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Keywords: [--------], ancp
Internet Engineering Task Force (IETF) S. Wadhwa
Request for Comments: 6320 Alcatel-Lucent
Category: Standards Track J. Moisand
ISSN: 2070-1721 Juniper Networks
T. Haag
Deutsche Telekom
N. Voigt
Nokia Siemens Networks
T. Taylor, Ed.
Huawei Technologies
October 2011
Protocol for Access Node Control Mechanism in Broadband Networks
Abstract
This document describes the Access Node Control Protocol (ANCP).
ANCP operates between a Network Access Server (NAS) and an Access
Node (e.g., a Digital Subscriber Line Access Multiplexer (DSLAM)) in
a multi-service reference architecture in order to perform operations
related to Quality of Service, service, and subscribers. Use cases
for ANCP are documented in RFC 5851. As well as describing the base
ANCP protocol, this document specifies capabilities for Digital
Subscriber Line (DSL) topology discovery, line configuration, and
remote line connectivity testing. The design of ANCP allows for
protocol extensions in other documents if they are needed to support
other use cases and other access technologies.
ANCP is based on the General Switch Management Protocol version 3
(GSMPv3) described in RFC 3292, but with many modifications and
extensions, to the point that the two protocols are not
interoperable. For this reason, ANCP was assigned a separate version
number to distinguish it.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6320.
Wadhwa, et al. Standards Track [Page 1]
RFC 6320 ANCP Protocol October 2011
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this
material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
Table of Contents
1. Introduction ....................................................5
1.1. Historical Note ............................................6
1.2. Requirements Language ......................................6
1.3. Terminology ................................................6
2. Broadband Access Aggregation ....................................8
2.1. ATM-Based Broadband Aggregation ............................8
2.2. Ethernet-Based Broadband Aggregation .......................9
3. Access Node Control Protocol -- General Aspects ................10
3.1. Protocol Version ..........................................10
3.2. ANCP Transport ............................................10
3.3. Encoding of Text Fields ...................................11
3.4. Treatment of Reserved and Unused Fields ...................12
3.5. The ANCP Adjacency Protocol ...............................12
3.5.1. ANCP Adjacency Message Format ......................12
3.5.2. ANCP Adjacency Procedures ..........................18
3.6. ANCP General Message Formats ..............................29
3.6.1. The ANCP Message Header ............................29
3.6.2. The ANCP Message Body ..............................36
3.7. General Principles for the Design of ANCP Messages ........37
Wadhwa, et al. Standards Track [Page 2]
RFC 6320 ANCP Protocol October 2011
4. Generally Useful ANCP Messages and TLVs ........................38
4.1. Provisioning Message ......................................38
4.2. Generic Response Message ..................................39
4.3. Target TLV ................................................41
4.4. Command TLV ...............................................41
4.5. Status-Info TLV ...........................................42
5. Introduction to ANCP Capabilities for Digital
Subscriber Lines (DSLs) ........................................43
5.1. DSL Access Line Identification ............................44
5.1.1. Control Context (Informative) ......................44
5.1.2. TLVs for DSL Access Line Identification ............45
6. ANCP-Based DSL Topology Discovery ..............................48
6.1. Control Context (Informative) .............................48
6.2. Protocol Requirements .....................................50
6.2.1. Protocol Requirements on the AN Side ...............50
6.2.2. Protocol Requirements on the NAS Side ..............50
6.3. ANCP Port Up and Port Down Event Message Descriptions .....51
6.4. Procedures ................................................52
6.4.1. Procedures on the AN Side ..........................52
6.4.2. Procedures on the NAS Side .........................53
6.5. TLVs for DSL Line Attributes ..............................53
6.5.1. DSL-Line-Attributes TLV ............................53
6.5.2. DSL-Type TLV .......................................54
6.5.3. Actual-Net-Data-Rate-Upstream TLV ..................54
6.5.4. Actual-Net-Data-Rate-Downstream TLV ................54
6.5.5. Minimum-Net-Data-Rate-Upstream TLV .................55
6.5.6. Minimum-Net-Data-Rate-Downstream TLV ...............55
6.5.7. Attainable-Net-Data-Rate-Upstream TLV ..............55
6.5.8. Attainable-Net-Data-Rate-Downstream TLV ............55
6.5.9. Maximum-Net-Data-Rate-Upstream TLV .................56
6.5.10. Maximum-Net-Data-Rate-Downstream TLV ..............56
6.5.11. Minimum-Net-Low-Power-Data-Rate-Upstream TLV ......56
6.5.12. Minimum-Net-Low-Power-Data-Rate-Downstream TLV ....56
6.5.13. Maximum-Interleaving-Delay-Upstream TLV ...........57
6.5.14. Actual-Interleaving-Delay-Upstream TLV ............57
6.5.15. Maximum-Interleaving-Delay-Downstream TLV .........57
6.5.16. Actual-Interleaving-Delay-Downstream ..............57
6.5.17. DSL-Line-State TLV ................................58
6.5.18. Access-Loop-Encapsulation TLV .....................58
7. ANCP-Based DSL Line Configuration ..............................59
7.1. Control Context (Informative) .............................59
7.2. Protocol Requirements .....................................61
7.2.1. Protocol Requirements on the NAS Side ..............61
7.2.2. Protocol Requirements on the AN Side ...............61
7.3. ANCP Port Management (Line Configuration) Message Format ..62
7.4. Procedures ................................................64
7.4.1. Procedures on the NAS Side .........................64
7.4.2. Procedures on the AN Side ..........................64
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RFC 6320 ANCP Protocol October 2011
7.5. TLVs for DSL Line Configuration ...........................64
7.5.1. Service-Profile-Name TLV ...........................65
8. ANCP-Based DSL Remote Line Connectivity Testing ................65
8.1. Control Context (Informative) .............................65
8.2. Protocol Requirements .....................................66
8.2.1. Protocol Requirements on the NAS Side ..............66
8.2.2. Protocol Requirements on the AN Side ...............66
8.3. Port Management (OAM) Message Format ......................67
8.4. Procedures ................................................68
8.4.1. NAS-Side Procedures ................................68
8.4.2. AN-Side Procedures .................................69
8.5. TLVs for the DSL Line Remote Connectivity Testing
Capability ................................................70
8.5.1. OAM-Loopback-Test-Parameters TLV ...................70
8.5.2. Opaque-Data TLV ....................................71
8.5.3. OAM-Loopback-Test-Response-String TLV ..............71
9. IANA Considerations ............................................71
10. IANA Actions ..................................................72
10.1. ANCP Message Type Registry ...............................72
10.2. ANCP Result Code Registry ................................73
10.3. ANCP Port Management Function Registry ...................74
10.4. ANCP Technology Type Registry ............................75
10.5. ANCP Command Code Registry ...............................75
10.6. ANCP TLV Type Registry ...................................75
10.7. ANCP Capability Type Registry ............................77
10.8. Joint GSMP / ANCP Version Registry .......................77
11. Security Considerations .......................................77
12. Contributors ..................................................79
13. Acknowledgements ..............................................79
14. References ....................................................79
14.1. Normative References .....................................79
14.2. Informative References ...................................80
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RFC 6320 ANCP Protocol October 2011
1. Introduction
This document defines a new protocol, the Access Node Control
Protocol (ANCP), to realize a control plane between a service-
oriented layer 3 edge device (the Network Access Server, NAS) and a
layer 2 Access Node (e.g., Digital Subscriber Line Access
Multiplexer, DSLAM) in order to perform operations related to quality
of service (QoS), services, and subscriptions. The requirements for
ANCP and the context within which it operates are described in
[RFC5851].
ANCP provides its services to control applications operating in the
AN and NAS, respectively. This relationship is shown in Figure 1.
Specification of the control applications is beyond the scope of this
document, but informative partial descriptions are provided as
necessary to give a context for the operation of the protocol.
Access Node Network Access Server
+--------------------+ +--------------------+
| +----------------+ | | +----------------+ |
| | AN Control | | | | NAS Control | |
| | Application | | | | Application | |
| +----------------+ | | +----------------+ |
| +----------------+ | | +----------------+ |
| | ANCP Agent | | ANCP Messages | | ANCP Agent | |
| | (AN side) |<----------------------->| (NAS side) | |
| +----------------+ | | +----------------+ |
+--------------------+ +--------------------+
Figure 1: Architectural Context for the Access Node Control Protocol
At various points in this document, information flows between the
control applications and ANCP are described. The purpose of such
descriptions is to clarify the boundary between this specification
and, for example, [TR-147]. There is no intention to place limits on
the degree to which the control application and the protocol
implementation are integrated.
This specification specifies ANCP transport over TCP/IP. TCP
encapsulation for ANCP is as defined in Section 3.2.
The organization of this document is as follows:
o Sections 1.2 and 1.3 introduce some terminology that will be
useful in understanding the rest of the document.
o Section 2 provides a description of the access networks within
which ANCP will typically be deployed.
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RFC 6320 ANCP Protocol October 2011
o Section 3 specifies generally applicable aspects of ANCP.
o Section 4 specifies some messages and TLVs intended for use by
multiple capabilities spanning multiple technologies.
o Section 5 and the three following sections describe and specify
the ANCP implementation of three capabilities applicable to the
control of DSL access technology: topology discovery, line
configuration, and remote line connectivity testing.
o Section 9 is the IANA Considerations section. This section
defines a number of new ANCP-specific registries as well as the
joint GSMP/ANCP version registry mentioned below.
o Section 11 addresses security considerations relating to ANCP,
beginning with the requirements stated in [RFC5713].
1.1. Historical Note
Initial implementations of the protocol that became ANCP were based
on the General Switch Management Protocol version 3 (GSMPv3)
[RFC3292]. The ANCP charter required the Working Group to develop
its protocol based on these implementations. In the end, ANCP
introduced so many extensions and modifications to GSMPv3 that the
two protocols are not interoperable. Nevertheless, although this
specification has no normative dependencies on [RFC3292], the mark of
ANCP's origins can be seen in the various unused fields within the
ANCP message header.
Early in ANCP's development, the decision was made to use the same
TCP port and encapsulation as GSMPv3, and by the time ANCP was
finished, it was too late to reverse that decision because of
existing implementations. As a result, it is necessary to have a way
for an ANCP peer to quickly distinguish ANCP from GSMP during initial
adjacency negotiations. This has been provided by a joint registry
of GSMP and ANCP version numbers. GSMP has version numbers 1 through
3. ANCP has the initial version number 50.
1.2. Requirements Language
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 [RFC2119].
1.3. Terminology
This section repeats some definitions from [RFC5851], but it also
adds definitions for terms used only in this document.
Wadhwa, et al. Standards Track [Page 6]
RFC 6320 ANCP Protocol October 2011
Access Node (AN): [RFC5851] Network device, usually located at a
service provider central office or street cabinet that terminates
access (local) loop connections from subscribers. In case the
access loop is a Digital Subscriber Line (DSL), the Access Node
provides DSL signal termination and is referred to as a DSL Access
Multiplexer (DSLAM).
Network Access Server (NAS): [RFC5851] Network element that
aggregates subscriber traffic from a number of Access Nodes. The
NAS is an enforcement point for policy management and IP QoS in
the access network. It is also referred to as a Broadband Network
Gateway (BNG) or Broadband Remote Access Server (BRAS).
Home Gateway (HGW): Network element that connects subscriber devices
to the Access Node and the access network. In the case of DSL,
the Home Gateway is a DSL network termination that may operate
either as a layer 2 bridge or as a layer 3 router. In the latter
case, such a device is also referred to as a Routing Gateway (RG).
ANCP agent: A logical entity that implements ANCP in the Access Node
(AN-side) or NAS (NAS-side).
Access Node control adjacency: (modified from [RFC5851]) The
relationship between the AN-side ANCP agent and the NAS-side ANCP
agent for the purpose of exchanging Access Node Control Protocol
messages. The adjacency may be either up or down, depending on
the result of the Access Node Control adjacency protocol
operation.
ANCP capability: A specific set of ANCP messages, message content,
and procedures required to implement a specific use case or set of
use cases. Some ANCP capabilities are applicable to just one
access technology while others are technology independent. The
capabilities applicable to a given ANCP adjacency are negotiated
during adjacency startup.
Type-Length-Value (TLV): A data structure consisting of a 16-bit
type field, a sixteen-bit length field, and a variable-length
value field padded to the nearest 32-bit word boundary, as
described in Section 3.6.2. The value field of a TLV can contain
other TLVs. An IANA registry is maintained for values of the ANCP
TLV Type field.
Net data rate: [RFC5851] Defined by ITU-T G.993.2 [G.993.2], Section
3.39, i.e., the portion of the total data rate that can be used to
transmit user information (e.g., ATM cells or Ethernet frames).
It excludes overhead that pertains to the physical transmission
mechanism (e.g., trellis coding in the case of DSL). It includes
Wadhwa, et al. Standards Track [Page 7]
RFC 6320 ANCP Protocol October 2011
TPS-TC (Transport Protocol Specific - Transmission Convergence)
encapsulation; this is zero for ATM encapsulation and non-zero for
64/65 encapsulation.
Line rate: [RFC5851] Defined by ITU-T G.993.2. It contains the
complete overhead including Reed-Solomon and trellis coding.
DSL multi-pair bonding: Method for bonding (or aggregating) multiple
xDSL access lines into a single bidirectional logical link,
henceforth referred to in this document as "DSL bonded circuit".
DSL "multi-pair" bonding allows an operator to combine the data
rates on two or more copper pairs, and deliver the aggregate data
rate to a single customer. ITU-T recommendations G.998.1
[G.998.1] and G.998.2 [G.998.2], respectively, describe ATM- and
Ethernet-based multi-pair bonding.
2. Broadband Access Aggregation
2.1. ATM-Based Broadband Aggregation
The end-to-end DSL network consists of network service provider (NSP)
and application service provider (ASP) networks, regional/access
network, and customer premises network. Figure 2 shows ATM broadband
access network components.
The regional/access network consists of the regional network, Network
Access Server (NAS), and the access network as shown in Figure 2.
Its primary function is to provide end-to-end transport between the
customer premises and the NSP or ASP.
The Access Node terminates the DSL signal. It may be in the form of
a DSLAM in the central office, a remote DSLAM, or a Remote Access
Multiplexer (RAM). The Access Node is the first point in the network
where traffic on multiple DSL access lines will be aggregated onto a
single network.
The NAS performs multiple functions in the network. The NAS is the
aggregation point for subscriber traffic. It provides aggregation
capabilities (e.g., IP, PPP, ATM) between the Regional/Access Network
and the NSP or ASP. These include traditional ATM-based offerings
and newer, more native IP-based services. This includes support for
Point-to-Point Protocol over ATM (PPPoA) and PPP over Ethernet
(PPPoE), as well as direct IP services encapsulated over an
appropriate layer 2 transport.
Beyond aggregation, the NAS is also the enforcement point for policy
management and IP QoS in the regional/access networks. To allow IP
QoS support over an existing non-IP-aware layer 2 access network
Wadhwa, et al. Standards Track [Page 8]
RFC 6320 ANCP Protocol October 2011
without using multiple layer 2 QoS classes, a mechanism based on
hierarchical scheduling is used. This mechanism, defined in
[TR-059], preserves IP QoS over the ATM network between the NAS and
the Routing Gateway (RG) at the edge of the subscriber network, by
carefully controlling downstream traffic in the NAS, so that
significant queuing and congestion do not occur farther down the ATM
network. This is achieved by using a Diffserv-aware hierarchical
scheduler in the NAS that will account for downstream trunk
bandwidths and DSL synchronization rates.
[RFC5851] provides detailed definitions of the functions of each
network element in the broadband reference architecture.
Access Customer
<--- Aggregation --> <------- Premises ------->
Network Network
+------------------+ +--------------------------+
+---------+ +---+ | +-----+ +------+ | |+-----+ +---+ +---------+ |
NSP| | +-|NAS|-| |ATM |-|Access| --||DSL |-|HGW|-|Subscriber||
---+ Regional| | +---+ | +-----+ | Node | | ||Modem| +---+ |Devices ||
|Broadband| | +---+ | +------+ | |+-----+ +----------+|
ASP|Network |-+-|NAS| +--------------|---+ +--------------------------+
---+ | | +---+ | +--------------------------+
| | | +---+ | |+-----+ +---+ +----------+|
+---------+ +-|NAS| +-----|| DSL |-|HGW|-|Subscriber||
+---+ ||Modem| +---+ |Devices ||
|+-----+ +----------+|
+--------------------------+
HGW: Home Gateway
NAS: Network Access Server
Figure 2: ATM Broadband Aggregation Topology
2.2. Ethernet-Based Broadband Aggregation
The Ethernet aggregation network architecture builds on the Ethernet
bridging/switching concepts defined in IEEE 802. The Ethernet
aggregation network provides traffic aggregation, class of service
distinction, and customer separation and traceability. VLAN tagging,
defined in [IEEE802.1Q] and enhanced by [IEEE802.1ad], is used as the
standard virtualization mechanism in the Ethernet aggregation
network. The aggregation devices are "provider edge bridges" defined
in [IEEE802.1ad].
Stacked VLAN tags provide one possible way to create an equivalent of
"virtual paths" and "virtual circuits" in the aggregation network.
The "outer" VLAN can be used to create a form of "virtual path"
Wadhwa, et al. Standards Track [Page 9]
RFC 6320 ANCP Protocol October 2011
between a given DSLAM and a given NAS. "Inner" VLAN tags create a
form of "virtual circuit" on a per-DSL-line basis. This is the 1:1
VLAN allocation model. An alternative model is to bridge sessions
from multiple subscribers behind a DSLAM into a single VLAN in the
aggregation network. This is the N:1 VLAN allocation model. Section
1.6 of [TR-101] provides brief definitions of these two models, while
Section 2.5.1 describes them in more detail.
3. Access Node Control Protocol -- General Aspects
This section specifies aspects of the Access Node Control Protocol
(ANCP) that are generally applicable.
3.1. Protocol Version
ANCP messages contain an 8-bit protocol version field. For the
protocol version specified in this document, the value of that field
MUST be set to 50.
3.2. ANCP Transport
This document specifies the use of TCP / IPsec+IKEv2 / IP for
transport of ANCP messages. For further discussion of the use of
IPsec and IKEv2, see Section 11. The present section deals with the
TCP aspects. Other specifications may introduce additional
transports in the future.
In the case of ATM access, a separate permanent virtual circuit
(PVC) that is a control channel and is capable of transporting IP
MAY be configured between the NAS and the AN for ANCP messages.
In the case of an Ethernet access/aggregation network, a typical
practice is to send the Access Node Control Protocol messages over
a dedicated Ethernet virtual LAN (VLAN) using a separate VLAN
identifier (VLAN ID).
When transported over TCP, ANCP messages MUST use an encapsulation
consisting of a 4-byte header field prepended to the ANCP message as
shown in Figure 3.
Wadhwa, et al. Standards Track [Page 10]
RFC 6320 ANCP Protocol October 2011
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier (0x880C) | Length |
|-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ ANCP Message ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Encapsulation of ANCP Messages over TCP/IP
The fields of the encapsulating header are as follows:
Identifier (16 bits): This identifies a GSMP or ANCP message. It
MUST be set to 0x880C.
Length (16 bits): Total length of the ANCP message in bytes, not
including the 4-byte encapsulating header.
The Access Node MUST initiate the TCP session to the NAS, using
destination port 6068.
This is necessary to avoid static address provisioning on the NAS
for all the ANs that are being served by the NAS. It is easier to
configure a given AN with the single IP address of the NAS that
serves the AN.
The NAS MUST listen on port 6068 for incoming connections from the
Access Nodes.
In the event of an ANCP transport protocol failure, all pending ANCP
messages destined to the disconnected recipient SHOULD be discarded
until the transport connection is re-established.
3.3. Encoding of Text Fields
In ANCP, all text fields use UTF-8 encoding [RFC3629]. Note that US-
ASCII characters have the same representation when coded as UTF-8 as
they do when coded according to [US_ASCII].
When extracting text fields from a message, the ANCP agent MUST NOT
assume that the fields are zero-terminated.
Wadhwa, et al. Standards Track [Page 11]
RFC 6320 ANCP Protocol October 2011
3.4. Treatment of Reserved and Unused Fields
ANCP messages contain a number of fields that are unused or reserved.
Some fields are always unused (typically because they were inherited
from GSMPv3 but are not useful in the ANCP context). Others are
reserved in the current specification, but are provided for
flexibility in future extensions to ANCP. Both reserved and unused
fields MUST be set to zeroes by the sender and MUST be ignored by the
receiver.
Unused bits in a flag field are shown in figures as 'x'. The above
requirement (sender set to zero, receiver ignore) applies to such
unused bits.
3.5. The ANCP Adjacency Protocol
ANCP uses the adjacency protocol to synchronize the NAS and Access
Nodes and maintain the ANCP session. After the TCP connection is
established, adjacency protocol messages MUST be exchanged as
specified in this section. ANCP messages other than adjacency
protocol messages MUST NOT be sent until the adjacency protocol has
achieved synchronization.
3.5.1. ANCP Adjacency Message Format
The ANCP adjacency message format is shown in Figure 4 below.
Wadhwa, et al. Standards Track [Page 12]
RFC 6320 ANCP Protocol October 2011
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version | Message Type | Timer |M| Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Name |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| Receiver Name |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receiver Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PType |P Flag | Sender Instance |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Partition ID | Receiver Instance |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | # of Caps | Total Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Capability Fields ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: ANCP Adjacency Message Format
The fields of the ANCP adjacency message are as follows:
Version (8 bits): ANCP version, which is subject to negotiation.
This is the key parameter by means of which ANCP messages can be
distinguished from GSMP messages received over the same port.
Message Type (8 bits): Always has value 10 (adjacency protocol).
Timer (8 bits): The Timer field is used to negotiate the timer value
used in the adjacency protocol with the peer. The timer specifies
the nominal time between periodic adjacency protocol messages. It
is a constant for the duration of an ANCP session. The Timer
field is specified in units of 100 ms, with a default value of 250
(i.e., 25 seconds).
M flag (1 bit): Used in the SYN message to prevent the NAS from
synchronizing with another NAS and the AN from synchronizing with
another AN. In the SYN message, it is always set to 1 by the NAS
and to 0 by the AN. In other adjacency message types, it is
always set to 0 by the sender and ignored by the receiver.
Wadhwa, et al. Standards Track [Page 13]
RFC 6320 ANCP Protocol October 2011
Code (7 bits): The adjacency protocol message type. It MUST have
one of the following values:
Code = 1: SYN;
Code = 2: SYNACK;
Code = 3: ACK;
Code = 4: RSTACK.
Sender Name (48 bits): For the SYN, SYNACK, and ACK messages, is the
identifier of the entity sending the message. The Sender Name is
a 48-bit quantity that is unique within the operational context of
the device. A 48-bit IEEE 802 Media Access Control (MAC) address,
if available, may be used for the Sender Name. If the Ethernet
encapsulation is used, the Sender Name MUST be the Source Address
from the MAC header. For the RSTACK message, the Sender Name
field is set to the value of the Receiver Name field from the
incoming message that caused the RSTACK message to be generated.
Receiver Name (48 bits) For the SYN, SYNACK, and ACK messages, is
the name of the entity that the sender of the message believes is
at the far end of the link. If the sender of the message does not
know the name of the entity at the far end of the link, this field
SHOULD be set to zero. For the RSTACK message, the Receiver Name
field is set to the value of the Sender Name field from the
incoming message that caused the RSTACK message to be generated.
Sender Port (32 bits): For the SYN, SYNACK, and ACK messages, is the
local port number of the link across which the message is being
sent. For the RSTACK message, the Sender Port field is set to the
value of the Receiver Port field from the incoming message that
caused the RSTACK message to be generated.
Receiver Port (32 bits): For the SYN, SYNACK, and ACK messages, is
what the sender believes is the local port number for the link,
allocated by the entity at the far end of the link. If the sender
of the message does not know the port number at the far end of the
link, this field SHOULD be set to zero. For the RSTACK message,
the Receiver Port field is set to the value of the Sender Port
field from the incoming message that caused the RSTACK message to
be generated.
PType (4 bits): PType is used to specify if partitions are used and
how the Partition ID is negotiated.
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Type of partition being requested:
0 - no partition;
1 - fixed partition request;
2 - fixed partition assigned.
P Flag (4 bits): Used to indicate the type of partition request.
1 - new adjacency;
2 - recovered adjacency.
In case of a conflict between the peers' views of the value of the
P Flag, the lower value is used.
Sender Instance (24 bits): For the SYN, SYNACK, and ACK messages, is
the sender's instance number for the link to the peer. It is used
to detect when the link comes back up after going down or when the
identity of the entity at the other end of the link changes. The
instance number is a 24-bit number that is guaranteed to be unique
within the recent past and to change when the link or node comes
back up after going down. Zero is not a valid instance number.
For the RSTACK message, the Sender Instance field is set to the
value of the Receiver Instance field from the incoming message
that caused the RSTACK message to be generated.
Partition ID (8 bits): Field used to associate the message with a
specific partition of the AN. The value of this field is
negotiated during the adjacency procedure. The AN makes the final
decision, but will consider a request from the NAS. If the AN
does not support partitions, the value of this field MUST be 0.
Otherwise, it MUST be non-zero.
Receiver Instance (24 bits): For the SYN, SYNACK, and ACK messages,
is what the sender believes is the current instance number for the
link, allocated by the entity at the far end of the link. If the
sender of the message does not know the current instance number at
the far end of the link, this field SHOULD be set to zero. For
the RSTACK message, the Receiver Instance field is set to the
value of the Sender Instance field from the incoming message that
caused the RSTACK message to be generated.
Reserved (8 bits): Reserved for use by a future version of this
specification.
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# of Caps (8 bits): Indicates the number of Capability fields that
follow.
Total Length (16 bits): Indicates the total number of bytes occupied
by the Capability fields that follow.
Capability Fields: Each Capability field indicates one ANCP
capability supported by the sender of the adjacency message.
Negotiation of a common set of capabilities to be supported within
the ANCP session is described below. The detailed format of a
Capability field is shown in Figure 5 and described below.
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Capability Type | Capability Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ ~
~ Capability Data ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Capability Field
The sub-fields of this structure are as follows:
Capability Type (16 bits): Indicates the specific capability
supported. An IANA registry exists for values of this sub-field.
The values specified by this document are listed below.
Capability Length (16 bits): The number of bytes of data contained
in the Capability Data sub-field, excluding padding. If the
definition of a particular capability includes no capability data,
the value of the Capability Length sub-field is zero.
Capability Data (as indicated by Capability Length): Contains data
associated with the capability as specified for that capability.
If the definition of a particular capability includes no
capability data, the Capability Data sub-field is absent (has zero
length). Otherwise, the Capability Data sub-field MUST be padded
with zeroes as required to terminate on a 4-byte word boundary.
The possibility of specifying capability data provides the
flexibility to advertise more than the mere presence or absence of
a capability if needed.
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The following capabilities are defined for ANCP as applied to DSL
access:
o Capability Type: DSL Topology Discovery = 0x01
Access technology: DSL
Length (in bytes): 0
Capability Data: NULL
For the detailed protocol specification of this capability, see
Section 6.
o Capability Type: DSL Line Configuration = 0x02
Access technology: DSL
Length (in bytes): 0
Capability Data: NULL
For the detailed protocol specification of this capability, see
Section 7.
o Capability Type: DSL Remote Line Connectivity Testing = 0x04
Access technology: DSL
Length (in bytes): 0
Capability Data: NULL
For the detailed protocol specification of this capability, see
Section 8.
In addition to the adjacency messages whose format is shown in
Figure 6, ANCP adjacency procedures use the Adjacency Update message
(Figure 6) to inform other NASs controlling the same AN partition
when a particular NAS joins or loses an adjacency with that
partition.
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0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version | Message Type | Result| Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Partition ID | Transaction Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|I| SubMessage Number | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: The Adjacency Update Message
The Adjacency Update message is identical to the general ANCP message
header described in Section 3.6, but the field settings are in part
specific to the Adjacency Update message. The fields in this message
are as follows:
Version (8 bits): The ANCP version negotiated and running in this
adjacency.
Message Type (8 bits): Always 85.
Result (4 bits): Set to Ignore (0).
Code (12 bits): Set to the total number of adjacencies currently
established on this partition, from the point of view of the AN.
Partition ID (8 bits): The partition identifier of the partition for
which this notification is being sent.
Transaction Identifier (24 bits): MUST be set to 0.
I (1 bit), SubMessage number (15 bits): Set as described in
Section 3.6.1.7.
Length (16 bits): Set as described in Section 3.6.1.8.
3.5.2. ANCP Adjacency Procedures
3.5.2.1. Overview
The ANCP adjacency protocol operates symmetrically between the NAS
and the AN. In the absence of errors or race conditions, each peer
sends a SYN message, receives a SYNACK message in acknowledgement,
and completes the establishment of the adjacency by sending an ACK
message. Through this exchange, each peer learns the values of the
Name, Port, and Instance parameters identifying the other peer, and
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the two peers negotiate the values of the Version, Timer, P Flag, and
Partition ID parameters and the set of capabilities that the
adjacency will support.
Once the adjacency has been established, its liveness is periodically
tested. The peers engage in an ACK message exchange at a frequency
determined by the negotiated value of the Timer field.
If an inconsistency, loss of contact, or protocol violation is
detected, the detecting peer can force a restart of the
synchronization process by sending an RSTACK message to the other
end.
Once an adjacency has been established, if more than one NAS has
established an adjacency to the same partition, then the AN sends an
Adjacency Update message to each such NAS to let it know how many
established adjacencies the partition currently supports. Similarly,
if an adjacency is lost, the AN sends an Adjacency Update message to
each of the remaining adjacent NASs to let them know about the change
in status.
3.5.2.2. Adjacency Protocol State Machine
The adjacency protocol is described by the following rules and state
tables. It begins with the sending of a SYN by each end as soon as
the transport connection has been established. If at any point the
operations A, B, C, or "Verify Adjacent State" defined below detect a
mismatch, a log SHOULD be generated, identifying the fields concerned
and the expected and received values for each.
The rules and state tables use the following operations:
o The "Record Adjacency State" operation is defined in
Section 3.5.2.3.2.
o The "Verify Adjacency State" operation consists of verifying that
the contents of the incoming SYNACK message match the adjacency
state values previously recorded.
o The procedure "Reset the link" is defined as:
1. Generate a new instance number for the link.
2. Delete the peer verifier (set to zero the values of Sender
Instance, Sender Port, and Sender Name previously stored by
the "Record Adjacency State" operation).
3. Send a SYN message (Section 3.5.2.3.1).
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4. Enter the SYNSENT state.
o The state tables use the following Boolean terms and operators.
A. The Sender Instance in the incoming message matches the value
stored from a previous message by the "Record Adjacency State"
operation.
B. The Sender Instance, Sender Port, Sender Name, and Partition
ID fields in the incoming message match the values stored from
a previous message by the "Record Adjacency State" operation.
C. The Receiver Instance, Receiver Port, Receiver Name, and
Partition ID fields in the incoming message match the values
of the Sender Instance, Sender Port, Sender Name, and
Partition ID currently sent in outgoing SYN, SYNACK, and ACK
messages, except that the NAS always accepts the Partition ID
value presented to it in a SYN or SYNACK message.
"&&" Represents the logical AND operation.
"||" Represents the logical OR operation.
"!" Represents the logical negation (NOT) operation.
o A timer is required for the periodic generation of SYN, SYNACK,
and ACK messages. The value of the timer is negotiated in the
Timer field. The period of the timer is unspecified, but a value
of 25 seconds is suggested. Note that since ANCP uses a reliable
transport protocol, the timer is unlikely to expire in any state
other than ESTAB.
There are two independent events: the timer expires, and a packet
arrives. The processing rules for these events are:
Timer Expires: Reset Timer
If state = SYNSENT Send SYN
If state = SYNRCVD Send SYNACK
If state = ESTAB Send ACK
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Packet Arrives:
If incoming message is an RSTACK:
If (A && C && !SYNSENT) Reset the link
Else discard the message.
If incoming message is a SYN, SYNACK, or ACK:
Response defined by the following state tables.
If incoming message is any other ANCP message and state !=
ESTAB:
Discard incoming message.
If state = SYNSENT Send SYN (Note 1)
If state = SYNRCVD Send SYNACK (Note 1)
Note 1: No more than two SYN or SYNACK messages should be sent
within any time period of length defined by the timer.
o State synchronization across a link is considered to be achieved
when the protocol reaches the ESTAB state. All ANCP messages,
other than adjacency protocol messages, that are received before
synchronization is achieved will be discarded.
3.5.2.2.1. State Tables
State: SYNSENT
+===================================================================+
| Condition | Action | New State |
+=================+=====================================+===========+
| SYNACK && C | Update Peer Verifier; Send ACK | ESTAB |
+-----------------+-------------------------------------+-----------+
| SYNACK && !C | Send RSTACK | SYNSENT |
+-----------------+-------------------------------------+-----------+
| SYN | Update Peer Verifier; Send SYNACK | SYNRCVD |
+-----------------+-------------------------------------+-----------+
| ACK | Send RSTACK | SYNSENT |
+===================================================================+
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State: SYNRCVD
+===================================================================+
| Condition | Action | New State |
+=================+=====================================+===========+
| SYNACK && C | Verify Adjacency State; Send ACK | ESTAB |
+-----------------+-------------------------------------+-----------+
| SYNACK && !C | Send RSTACK | SYNRCVD |
+-----------------+-------------------------------------+-----------+
| SYN | Record Adjacency State; Send SYNACK | SYNRCVD |
+-----------------+-------------------------------------+-----------+
| ACK && B && C | Send ACK | ESTAB |
+-----------------+-------------------------------------+-----------+
| ACK && !(B && C)| Send RSTACK | SYNRCVD |
+===================================================================+
State: ESTAB
+===================================================================+
| Condition | Action | New State |
+=================+=====================================+===========+
| SYN || SYNACK | Send ACK (Note 2) | ESTAB |
+-----------------+-------------------------------------+-----------+
| ACK && B && C | Send ACK (Note 3) | ESTAB |
+-----------------+-------------------------------------+-----------+
| ACK && !(B && C)| Send RSTACK | ESTAB |
+===================================================================+
Note 2: No more than two ACKs should be sent within any time period
of length defined by the timer. Thus, one ACK MUST be sent every
time the timer expires. In addition, one further ACK may be sent
between timer expirations if the incoming message is a SYN or SYNACK.
This additional ACK allows the adjacency protocol to reach
synchronization more quickly.
Note 3: No more than one ACK should be sent within any time period of
length defined by the timer.
3.5.2.3. The Adjacency Protocol SYN Message
3.5.2.3.1. Action by the Sender
The SYN message is sent in accordance with the state tables just
described. The sender sets the individual fields as follows:
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Version: SHOULD be set to the highest version of ANCP that the
sender supports.
Message Type: MUST be set to 10.
Timer: SHOULD be set to the value configured in the AN or NAS
sending the message.
M Flag: MUST be set to 1 by the NAS, and 0 by the AN.
Code: MUST be set to 1 (SYN).
Sender Name: Set as described in Section 3.5.1.
Receiver Name: SHOULD be set to 0.
Sender Port: Set as described in Section 3.5.1.
Receiver Port: SHOULD be set to 0.
PType: Set according to the following rules:
Settings by the AN:
0 - the AN does not support partitions;
2 - the value of Partition ID contained in this message is
assigned to the current partition.
Settings by the NAS:
0 - the NAS leaves the decision on partitioning to the AN
(RECOMMENDED setting);
1 - the NAS requests that the AN use the value of Partition
ID contained in this message for the current partition. The
NAS MAY use this setting even if it has already received a
SYN message from the AN, provided that the AN has indicated
support for partitions. The NAS MUST be prepared to use
whatever value it receives in a subsequent SYN or SYNACK
message, even if this differs from the requested value.
P Flag: Set to the mode of adjacency setup (new adjacency vs.
recovered adjacency) requested by the sender. Warning: setting P
Flag=1 runs the risk of state mismatch because ANCP does not
provide the means for the NAS to audit the current state of the
AN.
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Sender Instance: Set as described in Section 3.5.1.
Partition ID: MUST be set to 0 if PType=0; otherwise, set to the
assigned or requested partition identifier value.
Receiver Instance: SHOULD be set to 0.
# of Caps: MUST be set to the number of Capability fields that
follow.
Total Length: MUST be set to the total number of bytes in the
Capability fields that follow.
Capability Fields: One Capability field MUST be present for each
ANCP capability for which the sender wishes to advertise support.
3.5.2.3.2. Action by the Receiver
Upon receiving a validly formed SYN message, the receiver first
checks the value of the Version field. If this value is not within
the range of ANCP versions that the receiver supports, the message
MUST be silently ignored. Similarly, the message is silently ignored
if the M flag is 0 and the receiver is an AN or if the M flag is 1
and the receiver is a NAS. If these checks are passed and the
receiver is in ESTAB state, it returns an ACK (as indicated by the
ESTAB state table in Section 3.5.2.2.1). The contents of the ACK
MUST reflect the adjacency state as previously recorded by the
receiver.
Otherwise, the receiver MUST perform the "Record Adjacency State"
operation by recording the following fields:
Version: The supported Version value received in the SYN message.
This value MUST be used for all subsequent ANCP messages sent
during the life of the adjacency.
Timer: The larger of the Timer value received in the SYN message and
the value with which the receiver is configured.
Sender Name: The value of the Sender Name field in the SYN message
just received.
Receiver Name: The value used by the receiver in the Sender Name
field of SYN, SYNACK, and ACK messages it sends in this adjacency.
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Sender Port: The value of the Sender Port field in the SYN message
just received.
Receiver Port: The value used by the receiver in the Sender Port
field of SYN, SYNACK, and ACK messages it sends in this adjacency.
Sender Instance: The value of the Sender Instance field in the SYN
message just received.
P Flag: The lesser of the value determined by local policy and the
value received in the SYN message. That is, preference is given
to "0 - New adjacency" if there is a conflict.
Partition ID: If the SYN receiver is the AN, this is set to 0 if the
AN does not support partitions or to the non-zero value of the
partition identifier it chooses to assign otherwise. If the SYN
receiver is the NAS, this is set to the value of the Partition ID
field copied from the SYN.
Receiver Instance: The value used by the receiver in the Sender
Instance field of SYN, SYNACK, and ACK messages it sends in this
adjacency.
Capabilities: The set of ANCP capabilities that were offered in the
SYN and are supported by the receiver.
3.5.2.4. The Adjacency Protocol SYNACK Message
3.5.2.4.1. Action by the Sender
The SYNACK is sent in response to a successfully received SYN
message, as indicated by the state tables. The Version, Timer, P
Flag, and Partition ID fields MUST be populated with the values
recorded as part of adjacency state. The # of Caps, Total Length,
and Capability fields MUST also be populated in accordance with the
Capabilities recorded as part of adjacency state. The remaining
fields of the SYNACK message MUST be populated as follows:
Message Type: MUST be 10.
M flag: MUST be set to 0.
Code: MUST be 2 (SYNACK).
PType: MUST be 0 if the Partition ID value is 0 or 2 if the
Partition ID value is non-zero.
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Sender Name: MUST be set to the Receiver Name value recorded as part
of adjacency state.
Receiver Name: MUST be set to the Sender Name value recorded as part
of adjacency state.
Sender Port: MUST be set to the Receiver Port value recorded as part
of adjacency state.
Receiver Port: MUST be set to the Sender Port value recorded as part
of adjacency state.
Sender Instance: MUST be set to the Receiver Instance value recorded
as part of adjacency state.
Receiver Instance: MUST be set to the Sender Instance value recorded
as part of adjacency state.
If the set of capabilities recorded in the adjacency state is empty,
then after sending the SYNACK the sender MUST raise an alarm to
management, halt the adjacency procedure, and tear down the TCP
session if it is not being used by another adjacency. The sender MAY
also terminate the IPsec security association if no other adjacency
is using it.
3.5.2.4.2. Action by the Receiver
As indicated by the state tables, the receiver of a SYNACK first
checks that the Receiver Name, Receiver Port, and Receiver Instance
values match the Sender Name, Sender Port, and Sender Instance values
it sent in SYN message that is being acknowledged. The AN also
checks that the PType and Partition ID match. If any of these checks
fail, the receiver sends an RSTACK as described in Section 3.5.2.6.1.
The receiver next checks whether the set of capabilities provided in
the SYNACK is empty. If so, the receiver MUST raise an alarm to
management and halt the adjacency procedure.
Assuming that the SYNACK passes these checks, two cases arise. The
first possibility is that the receiver has already recorded adjacency
state. This will occur if the SYNACK is received while the receiver
is in SYNRCVD state. In this case, the Version, Timer, Sender Name,
Sender Port, Sender Instance, P Flag, and capability-related fields
in the SYNACK MUST match those recorded as part of adjacency state.
If a mismatch is detected, the receiver sends an RSTACK. This is the
"Verify Adjacency State" procedure shown in the SYNRCVD state table.
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If, on the other hand, the SYNACK is received while the receiver is
in SYNSENT state, the receiver MUST record session state as described
in Section 3.5.2.3.2.
In either case, if the receiver is the NAS, it MUST accept the
Partition ID value provided in the SYNACK, updating its recorded
adjacency state if necessary.
3.5.2.5. The Adjacency Protocol ACK Message
3.5.2.5.1. Actions by the Sender
As indicated by the state tables, the ACK message is sent in a number
of different circumstances. The main-line usages are as a response
to SYNACK, leading directly to the ESTAB state, and as a periodic
test of liveness once the ESTAB state has been reached.
The sender MUST populate the ACK from recorded adjacency state,
exactly as described in Section 3.5.2.4.1. The only difference is
that Code MUST be set to 3 (ACK).
3.5.2.5.2. Actions by the Receiver
The required actions by the receiver are specified by the state
tables. In addition to the checks B and C, the receiver SHOULD
verify that the remaining contents of the ACK match the recorded
adjacency state at the receiver. If that check fails, the receiver
MUST send an RSTACK as described in Section 3.5.2.6.1.
Once the adjacency has been established, either peer can initiate the
ACK exchange that tests for liveness. To meet the restrictions on
ACK frequency laid down in the notes to the state tables, it is
desirable that only one such exchange occur during any one interval.
Hence, if a peer receives an ACK when in ESTAB state, it MUST reply
to that ACK as directed by the state tables, but SHOULD NOT initiate
another ACK exchange in the same interval. To meet this objective,
the receiver MUST reset its timer when it receives an ACK while in
ESTAB state.
It is, of course, possible that two exchanges happen because of
race conditions.
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3.5.2.6. The Adjacency Protocol RSTACK Message
3.5.2.6.1. Action by the Sender
The RSTACK is sent in response to various error conditions as
indicated by the state tables. In general, it leads to a restart of
adjacency negotiations (although this takes a few steps when the
original sender of the RSTACK is in ESTAB state).
As indicated in Section 3.5.1, the Sender Name, Port, and Instance
fields in the RSTACK MUST be copied from the Receiver, Name, Port,
and Instance fields in the message that caused the RSTACK to be sent.
Similarly, the Receiver identifier fields in the RSTACK MUST be
copied from the corresponding Sender identifier fields in the message
that triggered the RSTACK.
If the sender has recorded adjacency state, the Version, Timer,
PType, P Flag, Partition ID, and capability-related fields SHOULD be
set based on the recorded adjacency state. Otherwise, they SHOULD be
the same as the sender would send in a SYN message. The Message Type
MUST be 10, the M flag MUST be 0, and Code MUST be 4 (RSTACK).
3.5.2.6.2. Action by the Receiver
The receiver of an RSTACK MAY attempt to diagnose the problem that
caused the RSTACK to be generated by comparing its own adjacency
state with the contents of the RSTACK. However, the primary purpose
of the RSTACK is to trigger action as prescribed by Section 3.5.2.2.
3.5.2.7. Loss of Synchronization
Loss of synchronization MAY be declared if after synchronization is
achieved:
o no valid ANCP messages are received in any period of time in
excess of three times the value of the Timer field negotiated in
the adjacency protocol messages, or
o a mismatch in adjacency state is detected.
In either case, the peer detecting the condition MUST send an RSTACK
to the other peer, as directed in Section 3.5.2.6.1, in order to
initiate resynchronization.
While re-establishing synchronization with a controller, a switch
SHOULD maintain its connection state, deferring the decision about
resetting the state until after synchronization is re-established.
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Once synchronization is re-established, the decision about resetting
the connection state SHOULD be made based on the negotiated value of
the P Flag.
3.6. ANCP General Message Formats
This section describes the general format of ANCP messages other than
the adjacency messages. See Figure 7.
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version | Message Type | Result| Result Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Partition ID | Transaction Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|I| SubMessage Number | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Message Payload ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: ANCP General Message Format
3.6.1. The ANCP Message Header
A complete explanation of the ANCP general message header fields
follows.
3.6.1.1. Version Field (8 bits)
This field carries the version of ANCP that was agreed upon for the
session during adjacency negotiation.
3.6.1.2. Message Type Field (8 bits)
This field indicates the ANCP message type. Message type values are
registered in an IANA registry.
3.6.1.3. Result Field (4 bits)
In request messages, the Result field indicates the circumstances
under which a response is required. ANCP specifies what Result value
each request message type should have. In responses, the Result
field indicates either Success (0x3) or Failure (0x4), as the case
may be.
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Ignore: Res = 0x0 - Treat this field as a "no operation" and follow
the response procedures specified for the received message type.
Nack: Res = 0x1 - Result value indicating that a response is
expected to the request only in cases of failure caused during the
processing of the message contents or of the contained
directive(s).
AckAll: Res = 0x2 - Result value indicating that a response to the
message is requested in all cases.
Success: Res = 0x3 - Result value indicating that this is a response
and that the request was executed successfully. The Result Code
field for a successful result is typically 0, but it MAY take on
other values as specified for particular message types.
Failure: Res = 0x4 - Result value indicating that this is a response
and that the request was not executed successfully. The receiver
of the response SHOULD take further action as indicated by the
Result Code value and any diagnostic data contained in a Status-
Info TLV included in the response.
3.6.1.4. Result Code Field (12 bits)
This field gives further information concerning the result in a
response message. It is mostly used to pass an error code in a
failure response, but it can also be used to give further information
in a success response message or an event message. In a request
message, the Result Code field is not used and MUST be set to 0x0 (No
result).
A number of Result Code values are specified below. Specification of
additional Result Code values in extensions or updates to this
document MUST include the following information:
o Result Code value;
o One-line description;
o Where condition detected (control application or ANCP agent);
o Further description (if any);
o Required additional information in the response message;
o Target (control application or ANCP agent at the peer that sent
the original request);
Wadhwa, et al. Standards Track [Page 30]
RFC 6320 ANCP Protocol October 2011
o Action RECOMMENDED for the receiving ANCP agent.
In addition to any suggested action in the text that follows, a count
of the number of times a given non-zero Result Code value was
received SHOULD be provided for management. Where an action includes
the re-sending of a request, a given request SHOULD NOT be re-sent
more than once.
This document specifies the following Result Code values.
Result Code value: 0x2
* One-line description: Invalid request message
* Where condition detected: ANCP agent
* Further description: The request was a properly formed message
that violates the protocol through its timing or direction of
transmission. The most likely reason for this outcome in the
field will be a race condition.
* Required additional information in the response message: None,
if the response message is of the same type as the request. As
specified in Section 4.2, if the response message is a Generic
Response message.
* Target: ANCP agent at the peer that sent the original request
* Action RECOMMENDED for the receiving ANCP agent: The original
request MAY be re-sent once only after a short delay. Inform
the control application with appropriate identification of the
failed transaction if the second attempt fails or no second
attempt is made.
Result Code value: 0x6
* One-line description: One or more of the specified ports are
down
* Where condition detected: Control application
* Further description (if any): This Result Code value indicates
a state mismatch between the NAS and AN control applications,
possibly due to a race condition.
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* Required additional information in the response message: If the
request identified multiple access lines or the response is a
Generic Response message, then the response MUST contain a
Status-Info TLV encapsulating TLV(s) containing the line
identifier(s) of the access lines that are not operational.
* Target: Control application at the peer that sent the original
request
* Action RECOMMENDED for the receiving ANCP agent: Indicate the
error and forward the line identifier(s) to the control
application.
Result Code value: 0x13
* One-line description: Out of resources
* Where condition detected: ANCP protocol layer or control
application
* Further description (e.g., memory exhausted): This Result Code
value MUST be reported only by the AN, and indicates a
condition that is probably unrelated to specific access lines
(although it may be related to the specific request).
* Required additional information in the response message: None,
if the response message is of the same type as the request. As
specified in Section 4.2, if the response message is a Generic
Response message.
* Target: ANCP agent at the peer that sent the original request
* Action RECOMMENDED for the receiving ANCP agent: If the NAS
receives this Result Code value from multiple requests for the
same AN in a short interval, it SHOULD reduce the rate at which
it sends requests in proportion to the rate at which requests
are failing with Result Code = 19. It MAY retry individual
requests. If only a specific request is failing with Result
Code = 19, the ANCP agent in the NAS MAY request the control
application to decompose the request into simpler components if
this is possible.
Result Code value: 0x51
* One-line description: Request message type not implemented
* Where condition detected: ANCP agent
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* Further description: This could indicate a mismatch in protocol
version or capability state. It is also possible that support
of a specific message is optional within some ANCP capability.
* Required additional information in the response message: None,
if the response message is of the same type as the request. As
specified in Section 4.2, if the response message is a Generic
Response message.
* Target: ANCP agent at the peer that sent the original request
* Action RECOMMENDED for the receiving ANCP agent: If the
receiver of this Result Code value expects that support of the
message type concerned is mandatory according to the
capabilities negotiated for the session, it MAY re-send the
message in case the message was corrupted in transit the first
time. If that fails, and use of the message type cannot be
avoided, the ANCP agent MAY reset the adjacency by sending an
RSTACK adjacency message as described in Section 3.5.2.6.1,
where Sender and Receiver Name, Port, and Instance are taken
from recorded adjacency state. If a reset does not eliminate
the problem, the receiving ANCP agent SHOULD raise an alarm to
management and then cease to operate.
Result Code value: 0x53
* One-line description: Malformed message
* Where condition detected: ANCP agent
* Further description: This could be the result of corruption in
transit, or an error in implementation at one end or the other.
* Required additional information in the response message: None,
if the response message is of the same type as the request. As
specified in Section 4.2, if the response message is a Generic
Response message.
* Target: ANCP agent at the peer that sent the original request
* Action RECOMMENDED for the receiving ANCP agent: The request
SHOULD be re-sent once to eliminate the possibility of in-
transit corruption.
Result Code value: 0x54
* One-line description: Mandatory TLV missing
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* Where condition detected: ANCP agent
* Further description: None
* Required additional information in the response message: The
response message MUST contain a Status-Info message that
encapsulates an instance of each missing mandatory TLV, where
the length is set to zero and the value field is empty (i.e.,
only the 4-byte TLV header is present).
* Target: ANCP agent at the peer that sent the original request
* Action RECOMMENDED for the receiving ANCP agent: Re-send the
message with the missing TLV(s), if possible. Otherwise,
report the error to the control application with an indication
of the missing information required to construct the missing
TLV(s).
Result Code value: 0x55
* One-line description: Invalid TLV contents
* Where condition detected: ANCP agent
* Further description: The contents of one or more TLVs in the
request do not match the specifications provided for the those
TLVs.
* Required additional information in the response message: The
response MUST contain a Status-Info TLV encapsulating the
erroneous TLVs copied from the original request.
* Target: ANCP agent at the peer that sent the original request
* Action RECOMMENDED for the receiving ANCP agent: Correct the
error and re-send the request, if possible. Otherwise, report
the error to the control application with an indication of the
erroneous information associated with the invalid TLV(s).
Result Code value: 0x500
* One-line description: One or more of the specified ports do not
exist
* Where condition detected: Control application
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* Further description (if any): This may indicate a configuration
mismatch between the AN and the NAS or Authentication,
Authorization, and Accounting (AAA).
* Required additional information in the response message: If the
request identified multiple access lines or the response is a
Generic Response message, then the response MUST contain a
Status-Info TLV encapsulating TLV(s) containing the rejected
line identifier(s).
* Target: Control application at the peer that sent the original
request
* Action RECOMMENDED for the receiving ANCP agent: Indicate the
error and forward the line identifiers to the control
application.
3.6.1.5. Partition ID (8 bits)
The Partition ID field MUST contain the value that was negotiated for
Partition ID during the adjacency procedure as described above.
3.6.1.6. Transaction ID (24 bits)
The Transaction ID is set by the sender of a request message to
associate a response message with the original request message.
Unless otherwise specified for a given message type, the Transaction
ID in request messages MUST be set to a value in the range
(1, 2^24 - 1). When used in this manner, the Transaction ID
sequencing MUST be maintained independently for each message type
within each ANCP adjacency. Furthermore, it SHOULD be incremented by
1 for each new message of the given type, cycling back to 1 after
running the full range. For event messages, the Transaction ID
SHOULD be set to zero.
Unless otherwise specified, the default behavior for all ANCP
responses is that the value of the Transaction ID MUST be copied from
the corresponding request message.
3.6.1.7. I Flag and SubMessage Number (1 + 15 bits)
In GSMPv3, these provide a mechanism for message fragmentation.
Because ANCP uses TCP transport, this mechanism is unnecessary. An
ANCP agent MUST set the I Flag and subMessage Number fields to 1 to
signify "no fragmentation".
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3.6.1.8. Length (16 bits)
This field MUST be set to the length of the ANCP message in bytes,
including its header fields and message body but excluding the 4-byte
encapsulating header defined in Section 3.2.
3.6.2. The ANCP Message Body
The detailed contents of the message payload portion of a given ANCP
message can vary with the capability in the context of which it is
being used. However, the general format consists of zero or more
fixed fields, followed by a variable amount of data in the form of
Type-Length-Value (TLV) data structures.
The general format of a TLV is shown in Figure 8:
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (IANA registered) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Value ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: General TLV Format
The fields of a TLV are defined as follows:
Type (16 bits): The TLV Type is an unsigned value identifying the
TLV type and nature of its contents. An IANA registry has been
established for ANCP TLV Type codes.
Length (16 bits): The number of bytes of data in the Value field of
the TLV, excluding any padding required to bring this TLV to a
4-byte word boundary (see "Value" below). If a TLV contains other
TLVs, any padding in the contained TLVs MUST be included in the
value of Length. Depending on the specification of the TLV, the
value of Length can be zero, a constant for all instances of the
TLV, or a varying quantity.
Value (variable): The actual data carried by the TLV, if any. The
Value field in each TLV MUST be padded with zeroes as required to
align with a 4-byte word boundary. The Value field of a TLV MAY
include fixed fields and/or other TLVs.
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Unless otherwise specified, TLVs MAY be added to a message in any
order. If the recipient of a message does not understand a
particular TLV, it MUST silently ignore it.
A number of TLVs are specified in the remainder of this document.
3.7. General Principles for the Design of ANCP Messages
ANCP allows for two messaging constructs to support request/response
interaction:
a. The same message type is used for both the request message and
the response message. The Result and Result Code field settings
are used to differentiate between request and response messages.
b. The request and response messages use two different message
types.
The first approach is illustrated by the protocol specifications in
Section 8.4, the second by specifications in Section 6.4. The
purpose of this section is to provide more details about the second
approach in order to allow the use of this messaging construct for
the development of additional ANCP extensions.
As Section 3.6 indicated, all ANCP messages other than adjacency
messages share a common header format. When the response message
type is different from that of the request, the specification of the
request message will typically indicate that the Result field is set
to Ignore (0x0) and provide procedures indicating explicitly when the
receiver should generate a response and what message type it should
use.
The Transaction ID field is used to distinguish between multiple
request messages of the same type and to associate a response message
to a request. Specifications of ANCP messages for applications not
requiring response correlation SHOULD indicate that the Transaction
ID MUST be set to zero in requests. Applications that require
response correlation SHOULD refer to the Transaction ID behavior
described in Section 3.6.1.
The specification for a response message SHOULD indicate in all cases
that the value of the Transaction Identifier MUST be set to that of
the corresponding request message. This allows the requester to
establish whether or not correlation is needed (by setting a non-zero
or zero value for the Transaction ID).
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4. Generally Useful ANCP Messages and TLVs
This section defines two messages and a number of TLVs that could be
useful in multiple capabilities. In some cases, the content is
under-specified, with the intention that particular capabilities
spell out the remaining details.
4.1. Provisioning Message
The Provisioning message is sent by the NAS to the AN to provision
information of global scope (i.e., not associated with specific
access lines) on the AN. The Provisioning message has the format
shown in Figure 9. Support of the Provisioning message is OPTIONAL
unless the ANCP agent claims support for a capability that requires
its use.
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TCP/IP Encapsulating Header (Section 3.2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ANCP General Message Header |
+ (Section 3.6.1) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ TLVs ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: Format of the Provisioning Message
The message header field settings given below are REQUIRED in the
Provisioning message. The remaining message header fields MUST be
set as specified in Section 3.6.1. Which TLVs to carry in the
Provisioning message is specified as part of the specification of the
capabilities that use that message. The Provisioning message MAY be
used to carry data relating to more than one capability at once,
assuming that the capabilities concerned can coexist and have all
been negotiated during adjacency establishment.
Message Type: MUST be set to 93.
Result: MUST be set to 0x0 (Ignore).
Result Code: MUST be set to zero.
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Transaction ID: MUST be populated with a non-zero value chosen in
the manner described in Section 3.6.1.6.
If the AN can process the message successfully and accept all the
provisioning directives contained in it, the AN MUST NOT send any
response.
Unless otherwise specified for a particular capability, if the AN
fails to process the message successfully it MUST send a Generic
Response message (Section 4.2) indicating failure and providing
appropriate diagnostic information.
4.2. Generic Response Message
This section defines the Generic Response message. The Generic
Response message MAY be specified as the appropriate response to a
message defined in an extension to ANCP, instead of a more specific
response message. As a general guideline, specification of the
Generic Response message as a response is appropriate where no data
needs to be returned to the peer other than a result (success or
failure), plus, in the case of a failure, a code indicating the
reason for failure and a limited amount of diagnostic data.
Depending on the particular use case, the Generic Response message
MAY be sent by either the NAS or the AN.
Support of the Generic Response message, both as sender and as
receiver, is REQUIRED for all ANCP agents, regardless of what
capabilities they support.
The AN or NAS MAY send a Generic Response message indicating a
failure condition independently of a specific request before closing
the adjacency as a consequence of that failure condition. In this
case, the sender MUST set the Transaction ID field in the header and
the Message Type field within the Status-Info TLV to zeroes. The
receiver MAY record the information contained in the Status-Info TLV
for management use.
The format of the Generic Response message is shown in Figure 10.
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0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TCP/IP Encapsulating Header (Section 3.2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ANCP General Message Header |
+ (Section 3.6.1) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Access line identifying TLV(s) |
+ (copied from original request) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status-Info TLV |
~ (Section 4.5) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
NOTE: TLVs MAY be in a different order from what is shown in this
figure.
Figure 10: Structure of the Generic Response Message
This document specifies the following header fields. The remaining
fields in the ANCP general message header MUST be set as specified in
Section 3.6.1.
Message Type: MUST be set to 91.
Result: MUST be set to 0x3 (Success) or 0x4 (Failure).
Result Code: MUST be set to zero for success or an appropriate non-
zero value for failure.
Transaction ID: MUST be copied from the message to which this
message is a response.
If the original request applied to a specific access line or set of
lines, the TLVs identifying the line(s) and possibly the user MUST be
copied into the Generic Response message at the top level.
The Status-Info TLV MAY be present in a success response, to provide
a warning as defined for a specific request message type. It MUST be
present in a failure response. See Section 4.5 for a detailed
description of the Status-Info TLV. The actual contents will depend
on the request message type this message is responding to and the
value of the Result Code field.
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To prevent an infinite loop of error responses, if the Generic
Response message is itself in error, the receiver MUST NOT generate
an error response in return.
4.3. Target TLV
Type: 0x1000 to 0x1020 depending on the specific content. Only
0x1000 has been assigned in this specification (see below).
Support of any specific variant of the Target TLV is OPTIONAL
unless the ANCP agent claims support for a capability that
requires its use.
Description: The Target TLV (0x1000 - 0x1020) is intended to be a
general means to represent different types of objects.
Length: Variable, depending on the specific object type.
Value: Target information as defined for each object type. The
Value field MAY consist of sub-TLVs.
TLV Type 0x1000 is assigned to a variant of the Target TLV
representing a single access line and encapsulating one or more sub-
TLVs identifying the target. Figure 11 is an example illustrating
the TLV format for a single port identified by an Access-Loop-
Circuit-ID TLV (0x0001) (Section 5.1.2.1).
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV Type = 0x1000 |Length = Circuit-ID Length + 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Access-Loop-Circuit-ID=0x0001 | Circuit-ID Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Access Loop Circuit ID ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11: Example of Target TLV for Single Access Line
4.4. Command TLV
Type: 0x0011
Description: The Command TLV (0x0011) is intended to be a general
means of encapsulating one or more command directives in a TLV-
oriented message. The semantics of the command can be specified
for each message type using it. That is, the specification of
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each message type that can carry the Command TLV is expected to
define the meaning of the content of the payload, although re-use
of specifications is, of course, permissible when appropriate.
Support of any specific variant of the Command TLV is OPTIONAL
unless the ANCP agent claims support for a capability that
requires its use.
Length: Variable, depending on the specific contents.
Value: Command information as defined for each message type. The
field MAY include sub-TLVs. The contents of this TLV MUST be
specified as one "command" or alternatively a sequence of one or
more "commands", each beginning with a 1-byte Command Code and
possibly including other data following the Command Code. An IANA
registry has been established for Command Code values. This
document reserves the Command Code value 0 as an initial entry in
the registry.
4.5. Status-Info TLV
Name: Status-Info
Type: 0x0106
Description: The Status-Info-TLV is intended to be a general
container for warning or error diagnostics relating to commands
and/or requests. It is a supplement to the Result Code field in
the ANCP general header. The specifications for individual
message types MAY indicate the use of this TLV as part of
responses, particularly for failures. As mentioned above, the
Generic Response message will usually include an instance of the
Status-Info TLV. Support of the Status-Info TLV, both as sender
and as receiver, is REQUIRED for all ANCP agents, regardless of
what capabilities they support.
Length: Variable, depending on the specific contents.
Value: The following fixed fields. In addition, sub-TLVs MAY be
appended to provide further diagnostic information.
Reserved (8 bits): See Section 3.4 for handling of reserved
fields.
Msg Type (8 bits): Message Type of the request for which this TLV
is providing diagnostics.
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Error Message Length (16 bits): Number of bytes in the error
message, excluding padding, but including the language tag and
delimiter. This MAY be zero if no error message is provided.
Error Message: Human-readable string providing information about
the warning or error condition. The initial characters of the
string MUST be a language tag as described in [RFC5646],
terminated by a colon (":"). The actual text string follows
the delimiter. The field is padded at the end with zeroes as
necessary to extend it to a 4-byte word boundary.
Section 3.6.1.4 provides recommendations for what TLVs to add in
the Status-Info TLV for particular values of the message header
Result Code field.
Figure 12 illustrates the Status-Info TLV.
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV Type = 0x0106 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Msg Type | Error Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Message (padded to 4-byte boundary) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| optional sub-TLVs... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12: The Status-Info TLV
5. Introduction to ANCP Capabilities for Digital Subscriber Lines
(DSLs)
DSL is a widely deployed access technology for Broadband Access for
Next Generation Networks. Specifications such as [TR-059], [TR-058],
and [TR-092] describe possible architectures for these access
networks. The scope of these specifications includes the delivery of
voice, video, and data services.
The next three sections of this document specify basic ANCP
capabilities for use specifically in controlling Access Nodes serving
DSL access (Tech Type = 0x05). The same ANs could be serving other
access technologies (e.g., Metro-Ethernet, Passive Optical
Networking, WiMax), in which case the AN will also have to support
the corresponding other-technology-specific capabilities. Those
additional capabilities are outside the scope of the present
document.
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5.1. DSL Access Line Identification
Most ANCP messages involve actions relating to a specific access
line. Thus, it is necessary to describe how access lines are
identified within those messages. This section defines four TLVs for
that purpose and provides an informative description of how they are
used.
5.1.1. Control Context (Informative)
Three types of identification are described in [TR-101] and provided
for in the TLVs defined in this section:
o identification of an access line by its logical appearance on the
user side of the Access Node;
o identification of an access line by its logical appearance on the
NAS side of the Access Node; and
o identification down to the user or host level as a supplement to
access line identification in one of the other two forms.
All of these identifiers originate with the AN control application,
during the process of DSL topology discovery. The control
application chooses which identifiers to use and the values to place
into them on a line-by-line basis, based on AN configuration and
deployment considerations.
Aside from its use in ANCP signalling, access line identification is
also used in DHCP ([RFC2131], [RFC3315]) transactions involving hosts
served by DSL. Either the AN or the NAS can serve as a DHCP relay
node. [TR-101] requires the AN or NAS in this role to add access
line identification in Option 82 (Information) ([RFC3046], with its
IPv6 equivalent in [RFC4649]) to each DHCP request it forwards to the
DHCP server. It is desirable for efficiency that the identification
used in this signalling should be the same as the identification used
in ANCP messages.
From the point of view of ANCP itself, the identifiers are opaque.
From the point of view of the AN control application, the syntax for
the user-side access line identifier is the same as specified in
Section 3.9.3 of [TR-101] for DHCP Option 82. The syntax for the
ASCII form of the NAS-side access line identifier will be similar.
Access line identification by logical appearance on the user side of
the Access Node will always identify a DSL access line uniquely.
Identification by the logical appearance on the NAS side of the
Access Node is unique only if there is a one-to-one mapping between
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the appearances on the two sides and no identity-modifying
aggregation between the AN and the NAS. In other cases, and in
particular in the case of Ethernet aggregation using the N:1 VLAN
model, the user-side access line identification is necessary, but the
NAS-side identification is potentially useful information allowing
the NAS to build up a picture of the aggregation network topology.
Additional identification down to the user or host level is intended
to supplement rather than replace either of the other two forms of
identification.
Sections 3.8 and 3.9 of [TR-101] are contradictory on this point.
It is assumed here that Section 3.9 is meant to be authoritative.
The user-level identification takes the form of an administered
string that again is opaque at the ANCP level.
The NAS control application will use the identifying information it
receives from the AN directly for some purposes. For examples, see
the introductory part of Section 3.9 of [TR-101]. For other
purposes, the NAS will build a mapping between the unique access line
identification provided by the AN, the additional identification of
the user or host (where provided), and the IP interface on a
particular host. For access lines with static IP address assignment,
that mapping could be configured instead.
5.1.2. TLVs for DSL Access Line Identification
This section provides a normative specification of the TLVs that ANCP
provides to carry the types of identification just described. The
Access-Loop-Circuit-ID TLV identifies an access line by its logical
appearance on the user side of the Access Node. Two alternatives,
the Access-Aggregation-Circuit-ID-ASCII TLV and the Access-
Aggregation-Circuit-ID-Binary TLV, identify an access line by its
logical appearance on the NAS side of the Access Node. It is
unlikely that a given AN uses both of these TLVs, either for the same
line or for different lines, since they carry equivalent information.
Finally, the Access-Loop-Remote-ID TLV contains an operator-
configured string that uniquely identifies the user on the associated
access line, as described in Sections 3.9.1 and 3.9.2 of [TR-101].
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ANCP agents conforming to this section MUST satisfy the following
requirements:
o ANCP agents MUST be able to build and send the Access-Loop-
Circuit-ID TLV, the Access-Loop-Remote-ID TLV, and either the
Access-Aggregation-Circuit-ID-ASCII TLV or the Access-Aggregation-
Circuit-ID-Binary TLV (implementation choice), when passed the
associated information from the AN control application.
o ANCP agents MUST be able to receive all four TLV types, extract
the relevant information, and pass it to the control application.
o If the Access-Loop-Remote-ID TLV is present in a message, it MUST
be accompanied by an Access-Loop-Circuit-ID TLV and/or an Access-
Aggregation-Circuit-ID-ASCII TLV or Access-Aggregation-Circuit-ID-
Binary TLV with two VLAN identifiers.
The Access-Loop-Remote-ID TLV is not enough to identify an
access line uniquely on its own. As indicated above, an
Access-Aggregation-Circuit-ID-ASCII TLV or Access-Aggregation-
Circuit-ID-Binary TLV with two VLAN identifiers may or may not
identify an access line uniquely, but this is up to the control
application to decide.
o If the Access-Aggregation-Circuit-ID-ASCII TLV or Access-
Aggregation-Circuit-ID-Binary TLV is present in a message with
just one VLAN identifier, it MUST be accompanied by an Access-
Loop-Circuit-ID TLV.
5.1.2.1. Access-Loop-Circuit-ID TLV
Type: 0x0001
Description: A locally administered human-readable string generated
by or configured on the Access Node, identifying the corresponding
access loop logical port on the user side of the Access Node.
Length: Up to 63 bytes
Value: ASCII string
5.1.2.2. Access-Loop-Remote-ID TLV
Type: 0x0002
Description: An operator-configured string that uniquely identifies
the user on the associated access line, as described in Sections
3.9.1 and 3.9.2 of [TR-101].
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Length: Up to 63 bytes
Value: ASCII string
5.1.2.3. Access-Aggregation-Circuit-ID-Binary TLV
Type: 0x0006
Description: This TLV identifies or partially identifies a specific
access line by means of its logical circuit identifier on the NAS
side of the Access Node.
For Ethernet access aggregation, where a per-subscriber (stacked)
VLAN can be applied (1:1 model as defined in [TR-101]), the TLV
contains two value fields. Each field carries a 12-bit VLAN
identifier (which is part of the VLAN tag defined by
[IEEE802.1Q]). The first field MUST carry the inner VLAN
identifier, while the second field MUST carry the outer VLAN
identifier.
When the N:1 VLAN model is used, only one VLAN tag is available.
For the N:1 model, the Access-Aggregation-Circuit-ID-Binary TLV
contains a single value field, which MUST carry the 12-bit VLAN
identifier derived from the single available VLAN tag.
In the case of an ATM aggregation network, where the DSLAM is
directly connected to the NAS (without an intermediate ATM
switch), the Virtual Path Identifier (VPI) and Virtual Circuit
Identifier (VCI) on the DSLAM uplink correspond uniquely to the
DSL access line on the DSLAM. The Access-Aggregation-Circuit-ID-
Binary TLV MAY be used to carry the VPI and VCI. The first value
field of the TLV MUST carry the VCI, while the second value field
MUST carry the VPI.
Each identifier MUST be placed in the low-order bits of its
respective 32-bit field, with the higher-order bits set to zero.
The ordering of the bits of the identifier MUST be the same as
when the identifier is transmitted on the wire to identify an
Ethernet frame or ATM cell.
The Access-Aggregation-Circuit-ID-Binary is illustrated in
Figure 13.
Length: 4 or 8 bytes
Value: One or two 32-bit binary fields.
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0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV Type = 0x0006 | Length = 4 or 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Single VLAN Identifier, inner VLAN identifier, or VCI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Outer VLAN identifier or VPI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 13: The Access-Aggregation-Circuit-ID-Binary TLV
5.1.2.4. Access-Aggregation-Circuit-ID-ASCII TLV
Type: 0x0003
Description: This TLV transmits the ASCII equivalent of the Access-
Aggregation-Circuit-ID-Binary TLV. As mentioned in the previous
section, the AN control application will use a format similar to
that specified in Section 3.9.3 of [TR-101] for the format of the
"circuit-id".
As an extension to the present document, the Access Node could
convey to the NAS the characteristics (e.g., bandwidth) of the
uplink on the Access Node. This TLV or the binary equivalent
defined above then serves the purpose of uniquely identifying the
uplink whose characteristics are being defined. The present
document does not specify the TLVs needed to convey the uplink
characteristics.
Length: Up to 63 bytes
Value: ASCII string
6. ANCP-Based DSL Topology Discovery
Section 3.1 of [RFC5851] describes the requirements for the DSL
Topology Discovery capability.
6.1. Control Context (Informative)
The AN control application in the DSLAM requests ANCP to send a DSL-
specific Port Up message to the NAS under the following
circumstances:
o when a new adjacency with the NAS is established, for each DSL
loop that is synchronized at that time;
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o subsequent to that, whenever a DSL access line resynchronizes; and
o whenever the AN control application wishes to signal that a line
attribute has changed.
The AN control application in the DSLAM requests ANCP to send a DSL-
specific Port Down message to the NAS under the following
circumstances:
o when a new adjacency with the NAS is established, for each DSL
loop that is provisioned but not synchronized at that time;
o whenever a DSL access line that is equipped in an AN but
administratively disabled is signaled as "IDLE"; and
o subsequent to that, whenever a DSL access line loses
synchronization.
The AN control application passes information to identify the DSL
loop to ANCP to include in the Port Up or Port Down message, along
with information relating to DSL access line attributes.
In the case of bonded copper loops to the customer premise (as per
DSL multi-pair bonding described by [G.998.1] and [G.998.2]), the AN
control application requests that ANCP send DSL-specific Port Up and
Port Down messages for the aggregate "DSL bonded circuit"
(represented as a single logical port) as well as the individual DSL
access lines of which it is comprised. The information relating to
DSL access line attributes that is passed by the AN control
application is aggregate information.
ANCP generates the DSL-specific Port Up or Port Down message and
transfers it to the NAS. ANCP on the NAS side passes an indication
to the NAS control application that a DSL Port Up or Port Down
message has been received along with the information contained in the
message.
The NAS control application updates its view of the DSL access line
state, performs any required accounting operations, and uses any
included line attributes to adjust the operation of its queuing/
scheduling mechanisms as they apply to data passing to and from that
DSL access line.
Figure 14 summarizes the interaction.
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1. Home Access NAS
Gateway Node
-----------> -------------------------->
DSL Port Up (Event message)
Signal (default line parameters)
2. Home Access NAS
Gateway Node
-----------> -------------------------->
DSL Port Up (Event message)
Resynch (updated line parameters)
3. Home Access NAS
Gateway Node
-----------> -------------------------->
Loss of Port Down (Event message)
DSL Signal (selected line parameters)
Figure 14: ANCP Message Flow for DSL Topology Discovery
6.2. Protocol Requirements
The DSL topology discovery capability is assigned capability type
0x0001. No capability data is associated with this capability.
6.2.1. Protocol Requirements on the AN Side
The AN-side ANCP agent MUST be able to create DSL-specific Port Up
and Port Down messages according to the format specified in
Section 6.3.
The AN-side ANCP agent MUST conform to the normative requirements of
Section 5.1.2.
The AN-side ANCP agent MUST follow the AN-side procedures associated
with DSL-specific Port Up and Port Down messages as they are
specified in Section 6.4.
6.2.2. Protocol Requirements on the NAS Side
The NAS-side ANCP agent MUST be able to receive and validate DSL-
specific Port Up and Port Down messages according to the format
specified in Section 6.3.
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The NAS-side ANCP agent MUST conform to the normative requirements of
Section 5.1.2.
The NAS-side ANCP agent MUST follow the NAS-side procedures
associated with DSL-specific Port Up and Port Down messages as they
are specified in Section 6.4.
6.3. ANCP Port Up and Port Down Event Message Descriptions
The format of the ANCP Port Up and Port Down Event messages is shown
in Figure 15.
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TCP/IP Encapsulating Header (Section 3.2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ANCP General Message Header |
+ (Section 3.6.1) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Unused (20 bytes) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|x|x|x|x|x|x|x|x| Message Type | Tech Type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| # of TLVs | Extension Block length (bytes)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Access line identifying TLV(s) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DSL-Line-Attributes TLV |
~ (MANDATORY in Port Up, OPTIONAL in Port Down) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
NOTE: TLVs MAY be in a different order from what is shown in this
figure.
Figure 15: Format of the ANCP Port Up and Port Down Event Messages
for DSL Topology Discovery
See Section 3.6.1 for a description of the ANCP general message
header. The Message Type field MUST be set to 80 for Port Up, 81 for
Port Down. The 4-bit Result field MUST be set to zero (signifying
Ignore). The 12-bit Result Code field and the 24-bit Transaction
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Identifier field MUST also be set to zeroes. Other fields in the
general header MUST be set a as described in Section 3.6.
The five-word Unused field is a historical leftover. The handling of
unused/reserved fields is described in Section 3.4.
The remaining message fields belong to the "extension block", and are
described as follows:
Extension Flags (8 bits): The flag bits denoted by 'x' are currently
unspecified and reserved.
Message Type (8 bits): Message Type has the same value as in the
general header (i.e., 80 or 81).
Tech Type (8 bits): MUST be set to 0x05 (DSL).
Reserved (8 bits): set as described in Section 3.4.
# of TLVs (16 bits): The number of TLVs that follow, not counting
TLVs encapsulated within other TLVs.
Extension Block Length (16 bits): The total length of the TLVs
carried in the extension block in bytes, including any padding
within individual TLVs.
TLVs: One or more TLVs to identify a DSL access line and zero or
more TLVs to define its characteristics.
6.4. Procedures
6.4.1. Procedures on the AN Side
The AN-side ANCP agent creates and transmits a DSL-specific Port Up
or Port Down message when requested by the AN control application and
presented with the information needed to build a valid message. It
is RECOMMENDED that the Access Node use a dampening mechanism per DSL
access line to control the rate at which state changes are
communicated to the NAS.
At the top level, the extension block within a DSL-specific Port Up
or Port Down message MUST include TLVs from Section 5.1.2 to identify
the DSL access line.
TLVs presenting DSL access line attributes (i.e., the TLVs specified
in Section 6.5) MUST be encapsulated within the DSL-Line-Attributes
TLV. When the DSL-Line-Attributes TLV is present in a message, it
MUST contain at least one such TLV and will generally contain more
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than one. In the Port Up message, the DSL-Line-Attributes TLV MUST
be present. In the Port Down message, the DSL-Line-Attributes TLV
MAY be present.
6.4.2. Procedures on the NAS Side
The NAS-side ANCP agent MUST be prepared to receive Port Up and Port
Down messages for a given DSL access line or logical port at any time
after negotiation of an adjacency has been completed. It is possible
for two Port Up messages in succession to be received for the same
DSL access line without an intervening Port Down message, and vice
versa.
The NAS-side ANCP agent SHOULD validate each message against the
specifications given in Section 6.3 and the TLV specifications given
in Sections 5.1.2 and 6.5. If it finds an error, it MAY generate a
Generic Response message containing an appropriate Result Code value.
If it does so, the message MUST contain copies of all of the
identifier TLVs from Section 5.1.2 that were present in the Port Up
or Port Down message. The message MUST also contain a Status-Info
TLV that in turn contains other information appropriate to the
message header Result Code value as described in Section 3.6.1.4.
6.5. TLVs for DSL Line Attributes
As specified above, the DSL-Line-Attributes TLV is inserted into the
Port Up or Port Down message at the top level. The remaining TLVs
defined below are encapsulated within the DSL-Line-Attributes TLV.
6.5.1. DSL-Line-Attributes TLV
Type: 0x0004
Description: This TLV encapsulates attribute values for a DSL access
line serving a subscriber.
Length: Variable (up to 1023 bytes)
Value: One or more encapsulated TLVs corresponding to DSL access
line attributes. The DSL-Line-Attributes TLV MUST contain at
least one TLV when it is present in a Port Up or Port Down
message. The actual contents are determined by the AN control
application.
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6.5.2. DSL-Type TLV
Type: 0x0091
Description: Indicates the type of transmission system in use.
Length: 4 bytes
Value: 32-bit unsigned integer
ADSL1 = 1
ADSL2 = 2
ADSL2+ = 3
VDSL1 = 4
VDSL2 = 5
SDSL = 6
OTHER = 0
6.5.3. Actual-Net-Data-Rate-Upstream TLV
Type: 0x0081
Description: Actual upstream net data rate on a DSL access line.
Length: 4 bytes
Value: Rate in kbits/s as a 32-bit unsigned integer
6.5.4. Actual-Net-Data-Rate-Downstream TLV
Type: 0x0082
Description: Actual downstream net data rate on a DSL access line.
Length: 4 bytes
Value: Rate in kbits/s as a 32-bit unsigned integer
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6.5.5. Minimum-Net-Data-Rate-Upstream TLV
Type: 0x0083
Description: Minimum upstream net data rate desired by the operator.
Length: 4 bytes
Value: Rate in kbits/s as a 32-bit unsigned integer
6.5.6. Minimum-Net-Data-Rate-Downstream TLV
Type: 0x0084
Description: Minimum downstream net data rate desired by the
operator.
Length: 4 bytes
Value: Rate in kbits/s as a 32-bit unsigned integer
6.5.7. Attainable-Net-Data-Rate-Upstream TLV
Type: 0x0085
Description: Maximum net upstream rate that can be attained on the
DSL access line.
Length: 4 bytes
Value: Rate in kbits/s as a 32-bit unsigned integer
6.5.8. Attainable-Net-Data-Rate-Downstream TLV
Type: 0x0086
Description: Maximum net downstream rate that can be attained on the
DSL access line.
Length: 4 bytes
Value: Rate in kbits/s as a 32-bit unsigned integer
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6.5.9. Maximum-Net-Data-Rate-Upstream TLV
Type: 0x0087
Description: Maximum net upstream data rate desired by the operator.
Length: 4 bytes
Value: Rate in kbits/s as a 32-bit unsigned integer
6.5.10. Maximum-Net-Data-Rate-Downstream TLV
Type: 0x0088
Description: Maximum net downstream data rate desired by the
operator.
Length: 4 bytes
Value: Rate in kbits/s as a 32-bit unsigned integer
6.5.11. Minimum-Net-Low-Power-Data-Rate-Upstream TLV
Type: 0x0089
Description: Minimum net upstream data rate desired by the operator
in low power state.
Length: 4 bytes
Value: Rate in kbits/s as a 32-bit unsigned integer
6.5.12. Minimum-Net-Low-Power-Data-Rate-Downstream TLV
Type: 0x008A
Description: Minimum net downstream data rate desired by the
operator in low power state.
Length: 4 bytes
Value: Rate in kbits/s as a 32-bit unsigned integer
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6.5.13. Maximum-Interleaving-Delay-Upstream TLV
Type: 0x008B
Description: Maximum one-way interleaving delay.
Length: 4 bytes
Value: Time in ms as a 32-bit unsigned integer
6.5.14. Actual-Interleaving-Delay-Upstream TLV
Type: 0x008C
Description: Value corresponding to the interleaver setting.
Length: 4 bytes
Value: Time in ms as a 32-bit unsigned integer
6.5.15. Maximum-Interleaving-Delay-Downstream TLV
Type: 0x008D
Description: Maximum one-way interleaving delay.
Length: 4 bytes
Value: Time in ms as a 32-bit unsigned integer
6.5.16. Actual-Interleaving-Delay-Downstream
Type: 0x008E
Description: Value corresponding to the interleaver setting.
Length: 4 bytes
Value: Time in ms as a 32-bit unsigned integer
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6.5.17. DSL-Line-State TLV
Type: 0x008F
Description: The state of the DSL access line.
Length: 4 bytes
Value: 32-bit unsigned integer
SHOWTIME = 1
IDLE = 2
SILENT = 3
6.5.18. Access-Loop-Encapsulation TLV
Type: 0x0090
Description: The data link protocol and, optionally, the
encapsulation overhead on the access loop. When this TLV is
present, at least the data link protocol MUST be indicated. The
encapsulation overhead MAY be indicated. The Access Node MAY
choose to not convey the encapsulation on the access loop by
specifying values of 0 (NA) for the two encapsulation fields.
Length: 3 bytes
Value: The 3 bytes (most to least significant) and valid set of
values for each byte are defined as follows:
Byte 1: Data Link
ATM AAL5 = 0
ETHERNET = 1
Byte 2: Encapsulation 1
NA = 0
Untagged Ethernet = 1
Single-tagged Ethernet = 2
Double-tagged Ethernet = 3
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Byte 3: Encapsulation 2
NA = 0
PPPoA LLC = 1
PPPoA Null = 2
IPoA LLC = 3
IPoA Null = 4
Ethernet over AAL5 LLC with FCS = 5
Ethernet over AAL5 LLC without FCS = 6
Ethernet over AAL5 NULL with FCS = 7
Ethernet over AAL5 NULL without FCS = 8
The Access-Loop-Encapsulation TLV is illustrated in Figure 16.
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV Type = 0x0090 | Length = 3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data link | Encaps 1 | Encaps 2 | Padding (=0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 16: The Access-Loop-Encapsulation TLV
7. ANCP-Based DSL Line Configuration
The use case for ANCP-based DSL Line Configuration is described in
Section 3.2 of [RFC5851].
7.1. Control Context (Informative)
Triggered by topology information reporting a new DSL access line or
triggered by a subsequent user session establishment (via PPP or
DHCP), RADIUS/AAA sends service parameters to the NAS control
application for configuration on the access line. The NAS control
application passes the request on to the NAS-side agent, which sends
the information to the AN by means of a Port Management (line
configuration) message. The AN-side agent passes this information up
to the AN control application, which applies it to the line.
Figure 17 summarizes the interaction.
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RFC 6320 ANCP Protocol October 2011
Home Access NAS RADIUS/AAA
Gateway Node Policy Server
-----------> --------------->
DSL Port Up message)
Signal (line parameters)
--------------------------------> -------------->
PPP/DHCP Session Authentication &
authorization
<----------------
Port Management message
(line configuration)
Figure 17: Message Flow - ANCP Mapping for Initial Line Configuration
The NAS could update the line configuration as a result of a
subscriber service change (e.g., triggered by the policy server).
Figure 18 summarizes the interaction.
User Home Access NAS
Gateway Node
-------------------------->
PPP/DHCP Session
----------------------------------------------------> Web portal,
Service on demand OSS, etc.
|
<----------- RADIUS/AAA
Change of Policy Server
authorization
<------------
Port Management
message
(new profile)
OSS: Operations Support System
Figure 18: Message Flow - ANCP Mapping for Updated Line Configuration
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7.2. Protocol Requirements
The DSL access line configuration capability is assigned capability
type 0x0002. No capability data is associated with this capability.
7.2.1. Protocol Requirements on the NAS Side
The NAS-side ANCP agent MUST be able to create DSL-specific Port
Management (line configuration) messages according to the format
specified in Section 7.3.
The NAS-side ANCP agent MUST conform to the normative requirements of
Section 5.1.2.
The NAS-side ANCP agent MUST follow the NAS-side procedures
associated with DSL-specific Port Management (line configuration)
messages as they are specified in Section 7.4.
7.2.2. Protocol Requirements on the AN Side
The AN-side ANCP agent MUST conform to the normative requirements of
Section 5.1.2.
The AN-side ANCP agent MUST be able to receive and validate DSL-
specific Port Management (line configuration) messages according to
the format specified in Section 7.3.
The AN-side ANCP agent MUST follow the AN-side procedures associated
with DSL-specific Port Management (line configuration) messages as
specified in Section 7.4.
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7.3. ANCP Port Management (Line Configuration) Message Format
The ANCP Port Management message for DSL access line configuration
has the format shown in Figure 19.
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TCP/IP Encapsulating Header (Section 3.2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ANCP General Message Header |
+ (Section 3.6.1) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Unused (12 bytes) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unused (2 bytes) | Function=8 | X-Function=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unused (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|x|x|x|x|x|x|x|x| Message Type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| # of TLVs | Extension Block length (bytes)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Access line identifying TLV(s) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Line configuration TLV(s) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
NOTE: TLVs MAY be in a different order from what is shown in this
figure.
Figure 19: Port Management Message for DSL Line Configuration
See Section 3.6 for a description of the ANCP general message header.
The Message Type field MUST be set to 32. The 12-bit Result Code
field MUST be set to 0x0. The 4-bit Result field MUST be set to
either 0x1 (Nack) or 0x2 (AckAll), as determined by policy on the
NAS. The 24-bit Transaction Identifier field MUST be set to a
positive value. Other fields in the general header MUST be set as
described in Section 3.6.
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The handling of the various unused/reserved fields is described in
Section 3.4.
The remaining message fields are described as follows:
Function (8 bits): Action to be performed. For line configuration,
Function MUST be set to 8 (Configure Connection Service Data).
This action type requests the Access Node (i.e., DSLAM) to apply
service configuration data contained in the line configuration
TLVs to the DSL access line designated by the access line
identifying TLVs.
X-Function (8 bits): Qualifies the action set by Function. For DSL
access line configuration, this field MUST be set to 0.
Extension Flags (8 bits): The flag bits denoted by 'x' before the
Message Type field are reserved for future use.
Message Type (8 bits): Message Type has the same value as in the
general header (i.e., 32).
Reserved (16 bits): Reserved for future use.
# of TLVs (16 bits): The number of TLVs that follow, not counting
TLVs encapsulated within other TLVs.
Extension Block Length (16 bits): The total length of the TLVs
carried in the extension block in bytes, including any padding
within individual TLVs.
TLVs: Two or more TLVs to identify a DSL access line and configure
its service data.
Other ANCP capabilities, either specific to DSL or technology-
independent, MAY reuse the Port Management message for service
configuration. If the settings of the fixed fields are compatible
with the settings just described, the same Port Management message
that is used for DSL access line configuration MAY be used to carry
TLVs relating to the other capabilities that apply to the same DSL
access line.
Use of the Port Management message for configuration MAY also be
generalized to other access technologies, if the respective
capabilities specify use of access line identifiers appropriate to
those technologies in place of the identifiers defined in
Section 5.1.2.
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7.4. Procedures
Service configuration MAY be performed on an access line regardless
of its current state.
7.4.1. Procedures on the NAS Side
When requested by the NAS control application and presented with the
necessary information to do so, the NAS-side agent MUST create and
send a Port Management message with the fixed fields set as described
in the previous section. The message MUST contain one or more TLVs
to identify an access line according the requirements of
Section 5.1.2. The NAS MUST include one or more TLVs to configure
line service parameters for that line. Section 7.5 currently
identifies only one such TLV, Service-Profile-Name, but other TLVs
MAY be added by extensions to ANCP.
7.4.2. Procedures on the AN Side
The AN-side ANCP agent MUST be prepared to receive Port Management
(line configuration) messages for a given DSL access line or logical
port at any time after negotiation of an adjacency has been
completed.
The AN-side ANCP agent SHOULD validate each message against the
specifications given in Section 7.3 and the TLV specifications given
in Sections 5.1.2 and 7.5. If it finds an error it MUST return a
Port Management response message that copies the Port Management
request as it was received, but has the Result header field set to
0x04 (Failure) and the Result Code field set to the appropriate
value. The AN-side agent MAY add a Status-Info TLV (Section 4.5) to
provide further information on the error, particularly if this is
recommended in Section 3.6.1.4 for the given Result Code value. If
it does so, the various length fields and the # of TLVs field within
the message MUST be adjusted accordingly.
7.5. TLVs for DSL Line Configuration
Currently, only the following TLV is specified for DSL access line
configuration. More TLVs may be defined in a future version of this
specification or in ANCP extensions for individual service attributes
of a DSL access line (e.g., rates, interleaving delay, multicast
channel entitlement access-list).
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RFC 6320 ANCP Protocol October 2011
7.5.1. Service-Profile-Name TLV
Type: 0x0005
Description: Reference to a pre-configured profile on the DSLAM that
contains service-specific data for the subscriber.
Length: Up to 64 bytes
Value: ASCII string containing the profile name (which the NAS
learns from a policy server after a subscriber is authorized).
8. ANCP-Based DSL Remote Line Connectivity Testing
The use case and requirements for ANCP-Based DSL remote line
connectivity testing are specified in Section 3.3 of [RFC5851].
8.1. Control Context (Informative)
The NAS control application initiates a request for remote
connectivity testing for a given access line. The NAS control
application can provide loop count and timeout test parameters and
opaque data for its own use with the request. The loop count
parameter indicates the number of test messages or cells to be used.
The timeout parameter indicates the longest that the NAS control
application will wait for a result.
The request is passed in a Port Management (Operations,
Administration, and Maintenance, OAM) message. If the NAS control
application has supplied test parameters, they are used; otherwise,
the AN control application uses default test parameters. If a loop
count parameter provided by the NAS is outside the valid range, the
AN does not execute the test, but returns a result indicating that
the test has failed due to an invalid parameter. If the test takes
longer than the timeout value (default or provided by the NAS), the
AN control application can return a failure result indicating timeout
or else can send no response. The AN control application can provide
a human-readable string describing the test results, for both
failures and successes. If provided, this string is included in the
response. Responses always include the opaque data, if any, provided
by the NAS control application.
Figure 20 summarizes the interaction.
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RFC 6320 ANCP Protocol October 2011
+-------------+ +-----+ +-------+ +----------------+
|Radius/AAA |----|NAS |------| DSLAM |----------| CPE |
|Policy Server| +-----+ +-------+ | (DSL Modem + |
+-------------+ |Routing Gateway)|
+----------------+
Port Management Message
(Remote Loopback ATM loopback
Trigger Request) or EFM Loopback
1. ----------------> 2. -------->
<-------+
3. <---------------
Port Management Message
(Remote Loopback Test Response)
CPE: Customer Premises Equipment
EFM: Ethernet First Mile
Figure 20: Message Flow for ANCP-Based OAM
8.2. Protocol Requirements
The DSL remote line connectivity testing capability is assigned
capability type 0x0004. No capability data is associated with this
capability.
8.2.1. Protocol Requirements on the NAS Side
The NAS-side ANCP agent MUST be able to create DSL-specific Port
Management (OAM) messages according to the format specified in
Section 8.3.
The NAS-side ANCP agent MUST conform to the normative requirements of
Section 5.1.2.
The NAS-side ANCP agent MUST follow the NAS-side procedures
associated with DSL-specific Port Management (OAM) messages as they
are specified in Section 8.4.
8.2.2. Protocol Requirements on the AN Side
The AN-side ANCP agent MUST conform to the normative requirements of
Section 5.1.2.
The AN-side ANCP agent MUST be able to receive and validate DSL-
specific Port Management (OAM) messages according to the format
specified in Section 8.3.
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The AN-side ANCP agent MUST follow the AN-side procedures associated
with DSL-specific Port Management (OAM) messages as specified in
Section 8.4.
8.3. Port Management (OAM) Message Format
The Port Management message for DSL access line testing has the same
format as for DSL access line configuration (see Section 7.3), with
the following differences:
o The Result field in the request SHOULD be set to AckAll (0x2), to
allow the NAS to receive the information contained in a successful
test response.
o The Function field MUST be set to 9 (Remote Loopback). (The
X-Function field continues to be 0.)
o The appended TLVs in the extension value field include testing-
related TLVs rather than subscriber service information.
The Port Management (OAM) message is illustrated in Figure 21.
Wadhwa, et al. Standards Track [Page 67]
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0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TCP/IP Encapsulating Header (Section 3.2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ANCP General Message Header |
+ (Section 3.6.1) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Unused (12 bytes) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unused (2 bytes) | Function=9 | X-Function=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unused (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|x|x|x|x|x|x|x|x| Message Type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| # of TLVs | Extension Block length (bytes)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Access line identifying TLV(s) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Testing-related TLVs ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
NOTE: TLVs MAY be in a different order from what is shown in this
figure.
Figure 21: Port Management Message for
DSL Line Remote Connectivity Testing
8.4. Procedures
From the point of view of ANCP, it is permissible to attempt line
connectivity testing regardless of the state of the line. However,
testing could fail in some states due to technology limitations.
8.4.1. NAS-Side Procedures
When requested by the NAS control application and presented with the
necessary information to do so, the NAS-side agent creates and sends
a Port Management (OAM) request with the fixed fields set as
described in the previous section. The message MUST contain one or
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more TLVs to identify an access line according the requirements of
Section 5.1.2. The NAS MAY include the Opaque-Data TLV and/or the
OAM-Loopback-Test-Parameters TLV (defined in Section 8.5) to
configure the loopback test for that line.
8.4.2. AN-Side Procedures
The AN-side ANCP agent SHOULD validate each message against the
specifications given in Section 8.3 and the TLV specifications given
in Sections 5.1.2 and 8.5. If it finds an error it MUST return a
Port Management response message that copies the Port Management
request as it was received, but has the Result header field set to
0x04 (Failure) and the Result Code field set to the appropriate
value. Result Code value 0x509 as described below MAY apply, as well
as the other Result Code values documented in Section 3.6.1.4.
Result Code value 0x509 SHOULD be used if the OAM-Loopback-Test-
Parameters TLV is present with an invalid value of the Count field.
The AN-side agent MAY add a Status-Info TLV (Section 4.5) to provide
further information on the error, particularly if this is recommended
in Section 3.6.1.4 for the given Result Code value. If it does so,
the various length fields and the # of TLVs field within the message
MUST be adjusted accordingly.
If the received message passes validation, the AN-side ANCP agent
extracts the information from the TLVs contained in the message and
presents that information to the AN control application. It MUST NOT
generate an immediate response to the request, but it MUST instead
wait for the AN control application to indicate that the response
should be sent.
When requested by the AN control application and presented with the
necessary information to do so, the AN-side agent creates and sends a
Port Management (OAM) response to the original request. The Result
field MUST be set to Success (0x3) or Failure (0x4), and the Result
Code field SHOULD be set to one of the following values, as indicated
by the AN control application.
0x500: Specified access line does not exist. See the documentation
of Result Code 0x500 in Section 3.6.1.4 for more information. The
Result header field MUST be set to Failure (0x4).
0x501: Loopback test timed out. The Result header field MUST be set
to Failure (0x4).
0x503: DSL access line status showtime
Wadhwa, et al. Standards Track [Page 69]
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0x504: DSL access line status idle
0x505: DSL access line status silent
0x506: DSL access line status training
0x507: DSL access line integrity error
0x508: DSLAM resource not available. The Result header field MUST
be set to Failure (0x04).
0x509: Invalid test parameter. The Result header field MUST be set
to Failure (0x4).
All other fields of the request including the TLVs MUST be copied
into the response unchanged, except that in a successful response the
OAM-Loopback-Test-Parameters TLV MUST NOT appear. If the AN control
application has provided the necessary information, the AN-side agent
MUST also include an instance of the OAM-Loopback-Test-Response-
String TLV in the response.
8.5. TLVs for the DSL Line Remote Connectivity Testing Capability
The following TLVs have been defined for use with the DSL access line
testing capability.
8.5.1. OAM-Loopback-Test-Parameters TLV
Type: 0x0007
Description: Parameters intended to override the default values for
this loopback test.
Length: 2 bytes
Value: Two unsigned 1-byte fields described below (listed in order
of most to least significant).
Byte 1: Count. Number of loopback cells/messages that should
be generated on the local loop as part of the loopback test.
The Count value SHOULD be greater than 0 and less than or equal
to 32.
Byte 2: Timeout. Upper bound on the time in seconds that the
NAS will wait for a response from the DSLAM. The value 0 MAY
be used to indicate that the DSLAM MUST use a locally
determined value for the timeout.
Wadhwa, et al. Standards Track [Page 70]
RFC 6320 ANCP Protocol October 2011
The OAM-Loopback-Test-Parameters TLV is illustrated in Figure 22.
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV Type = 0x0007 | Length = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Count | Timeout | Padding (=0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 22: The OAM-Loopback-Test-Parameters TLV
8.5.2. Opaque-Data TLV
Type: 0x0008
Description: An 8-byte opaque field used by the NAS control
application for its own purposes (e.g., response correlation).
The procedures in Section 8.4.2 ensure that if it is present in
the request it is copied unchanged to the response.
Length: 8 bytes
Value: Two 32-bit unsigned integers.
8.5.3. OAM-Loopback-Test-Response-String TLV
Type: 0x0009
Description: Suitably formatted string containing useful details
about the test that the NAS will display for the operator, exactly
as received from the DSLAM (no manipulation or interpretation by
the NAS).
Length: Up to 128 bytes
Value: UTF-8 encoded string of text.
9. IANA Considerations
This section documents the following IANA actions:
o establishment of the following new ANCP registries:
ANCP Message Types;
ANCP Result Codes;
Wadhwa, et al. Standards Track [Page 71]
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ANCP Port Management Functions;
ANCP Technology Types;
ANCP Command Codes;
ANCP TLV Types;
ANCP Capabilities.
o establishment of a new joint GSMP/ANCP version registry;
o addition of ANCP as another user of TCP port 6068 in the port
number registry available from http://www.iana.org. The current
user is GSMP.
All of these actions are described in detail below except for the
port registration, for which the final point above provides
sufficient information.
10. IANA Actions
10.1. ANCP Message Type Registry
IANA has created a new registry, ANCP Message Types. Additions to
that registry are permitted by Standards Action, as defined by
[RFC5226]. The values for Message Type MAY range from 0 to 255, but
new Message Types SHOULD be assigned values sequentially from 90
onwards (noting that 91 and 93 are already assigned). The initial
contents of the ANCP Message Types registry are as follows:
+--------------+--------------------+-----------+
| Message Type | Message Name | Reference |
+--------------+--------------------+-----------+
| 10 | Adjacency Protocol | RFC 6320 |
| 32 | Port Management | RFC 6320 |
| 80 | Port Up | RFC 6320 |
| 81 | Port Down | RFC 6320 |
| 85 | Adjacency Update | RFC 6320 |
| 91 | Generic Response | RFC 6320 |
| 93 | Provisioning | RFC 6320 |
+--------------+--------------------+-----------+
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10.2. ANCP Result Code Registry
IANA has created a new registry, ANCP Result Codes. The
documentation of new Result Codes MUST include the following
information:
o Result Code value (as assigned by IANA);
o One-line description;
o Where condition detected (control application or ANCP agent);
o Further description (if any);
o Required additional information in the response message;
o Target (control application or ANCP agent at the peer that sent
the original request);
o Action RECOMMENDED for the receiving ANCP agent.
The values for Result Code are expressed in hexadecimal and MAY range
from 0x0 to 0xFFFFFF. The range 0x0 to 0xFFF is allocated by the
criterion of IETF Review, as defined by [RFC5226]. IANA SHOULD
allocate new Result Code values from this range sequentially
beginning at 0x100. The range 0x1000 onwards is allocated by the
criterion of Specification Required, as defined by [RFC5226]. IANA
SHOULD allocate new Result Code values from this range sequentially
beginning at 0x1000. The initial contents of the ANCP Message Types
registry are as follows:
Wadhwa, et al. Standards Track [Page 73]
RFC 6320 ANCP Protocol October 2011
+------------+------------------------------------------+-----------+
| Result | One-line description | Reference |
| Code | | |
+------------+------------------------------------------+-----------+
| 0x0 | No result | RFC 6320 |
| 0x2 | Invalid request message | RFC 6320 |
| 0x6 | One or more of the specified ports are | RFC 6320 |
| | down | |
| 0x13 | Out of resources | RFC 6320 |
| 0x51 | Request message type not implemented | RFC 6320 |
| 0x53 | Malformed message | RFC 6320 |
| 0x54 | Mandatory TLV missing | RFC 6320 |
| 0x55 | Invalid TLV contents | RFC 6320 |
| 0x500 | One or more of the specified ports do | RFC 6320 |
| | not exist | |
| 0x501 | Loopback test timed out | RFC 6320 |
| 0x502 | Reserved | RFC 6320 |
| 0x503 | DSL access line status showtime | RFC 6320 |
| 0x504 | DSL access line status idle | RFC 6320 |
| 0x505 | DSL access line status silent | RFC 6320 |
| 0x506 | DSL access line status training | RFC 6320 |
| 0x507 | DSL access line integrity error | RFC 6320 |
| 0x508 | DSLAM resource not available | RFC 6320 |
| 0x509 | Invalid test parameter | RFC 6320 |
+------------+------------------------------------------+-----------+
10.3. ANCP Port Management Function Registry
IANA has created a new ANCP Port Management Function registry, with
the following initial entries. Additions to this registry will be by
Standards Action, as defined by [RFC5226]. Values may range from 0
to 255. IANA SHOULD assign values sequentially beginning with 1,
taking account of the values already assigned below.
NOTE: Future extensions of ANCP may need to establish sub-
registries of permitted X-Function values for specific values of
Function.
+----------------+-----------------------------------+-----------+
| Function Value | Function Name | Reference |
+----------------+-----------------------------------+-----------+
| 0 | Reserved | RFC 6320 |
| 8 | Configure Connection Service Data | RFC 6320 |
| 9 | Remote Loopback | RFC 6320 |
+----------------+-----------------------------------+-----------+
Wadhwa, et al. Standards Track [Page 74]
RFC 6320 ANCP Protocol October 2011
10.4. ANCP Technology Type Registry
IANA has created a new ANCP Technology Type registry, with additions
by Expert Review, as defined by [RFC5226]. The Technology Type MUST
designate a distinct access transport technology. Values may range
from 0 to 255. IANA SHOULD assign new values sequentially beginning
at 2, taking into account of the values already assigned below. The
initial entries are as follows:
+-----------------+-------------------------------+-----------+
| Tech Type Value | Tech Type Name | Reference |
+-----------------+-------------------------------+-----------+
| 0 | Not technology dependent | RFC 6320 |
| 1 | Passive Optical Network (PON) | RFC 6320 |
| 5 | Digital Subscriber Line (DSL) | RFC 6320 |
| 255 | Reserved | RFC 6320 |
+-----------------+-------------------------------+-----------+
10.5. ANCP Command Code Registry
IANA has created a new ANCP Command Code registry, with additions by
Standards Action, as defined by [RFC5226]. Values may range from 0
to 255. IANA SHOULD assign new values sequentially beginning with 1.
The initial entry is as follows:
+--------------------+-----------------------------+-----------+
| Command Code Value | Command Code Directive Name | Reference |
+--------------------+-----------------------------+-----------+
| 0 | Reserved | RFC 6320 |
+--------------------+-----------------------------+-----------+
10.6. ANCP TLV Type Registry
IANA has created a new ANCP TLV Type registry. Values are expressed
in hexadecimal and may range from 0x0000 to 0xFFFF. Additions in the
range 0x0000 to 0x1FFF are by IETF Review, as defined by [RFC5226].
IANA SHOULD assign new values in this range sequentially beginning at
0x100, taking account of the assignments already made below.
Additions in the range 0x2000 to 0xFFFF are by Specification
Required, again as defined by [RFC5226]. IANA SHOULD assign new
values in this range sequentially beginning at 0x2000. In both
cases, the documentation of the TLV MUST provide:
o a TLV name following the convention used for the initial entries
(capitalized words separated by hyphens);
o a brief description of the intended use;
Wadhwa, et al. Standards Track [Page 75]
RFC 6320 ANCP Protocol October 2011
o a precise description of the contents of each fixed field,
including its length, type, and units (if applicable);
o identification of any mandatory encapsulated TLVs;
o an indication of whether optional TLVs may be encapsulated, with
whatever information is available on their identity (could range
from a general class of information to specific TLV names,
depending on the nature of the TLV being defined).
The initial entries are as follows:
+----------+--------------------------------------------+-----------+
| Type Code| TLV Name | Reference |
+----------+--------------------------------------------+-----------+
| 0x0000 | Reserved | RFC 6320 |
| 0x0001 | Access-Loop-Circuit-ID | RFC 6320 |
| 0x0002 | Access-Loop-Remote-ID | RFC 6320 |
| 0x0003 | Access-Aggregation-Circuit-ID-ASCII | RFC 6320 |
| 0x0004 | DSL-Line-Attributes | RFC 6320 |
| 0x0005 | Service-Profile-Name | RFC 6320 |
| 0x0006 | Access-Aggregation-Circuit-ID-Binary | RFC 6320 |
| 0x0007 | OAM-Loopback-Test-Parameters | RFC 6320 |
| 0x0008 | Opaque-Data | RFC 6320 |
| 0x0009 | OAM-Loopback-Test-Response-String | RFC 6320 |
| 0x0011 | Command | RFC 6320 |
| 0x0081 | Actual-Net-Data-Rate-Upstream | RFC 6320 |
| 0x0082 | Actual-Net-Data-Rate-Downstream | RFC 6320 |
| 0x0083 | Minimum-Net-Data-Rate-Upstream | RFC 6320 |
| 0x0084 | Minimum-Net-Data-Rate-Downstream | RFC 6320 |
| 0x0085 | Attainable-Net-Data-Rate-Upstream | RFC 6320 |
| 0x0086 | Attainable-Net-Data-Rate-Downstream | RFC 6320 |
| 0x0087 | Maximum-Net-Data-Rate-Upstream | RFC 6320 |
| 0x0088 | Maximum-Net-Data-Rate-Downstream | RFC 6320 |
| 0x0089 | Minimum-Net-Low-Power-Data-Rate-Upstream | RFC 6320 |
| 0x008A | Minimum-Net-Low-Power-Data-Rate-Downstream | RFC 6320 |
| 0x008B | Maximum-Interleaving-Delay-Upstream | RFC 6320 |
| 0x008C | Actual-Interleaving-Delay-Upstream | RFC 6320 |
| 0x008D | Maximum-Interleaving-Delay-Downstream | RFC 6320 |
| 0x008E | Actual-Interleaving-Delay-Downstream | RFC 6320 |
| 0x008F | DSL-Line-State | RFC 6320 |
| 0x0090 | Access-Loop-Encapsulation | RFC 6320 |
| 0x0091 | DSL-Type | RFC 6320 |
| 0x0106 | Status-Info | RFC 6320 |
| 0x1000 | Target (single access line variant) | RFC 6320 |
| 0x1001 - | Reserved for Target variants | RFC 6320 |
| 0x1020 | | |
+----------+--------------------------------------------+-----------+
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10.7. ANCP Capability Type Registry
IANA has created a new ANCP Capability Type registry, with additions
by Standards Action as defined by [RFC5226]. Values may range from 0
to 255. IANA SHOULD assign values sequentially beginning at 5. The
specification for a given capability MUST indicate the Technology
Type value with which it is associated. The specification MUST
further indicate whether the capability is associated with any
capability data. Normally, a capability is expected to be defined in
the same document that specifies the implementation of that
capability in protocol terms. The initial entries in the ANCP
capability registry are as follows:
+-------+------------------------+--------+-------------+-----------+
| Value | Capability Type Name | Tech | Capability | Reference |
| | | Type | Data? | |
+-------+------------------------+--------+-------------+-----------+
| 0 | Reserved | | | RFC 6320 |
| 1 | DSL Topology Discovery | 5 | No | RFC 6320 |
| 2 | DSL Line Configuration | 5 | No | RFC 6320 |
| 3 | Reserved | | | RFC 6320 |
| 4 | DSL Line Testing | 5 | No | RFC 6320 |
+-------+------------------------+--------+-------------+-----------+
10.8. Joint GSMP / ANCP Version Registry
IANA has created a new joint GSMP / ANCP Version registry. Additions
to this registry are by Standards Action as defined by [RFC5226].
Values may range from 0 to 255. Values for the General Switch
Management Protocol (GSMP) MUST be assigned sequentially beginning
with 4 for the next version. Values for the Access Network Control
Protocol (ANCP) MUST be assigned sequentially beginning with 50 for
the present version. The initial entries are as follows:
+---------+----------------+-----------+
| Version | Description | Reference |
+---------+----------------+-----------+
| 1 | GSMP Version 1 | RFC 1987 |
| 2 | GSMP Version 2 | RFC 2297 |
| 3 | GSMP Version 3 | RFC 3292 |
| 50 | ANCP Version 1 | RFC 6320 |
+---------+----------------+-----------+
11. Security Considerations
Security of ANCP is discussed in [RFC5713]. A number of security
requirements on ANCP are stated in Section 8 of that document. Those
applicable to ANCP itself are copied to the present document:
Wadhwa, et al. Standards Track [Page 77]
RFC 6320 ANCP Protocol October 2011
o The protocol solution MUST offer authentication of the AN to the
NAS.
o The protocol solution MUST offer authentication of the NAS to the
AN.
o The protocol solution MUST allow authorization to take place at
the NAS and the AN.
o The protocol solution MUST offer replay protection.
o The protocol solution MUST provide data-origin authentication.
o The protocol solution MUST be robust against denial-of-service
(DoS) attacks. In this context, the protocol solution MUST
consider a specific mechanism for the DoS that the user might
create by sending many IGMP messages.
o The protocol solution SHOULD offer confidentiality protection.
o The protocol solution SHOULD ensure that operations in default
configuration guarantee a low number of AN/NAS protocol
interactions.
Most of these requirements relate to secure transport of ANCP.
Robustness against denial-of-service attacks partly depends on
transport and partly on protocol design. Ensuring a low number of
AN/NAS protocol interactions in default mode is purely a matter of
protocol design.
For secure transport, either the combination of IPsec with IKEv2
(references below) or the use of TLS [RFC5246] will meet the
requirements listed above. However, the use of TLS has been
rejected. The deciding point is a detail of protocol design that was
unavailable when [RFC5713] was written. The ANCP adjacency is a
major point of vulnerability for denial-of-service attacks. If the
adjacency can be shut down, either the AN clears its state pending
reestablishment of the adjacency, or the possibility of mismatches
between the AN's and NAS's view of state on the AN is opened up. Two
ways to cause an adjacency to be taken down are to modify messages so
that the ANCP agents conclude that they are no longer synchronized,
or to attack the underlying TCP session. TLS will protect message
contents but not the TCP connection. One has to use either IPsec or
the TCP authentication option [RFC5925] for that. Hence, the
conclusion that ANCP MUST run over IPsec with IKEv2 for
authentication and key management.
Wadhwa, et al. Standards Track [Page 78]
RFC 6320 ANCP Protocol October 2011
In greater detail: the ANCP stack MUST include IPsec [RFC4301]
running in transport mode, since the AN and NAS are the endpoints of
the path. The Encapsulating Security Payload (ESP) [RFC4303] MUST be
used, in order to satisfy the requirement for data confidentiality.
ESP MUST be configured for the combination of confidentiality,
integrity, and anti-replay capability. The traffic flow
confidentiality service of ESP is unnecessary and, in fact,
unworkable in the case of ANCP.
IKEv2 [RFC5996] is also REQUIRED, to meet the requirements for mutual
authentication and authorization. Since the NAS and AN MAY be in
different trust domains, the use of certificates for mutual
authentication could be the most practical approach. However, this
is up to the operator(s) concerned.
The AN MUST play the role of initiator of the IKEv2 conversation.
12. Contributors
Swami Subramanian was an early member of the authors' team. The ANCP
Working Group is grateful to Roberta Maglione, who served as design
team member and primary editor of this document for two years before
stepping down.
13. Acknowledgements
The authors would like to thank everyone who provided comments or
inputs to this document. The authors acknowledge the inputs provided
by Wojciech Dec, Peter Arberg, Josef Froehler, Derek Harkness, Kim
Hyldgaard, Sandy Ng, Robert Peschi, and Michel Platnic, and the
further comments provided by Mykyta Yevstifeyev, Brian Carter, Ben
Campbell, Alexey Melnikov, Adrian Farrel, Robert Sparks, Peter St.
Andre, Sean Turner, Dan Romascanu, Brian Carter, and Michael Scott.
14. References
14.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3292] Doria, A., Hellstrand, F., Sundell, K., and T.
Worster, "General Switch Management Protocol (GSMP)
V3", RFC 3292, June 2002.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
Wadhwa, et al. Standards Track [Page 79]
RFC 6320 ANCP Protocol October 2011
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
RFC 4303, December 2005.
[RFC5646] Phillips, A. and M. Davis, "Tags for Identifying
Languages", BCP 47, RFC 5646, September 2009.
[RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
"Internet Key Exchange Protocol Version 2 (IKEv2)",
RFC 5996, September 2010.
14.2. Informative References
[G.993.2] "ITU-T Recommendation G.993.2, Very high speed digital
subscriber line transceivers 2 (VDSL2)", 2006.
[G.998.1] "ITU-T Recommendation G.998.1, ATM-based multi-pair
bonding", 2005.
[G.998.2] "ITU-T Recommendation G.998.2, Ethernet-based multi-
pair bonding,", 2005.
[IEEE802.1Q] IEEE, "IEEE 802.1Q-2005, IEEE Standard for Local and
Metropolitan Area Networks - Virtual Bridged Local
Area Networks - Revision", 2005.
[IEEE802.1ad] IEEE, "IEEE 802.1ad-2005, Amendment to IEEE 802.1Q-
2005. IEEE Standard for Local and Metropolitan Area
Networks - Virtual Bridged Local Area Networks -
Revision - Amendment 4: Provider Bridges", 2005.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, March 1997.
[RFC3046] Patrick, M., "DHCP Relay Agent Information Option",
RFC 3046, January 2001.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins,
C., and M. Carney, "Dynamic Host Configuration
Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003.
[RFC4649] Volz, B., "Dynamic Host Configuration Protocol for
IPv6 (DHCPv6) Relay Agent Remote-ID Option", RFC 4649,
August 2006.
Wadhwa, et al. Standards Track [Page 80]
RFC 6320 ANCP Protocol October 2011
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing
an IANA Considerations Section in RFCs", BCP 26,
RFC 5226, May 2008.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer
Security (TLS) Protocol Version 1.2", RFC 5246,
August 2008.
[RFC5713] Moustafa, H., Tschofenig, H., and S. De Cnodder,
"Security Threats and Security Requirements for the
Access Node Control Protocol (ANCP)", RFC 5713,
January 2010.
[RFC5851] Ooghe, S., Voigt, N., Platnic, M., Haag, T., and S.
Wadhwa, "Framework and Requirements for an Access Node
Control Mechanism in Broadband Multi-Service
Networks", RFC 5851, May 2010.
[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, June 2010.
[TR-058] Broadband Forum, "TR-058, Multi-Service Architecture &
Framework Requirements", September 2003.
[TR-059] Broadband Forum, "TR-059, DSL Evolution - Architecture
Requirements for the Support of QoS-Enabled IP
Services", September 2003.
[TR-092] Broadband Forum, "TR-092, Broadband Remote access
server requirements document", 2005.
[TR-101] Broadband Forum, "TR-101, Architecture & Transport:
Migration to Ethernet Based DSL Aggregation", 2005.
[TR-147] Broadband Forum, "TR-147, Layer 2 Control Mechanism
For Broadband Multi-Service Architectures", 2008.
[US_ASCII] American National Standards Institute, "Coded
Character Set - 7-bit American Standard Code for
Information Interchange", ANSI X.34, 1986.
Wadhwa, et al. Standards Track [Page 81]
RFC 6320 ANCP Protocol October 2011
Authors' Addresses
Sanjay Wadhwa
Alcatel-Lucent
701 E Middlefield Rd
Mountain View, CA 94043-4079
USA
EMail: sanjay.wadhwa@alcatel-lucent.com
Jerome Moisand
Juniper Networks
10 Technology Park Drive
Westford, MA 01886
USA
EMail: jmoisand@juniper.net
Thomas Haag
Deutsche Telekom
Heinrich-Hertz-Strasse 3-7
Darmstadt 64295
Germany
EMail: haagt@telekom.de
Norbert Voigt
Nokia Siemens Networks
Siemensallee 1
Greifswald 17489
Germany
EMail: norbert.voigt@nsn.com
Tom Taylor (editor)
Huawei Technologies
1852 Lorraine Ave
Ottawa
Canada
EMail: tom111.taylor@bell.net
Wadhwa, et al. Standards Track [Page 82]