
work poorly across some intervening routers, firewalls, and NA(P)T
boxes. As a result, the endpoints may be unable to establish an
IPsec security association.
Due to these fragmentation shortcomings, IKE is most appropriate for
intra-domain usage. Known solutions to the fragmentation problem
include sending the end-entry machine certificate rather than the
chain, reducing the size of the certificate chain, using IKE
implementations over a reliable transport protocol (e.g., TCP)
assisted by Path MTU discovery and code against black-holing as per
[RFC2923], or installing network components that can properly handle
fragments.
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IKE negotiators SHOULD check the pertinent Certificate Revocation
List (CRL) [RFC2408] before accepting a certificate for use in IKE's
authentication procedures.
10.4. iSNS and iFCP Security
iFCP implementations MUST use iSNS for discovery and management
services. Consequently, the security of the iSNS protocol has an
impact on the security of iFCP gateways. For a discussion of
potential threats to iFCP gateways through use of iSNS, see [ISNS].
To provide security for iFCP gateways using the iSNS protocol for
discovery and management services, the IPSec ESP protocol in tunnel
mode MUST be supported for iFCP gateways. Further discussion of iSNS
security implementation requirements is found in [ISNS]. Note that
iSNS security requirements match those for iFCP described in Section
10.3.
10.5. Use of iSNS to Distribute Security Policy
Once communication between iFCP gateways and the iSNS server has been
secured through use of IPSec, the iFCP gateways have the capability
to discover the security settings that they need to use (or not use)
to protect iFCP traffic. This provides a potential scaling advantage
over device-by-device configuration of individual security policies
for each iFCP gateway. It also provides an efficient means for each
iFCP gateway to discover the use or non-use of specific security
capabilities by peer gateways.
Further discussion on use of iSNS to distribute security policies is
found in [ISNS].
10.6. Minimal Security Policy for an iFCP Gateway
An iFCP implementation may be able to disable security mechanisms for
an iFCP Portal administratively through a management interface or
through security policy elements set in the iSNS server. As a
consequence, IKE or IPsec security associations will not be
established for any iFCP sessions that traverse the portal.
For most IP networks, it is inappropriate to assume physical
security, administrative security, and correct configuration of the
network and all attached nodes (a physically isolated network in a
test lab may be an exception). Therefore, authentication SHOULD be
used in order to provide minimal assurance that connections have
initially been opened with the intended counterpart. The minimal
iFCP security policy only states that an iFCP gateway SHOULD
authenticate its iSNS server(s) as described in [ISNS].
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11. Quality of Service Considerations
11.1. Minimal Requirements
Conforming iFCP protocol implementations SHALL correctly communicate
gateway-to-gateway, even across one or more intervening best-effort
IP regions. The timings with which such gateway-to gateway
communication is performed, however, will greatly depend upon BER,
packet losses, latency, and jitter experienced throughout the best-
effort IP regions. The higher these parameters, the higher the gap
measured between iFCP observed behaviors and baseline iFCP behaviors
(i.e., as produced by two iFCP gateways directly connected to one
another).
11.2. High Assurance
It is expected that many iFCP deployments will benefit from a high
degree of assurance regarding the behavior of intervening IP regions,
with resulting high assurance on the overall end-to-end path, as
directly experienced by fibre channel applications. Such assurance
on the IP behaviors stems from the intervening IP regions supporting
standard Quality-of-Service (QoS) techniques that are fully
complementary to iFCP, such as:
a) congestion avoidance by over-provisioning of the network,
b) integrated Services [RFC1633] QoS,
c) differentiated Services [RFC2475] QoS, and
d) Multi-Protocol Label Switching [RFC3031].
One may load an MPLS forwarding equivalence class (FEC) with QoS
class significance, in addition to other considerations such as
protection and diversity for the given path. The complementarity and
compatibility of MPLS with Differentiated Services is explored in
[MPSLDS], wherein the PHB bits are copied to the EXP bits of the MPLS
shim header.
In the most general definition, two iFCP gateways are separated by
one or more independently managed IP regions that implement some of
the QoS solutions mentioned above. A QoS-capable IP region supports
the negotiation and establishment of a service contract specifying
the forwarding service through the region. Such contract and
negotiation rules are outside the scope of this document. In the
case of IP regions with DiffServ QoS, the reader should refer to
Service Level Specifications (SLS) and Traffic Conditioning
Specifications (TCS) (as defined in [DIFTERM]). Other aspects of a
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service contract are expected to be non-technical and thus are
outside of the IETF scope.
Because fibre channel Class 2 and Class 3 do not currently support
fractional bandwidth guarantees, and because iFCP is committed to
supporting fibre channel semantics, it is impossible for an iFCP
gateway to infer bandwidth requirements autonomously from streaming
fibre channel traffic. Rather, the requirements on bandwidth or
other network parameters need to be administratively set into an iFCP
gateway, or into the entity that will actually negotiate the
forwarding service on the gateway's behalf. Depending on the QoS
techniques available, the stipulation of a forwarding service may
require interaction with network ancillary functions, such as
admission control and bandwidth brokers (via RSVP or other signaling
protocols that an IP region may accept).
The administrator of a iFCP gateway may negotiate a forwarding
service with IP region(s) for one, several, or all of an iFCP
gateway's TCP sessions used by an iFCP gateway. Alternately, this
responsibility may be delegated to a node downstream. Since one TCP
connection is dedicated to each iFCP session, the traffic in an
individual N_PORT to N_PORT session can be singled out by iFCP-
unaware network equipment as well.
For rendering the best emulation of fibre channel possible over IP,
it is anticipated that typical forwarding services will specify a
fixed amount of bandwidth, null losses, and, to a lesser degree of
relevance, low latency and low jitter. For example, an IP region
using DiffServ QoS may support SLSes of this nature by applying EF
DSCPs to the iFCP traffic.
12. IANA Considerations
The IANA-assigned port for iFCP traffic is port number 3420.
An iFCP Portal may initiate a connection using any TCP port number
consistent with its implementation of the TCP/IP stack, provided each
port number is unique. To prevent the receipt of stale data
associated with a previous connection using a given port number, the
provisions of [RFC1323], Appendix B, SHOULD be observed.
13. Normative References
[AESCBC] Frankel, S. and H. Herbert, "The AES-XCBC-MAC-96 Algorithm
and Its Use With IPsec", RFC 3566, September 2003.
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[AESCTR] Housley, R., "Using Advanced Encryption Standard (AES)
Counter Mode With IPsec Encapsulating Security Payload
(ESP)", RFC 3686, January 2004.
[ENCAP] Weber, R., Rajagopal, M., Travostino, F., O'Donnell, M.,
Monia, C., and M. Merhar, "Fibre Channel (FC) Frame
Encapsulation", RFC 3643, December 2003.
[FC-FS] dpANS INCITS.XXX-200X, "Fibre Channel Framing and Signaling
(FC-FS), Rev 1.70, INCITS Project 1331D, February 2002
[FC-GS3] dpANS X3.XXX-200X, "Fibre Channel Generic Services -3 (FC-
GS3)", revision 7.01, INCITS Project 1356-D, November 2000
[FC-SW2] dpANS X3.XXX-2000X, "Fibre Channel Switch Fabric -2 (FC-
SW2)", revision 5.2, INCITS Project 1305-D, May 2001
[FCP-2] dpANS T10, "Fibre Channel Protocol for SCSI, Second
Version", revision 8, INCITS Project 1144D, September 2002
[ISNS] Tseng, J., Gibbons, K., Travostino, F., Du Laney, C., and
J. Souza, "Internet Storage Name Service (iSNS)", RFC 4171,
September 2005.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the
Internet Protocol", RFC 2401, November 1998.
[RFC2402] Kent, S. and R. Atkinson, "IP Authentication Header", RFC
2402, November 1998.
[RFC2404] Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within
ESP and AH", RFC 2404, November 1998.
[RFC2406] Kent, S. and R. Atkinson, "IP Encapsulating Security
Payload (ESP)", RFC 2406, November 1998.
[RFC2407] Piper, D., "The Internet IP Security Domain of
Interpretation for ISAKMP", RFC 2407, N.
[RFC2408] Maughan, D., Schertler, M., Schneider, M., and J. Turner,
"Internet Security Association and Key Management Protocol
(ISAKMP)", RFC 2408, November 1998.
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[RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange
(IKE)", RFC 2409, November 1998.
[RFC2410] Glenn, R. and S. Kent, "The NULL Encryption Algorithm and
Its Use With IPsec", RFC 2410, November 1998.
[RFC2451] Pereira, R. and R. Adams, "The ESP CBC-Mode Cipher
Algorithms", RFC 2451, November 1998.
[RFC793] Postel, J., "Transmission Control Protocol", STD 7, RFC
793, September 1981.
[SECIPS] Aboba, B., Tseng, J., Walker, J., Rangan, V., and F.
Travostino, "Securing Block Storage Protocols Over IP", RFC
3723, April 2004.
14. Informative References
[AES] FIPS Publication XXX, "Advanced Encryption Standard (AES)",
Draft, 2001, Available from
http://csrc.nist.gov/publications/drafts/dfips-AES.pdf
[DIFTERM] Grossman, D., "New Terminology and Clarifications for
Diffserv", RFC 3260, April 2002.
[FC-AL2] dpANS X3.XXX-199X, "Fibre Channel Arbitrated Loop (FC-AL-
2)", revision 7.0, NCITS Project 1133D, April 1999
[FC-FLA] TR-20-199X, "Fibre Channel Fabric Loop Attachment (FC-
FLA)", revision 2.7, NCITS Project 1235-D, August 1997
[FC-VI] ANSI/INCITS 357:2002, "Fibre Channel Virtual Interface
Architecture Mapping Protocol (FC-VI)", NCITS Project
1332-D, July 2000.
[KEMALP] Kembel, R., "The Fibre Channel Consultant, Arbitrated
Loop", Robert W. Kembel, Northwest Learning Associates,
2000, ISBN 0-931836-84-0
[KEMCMP] Kembel, R., "Fibre Channel, A Comprehensive Introduction",
Northwest Learning Associates Inc., 2000, ISBN
0-931836-84-0
[MPSLDS] Le Faucheur, F., Wu, L., Davie, B., Davari, S., Vaananen,
P., Krishnan, R., Cheval, P., and J. Heinanen, "Multi-
Protocol Label Switching (MPLS) Support of Differentiated
Services", RFC 3270, May 2002.
Monia, et al. Standards Track [Page 103]
RFC 4172 Internet Fibre Channel Networking September 2005
[RFC1122] Braden, R., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122, October 1989.
[RFC1323] Jacobson, V., Braden, R., and D. Borman, "TCP Extensions
for High Performance", RFC 1323, May 1992.
[RFC1633] Braden, R., Clark, D., and S. Shenker, "Integrated Services
in the Internet Architecture: an Overview", RFC 1633, June
1994.
[RFC2030] Mills, D., "Simple Network Time Protocol (SNTP) Version 4
for IPv4, IPv6 and OSI", RFC 2030, October 1996.
[RFC2405] Madson, C. and N. Doraswamy, "The ESP DES-CBC Cipher
Algorithm With Explicit IV", RFC 2405, November 1998.
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
and W. Weiss, "An Architecture for Differentiated Service",
RFC 2475, December 1998.
[RFC2625] Rajagopal, M., Bhagwat, R., and W. Rickard, "IP and ARP
over Fibre Channel", RFC 2625, June 1999.
[RFC2709] Srisuresh, P., "Security Model with Tunnel-mode IPsec for
NAT Domains", RFC 2709, October 1999.
[RFC2923] Lahey, K., "TCP Problems with Path MTU Discovery", RFC
2923, September 2000.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, January 2001.
[RFC896] Nagle, J., "Congestion control in IP/TCP internetworks",
RFC 896, January 1984.
Monia, et al. Standards Track [Page 104]
RFC 4172 Internet Fibre Channel Networking September 2005
Appendix A. iFCP Support for Fibre Channel Link Services
For reference purposes, this appendix enumerates all the fibre
channel link services and the manner in which each shall be processed
by an iFCP implementation. The iFCP processing policies are defined
in Section 7.
In the following sections, the name of a link service specific to a
particular FC-4 protocol is prefaced by a mnemonic identifying the
protocol.
A.1. Basic Link Services
The basic link services are shown in the following table:
Basic Link Services
Name Description iFCP Policy
---- ----------- ----------
ABTS Abort Sequence Transparent
BA_ACC Basic Accept Transparent
BA_RJT Basic Reject Transparent
NOP No Operation Transparent
PRMT Preempted Rejected
(Applies to
Class 1 only)
RMC Remove Connection Rejected
(Applies to
Class 1 only)
A.2. Pass-Through Link Services
As specified in Section 7, the link service requests of Table 10 and
the associated ACC response frames MUST be passed to the receiving
N_PORT without altering the payload.
Name Description
---- -----------
ADVC Advise Credit
CSR Clock Synchronization Request
CSU Clock Synchronization Update
ECHO Echo
ESTC Estimate Credit
ESTS Establish Streaming
FACT Fabric Activate Alias_ID
FAN Fabric Address Notification
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FCP_RJT FCP FC-4 Link Service Reject
FCP SRR FCP Sequence Retransmission
Request
FDACT Fabric Deactivate Alias_ID
FDISC Discover F_Port Service
Parameters
FLOGI F_Port Login
GAID Get Alias_ID
LCLM Login Control List Management
LINIT Loop Initialize
LIRR Link Incident Record
Registration
LPC Loop Port Control
LS_RJT Link Service Reject
LSTS Loop Status
NACT N_Port Activate Alias_ID
NDACT N_Port Deactivate Alias_ID
PDISC Discover N_Port Service
Parameters
PRLI Process Login
PRLO Process Logout
QoSR Quality of Service Request
RCS Read Connection Status
RLIR Registered Link Incident
Report
RNC Report Node Capability
RNFT Report Node FC-4 Types
RNID Request Node Identification
Data
RPL Read Port List
RPS Read Port Status Block
RPSC Report Port Speed
Capabilities
RSCN Registered State Change
Notification
RTV Read Timeout Value
RVCS Read Virtual Circuit Status
SBRP Set Bit-Error Reporting
Parameters
SCN State Change Notification
SCR State Change Registration
TEST Test
TPLS Test Process Login State
Table 10. Pass-Through Link Services
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RFC 4172 Internet Fibre Channel Networking September 2005
A.3. Special Link Services
The extended and FC-4 link services of Table 11 are processed by an
iFCP implementation as described in the sections referenced in the
table.
Name Description Section
---- ----------- -------
ABTX Abort Exchange 7.3.1.1
ADISC Discover Address 7.3.1.2
ADISC Discover Address Accept 7.3.1.3
ACC
FARP- Fibre Channel Address 7.3.1.4
REPLY Resolution Protocol
Reply
FARP- Fibre Channel Address 7.3.1.5
REQ Resolution Protocol
Request
LOGO N_PORT Logout 7.3.1.6
PLOGI Port Login 7.3.1.7
REC Read Exchange Concise 7.3.1.8
REC ACC Read Exchange Concise 7.3.1.9
Accept
FCP REC FCP Read Exchange 7.3.2.1.1
Concise (see [FCP-2])
FCP REC FCP Read Exchange 7.3.2.1.2
ACC Concise Accept (see
[FCP-2])
RES Read Exchange Status 7.3.1.10
Block
RES ACC Read Exchange Status 7.3.1.11
Block Accept
RLS Read Link Error Status 7.3.1.12
Block
RRQ Reinstate Recovery 7.3.1.14
Qualifier
RSI Request Sequence 7.3.1.15
Initiative
RSS Read Sequence Status 7.3.1.13
Block
SRL Scan Remote Loop 7.3.1.16
TPRLO Third Party Process 7.3.1.17
Logout
TPRLO Third Party Process 7.3.1.18
ACC Logout Accept
Table 11. Special Link Services
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Appendix B. Supporting the Fibre Channel Loop Topology
A loop topology may be optionally supported by a gateway
implementation in one of the following ways:
a) By implementing the FL_PORT public loop interface specified in
[FC-FLA].
b) By emulating the private loop environment specified in [FC-AL2].
Private loop emulation allows the attachment of fibre channel devices
that do not support fabrics or public loops. The gateway presents
such devices to the fabric as though they were fabric-attached.
Conversely, the gateway presents devices on the fabric, whether they
are locally or remotely attached, as though they were connected to
the private loop.
Private loop support requires gateway emulation of the loop
primitives and control frames specified in [FC-AL2]. These frames
and primitives MUST be locally emulated by the gateway. Loop control
frames MUST NOT be sent over an iFCP session.
B.1. Remote Control of a Public Loop
A gateway MAY disclose that a remotely attached device is connected
to a public loop. If it does, it MUST also provide aliases
representing the corresponding Loop Fabric Address (LFA), DOMAIN_ID,
and FL_PORT Address Identifier through which the public loop may be
remotely controlled.
The LFA and FL_PORT address identifier both represent an N_PORT that
services remote loop management requests contained in the LINIT and
SRL extended link service messages. To support these messages, the
gateway MUST allocate an NL_PORT alias so that the corresponding
alias for the LFA or FL_PORT address identifier can be derived by
setting the Port ID component of the NL_PORT alias to zero.
Monia, et al. Standards Track [Page 108]
RFC 4172 Internet Fibre Channel Networking September 2005
Acknowledgements
The authors are indebted to those who contributed material and who
took the time to carefully review and critique this specification
including David Black (EMC), Rory Bolt (Quantum/ATL), Victor Firoiu
(Nortel), Robert Peglar (XIOtech), David Robinson (Sun), Elizabeth
Rodriguez, Joshua Tseng (Nishan), Naoke Watanabe (HDS) and members of
the IPS working group. For review of the iFCP security policy, the
authors are further indebted to the authors of the IPS security
document [SECIPS], which include Bernard Aboba (Microsoft), Ofer
Biran (IBM), Uri Elzer (Broadcom), Charles Kunziger (IBM), Venkat
Rangan (Rhapsody Networks), Julian Satran (IBM), Joseph Tardo
(Broadcom), and Jesse Walker (Intel).
Monia, et al. Standards Track [Page 109]
RFC 4172 Internet Fibre Channel Networking September 2005
Author's Addresses
Comments should be sent to the ips mailing list (ips@ece.cmu.edu) or
to the authors.
Charles Monia
7553 Morevern Circle
San Jose, CA 95135
EMail: charles_monia@yahoo.com
Rod Mullendore
McDATA
4555 Great America Pkwy
Suite 301
Santa Clara, CA 95054
Phone: 408-519-3986
EMail: Rod.Mullendore@MCDATA.com
Franco Travostino
Nortel
600 Technology Park Drive
Billerica, MA 01821 USA
Phone: 978-288-7708
EMail: travos@nortel.com
Wayland Jeong
TROIKA Networks, Inc.
2555 Townsgate Road, Suite 105
Westlake Village, CA 91361
Phone: 805-371-1377
EMail: wayland@TroikaNetworks.com
Mark Edwards
Adaptec (UK) Ltd.
4th Floor, Howard House
Queens Ave, UK. BS8 1SD
Phone: +44 (0)117 930 9600
EMail: mark_edwards@adaptec.com
Monia, et al. Standards Track [Page 110]
RFC 4172 Internet Fibre Channel Networking September 2005
Full Copyright Statement
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Monia, et al. Standards Track [Page 111]