💾 Archived View for gemini.bortzmeyer.org › rfc-mirror › rfc5040.txt captured on 2023-12-28 at 17:42:19.
⬅️ Previous capture (2021-11-30)
-=-=-=-=-=-=-
Network Working Group R. Recio
Request for Comments: 5040 B. Metzler
Category: Standards Track IBM Corporation
P. Culley
J. Hilland
Hewlett-Packard Company
D. Garcia
October 2007
A Remote Direct Memory Access Protocol Specification
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Abstract
This document defines a Remote Direct Memory Access Protocol (RDMAP)
that operates over the Direct Data Placement Protocol (DDP protocol).
RDMAP provides read and write services directly to applications and
enables data to be transferred directly into Upper Layer Protocol
(ULP) Buffers without intermediate data copies. It also enables a
kernel bypass implementation.
Recio, et al. Standards Track [Page 1]
RFC 5040 RDMA Protocol Specification October 2007
Table of Contents
1. Introduction ....................................................4
1.1. Architectural Goals ........................................4
1.2. Protocol Overview ..........................................5
1.3. RDMAP Layering .............................................7
2. Glossary ........................................................8
2.1. General ....................................................8
2.2. LLP .......................................................10
2.3. Direct Data Placement (DDP) ...............................11
2.4. Remote Direct Memory Access (RDMA) ........................13
3. ULP and Transport Attributes ...................................15
3.1. Transport Requirements and Assumptions ....................15
3.2. RDMAP Interactions with the ULP ...........................16
4. Header Format ..................................................19
4.1. RDMAP Control and Invalidate STag Field ...................20
4.2. RDMA Message Definitions ..................................23
4.3. RDMA Write Header .........................................24
4.4. RDMA Read Request Header ..................................24
4.5. RDMA Read Response Header .................................26
4.6. Send Header and Send with Solicited Event Header ..........26
4.7. Send with Invalidate Header and Send with SE and
Invalidate Header .........................................26
4.8. Terminate Header ..........................................26
5. Data Transfer ..................................................32
5.1. RDMA Write Message ........................................32
5.2. RDMA Read Operation .......................................33
5.2.1. RDMA Read Request Message ..........................33
5.2.2. RDMA Read Response Message .........................35
5.3. Send Message Type .........................................36
5.4. Terminate Message .........................................37
5.5. Ordering and Completions ..................................38
6. RDMAP Stream Management ........................................41
6.1. Stream Initialization .....................................41
6.2. Stream Teardown ...........................................42
6.2.1. RDMAP Abortive Termination .........................43
7. RDMAP Error Management .........................................43
7.1. RDMAP Error Surfacing .....................................44
7.2. Errors Detected at the Remote Peer on Incoming
RDMA Messages .............................................45
8. Security Considerations ........................................46
8.1. Summary of RDMAP-Specific Security Requirements ...........46
8.1.1. RDMAP (RNIC) Requirements ..........................47
8.1.2. Privileged Resource Manager Requirements ...........48
8.2. Security Services for RDMAP ...............................49
8.2.1. Available Security Services ........................49
8.2.2. Requirements for IPsec Services for RDMAP ..........50
9. IANA Considerations ............................................51
Recio, et al. Standards Track [Page 2]
RFC 5040 RDMA Protocol Specification October 2007
10. References ....................................................52
10.1. Normative References .....................................52
10.2. Informative References ...................................53
Appendix A. DDP Segment Formats for RDMA Messages .................54
A.1. DDP Segment for RDMA Write ................................54
A.2. DDP Segment for RDMA Read Request .........................55
A.3. DDP Segment for RDMA Read Response ........................56
A.4. DDP Segment for Send and Send with Solicited Event ........56
A.5. DDP Segment for Send with Invalidate and Send with SE and
Invalidate ................................................57
A.6. DDP Segment for Terminate .................................58
Appendix B. Ordering and Completion Table .........................59
Appendix C. Contributors ..........................................61
Table of Figures
Figure 1: RDMAP Layering ...........................................7
Figure 2: Example of MPA, DDP, and RDMAP Header Alignment over TCP .8
Figure 3: DDP Control, RDMAP Control, and Invalidate STag Fields ..20
Figure 4: RDMA Usage of DDP Fields ................................22
Figure 5: RDMA Message Definitions ................................23
Figure 6: RDMA Read Request Header Format .........................24
Figure 7: Terminate Header Format .................................27
Figure 8: Terminate Control Field .................................27
Figure 9: Terminate Control Field Values ..........................29
Figure 10: Error Type to RDMA Message Mapping .....................32
Figure 11: RDMA Write, DDP Segment Format .........................54
Figure 12: RDMA Read Request, DDP Segment Format ..................55
Figure 13: RDMA Read Response, DDP Segment Format .................56
Figure 14: Send and Send with Solicited Event, DDP Segment Format .56
Figure 15: Send with Invalidate and Send with SE and Invalidate,
DDP Segment Format .....................................57
Figure 16: Terminate, DDP Segment Format ..........................58
Figure 17: Operation Ordering .....................................59
Recio, et al. Standards Track [Page 3]
RFC 5040 RDMA Protocol Specification October 2007
1. Introduction
Today, communications over TCP/IP typically require copy operations,
which add latency and consume significant CPU and memory resources.
The Remote Direct Memory Access Protocol (RDMAP) enables removal of
data copy operations and enables reduction in latencies by allowing a
local application to read or write data on a remote computer's memory
with minimal demands on memory bus bandwidth and CPU processing
overhead, while preserving memory protection semantics.
RDMAP is layered on top of Direct Data Placement (DDP) and uses the
two buffer models available from DDP. DDP-related terminology is
discussed in Section 2.3. As RDMAP builds on DDP, the reader is
advised to become familiar with [DDP].
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 RFC 2119 [RFC2119].
1.1. Architectural Goals
RDMAP has been designed with the following high-level architectural
goals:
* Provide a data transfer operation that allows a Local Peer to
transfer up to 2^32 - 1 octets directly into a previously
Advertised Buffer (i.e., Tagged Buffer) located at a Remote Peer
without requiring a copy operation. This is referred to as the
RDMA Write data transfer operation.
* Provide a data transfer operation that allows a Local Peer to
retrieve up to 2^32 - 1 octets directly from a previously
Advertised Buffer (i.e., Tagged Buffer) located at a Remote Peer
without requiring a copy operation. This is referred to as the
RDMA Read data transfer operation.
* Provide a data transfer operation that allows a Local Peer to send
up to 2^32 - 1 octets directly into a buffer located at a Remote
Peer that has not been explicitly Advertised. This is referred to
as the Send (Send with Invalidate, Send with Solicited Event, and
Send with Solicited Event and Invalidate) data transfer operation.
* Enable the local ULP to use the Send Operation Type (includes
Send, Send with Invalidate, Send with Solicited Event, and Send
with Solicited Event and Invalidate) to signal to the remote ULP
the Completion of all previous Messages initiated by the local
ULP.
Recio, et al. Standards Track [Page 4]
RFC 5040 RDMA Protocol Specification October 2007
* Provide for all operations on a single RDMAP Stream to be reliably
transmitted in the order that they were submitted.
* Provide RDMAP capabilities independently for each Stream when the
LLP supports multiple data Streams within an LLP connection.
1.2. Protocol Overview
RDMAP provides seven data transfer operations. Except for the RDMA
Read operation, each operation generates exactly one RDMA Message.
Following is a brief overview of the RDMA Operations and RDMA
Messages:
1. Send - A Send operation uses a Send Message to transfer data from
the Data Source into a buffer that has not been explicitly
Advertised by the Data Sink. The Send Message uses the DDP
Untagged Buffer Model to transfer the ULP Message into the Data
Sink's Untagged Buffer.
2. Send with Invalidate - A Send with Invalidate operation uses a
Send with Invalidate Message to transfer data from the Data
Source into a buffer that has not been explicitly Advertised by
the Data Sink. The Send with Invalidate Message includes all
functionality of the Send Message, with one addition: an STag
field is included in the Send with Invalidate Message. After the
message has been Placed and Delivered at the Data Sink, the
Remote Peer's buffer identified by the STag can no longer be
accessed remotely until the Remote Peer's ULP re-enables access
and Advertises the buffer.
3. Send with Solicited Event (Send with SE) - A Send with Solicited
Event operation uses a Send with Solicited Event Message to
transfer data from the Data Source into an Untagged Buffer at the
Data Sink. The Send with Solicited Event Message is similar to
the Send Message, with one addition: when the Send with Solicited
Event Message has been Placed and Delivered, an Event may be
generated at the recipient, if the recipient is configured to
generate such an Event.
4. Send with Solicited Event and Invalidate (Send with SE and
Invalidate) - A Send with Solicited Event and Invalidate
operation uses a Send with Solicited Event and Invalidate Message
to transfer data from the Data Source into a buffer that has not
been explicitly Advertised by the Data Sink. The Send with
Solicited Event and Invalidate Message is similar to the Send
with Invalidate Message, with one addition: when the Send with
Recio, et al. Standards Track [Page 5]
RFC 5040 RDMA Protocol Specification October 2007
Solicited Event and Invalidate Message has been Placed and
Delivered, an Event may be generated at the recipient, if the
recipient is configured to generate such an Event.
5. Remote Direct Memory Access Write - An RDMA Write operation uses
an RDMA Write Message to transfer data from the Data Source to a
previously Advertised Buffer at the Data Sink.
The ULP at the Remote Peer, which in this case is the Data Sink,
enables the Data Sink Tagged Buffer for access and Advertises the
buffer's size (length), location (Tagged Offset), and Steering
Tag (STag) to the Data Source through a ULP-specific mechanism.
The ULP at the Local Peer, which in this case is the Data Source,
initiates the RDMA Write operation. The RDMA Write Message uses
the DDP Tagged Buffer Model to transfer the ULP Message into the
Data Sink's Tagged Buffer. Note: the STag associated with the
Tagged Buffer remains valid until the ULP at the Remote Peer
invalidates it or the ULP at the Local Peer invalidates it
through a Send with Invalidate or Send with Solicited Event and
Invalidate.
6. Remote Direct Memory Access Read - The RDMA Read operation
transfers data to a Tagged Buffer at the Local Peer, which in
this case is the Data Sink, from a Tagged Buffer at the Remote
Peer, which in this case is the Data Source. The ULP at the Data
Source enables the Data Source Tagged Buffer for access and
Advertises the buffer's size (length), location (Tagged Offset),
and Steering Tag (STag) to the Data Sink through a ULP-specific
mechanism. The ULP at the Data Sink enables the Data Sink Tagged
Buffer for access and initiates the RDMA Read operation. The
RDMA Read operation consists of a single RDMA Read Request
Message and a single RDMA Read Response Message, and the latter
may be segmented into multiple DDP Segments.
The RDMA Read Request Message uses the DDP Untagged Buffer Model
to Deliver the STag, starting Tagged Offset, and length for both
the Data Source and Data Sink Tagged Buffers to the Remote Peer's
RDMA Read Request Queue.
The RDMA Read Response Message uses the DDP Tagged Buffer Model
to Deliver the Data Source's Tagged Buffer to the Data Sink,
without any involvement from the ULP at the Data Source.
Note: the Data Source STag associated with the Tagged Buffer
remains valid until the ULP at the Data Source invalidates it or
the ULP at the Data Sink invalidates it through a Send with
Recio, et al. Standards Track [Page 6]
RFC 5040 RDMA Protocol Specification October 2007
Invalidate or Send with Solicited Event and Invalidate. The Data
Sink STag associated with the Tagged Buffer remains valid until
the ULP at the Data Sink invalidates it.
7. Terminate - A Terminate operation uses a Terminate Message to
transfer to the Remote Peer information associated with an error
that occurred at the Local Peer. The Terminate Message uses the
DDP Untagged Buffer Model to transfer the Message into the Data
Sink's Untagged Buffer.
1.3. RDMAP Layering
RDMAP is dependent on DDP, subject to the requirements defined in
Section 3.1, "Transport Requirements and Assumptions". Figure 1,
"RDMAP Layering", depicts the relationship between Upper Layer
Protocols (ULPs), RDMAP, DDP protocol, the framing layer, and the
transport. For LLP protocol definitions of each LLP, see [MPA],
[TCP], and [SCTP].
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Upper Layer Protocol (ULP) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| RDMAP |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| DDP protocol |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
| MPA | |
| | |
+-+-+-+-+-+-+-+-+-+ SCTP |
| | |
| TCP | |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: RDMAP Layering
If RDMAP is layered over DDP/MPA/TCP, then the respective headers and
ULP Payload are arranged as follows (Note: For clarity, MPA header
and CRC fields are included but MPA markers are not shown):
Recio, et al. Standards Track [Page 7]
RFC 5040 RDMA Protocol Specification October 2007
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 Header //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MPA Header | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
// DDP Header //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// RDMA Header //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// ULP Payload //
// (shown with no pad bytes) //
// //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MPA CRC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Example of MPA, DDP, and RDMAP Header Alignment over TCP
2. Glossary
2.1. General
Advertisement (Advertised, Advertise, Advertisements, Advertises) -
the act of informing a Remote Peer that a local RDMA Buffer is
available to it. A Node makes available an RDMA Buffer for
incoming RDMA Read or RDMA Write access by informing its RDMA/DDP
peer of the Tagged Buffer identifiers (STag, base address, and
buffer length). This Advertisement of Tagged Buffer information
is not defined by RDMA/DDP and is left to the ULP. A typical
method would be for the Local Peer to embed the Tagged Buffer's
Steering Tag, base address, and length in a Send Message destined
for the Remote Peer.
Completion - Refer to "RDMA Completion" in Section 2.4.
Completed - See "RDMA Completion" in Section 2.4.
Complete - See "RDMA Completion" in Section 2.4.
Recio, et al. Standards Track [Page 8]
RFC 5040 RDMA Protocol Specification October 2007
Completes - See "RDMA Completion" in Section 2.4.
Data Sink - The peer receiving a data payload. Note that the Data
Sink can be required to both send and receive RDMA/DDP Messages
to transfer a data payload.
Data Source - The peer sending a data payload. Note that the Data
Source can be required to both send and receive RDMA/DDP Messages
to transfer a data payload.
Data Delivery (Delivery, Delivered, Delivers) - Delivery is defined
as the process of informing the ULP or consumer that a particular
Message is available for use. This is specifically different
from "Placement", which may generally occur in any order, while
the order of "Delivery" is strictly defined. See "Data
Placement" in Section 2.3.
Delivery - See Data Delivery in Section 2.1.
Delivered - See Data Delivery in Section 2.1.
Delivers - See Data Delivery in Section 2.1.
Fabric - The collection of links, switches, and routers that connect
a set of Nodes with RDMA/DDP protocol implementations.
Fence (Fenced, Fences) - To block the current RDMA Operation from
executing until prior RDMA Operations have Completed.
iWARP - A suite of wire protocols comprised of RDMAP, DDP, and MPA.
The iWARP protocol suite may be layered above TCP, SCTP, or other
transport protocols.
Local Peer - The RDMA/DDP protocol implementation on the local end of
the connection. Used to refer to the local entity when
describing a protocol exchange or other interaction between two
Nodes.
Node - A computing device attached to one or more links of a Fabric
(network). A Node in this context does not refer to a specific
application or protocol instantiation running on the computer. A
Node may consist of one or more RNICs installed in a host
computer.
Placement - See "Data Placement" in Section 2.3.
Placed - See "Data Placement" in Section 2.3.
Recio, et al. Standards Track [Page 9]
RFC 5040 RDMA Protocol Specification October 2007
Places - See "Data Placement" in Section 2.3.
Remote Peer - The RDMA/DDP protocol implementation on the opposite
end of the connection. Used to refer to the remote entity when
describing protocol exchanges or other interactions between two
Nodes.
RNIC - RDMA Network Interface Controller. In this context, this
would be a network I/O adapter or embedded controller with iWARP
and Verbs functionality.
RNIC Interface (RI) - The presentation of the RNIC to the Verbs
Consumer as implemented through the combination of the RNIC and
the RNIC driver.
Termination - See "RDMAP Abortive Termination" in Section 2.4.
Terminated - See "RDMAP Abortive Termination" in Section 2.4.
Terminate - See "RDMAP Abortive Termination" in Section 2.4.
Terminates - See "RDMAP Abortive Termination" in Section 2.4.
ULP - Upper Layer Protocol. The protocol layer above the one
currently being referenced. The ULP for RDMA/DDP is expected to
be an OS, Application, adaptation layer, or proprietary device.
The RDMA/DDP documents do not specify a ULP -- they provide a set
of semantics that allow a ULP to be designed to utilize RDMA/DDP.
ULP Payload - The ULP data that is contained within a single protocol
segment or packet (e.g., a DDP Segment).
Verbs - An abstract description of the functionality of an RNIC
Interface. The OS may expose some or all of this functionality
via one or more APIs to applications. The OS will also use some
of the functionality to manage the RNIC Interface.
2.2. LLP
LLP - Lower Layer Protocol. The protocol layer beneath the protocol
layer currently being referenced. For example, for DDP, the LLP
is SCTP, MPA, or other transport protocols. For RDMA, the LLP is
DDP.
LLP Connection - Corresponds to an LLP transport-level connection
between the peer LLP layers on two Nodes.
Recio, et al. Standards Track [Page 10]
RFC 5040 RDMA Protocol Specification October 2007
LLP Stream - Corresponds to a single LLP transport-level Stream
between the peer LLP layers on two Nodes. One or more LLP
Streams may map to a single transport-level LLP connection. For
transport protocols that support multiple Streams per connection
(e.g., SCTP), an LLP Stream corresponds to one transport-level
Stream.
MULPDU - Maximum ULPDU. The current maximum size of the record that
is acceptable for DDP to pass to the LLP for transmission.
ULPDU - Upper Layer Protocol Data Unit. The data record defined by
the layer above MPA.
2.3. Direct Data Placement (DDP)
Data Placement (Placement, Placed, Places) - For DDP, this term is
specifically used to indicate the process of writing to a data
buffer by a DDP implementation. DDP Segments carry Placement
information, which may be used by the receiving DDP
implementation to perform Data Placement of the DDP Segment ULP
Payload. See "Data Delivery".
DDP Abortive Teardown - The act of closing a DDP Stream without
attempting to Complete in-progress and pending DDP Messages.
DDP Graceful Teardown - The act of closing a DDP Stream such that all
in-progress and pending DDP Messages are allowed to Complete
successfully.
DDP Control Field - A fixed 16-bit field in the DDP Header. The DDP
Control Field contains an 8-bit field whose contents are reserved
for use by the ULP.
DDP Header - The header present in all DDP segments. The DDP Header
contains control and Placement fields that are used to define the
final Placement location for the ULP Payload carried in a DDP
Segment.
DDP Message - A ULP-defined unit of data interchange, which is
subdivided into one or more DDP segments. This segmentation may
occur for a variety of reasons, including segmentation to respect
the maximum segment size of the underlying transport protocol.
DDP Segment - The smallest unit of data transfer for the DDP
protocol. It includes a DDP Header and ULP Payload (if present).
A DDP Segment should be sized to fit within the underlying
transport protocol MULPDU.
Recio, et al. Standards Track [Page 11]
RFC 5040 RDMA Protocol Specification October 2007
DDP Stream - A sequence of DDP Messages whose ordering is defined by
the LLP. For SCTP, a DDP Stream maps directly to an SCTP Stream.
For MPA, a DDP Stream maps directly to a TCP connection, and a
single DDP Stream is supported. Note that DDP has no ordering
guarantees between DDP Streams.
Direct Data Placement - A mechanism whereby ULP data contained within
DDP Segments may be Placed directly into its final destination in
memory without processing of the ULP. This may occur even when
the DDP Segments arrive out of order. Out-of-order Placement
support may require the Data Sink to implement the LLP and DDP as
one functional block.
Direct Data Placement Protocol (DDP) - Also, a wire protocol that
supports Direct Data Placement by associating explicit memory
buffer placement information with the LLP payload units.
Message Offset (MO) - For the DDP Untagged Buffer Model, specifies
the offset, in bytes, from the start of a DDP Message.
Message Sequence Number (MSN) - For the DDP Untagged Buffer Model,
specifies a sequence number that is increasing with each DDP
Message.
Queue Number (QN) - For the DDP Untagged Buffer Model, identifies a
destination Data Sink queue for a DDP Segment.
Steering Tag - An identifier of a Tagged Buffer on a Node, valid as
defined within a protocol specification.
STag - Steering Tag
Tagged Buffer - A buffer that is explicitly Advertised to the Remote
Peer through exchange of an STag, Tagged Offset, and length.
Tagged Buffer Model - A DDP data transfer model used to transfer
Tagged Buffers from the Local Peer to the Remote Peer.
Tagged DDP Message - A DDP Message that targets a Tagged Buffer.
Tagged Offset (TO) - The offset within a Tagged Buffer on a Node.
Untagged Buffer - A buffer that is not explicitly Advertised to the
Remote Peer. Untagged Buffers support one of the two available
data transfer mechanisms called the Untagged Buffer Model. An
Untagged Buffer is used to send asynchronous control messages to
the Remote Peer for RDMA Read, Send, and Terminate requests.
Untagged Buffers handle Untagged DDP Messages.
Recio, et al. Standards Track [Page 12]
RFC 5040 RDMA Protocol Specification October 2007
Untagged Buffer Model - A DDP data transfer model used to transfer
Untagged Buffers from the Local Peer to the Remote Peer.
Untagged DDP Message - A DDP Message that targets an Untagged Buffer.
2.4. Remote Direct Memory Access (RDMA)
Completion Queues (CQs) - Logical components of the RNIC Interface
that conceptually represent how an RNIC notifies the ULP about
the completion of the transmission of data, or the completion of
the reception of data; see [RDMASEC].
Event - An indication provided by the RDMAP layer to the ULP to
indicate a Completion or other condition requiring immediate
attention.
Invalidate STag - A mechanism used to prevent the Remote Peer from
reusing a previous explicitly Advertised STag, until the Local
Peer makes it available through a subsequent explicit
Advertisement. The STag cannot be accessed remotely until it is
explicitly Advertised again.
RDMA Completion (Completion, Completed, Complete, Completes) - For
RDMA, Completion is defined as the process of informing the ULP
that a particular RDMA Operation has performed all functions
specified for the RDMA Operations, including Placement and
Delivery. The Completion semantic of each RDMA Operation is
distinctly defined.
RDMA Message - A data transfer mechanism used to fulfill an RDMA
Operation.
RDMA Operation - A sequence of RDMA Messages, including control
Messages, to transfer data from a Data Source to a Data Sink.
The following RDMA Operations are defined: RDMA Writes, RDMA
Read, Send, Send with Invalidate, Send with Solicited Event, Send
with Solicited Event and Invalidate, and Terminate.
RDMA Protocol (RDMAP) - A wire protocol that supports RDMA Operations
to transfer ULP data between a Local Peer and the Remote Peer.
RDMAP Abortive Termination (Termination, Terminated, Terminate,
Terminates) - The act of closing an RDMAP Stream without
attempting to Complete in-progress and pending RDMA Operations.
RDMAP Graceful Termination - The act of closing an RDMAP Stream such
that all in-progress and pending RDMA Operations are allowed to
Complete successfully.
Recio, et al. Standards Track [Page 13]
RFC 5040 RDMA Protocol Specification October 2007
RDMA Read - An RDMA Operation used by the Data Sink to transfer the
contents of a source RDMA buffer from the Remote Peer to the
Local Peer. An RDMA Read operation consists of a single RDMA
Read Request Message and a single RDMA Read Response Message.
RDMA Read Request - An RDMA Message used by the Data Sink to request
the Data Source to transfer the contents of an RDMA buffer. The
RDMA Read Request Message describes both the Data Source and Data
Sink RDMA buffers.
RDMA Read Request Queue - The queue used for processing RDMA Read
Requests. The RDMA Read Request Queue has a DDP Queue Number of
1.
RDMA Read Response - An RDMA Message used by the Data Source to
transfer the contents of an RDMA buffer to the Data Sink, in
response to an RDMA Read Request. The RDMA Read Response Message
only describes the data sink RDMA buffer.
RDMAP Stream - An association between a pair of RDMAP
implementations, possibly on different Nodes, which transfer ULP
data using RDMA Operations. There may be multiple RDMAP Streams
on a single Node. An RDMAP Stream maps directly to a single DDP
Stream.
RDMA Write - An RDMA Operation that transfers the contents of a
source RDMA Buffer from the Local Peer to a destination RDMA
Buffer at the Remote Peer using RDMA. The RDMA Write Message
only describes the Data Sink RDMA buffer.
Remote Direct Memory Access (RDMA) - A method of accessing memory on
a remote system in which the local system specifies the remote
location of the data to be transferred. Employing an RNIC in the
remote system allows the access to take place without
interrupting the processing of the CPU(s) on the system.
Send - An RDMA Operation that transfers the contents of a ULP Buffer
from the Local Peer to an Untagged Buffer at the Remote Peer.
Send Message Type - A Send Message, Send with Invalidate Message,
Send with Solicited Event Message, or Send with Solicited Event
and Invalidate Message.
Send Operation Type - A Send Operation, Send with Invalidate
Operation, Send with Solicited Event Operation, or Send with
Solicited Event and Invalidate Operation.
Recio, et al. Standards Track [Page 14]
RFC 5040 RDMA Protocol Specification October 2007
Solicited Event (SE) - A facility by which an RDMA Operation sender
may cause an Event to be generated at the recipient, if the
recipient is configured to generate such an Event, when a Send
with Solicited Event Message or Send with Solicited Event and
Invalidate Message is received. Note: The Local Peer's ULP can
use the Solicited Event mechanism to ensure that Messages
designated as important to the ULP are handled in an expeditious
manner by the Remote Peer's ULP. The ULP at the Local Peer can
indicate a given Send Message Type is important by using the Send
with Solicited Event Message or Send with Solicited Event and
Invalidate Message. The ULP at the Remote Peer can choose to
only be notified when valid Send with Solicited Event Messages
and/or Send with Solicited Event and Invalidate Messages arrive
and handle other valid incoming Send Messages or Send with
Invalidate Messages at its leisure.
Terminate - An RDMA Message used by a Node to pass an error
indication to the peer Node on an RDMAP Stream. This operation
is for RDMAP use only.
ULP Buffer - A buffer owned above the RDMAP layer and Advertised to
the RDMAP layer either as a Tagged Buffer or an Untagged ULP
Buffer.
ULP Message - The ULP data that is handed to a specific protocol
layer for transmission. Data boundaries are preserved as they
are transmitted through iWARP.
3. ULP and Transport Attributes
3.1. Transport Requirements and Assumptions
RDMAP MUST be layered on top of the Direct Data Placement Protocol
[DDP].
RDMAP requires the following DDP support:
* RDMAP uses three queues for Untagged Buffers:
* Queue Number 0 (used by RDMAP for Send, Send with Invalidate,
Send with Solicited Event, and Send with Solicited Event and
Invalidate operations).
* Queue Number 1 (used by RDMAP for RDMA Read operations).
* Queue Number 2 (used by RDMAP for Terminate operations).
* DDP maps a single RDMA Message to a single DDP Message.
Recio, et al. Standards Track [Page 15]
RFC 5040 RDMA Protocol Specification October 2007
* DDP uses the STag and Tagged Offset provided by the RDMAP for
Tagged Buffer Messages (i.e., RDMA Write and RDMA Read Response).
* When the DDP layer Delivers an Untagged DDP Message to the RDMAP
layer, DDP provides the length of the DDP Message. This ensures
that RDMAP does not have to carry a length field in its header.
* When the RDMAP layer provides an RDMA Message to the DDP layer,
DDP must insert the RsvdULP field value provided by the RDMAP
layer into the associated DDP Message.
* When the DDP layer Delivers a DDP Message to the RDMAP layer, DDP
provides the RsvdULP field.
* The RsvdULP field must be 1 octet for DDP Tagged Messages and 5
octets for DDP Untagged Messages.
* DDP propagates to RDMAP all operation or protection errors (used
by RDMAP Terminate) and, when appropriate, the DDP Header fields
of the DDP Segment that encountered the error.
* If an RDMA Operation is aborted by DDP or a lower layer, the
contents of the Data Sink buffers associated with the operation
are considered indeterminate.
* DDP, in conjunction with the lower layers, provides reliable, in-
order Delivery.
3.2. RDMAP Interactions with the ULP
RDMAP provides the ULP with access to the following RDMA Operations
as defined in this specification:
* Send
* Send with Solicited Event
* Send with Invalidate
* Send with Solicited Event and Invalidate
* RDMA Write
* RDMA Read
Recio, et al. Standards Track [Page 16]
RFC 5040 RDMA Protocol Specification October 2007
For Send Operation Types, the following are the interactions between
the RDMAP layer and the ULP:
* At the Data Source:
* The ULP passes to the RDMAP layer the following:
* ULP Message Length
* ULP Message
* An indication of the Send Operation Type, where the valid
types are: Send, Send with Solicited Event, Send with
Invalidate, or Send with Solicited Event and Invalidate.
* An Invalidate STag, if the Send Operation Type was Send with
Invalidate or Send with Solicited Event and Invalidate.
* When the Send Operation Type Completes, an indication of the
Completion results.
* At the Data Sink:
* If the Send Operation Type Completed successfully, the RDMAP
layer passes the following information to the ULP Layer:
* ULP Message Length
* ULP Message
* An Event, if the Data Sink is configured to generate an
Event.
* An Invalidated STag, if the Send Operation Type was Send
with Invalidate or Send with Solicited Event and Invalidate.
* If the Send Operation Type Completed in error, the Data Sink
RDMAP layer will pass up the corresponding error information to
the Data Sink ULP and send a Terminate Message to the Data
Source RDMAP layer. The Data Source RDMAP layer will then pass
up the Terminate Message to the ULP.
For RDMA Write operations, the following are the interactions between
the RDMAP layer and the ULP:
* At the Data Source:
* The ULP passes to the RDMAP layer the following:
Recio, et al. Standards Track [Page 17]
RFC 5040 RDMA Protocol Specification October 2007
* ULP Message Length
* ULP Message
* Data Sink STag
* Data Sink Tagged Offset
* When the RDMA Write operation Completes, an indication of
the Completion results.
* At the Data Sink:
* If the RDMA Write completed successfully, the RDMAP layer does
not Deliver the RDMA Write to the ULP. It does Place the ULP
Message transferred through the RDMA Write Message into the ULP
Buffer.
* If the RDMA Write completed in error, the Data Sink RDMAP layer
will pass up the corresponding error information to the Data
Sink ULP and send a Terminate Message to the Data Source RDMAP
layer. The Data Source RDMAP layer will then pass up the
Terminate Message to the ULP.
For RDMA Read operations, the following are the interactions between
the RDMAP layer and the ULP:
* At the Data Sink:
* The ULP passes to the RDMAP layer the following:
* ULP Message Length
* Data Source STag
* Data Sink STag
* Data Source Tagged Offset
* Data Sink Tagged Offset
* When the RDMA Read operation Completes, an indication of the
Completion results.
* At the Data Source:
* If no error occurred while processing the RDMA Read Request,
the Data Source will not pass up any information to the ULP.
Recio, et al. Standards Track [Page 18]
RFC 5040 RDMA Protocol Specification October 2007
* If an error occurred while processing the RDMA Read Request,
the Data Source RDMAP layer will pass up the corresponding
error information to the Data Source ULP and send a Terminate
Message to the Data Sink RDMAP layer. The Data Sink RDMAP
layer will then pass up the Terminate Message to the ULP.
For STags made available to the RDMAP layer, following are the
interactions between the RDMAP layer and the ULP:
* If the ULP enables an STag, the ULP passes the following to the
RDMAP layer:
* STag;
* range of Tagged Offsets that are associated with a given STag;
* remote access rights (read, write, or read and write)
associated with a given, valid STag; and
* association between a given STag and a given RDMAP Stream.
* If the ULP disables an STag, the ULP passes to the RDMAP layer the
STag.
If an error occurs at the RDMAP layer, the RDMAP layer may pass back
error information (e.g., the content of a Terminate Message) to the
ULP.
4. Header Format
The control information of RDMA Messages is included in DDP
protocol-defined header fields, with the following exceptions:
* The first octet reserved for ULP usage on all DDP Messages in the
DDP Protocol (i.e., the RsvdULP Field) is used by RDMAP to carry
the RDMA Message Opcode and the RDMAP version. This octet is
known as the RDMAP Control Field in this specification. For Send
with Invalidate and Send with Solicited Event and Invalidate,
RDMAP uses the second through fifth octets, provided by DDP on
Untagged DDP Messages, to carry the STag that will be Invalidated.
* The RDMA Message length is passed by the RDMAP layer to the DDP
layer on all outbound transfers.
* For RDMA Read Request Messages, the RDMA Read Message Size is
included in the RDMA Read Request Header.
Recio, et al. Standards Track [Page 19]
RFC 5040 RDMA Protocol Specification October 2007
* The RDMA Message length is passed to the RDMAP layer by the DDP
layer on inbound Untagged Buffer transfers.
* Two RDMA Messages carry additional RDMAP headers. The RDMA Read
Request carries the Data Sink and Data Source buffer descriptions,
including buffer length. The Terminate carries additional
information associated with the error that caused the Terminate.
4.1. RDMAP Control and Invalidate STag Field
The version of RDMAP defined by this specification uses all 8 bits of
the RDMAP Control Field. The first octet reserved for ULP use in the
DDP Protocol MUST be used by the RDMAP to carry the RDMAP Control
Field. The ordering of the bits in the first octet MUST be as
defined in Figure 3, "DDP Control, RDMAP Control, and Invalidate STag
Fields". For Send with Invalidate and Send with Solicited Event and
Invalidate, the second through fifth octets of the DDP RsvdULP field
MUST be used by RDMAP to carry the Invalidate STag. Figure 3 depicts
the format of the DDP Control and RDMAP Control fields. (Note: In
Figure 3, the DDP Header is offset by 16 bits to accommodate the MPA
header defined in [MPA]. The MPA header is only present if DDP is
layered on top of MPA.)
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|T|L| Resrv | DV| RV|Rsv| Opcode|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Invalidate STag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: DDP Control, RDMAP Control, and Invalidate STag Fields
All RDMA Messages handed by the RDMAP layer to the DDP layer MUST
define the value of the Tagged flag in the DDP Header. Figure 4,
"RDMA Usage of DDP Fields", MUST be used to define the value of the
Tagged flag that is handed to the DDP layer for each RDMA Message.
Figure 4 defines the value of the RDMA Opcode field that MUST be used
for each RDMA Message.
Figure 4 defines when the STag, Queue Number, and Tagged Offset
fields MUST be provided for each RDMA Message.
Recio, et al. Standards Track [Page 20]
RFC 5040 RDMA Protocol Specification October 2007
For this version of the RDMAP, all RDMA Messages MUST have:
* Bits 24-25; RDMA Version field: 01b for an RNIC that complies with
this RDMA protocol specification. 00b for an RNIC that complies
with the RDMA Consortium's RDMA protocol specification. Both
version numbers are valid. Interoperability is dependent on MPA
protocol version negotiation (e.g., MPA marker and MPA CRC).
* Bits 26-27; Reserved. MUST be set to zero by sender, ignored by
the receiver.
* Bits 28-31; OpCode field: see Figure 4.
* Bits 32-63; Invalidate STag. However, this field is only valid
for Send with Invalidate and Send with Solicited Event and
Invalidate Messages (see Figure 4).
For Send, Send with Solicited Event, RDMA Read Request, and
Terminate, the Invalidate STag field MUST be set to zero on
transmit and ignored by the receiver.
Recio, et al. Standards Track [Page 21]
RFC 5040 RDMA Protocol Specification October 2007
-------+-----------+-------+------+-------+-----------+--------------
RDMA | Message | Tagged| STag | Queue | Invalidate| Message
Message| Type | Flag | and | Number| STag | Length
OpCode | | | TO | | | Communicated
| | | | | | between DDP
| | | | | | and RDMAP
-------+-----------+-------+------+-------+-----------+--------------
0000b | RDMA Write| 1 | Valid| N/A | N/A | Yes
| | | | | |
-------+-----------+-------+------+-------+-----------+--------------
0001b | RDMA Read | 0 | N/A | 1 | N/A | Yes
| Request | | | | |
-------+-----------+-------+------+-------+-----------+--------------
0010b | RDMA Read | 1 | Valid| N/A | N/A | Yes
| Response | | | | |
-------+-----------+-------+------+-------+-----------+--------------
0011b | Send | 0 | N/A | 0 | N/A | Yes
| | | | | |
-------+-----------+-------+------+-------+-----------+--------------
0100b | Send with | 0 | N/A | 0 | Valid | Yes
| Invalidate| | | | |
-------+-----------+-------+------+-------+-----------+--------------
0101b | Send with | 0 | N/A | 0 | N/A | Yes
| SE | | | | |
-------+-----------+-------+------+-------+-----------+--------------
0110b | Send with | 0 | N/A | 0 | Valid | Yes
| SE and | | | | |
| Invalidate| | | | |
-------+-----------+-------+------+-------+-----------+--------------
0111b | Terminate | 0 | N/A | 2 | N/A | Yes
| | | | | |
-------+-----------+-------+------+-------+-----------+--------------
1000b | |
to | Reserved | Not Specified
1111b | |
-------+-----------+-------------------------------------------------
Figure 4: RDMA Usage of DDP Fields
Note: N/A means Not Applicable.
Recio, et al. Standards Track [Page 22]
RFC 5040 RDMA Protocol Specification October 2007
4.2. RDMA Message Definitions
The following figure defines which RDMA Headers MUST be used on each
RDMA Message and which RDMA Messages are allowed to carry ULP
Payload:
-------+-----------+-------------------+-------------------------
RDMA | Message | RDMA Header Used | ULP Message allowed in
Message| Type | | the RDMA Message
OpCode | | |
| | |
-------+-----------+-------------------+-------------------------
0000b | RDMA Write| None | Yes
| | |
-------+-----------+-------------------+-------------------------
0001b | RDMA Read | RDMA Read Request | No
| Request | Header |
-------+-----------+-------------------+-------------------------
0010b | RDMA Read | None | Yes
| Response | |
-------+-----------+-------------------+-------------------------
0011b | Send | None | Yes
| | |
-------+-----------+-------------------+-------------------------
0100b | Send with | None | Yes
| Invalidate| |
-------+-----------+-------------------+-------------------------
0101b | Send with | None | Yes
| SE | |
-------+-----------+-------------------+-------------------------
0110b | Send with | None | Yes
| SE and | |
| Invalidate| |
-------+-----------+-------------------+-------------------------
0111b | Terminate | Terminate Header | No
| | |
-------+-----------+-------------------+-------------------------
1000b | |
to | Reserved | Not Specified
1111b | |
-------+-----------+-------------------+-------------------------
Figure 5: RDMA Message Definitions
Recio, et al. Standards Track [Page 23]
RFC 5040 RDMA Protocol Specification October 2007
4.3. RDMA Write Header
The RDMA Write Message does not include an RDMAP header. The RDMAP
layer passes to the DDP layer an RDMAP Control Field. The RDMA Write
Message is fully described by the DDP Headers of the DDP Segments
associated with the Message.
See Appendix A for a description of the DDP Segment format associated
with RDMA Write Messages.
4.4. RDMA Read Request Header
The RDMA Read Request Message carries an RDMA Read Request Header
that describes the Data Sink and Data Source Buffers used by the RDMA
Read operation. The RDMA Read Request Header immediately follows the
DDP header. The RDMAP layer passes to the DDP layer an RDMAP Control
Field. The following figure depicts the RDMA Read Request Header
that MUST be used for all RDMA Read Request Messages:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Sink STag (SinkSTag) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Data Sink Tagged Offset (SinkTO) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RDMA Read Message Size (RDMARDSZ) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Source STag (SrcSTag) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Data Source Tagged Offset (SrcTO) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: RDMA Read Request Header Format
Data Sink Steering Tag: 32 bits.
The Data Sink Steering Tag identifies the Data Sink's Tagged
Buffer. This field MUST be copied, without interpretation,
from the RDMA Read Request into the corresponding RDMA Read
Response; this field allows the Data Sink to place the
returning data. The STag is associated with the RDMAP Stream
through a mechanism that is outside the scope of the RDMAP
specification.
Recio, et al. Standards Track [Page 24]
RFC 5040 RDMA Protocol Specification October 2007
Data Sink Tagged Offset: 64 bits.
The Data Sink Tagged Offset specifies the starting offset, in
octets, from the base of the Data Sink's Tagged Buffer, where
the data is to be written by the Data Source. This field is
copied from the RDMA Read Request into the corresponding RDMA
Read Response and allows the Data Sink to place the returning
data. The Data Sink Tagged Offset MAY start at an arbitrary
offset.
The Data Sink STag and Data Sink Tagged Offset fields
describe the buffer to which the RDMA Read data is written.
Note: the DDP layer protects against a wrap of the Data Sink
Tagged Offset.
RDMA Read Message Size: 32 bits.
The RDMA Read Message Size is the amount of data, in octets,
read from the Data Source. A single RDMA Read Request
Message can retrieve from 0 to 2^32-1 data octets from the
Data Source.
Data Source Steering Tag: 32 bits.
The Data Source Steering Tag identifies the Data Source's
Tagged Buffer. The STag is associated with the RDMAP Stream
through a mechanism that is outside the scope of the RDMAP
specification.
Data Source Tagged Offset: 64 bits.
The Tagged Offset specifies the starting offset, in octets,
that is to be read from the Data Source's Tagged Buffer. The
Data Source Tagged Offset MAY start at an arbitrary offset.
The Data Source STag and Data Source Tagged Offset fields
describe the buffer from which the RDMA Read data is read.
See Section 7.2, "Errors Detected at the Remote Peer on Incoming RDMA
Messages", for a description of error checking required upon
processing of an RDMA Read Request at the Data Source.
Recio, et al. Standards Track [Page 25]
RFC 5040 RDMA Protocol Specification October 2007
4.5. RDMA Read Response Header
The RDMA Read Response Message does not include an RDMAP header. The
RDMAP layer passes to the DDP layer an RDMAP Control Field. The RDMA
Read Response Message is fully described by the DDP Headers of the
DDP Segments associated with the Message.
See Appendix A for a description of the DDP Segment format associated
with RDMA Read Response Messages.
4.6. Send Header and Send with Solicited Event Header
The Send and Send with Solicited Event Messages do not include an
RDMAP header. The RDMAP layer passes to the DDP layer an RDMAP
Control Field. The Send and Send with Solicited Event Messages are
fully described by the DDP Headers of the DDP Segments associated
with the Messages.
See Appendix A for a description of the DDP Segment format associated
with Send and Send with Solicited Event Messages.
4.7. Send with Invalidate Header and Send with SE and Invalidate Header
The Send with Invalidate and Send with Solicited Event and Invalidate
Messages do not include an RDMAP header. The RDMAP layer passes to
the DDP layer an RDMAP Control Field and the Invalidate STag field
(see section 4.1 RDMAP Control and Invalidate STag Field). The Send
with Invalidate and Send with Solicited Event and Invalidate Messages
are fully described by the DDP Headers of the DDP Segments associated
with the Messages.
See Appendix A for a description of the DDP Segment format associated
with Send and Send with Solicited Event Messages.
4.8. Terminate Header
The Terminate Message carries a Terminate Header that contains
additional information associated with the cause of the Terminate.
The Terminate Header immediately follows the DDP header. The RDMAP
layer passes to the DDP layer an RDMAP Control Field. The following
figure depicts a Terminate Header that MUST be used for the Terminate
Message:
Recio, et al. Standards Track [Page 26]
RFC 5040 RDMA Protocol Specification October 2007
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Terminate Control | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP Segment Length (if any) | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
// //
| Terminated DDP Header (if any) |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// //
| Terminated RDMA Header (if any) |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: Terminate Header Format
Terminate Control: 19 bits.
The Terminate Control field MUST have the format defined in
Figure 8 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Layer | EType | Error Code |HdrCt|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Terminate Control Field
* Figure 9, "Terminate Control Field Values", defines the valid
values that MUST be used for this field.
* Layer: 4 bits.
Identifies the layer that encountered the error.
* EType (RDMA Error Type): 4 bits.
Identifies the type of error that caused the Terminate. When
the error is detected at the RDMAP layer, the RDMAP layer
inserts the Error Type into this field. When the error is
detected at an LLP layer, an LLP layer creates the Error Type
Recio, et al. Standards Track [Page 27]
RFC 5040 RDMA Protocol Specification October 2007
and the DDP layer passes it up to the RDMAP layer, and the
RDMAP layer inserts it into this field.
* Error Code: 8 bits.
This field identifies the specific error that caused the
Terminate. When the error is detected at the RDMAP layer, the
RDMAP layer creates the Error Code. When the error is detected
at an LLP layer, the LLP layer creates the Error Code, the DDP
layer passes it up to the RDMAP layer, and the RDMAP layer
inserts it into this field.
* HdrCt: 3 bits.
Header control bits:
* M: bit 16. DDP Segment Length valid. See Figure 10 for
when this bit SHOULD be set.
* D: bit 17. DDP Header Included. See Figure 10 for when
this bit SHOULD be set.
* R: bit 18. RDMAP Header Included. See Figure 10 for when
this bit SHOULD be set.
Recio, et al. Standards Track [Page 28]
RFC 5040 RDMA Protocol Specification October 2007
-------+-----------+-------+-------------+------+--------------------
Layer | Layer | Error | Error Type | Error| Error Code Name
| Name | Type | Name | Code |
-------+-----------+-------+-------------+------+--------------------
| | 0000b | Local | None | None - This error
| | | Catastrophic| | type does not have
| | | Error | | an error code. Any
| | | | | value in this field
| | | | | is acceptable.
| +-------+-------------+------+--------------------
| | | | 00X | Invalid STag
| | | +------+--------------------
| | | | 01X | Base or bounds
| | | | | violation
| | | Remote +------+--------------------
| | 0001b | Protection | 02X | Access rights
| | | Error | | violation
| | | +------+--------------------
0000b | RDMA | | | 03X | STag not associated
| | | | | with RDMAP Stream
| | | +------+--------------------
| | | | 04X | TO wrap
| | | +------+--------------------
| | | | 09X | STag cannot be
| | | | | Invalidated
| | | +------+--------------------
| | | | FFX | Unspecified Error
| +-------+-------------+------+--------------------
| | | | 05X | Invalid RDMAP
| | | | | version
| | | +------+--------------------
| | | | 06X | Unexpected OpCode
| | | Remote +------+--------------------
| | 0010b | Operation | 07X | Catastrophic error,
| | | Error | | localized to RDMAP
| | | | | Stream
| | | +------+--------------------
| | | | 08X | Catastrophic error,
| | | | | global
| | | +------+--------------------
| | | | 09X | STag cannot be
| | | | | Invalidated
| | | +------+--------------------
| | | | FFX | Unspecified Error
Recio, et al. Standards Track [Page 29]
RFC 5040 RDMA Protocol Specification October 2007
-------+-----------+-------+-------------+------+--------------------
0001b | DDP | See DDP Specification [DDP] for a description of
| | the values and names.
-------+-----------+-------+-----------------------------------------
0010b | LLP | For MPA, see MPA Specification [MPA] for a
|(e.g., MPA)| description of the values and names.
-------+-----------+-------+-----------------------------------------
Figure 9: Terminate Control Field Values
Reserved: 13 bits. This field MUST be set to zero on transmit,
ignored on receive.
DDP Segment Length: 16 bits
The length handed up by the DDP layer when the error was
detected. It MUST be valid if the M bit is set. It MUST be
present when the D bit is set.
Terminated DDP Header: 112 bits for Tagged Messages and 144 bits
for Untagged Messages.
The DDP Header of the incoming Message that is associated
with the Terminate. The DDP Header is not present if the
Terminate Error Type is a Local Catastrophic Error. It MUST
be present if the D bit is set.
Terminated RDMA Header: 224 bits.
The Terminated RDMA Header is only sent back if the terminate
is associated with an RDMA Read Request Message. It MUST be
present if the R bit is set.
If the terminate occurs before the first RDMA Read Request
byte is processed, the original RDMA Read Request Header is
sent back.
If the terminate occurs after the first RDMA Read Request
byte is processed, the RDMA Read Request Header is updated to
reflect the current location of the RDMA Read operation that
is in process:
* Data Sink STag = Data Sink STag originally sent in the
RDMA Read Request.
Recio, et al. Standards Track [Page 30]
RFC 5040 RDMA Protocol Specification October 2007
* Data Sink Tagged Offset = Current offset into the Data
Sink Tagged Buffer. For example, if the RDMA Read
Request was terminated after 2048 octets were sent,
then the Data Sink Tagged Offset = the original Data
Sink Tagged Offset + 2048.
* Data Message size = Number of bytes left to transfer.
* Data Source STag = Data Source STag in the RDMA Read
Request.
* Data Source Tagged Offset = Current offset into the
Data Source Tagged Buffer. For example, if the RDMA
Read Request was terminated after 2048 octets were
sent, then the Data Source Tagged Offset = the
original Data Source Tagged Offset + 2048.
Note: if a given LLP does not define any termination codes for the
RDMAP Termination message to use, then none would be used for that
LLP.
Figure 10, "Error Type to RDMA Message Mapping", maps layer name and
error types to each RDMA Message type:
Recio, et al. Standards Track [Page 31]
RFC 5040 RDMA Protocol Specification October 2007
---------+-------------+------------+------------+-----------------
Layer | Error Type | Terminate | Terminate | What type of
Name | Name | Includes | Includes | RDMA Message can
| | DDP Header | RDMA Header| cause the error
| | and DDP | |
| | Segment | |
| | Length | |
---------+-------------+------------+------------+-----------------
| Local | No | No | Any
| Catastrophic| | |
| Error | | |
+-------------+------------+------------+-----------------
| Remote | Yes, if | Yes | Only RDMA Read
RDMA | Protection | possible | | Request, Send
| Error | | | with Invalidate,
| | | | and Send with SE
| | | | and Invalidate
+-------------+------------+------------+-----------------
| Remote | Yes, if | No | Any
| Operation | possible | |
| Error | | |
---------+-------------+------------+------------+-----------------
DDP | See DDP Spec| Yes | No | Any
| [DDP] | | |
---------+-------------+------------+------------+-----------------
LLP | See LLP Spec| No | No | Any
| (e.g., MPA) | | |
Figure 10: Error Type to RDMA Message Mapping
5. Data Transfer
5.1. RDMA Write Message
An RDMA Write is used by the Data Source to transfer data to a
previously Advertised Tagged Buffer at the Data Sink. The RDMA Write
Message has the following semantics:
* An RDMA Write Message MUST reference a Tagged Buffer. That is,
the Data Source RDMAP layer MUST request that the DDP layer mark
the Message as Tagged.
* A valid RDMA Write Message MUST NOT be delivered to the Data
Sink's ULP (i.e., it is placed by the DDP layer).
* At the Remote Peer, when an invalid RDMA Write Message is
delivered to the Remote Peer's RDMAP layer, an error is surfaced
(see Section 7.1, "RDMAP Error Surfacing").
Recio, et al. Standards Track [Page 32]
RFC 5040 RDMA Protocol Specification October 2007
* The Tagged Offset of a Tagged Buffer MAY start at a non-zero
value.
* An RDMA Write Message MAY target all or part of a previously
Advertised Buffer.
* The RDMAP does not define how the buffer(s) are used by an
outbound RDMA Write or how they are addressed. For example, an
implementation of RDMA may choose to allow a gather-list of non-
contiguous data blocks to be the source of an RDMA Write. In this
case, the data blocks would be combined by the Data Source and
sent as a single RDMA Write Message to the Data Sink.
* The Data Source RDMAP layer MUST issue RDMA Write Messages to the
DDP layer in the order they were submitted by the ULP.
* At the Data Source, a subsequent Send (Send with Invalidate, Send
with Solicited Event, or Send with Solicited Event and Invalidate)
Message MAY be used to signal Delivery of previous RDMA Write
Messages to the Data Sink, if the ULP chooses to signal Delivery
in this fashion.
* If the Local Peer wishes to write to multiple Tagged Buffers on
the Remote Peer, the Local Peer MUST use multiple RDMA Write
Messages. That is, a single RDMA Write Message can only write to
one remote Tagged Buffer.
* The Data Source MAY issue a zero-length RDMA Write Message.
5.2. RDMA Read Operation
The RDMA Read operation MUST consist of a single RDMA Read Request
Message and a single RDMA Read Response Message.
5.2.1. RDMA Read Request Message
An RDMA Read Request is used by the Data Sink to transfer data from a
previously Advertised Tagged Buffer at the Data Source to a Tagged
Buffer at the Data Sink. The RDMA Read Request Message has the
following semantics:
* An RDMA Read Request Message MUST reference an Untagged Buffer.
That is, the Local Peer's RDMAP layer MUST request that the DDP
mark the Message as Untagged.
* One RDMA Read Request Message MUST consume one Untagged Buffer.
Recio, et al. Standards Track [Page 33]
RFC 5040 RDMA Protocol Specification October 2007
* The Remote Peer's RDMAP layer MUST process an RDMA Read Request
Message. A valid RDMA Read Request Message MUST NOT be delivered
to the Data Sink's ULP (i.e., it is processed by the RDMAP layer).
* At the Remote Peer, when an invalid RDMA Read Request Message is
delivered to the Remote Peer's RDMAP layer, an error is surfaced
(see Section 7.1, "RDMAP Error Surfacing").
* An RDMA Read Request Message MUST reference the RDMA Read Request
Queue. That is, the Local Peer's RDMAP layer MUST request that
the DDP layer set the Queue Number field to one.
* The Local Peer MUST pass to the DDP layer RDMA Read Request
Messages in the order they were submitted by the ULP.
* The Remote Peer MUST process the RDMA Read Request Messages in the
order they were sent.
* If the Local Peer wishes to read from multiple Tagged Buffers on
the Remote Peer, the Local Peer MUST use multiple RDMA Read
Request Messages. That is, a single RDMA Read Request Message
MUST only read from one remote Tagged Buffer.
* AN RDMA Read Request Message MAY target all or part of a
previously Advertised Buffer.
* If the Data Source receives a valid RDMA Read Request Message, it
MUST respond with a valid RDMA Read Response Message.
* The Data Sink MAY issue a zero-length RDMA Read Request Message by
setting the RDMA Read Message Size field to zero in the RDMA Read
Request Header.
* If the Data Source receives a non-zero-length RDMA Read Message
Size, the Data Source RDMAP MUST validate the Data Source STag and
Data Source Tagged Offset contained in the RDMA Read Request
Header.
* If the Data Source receives an RDMA Read Request Header with the
RDMA Read Message Size set to zero, the Data Source RDMAP:
* MUST NOT validate the Data Source STag and Data Source Tagged
Offset contained in the RDMA Read Request Header, and
* MUST respond with a zero-length RDMA Read Response Message.
Recio, et al. Standards Track [Page 34]
RFC 5040 RDMA Protocol Specification October 2007
5.2.2. RDMA Read Response Message
The RDMA Read Response Message uses the DDP Tagged Buffer Model to
Deliver the contents of a previously requested Data Source Tagged
Buffer to the Data Sink, without any involvement from the ULP at the
Remote Peer. The RDMA Read Response Message has the following
semantics:
* The RDMA Read Response Message for the associated RDMA Read
Request Message travels in the opposite direction.
* An RDMA Read Response Message MUST reference a Tagged Buffer.
That is, the Data Source RDMAP layer MUST request that the DDP
mark the Message as Tagged.
* The Data Source MUST ensure that a sufficient number of Untagged
Buffers are available on the RDMA Read Request Queue (Queue with
DDP Queue Number 1) to support the maximum number of RDMA Read
Requests negotiated by the ULP.
* The RDMAP layer MUST Deliver the RDMA Read Response Message to the
ULP.
* At the Remote Peer, when an invalid RDMA Read Response Message is
delivered to the Remote Peer's RDMAP layer, an error is surfaced
(see Section 7.1, "RDMAP Error Surfacing").
* The Tagged Offset of a Tagged Buffer MAY start at a non-zero
value.
* The Data Source RDMAP layer MUST pass RDMA Read Response Messages
to the DDP layer, in the order that the RDMA Read Request Messages
were received by the RDMAP layer, at the Data Source.
* The Data Sink MAY validate that the STag, Tagged Offset, and
length of the RDMA Read Response Message are the same as the STag,
Tagged Offset, and length included in the corresponding RDMA Read
Request Message.
* A single RDMA Read Response Message MUST write to one remote
Tagged Buffer. If the Data Sink wishes to read multiple Tagged
Buffers, the Data Sink can use multiple RDMA Read Request
Messages.
Recio, et al. Standards Track [Page 35]
RFC 5040 RDMA Protocol Specification October 2007
5.3. Send Message Type
The Send Message Type uses the DDP Untagged Buffer Model to transfer
data from the Data Source into an Untagged Buffer at the Data Sink.
* A Send Message Type MUST reference an Untagged Buffer. That is,
the Local Peer's RDMAP layer MUST request that the DDP layer mark
the Message as Untagged.
* One Send Message Type MUST consume one Untagged Buffer.
* The ULP Message sent using a Send Message Type MAY be less than
or equal to the size of the consumed Untagged Buffer. The
RDMAP layer communicates to the ULP the size of the data
written into the Untagged Buffer.
* If the ULP Message sent via Send Message Type is larger than
the Data Sink's Untagged Buffer, it is an error (see Section
9.1, "RDMAP Error Surfacing").
* At the Remote Peer, the Send Message Type MUST be Delivered to the
Remote Peer's ULP in the order they were sent.
* After the Send with Solicited Event or Send with Solicited Event
and Invalidate Message is Delivered to the ULP, the RDMAP MAY
generate an Event, if the Data Sink is configured to generate such
an Event.
* At the Remote Peer, when an invalid Send Message Type is Delivered
to the Remote Peer's RDMAP layer, an error is surfaced (see
Section 7.1, "RDMAP Error Surfacing").
* The RDMAP does not specify the structure of the buffer(s) used by
an outbound RDMA Write nor does it specify how the buffer(s) are
addressed. For example, an implementation of RDMA may choose to
allow a gather-list of non-contiguous data blocks to be the source
of a Send Message Type. In this case, the data blocks would be
combined by the Data Source and sent as a single Send Message Type
to the Data Sink.
* For a Send Message Type, the Local Peer's RDMAP layer MUST request
that the DDP layer set the Queue Number field to zero.
* The Local Peer MUST issue Send Message Type Messages in the order
they were submitted by the ULP.
Recio, et al. Standards Track [Page 36]
RFC 5040 RDMA Protocol Specification October 2007
* The Data Source MAY pass a zero-length Send Message Type. A
zero-length Send Message Type MUST consume an Untagged Buffer at
the Data Sink. A Send with Invalidate or Send with Solicited
Event and Invalidate Message MUST reference an STag. That is, the
Local Peer's RDMAP layer MUST pass the RDMA control field and the
STag that will be Invalidated to the DDP layer.
* When the Send with Invalidate and Send with Solicited Event and
Invalidate Message are Delivered to the Remote Peer's RDMAP layer,
the RDMAP layer MUST:
* Verify the STag that is associated with the RDMAP Stream; and
* Invalidate the STag if it is associated with the RDMAP Stream;
or issue a Terminate Message with the STag Cannot be
Invalidated Terminate Error Code, if the STag is not associated
with the RDMAP Stream.
5.4. Terminate Message
The Terminate Message uses the DDP Untagged Buffer Model to
transfer-error-related information from the Data Source into an
Untagged Buffer at the Data Sink and then ceases all further
communications on the underlying DDP Stream. The Terminate Message
has the following semantics:
* A Terminate Message MUST reference an Untagged Buffer. That is,
the Local Peer's RDMAP layer MUST request that the DDP layer mark
the Message as Untagged.
* A Terminate Message references the Terminate Queue. That is, the
Local Peer's RDMAP layer MUST request that the DDP layer set the
Queue Number field to two.
* One Terminate Message MUST consume one Untagged Buffer.
* On a single RDMAP Stream, the RDMAP layer MUST guarantee placement
of a single Terminate Message.
* A Terminate Message MUST be Delivered to the Remote Peer's RDMAP
layer. The RDMAP layer MUST Deliver the Terminate Message to the
ULP.
* At the Remote Peer, when an invalid Terminate Message is delivered
to the Remote Peer's RDMAP layer, an error is surfaced (see
Section 7.1 "RDMAP Error Surfacing").
Recio, et al. Standards Track [Page 37]
RFC 5040 RDMA Protocol Specification October 2007
* The RDMAP layer Completes in error all ULP operations that have
not been provided to the DDP layer.
* After sending a Terminate Message on an RDMAP Stream, the Local
Peer MUST NOT send any more Messages on that specific RDMAP
Stream.
* After receiving a Terminate Message on an RDMAP Stream, the Remote
Peer MAY stop sending Messages on that specific RDMAP Stream.
5.5. Ordering and Completions
It is important to understand the difference between Placement and
Delivery ordering since RDMAP provides quite different semantics for
the two.
Note that many current protocols, both as used in the Internet and
elsewhere, assume that data is both Placed and Delivered in order.
Taking advantage of this fact allowed applications to take a variety
of shortcuts. For RDMAP, many of these shortcuts are no longer safe
to use, and could cause application failure.
The following rules apply to implementations of the RDMAP protocol.
Note that in these rules, Send includes Send, Send with Invalidate,
Send with Solicited Event, and Send with Solicited Event and
Invalidate:
1. RDMAP does not provide ordering among Messages on different RDMAP
Streams.
2. RDMAP does not provide ordering between operations that are
generated from the two ends of an RDMAP Stream.
3. RDMA Messages that use Tagged and Untagged Buffers MAY be Placed
in any order. If an application uses overlapping buffers (points
different Messages or portions of a single Message at the same
buffer), then it is possible that the last incoming write to the
Data Sink buffer will not be the last outgoing data sent from the
Data Source.
4. For a Send operation, the contents of an Untagged Buffer at the
Data Sink MAY be indeterminate until the Send is Delivered to the
ULP at the Data Sink.
5. For an RDMA Write operation, the contents of the Tagged Buffer at
the Data Sink MAY be indeterminate until a subsequent Send is
Delivered to the ULP at the Data Sink.
Recio, et al. Standards Track [Page 38]
RFC 5040 RDMA Protocol Specification October 2007
6. For an RDMA Read operation, the contents of the Tagged Buffer at
the Data Sink MAY be indeterminate until the RDMA Read Response
Message has been Delivered at the Local Peer.
Statements 4, 5, and 6 imply "no peeking" at the data to see if it is
done. It is possible for some data to arrive before logically
earlier data does, and peeking may cause unpredictable application
failure.
7. If the ULP or Application modifies the contents of Tagged or
Untagged Buffers, which are being modified by an RDMA Operation
while the RDMAP is processing the RDMA Operation, the state of
the Buffers is indeterminate.
8. If the ULP or Application modifies the contents of Tagged or
Untagged Buffers, which are read by an RDMA Operation while the
RDMAP is processing the RDMA Operation, the results of the read
are indeterminate.
9. The Completion of an RDMA Write or Send Operation at the Local
Peer does not guarantee that the ULP Message has yet reached the
Remote Peer ULP Buffer or been examined by the Remote ULP.
10. Send Messages MUST be Delivered to the ULP at the Remote Peer
after they are Delivered to RDMAP by DDP and in the order that
they were Delivered to RDMAP.
Note that DDP ordering rules ensure that this will be the same
order that they were submitted at the Local Peer and that any
prior RDMA Writes have been submitted for ordered Placement at
the Remote Peer. This means that when the ULP sees the Delivery
of the Send, the memory buffers targeted by any preceding RDMA
Writes and Sends are available to be accessed locally or remotely
as authorized. If the ULP overlaps its buffers for different
operations, the data from the RDMA Write or Send may be
overwritten by subsequent RDMA Operations before the ULP receives
and processes the Delivery.
11. RDMA Read Response Messages MUST be Delivered to the ULP at the
Remote Peer after they are Delivered to RDMAP by DDP and in the
order that the they were Delivered to RDMAP.
DDP ordering rules ensure that this will be the same order that
they were submitted at the Local Peer. This means that when the
ULP sees the Delivery of the RDMA Read Response, the memory
buffers targeted by the RDMA Read Response are available to be
accessed locally or remotely as authorized. If the ULP overlaps
Recio, et al. Standards Track [Page 39]
RFC 5040 RDMA Protocol Specification October 2007
its buffers for different operations, the data from the RDMA Read
Response may be overwritten by subsequent RDMA Operations before
the ULP receives and processes the Delivery.
12. RDMA Read Request Messages, including zero-length RDMA Read
Requests, MUST NOT start processing at the Remote Peer until they
have been Delivered to RDMAP by DDP.
Note: the ULP is assured that data written can be read back. For
example, if
a) an RDMA Read Request is issued by the local peer,
b) the Request targets the same ULP Buffer as a preceding Send
or RDMA Write (in the same direction as the RDMA Read
Request), and
c) there are no other sources of update for the ULP Buffer,
then the Remote Peer will send back the data written by the Send
or RDMA Write. That is, for this example, the ULP Buffer is
Advertised for use on a series of RDMA Messages, is only valid on
the RDMAP Stream for which it is Advertised, and is not locally
updated while the series of RDMAP Messages are performed. For
this example, order rule (12) assures that subsequent local or
remote accesses to the ULP Buffer contain the data written by the
Send or RDMA Write.
RDMA Read Response Messages MAY be generated at the Remote Peer
after subsequent RDMA Write Messages or Send Messages have been
Placed or Delivered. Therefore, when an application does an RDMA
Read Request followed by an RDMA Write (or Send) to the same
buffer, it may get the data from the later RDMA Write (or Send)
in the RDMA Read Response Message, even though the operations
completed in order at the Local Peer. If this behavior is not
desired, the Local Peer ULP must Fence the later RDMA write (or
Send) by withholding the RDMA Write Message until all outstanding
RDMA Read Responses have been Delivered.
13. The RDMAP layer MUST submit RDMA Messages to the DDP layer in the
order the RDMA Operations are submitted to the RDMAP layer by the
ULP.
14. A Send or RDMA Write Message MUST NOT be considered Complete at
the Local Peer (Data Source) until it has been successfully
completed at the DDP layer.
15. RDMA Operations MUST be Completed at the Local Peer in the order
that they were submitted by the ULP.
Recio, et al. Standards Track [Page 40]
RFC 5040 RDMA Protocol Specification October 2007
16. At the Data Sink, an incoming Send Message MUST be Delivered to
the ULP only after the DDP Message has been Delivered to the
RDMAP layer by the DDP layer.
17. RDMA Read Response Message processing at the Remote Peer (reading
the specified Tagged Buffer) MUST be started only after the RDMA
Read Request Message has been Delivered by the DDP layer (thus,
all previous RDMA Messages have been properly submitted for
ordered Placement).
18. Send Messages MAY be Completed at the Remote Peer (Data Sink)
before prior incoming RDMA Read Request Messages have completed
their response processing.
19. An RDMA Read operation MUST NOT be Completed at the Local Peer
until the DDP layer Delivers the associated incoming RDMA Read
Response Message.
20. If more than one outstanding RDMA Read Request Messages are
supported by both peers, the RDMA Read Response Messages MUST be
submitted to the DDP layer on the Remote Peer in the order the
RDMA Read Request Messages were Delivered by DDP, but the actual
read of the buffer contents MAY take place in any order at the
Remote Peer.
This simplifies Local Peer Completion processing for RDMA Reads
in that a Delivered RDMA Read Response MUST be sufficient to
Complete the RDMA Read operation.
6. RDMAP Stream Management
RDMAP Stream management consists of RDMAP Stream Initialization and
RDMAP Stream Termination.
6.1. Stream Initialization
RDMAP Stream initialization occurs after the LLP Stream has been
created (e.g., for DDP/MPA over TCP, the first TCP Segment after the
SYN, SYN/ACK exchange). The ULP is responsible for transitioning the
LLP Stream into RDMA-enabled mode. The switch to RDMA mode typically
occurs sometime after LLP Stream setup. Once in RDMA enabled mode,
an implementation MUST send only RDMA Messages across the transport
Stream until the RDMAP Stream is torn down.
For each direction of an RDMAP Stream:
* For a given RDMAP Stream, the number of outstanding RDMA Read
Requests is limited per RDMAP Stream direction.
Recio, et al. Standards Track [Page 41]
RFC 5040 RDMA Protocol Specification October 2007
* It is the ULP's responsibility to set the maximum number of
outstanding, inbound RDMA Read Requests per RDMAP Stream
direction.
* The RDMAP layer MUST provide the maximum number of outstanding,
inbound RDMA Read Requests per RDMAP Stream direction that were
negotiated between the ULP and the Local Peer's RDMAP layer. The
negotiation mechanism is outside the scope of this specification.
* It is the ULP's responsibility to set the maximum number of
outstanding, outbound RDMA Read Requests per RDMAP Stream
direction.
* The RDMAP layer MUST provide the maximum number of outstanding,
outbound RDMA Read Requests for the RDMAP Stream direction that
were negotiated between the ULP and the Local Peer's RDMAP layer.
The negotiation mechanism is outside the scope of this
specification.
* The Local Peer's ULP is responsible for negotiating with the
Remote Peer's ULP the maximum number of outstanding RDMA Read
Requests for the RDMAP Stream direction. It is recommended that
the ULP set the maximum number of outstanding, inbound RDMA Read
Requests equal to the maximum number of outstanding, outbound RDMA
Read Requests for a given RDMAP Stream direction.
* For outbound RDMA Read Requests, the RDMAP layer MUST NOT exceed
the maximum number of outstanding, outbound RDMA Read Requests
that were negotiated between the ULP and the Local Peer's RDMAP
layer.
* For inbound RDMA Read Requests, the RDMAP layer MUST NOT exceed
the maximum number of outstanding, inbound RDMA Read Requests that
were negotiated between the ULP and the Local Peer's RDMAP layer.
6.2. Stream Teardown
There are three methods for terminating an RDMAP Stream: ULP Graceful
Termination, RDMAP Abortive Termination, and LLP Abortive
Termination.
The ULP is responsible for performing ULP Graceful Termination.
After a ULP Graceful Termination, either side of the Stream can
initiate LLP Graceful Termination, using the graceful termination
mechanism provided by the LLP.
Recio, et al. Standards Track [Page 42]
RFC 5040 RDMA Protocol Specification October 2007
RDMAP Abortive Termination allows the RDMAP to issue a Terminate
Message describing the reason the RDMAP Stream was terminated. The
next section (6.2.1, "RDMAP Abortive Termination") describes the
RDMAP Abortive Termination in detail.
LLP Abortive Termination results due to an LLP error and causes the
RDMAP Stream to be torn down midstream, without an RDMAP Terminate
Message. While this last method is highly undesirable, it is
possible, and the ULP should take this into consideration.
6.2.1. RDMAP Abortive Termination
RDMAP defines a Terminate operation that SHOULD be invoked when
either an RDMAP error is encountered or an LLP error is surfaced to
the RDMAP layer by the LLP.
It is not always possible to send the Terminate Message. For
example, certain LLP errors may occur that cause the LLP Stream to be
torn down a) before RDMAP is aware of the error, b) before RDMAP is
able to send the Terminate Message, or c) after RDMAP has posted the
Terminate Message to the LLP, but it has not yet been transmitted by
the LLP.
Note that an RDMAP Abortive Termination may entail loss of data. In
general, when a Terminate Message is received, it is impossible to
tell for sure what unacknowledged RDMA Messages were Completed
successfully at the Remote Peer. Thus, the state of all outstanding
RDMA Messages is indeterminate, and the Messages SHOULD be considered
Completed in error.
When a peer sends or receives a Terminate Message, it MAY immediately
tear down the LLP Stream. The peer SHOULD perform a graceful LLP
teardown to ensure the Terminate Message is successfully Delivered.
See Section 4.8, "Terminate Header", for a description of the
Terminate Message and its contents. See Section 5.4, "Terminate
Message", for a description of the Terminate Message semantics.
7. RDMAP Error Management
The RDMAP protocol does not have RDMAP- or DDP-layer error recovery
operations built in. If everything is working, the LLP guarantees
will ensure that the Messages are arriving at the destination.
If errors are detected at the RDMAP or DDP layer, then the RDMAP,
DDP, and LLP Streams are Abortively Terminated (see Section 4.8,
"Terminate Header").
Recio, et al. Standards Track [Page 43]
RFC 5040 RDMA Protocol Specification October 2007
In general, poor implementations or improper ULP programming cause
the errors detected at the RDMAP and DDP layers. In these cases,
returning a diagnostic termination error Message and closing the
RDMAP Stream is far simpler than attempting to maintain the RDMAP
Stream, particularly when the cause of the error is not known.
If an LLP does not support teardown of a Stream independent of other
Streams, and an RDMAP error results in the Termination of a specific
Stream, then the LLP MUST label the Stream as an erroneous Stream and
MUST NOT allow any further data transfer on that Stream after RDMAP
requests the Stream to be torn down.
For a specific LLP connection, when all Streams are either gracefully
torn down or are labeled as erroneous Streams, the LLP connection
MUST be torn down.
Since errors are detected at the Remote Peer (possibly long) after
RDMA Messages are passed to the DDP and the LLP at the Local Peer and
after the RDMA Operations conveyed by the Messages are Completed, the
sender cannot easily determine which of its Messages have been
received. (RDMA Reads are an exception to this rule.)
For a list of errors returned to the Remote Peer as a result of an
Abortive Termination, see Section 4.8, "Terminate Header".
7.1. RDMAP Error Surfacing
If an error occurs at the Local Peer, the RDMAP layer MUST attempt to
inform the local ULP that the error has occurred.
The Local Peer MUST send a Terminate Message for each of the
following cases:
1. For errors detected while creating RDMA Write, Send, Send with
Invalidate, Send with Solicited Event, Send with Solicited Event
and Invalidate, or RDMA Read Requests, or other reasons not
directly associated with an incoming Message, the Terminate
Message and Error code are sent instead of the request. In this
case, the Error Type and Error Code fields are included in the
Terminate Message, but the Terminated DDP Header and Terminated
RDMA Header fields are set to zero.
2. For errors detected on an incoming RDMA Write, Send, Send with
Invalidate, Send with Solicited Event, Send with Solicited Event
and Invalidate, or Read Response Message (after the Message has
been Delivered by DDP), the Terminate Message is sent at the
earliest possible opportunity, preferably in the next outgoing
RDMA Message. In this case, the Error Type, Error Code, ULP PDU
Recio, et al. Standards Track [Page 44]
RFC 5040 RDMA Protocol Specification October 2007
Length, and Terminated DDP Header fields are included in the
Terminate Message, but the Terminated RDMA Header field is set to
zero.
3. For errors detected on an incoming RDMA Read Request Message
(after the Message has been Delivered by DDP), the Terminate
Message is sent at the earliest possible opportunity, preferably
in the next outgoing RDMA Message. In this case, the Error Type,
Error Code, ULP PDU Length, Terminated DDP Header, and Terminated
RDMA Header fields are included in the Terminate Message.
4. If more than one error is detected on incoming RDMA Messages,
before the Terminate Message can be sent, then the first RDMA
Message (and its associated DDP Segment) that experienced an
error MUST be captured by the Terminate Message, in accordance
with rules 2 and 3 above.
7.2. Errors Detected at the Remote Peer on Incoming RDMA Messages
On incoming RDMA Writes, RDMA Read Response, Sends, Send with
Invalidate, Send with Solicited Event, Send with Solicited Event and
Invalidate, and Terminate Messages, the following must be validated:
1. The DDP layer MUST validate all DDP Segment fields.
2. The RDMA OpCode MUST be valid.
3. The RDMA Version MUST be valid.
Additionally, on incoming Send with Invalidate and Send with
Solicited Event and Invalidate Messages, the following must also
be validated:
4. The Invalidate STag MUST be valid.
5. The STag MUST be associated to this RDMAP Stream.
On incoming RDMA Request Messages, the following must be validated:
1. The DDP layer MUST validate all Untagged DDP Segment fields.
2. The RDMA OpCode MUST be valid.
3. The RDMA Version MUST be valid.
4. For non-zero length RDMA Read Request Messages:
a. The Data Source STag MUST be valid.
Recio, et al. Standards Track [Page 45]
RFC 5040 RDMA Protocol Specification October 2007
b. The Data Source STag MUST be associated to this RDMAP Stream.
c. The Data Source Tagged Offset MUST fall in the range of legal
offsets associated with the Data Source STag.
d. The sum of the Data Source Tagged Offset and the RDMA Read
Message Size MUST fall in the range of legal offsets
associated with the Data Source STag.
e. The sum of the Data Source Tagged Offset and the RDMA Read
Message Size MUST NOT cause the Data Source Tagged Offset to
wrap.
8. Security Considerations
This section references the resources that discuss protocol- specific
security considerations and implications of using RDMAP with existing
security services. A detailed analysis of the security issues around
implementation and use of the RDMAP can be found in [RDMASEC].
[RDMASEC] introduces the RDMA reference model and discusses how the
resources of this model are vulnerable to attacks and the types of
attack these vulnerabilities are subject to. It also details the
levels of Trust available in this peer-to-peer model and how this
defines the nature of resource sharing.
The IPsec requirements for RDDP are based on the version of IPsec
specified in RFC 2401 [RFC2401] and related RFCs, as profiled by RFC
3723 [RFC3723], despite the existence of a newer version of IPsec
specified in RFC 4301 [RFC4301] and related RFCs [RFC4303],
[RFC4306], [RFC4835]. One of the important early applications of the
RDDP protocols is their use with iSCSI [iSER]; RDDP's IPsec
requirements follow those of IPsec in order to facilitate that usage
by allowing a common profile of IPsec to be used with iSCSI and the
RDDP protocols. In the future, RFC 3723 may be updated to the newer
version of IPsec, and the IPsec security requirements of any such
update should apply uniformly to iSCSI and the RDDP protocols.
8.1. Summary of RDMAP-Specific Security Requirements
[RDMASEC] defines the security requirements for the implementation of
the components of the RDMA reference model, namely the RDMA enabled
NIC (RNIC) and the Privileged Resource Manager. An RDMAP
implementation conforming to this specification MUST conform to these
requirements.
Recio, et al. Standards Track [Page 46]
RFC 5040 RDMA Protocol Specification October 2007
8.1.1. RDMAP (RNIC) Requirements
RDMAP provides several countermeasures for all types of attacks as
introduced in [RDMASEC]. In the following, this specification lists
all security requirements that MUST be implemented by the RNIC. A
more detailed discussion of RNIC security requirements can be found
in Section 5 of [RDMASEC].
1. An RNIC MUST ensure that a specific Stream in a specific
Protection Domain cannot access an STag in a different Protection
Domain.
2. An RNIC MUST ensure that if an STag is limited in scope to a
single Stream, no other Stream can use the STag.
3. An RNIC MUST ensure that a Remote Peer is not able to access
memory outside of the buffer specified when the STag was enabled
for remote access.
4. An RNIC MUST provide a mechanism for the ULP to establish and
revoke the association of a ULP Buffer to an STag and TO range.
5. An RNIC MUST provide a mechanism for the ULP to establish and
revoke read, write, or read and write access to the ULP Buffer
referenced by an STag.
6. An RNIC MUST ensure that the network interface can no longer
modify an Advertised Buffer after the ULP revokes remote access
rights for an STag.
7. An RNIC MUST ensure that a Remote Peer is not able to invalidate
an STag enabled for remote access, if the STag is shared on
multiple streams.
8. An RNIC MUST choose the value of STags in a way difficult to
predict. It is RECOMMENDED to sparsely populate them over the
full available range.
9. An RNIC MUST NOT enable sharing a Completion Queue (CQ) across
ULPs that do not share partial mutual trust.
10. An RNIC MUST ensure that if a CQ overflows, any Streams that do
not use the CQ MUST remain unaffected.
11. An RNIC implementation SHOULD provide a mechanism to cap the
number of outstanding RDMA Read Requests.
Recio, et al. Standards Track [Page 47]
RFC 5040 RDMA Protocol Specification October 2007
12. An RNIC MUST NOT enable firmware to be loaded on the RNIC
directly from an untrusted Local Peer or Remote Peer, unless the
Peer is properly authenticated*, and the update is done via a
secure protocol, such as IPsec.
* by a mechanism outside the scope of this specification. The
mechanism presumably entails authenticating that the remote ULP
has the right to perform the update.
8.1.2. Privileged Resource Manager Requirements
With RDMAP, all reservations of local resources are initiated from
local ULPs. To protect from local attacks including unfair resource
distribution and gaining unauthorized access to RNIC resources, a
Privileged Resource Manager (PRM) must be implemented, which manages
all local resource allocation. Note that the PRM must not be
provided as an independent component, and its functionality can also
be implemented as part of the privileged ULP or as part of the RNIC
itself.
A PRM implementation must meet the following security requirements (a
more detailed discussion of PRM security requirements can be found in
Section 5 of [RDMASEC]):
1. All Non-Privileged ULP interactions with the RNIC Engine that
could affect other ULPs MUST be done using the Resource Manager
as a proxy.
2. All ULP resource allocation requests for scarce resources MUST
also be done using a Privileged Resource Manager.
3. The Privileged Resource Manager MUST NOT assume that different
ULPs share Partial Mutual Trust unless there is a mechanism to
ensure that the ULPs do indeed share partial mutual trust.
4. If Non-Privileged ULPs are supported, the Privileged Resource
Manager MUST verify that the Non-Privileged ULP has the right to
access a specific Data Buffer before allowing an STag for which
the ULP has access rights to be associated with a specific Data
Buffer.
5. The Privileged Resource Manager MUST control the allocation of CQ
entries.
6. The Privileged Resource Manager SHOULD prevent a Local Peer from
allocating more than its fair share of resources.
Recio, et al. Standards Track [Page 48]
RFC 5040 RDMA Protocol Specification October 2007
7. RDMA Read Request Queue resource consumption MUST be controlled
by the Privileged Resource Manager such that RDMAP/DDP Streams
that do not share Partial Mutual Trust do not share RDMA Read
Request Queue resources.
8. If an RNIC provides the ability to share receive buffers across
multiple Streams, the combination of the RNIC and the Privileged
Resource Manager MUST be able to detect if the Remote Peer is
attempting to consume more than its fair share of resources so
that the Local Peer can apply countermeasures to detect and
prevent the attack.
8.2. Security Services for RDMAP
RDMAP is using IP-based network services to control, read, and write
data buffers over the network. Therefore, all exchanged control and
data packets are vulnerable to spoofing, tampering, and information
disclosure attacks.
RDMAP Streams that are subject to impersonation attacks or Stream
hijacking attacks can be authenticated, have their integrity
protected, and be protected from replay attacks. Furthermore,
confidentiality protection can be used to protect from eavesdropping.
8.2.1. Available Security Services
The IPsec protocol suite [RFC2401] defines strong countermeasures to
protect an IP stream from those attacks. Several levels of
protection can guarantee session confidentiality, per-packet source
authentication, per-packet integrity, and correct packet sequencing.
RDMAP security may also profit from SSL or TLS security services
provided for TCP-based ULPs [RFC4346]. Used underneath RDMAP, these
security services also provide for stream authentication, data
integrity, and confidentiality. As discussed in [RDMASEC],
limitations on the maximum packet length to be carried over the
network and potentially inefficient out-of-order packet processing at
the data sink make SSL and TLS less appropriate for RDMAP than IPsec.
If SSL is layered on top of RDMAP, SSL does not protect the RDMAP
headers. Thus, a man-in-the-middle attack can still occur by
modifying the RDMAP header to incorrectly place the data into the
wrong buffer, thus effectively corrupting the data stream.
By remaining independent of ULP and LLP security protocols, RDMAP
will benefit from continuing improvements at those layers. Users are
provided flexibility to adapt to their specific security requirements
and the ability to adapt to future security challenges. Given this,
Recio, et al. Standards Track [Page 49]
RFC 5040 RDMA Protocol Specification October 2007
the vulnerabilities of RDMAP to active third-party interference are
no greater than any other protocol running over an LLP such as TCP or
SCTP.
8.2.2. Requirements for IPsec Services for RDMAP
Because IPsec is designed to secure arbitrary IP packet streams,
including streams where packets are lost, RDMAP can run on top of
IPsec without any change. IPsec packets are processed (e.g.,
integrity checked and possibly decrypted) in the order they are
received, and an RDMAP Data Sink will process the decrypted RDMA
Messages contained in these packets in the same manner as RDMA
Messages contained in unsecured IP packets.
The IP Storage working group has defined the normative IPsec
requirements for IP Storage [RFC3723]. Portions of this
specification are applicable to the RDMAP. In particular, a
compliant implementation of IPsec services for RDMAP MUST meet the
requirements as outlined in Section 2.3 of [RFC3723]. Without
replicating the detailed discussion in [RFC3723], this includes the
following requirements:
1. The implementation MUST support IPsec ESP [RFC2406], as well as
the replay protection mechanisms of IPsec. When ESP is utilized,
per-packet data origin authentication, integrity, and replay
protection MUST be used.
2. It MUST support ESP in tunnel mode and MAY implement ESP in
transport mode.
3. It MUST support IKE [RFC2409] for peer authentication,
negotiation of security associations, and key management, using
the IPsec DOI [RFC2407].
4. It MUST NOT interpret the receipt of a IKE Phase 2 delete message
as a reason for tearing down the RDMAP stream. Since IPsec
acceleration hardware may only be able to handle a limited number
of active IKE Phase 2 SAs, idle SAs may be dynamically brought
down, and a new SA be brought up again, if activity resumes.
5. It MUST support peer authentication using a pre-shared key, and
MAY support certificate-based peer authentication using digital
signatures. Peer authentication using the public key encryption
methods [RFC2409] SHOULD NOT be used.
Recio, et al. Standards Track [Page 50]
RFC 5040 RDMA Protocol Specification October 2007
6. It MUST support IKE Main Mode and SHOULD support Aggressive Mode.
IKE Main Mode with pre-shared key authentication SHOULD NOT be
used when either of the peers uses a dynamically assigned IP
address.
7. When digital signatures are used to achieve authentication,
either IKE Main Mode or IKE Aggressive Mode MAY be used. In
these cases, an IKE negotiator SHOULD use IKE Certificate Request
Payload(s) to specify the certificate authority (or authorities)
that are trusted in accordance with its local policy. IKE
negotiators SHOULD check the pertinent Certificate Revocation
List (CRL) before accepting a PKI certificate for use in IKE's
authentication procedures.
8. Access to locally stored secret information (pre-shared or
private key for digital signing) must be suitably restricted,
since compromise of the secret information nullifies the security
properties of the IKE/IPsec protocols.
9. It MUST follow the guidelines of Section 2.3.4 of [RFC3723] on
the setting of IKE parameters to achieve a high level of
interoperability without requiring extensive configuration.
Furthermore, implementation and deployment of the IPsec services for
RDDP should follow the Security Considerations outlined in Section 5
of [RFC3723].
9. IANA Considerations
This document requests no direct action from IANA. The following
consideration is listed here as commentary.
If RDMAP was enabled a priori for a ULP by connecting to a well-known
port, this well-known port would be registered for the RDMAP with
IANA. The registration of the well-known port will be the
responsibility of the ULP specification.
Recio, et al. Standards Track [Page 51]
RFC 5040 RDMA Protocol Specification October 2007
10. References
10.1. Normative References
[DDP] Shah, H., Pinkerton, J., Recio, R., and P. Culley, "Direct
Data Placement over Reliable Transports", RFC 5041, October
2007.
[iSER] Ko, M., Chadalapaka, M., Hufferd, J., Elzur, U., Shah, H.,
and P. Thaler, "Internet Small Computer System Interface
(iSCSI) Extensions for Remote Direct Memory Access (RDMA)"
RFC 5046, October 2007.
[MPA] Culley, P., Elzur, U., Recio, R., Bailey, S., and J.
Carrier, "Marker PDU Aligned Framing for TCP
Specification", RFC 5044, October 2007.
[RDMASEC] Pinkerton, J. and E. Deleganes, "Direct Data Placement
Protocol (DDP) / Remote Direct Memory Access Protocol
(RDMAP) Security", RFC 5042, October 2007.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2406] Kent, S. and R. Atkinson, "IP Encapsulating Security
Payload (ESP)", RFC 2406, November 1998.
[RFC2407] Piper, D., "The Internet IP Security Domain of
Interpretation of ISAKMP", RFC 2407, November 1998.
[RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange
(IKE)", RFC 2409, November 1998.
[RFC3723] Aboba, B., Tseng, J., Walker, J., Rangan, V., and F.
Travostino, "Securing Block Storage Protocols over IP", RFC
3723, April 2004.
[RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the
Internet Protocol", RFC 2401, November 1998.
[SCTP] Stewart, R., Ed., "Stream Control Transmission Protocol",
RFC 4960, September 2007.
[TCP] Postel, J., "Transmission Control Protocol", STD 7, RFC
793, September 1981.
Recio, et al. Standards Track [Page 52]
RFC 5040 RDMA Protocol Specification October 2007
10.2. Informative References
[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.
[RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", RFC
4306, December 2005.
[RFC4346] Dierks, T. and E. Rescorla, "The TLS Protocol Version 1.1",
RFC 4346, April 2006.
[RFC4835] Manral, V., "Cryptographic Algorithm Implementation
Requirements for Encapsulating Security Payload (ESP) and
Authentication Header (AH)", RFC 4835, April 2007.
Recio, et al. Standards Track [Page 53]
RFC 5040 RDMA Protocol Specification October 2007
Appendix A. DDP Segment Formats for RDMA Messages
This appendix is for information only and is NOT part of the
standard. It simply depicts the DDP Segment format for the various
RDMA Messages.
A.1. DDP Segment for RDMA Write
The following figure depicts an RDMA Write, DDP Segment:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP Control | RDMA Control |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Sink STag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Sink Tagged Offset |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RDMA Write ULP Payload |
// //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11: RDMA Write, DDP Segment Format
Recio, et al. Standards Track [Page 54]
RFC 5040 RDMA Protocol Specification October 2007
A.2. DDP Segment for RDMA Read Request
The following figure depicts an RDMA Read Request, DDP Segment:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP Control | RDMA Control |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved (Not Used) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP (RDMA Read Request) Queue Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP (RDMA Read Request) Message Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP (RDMA Read Request) Message Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Sink STag (SinkSTag) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Data Sink Tagged Offset (SinkTO) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RDMA Read Message Size (RDMARDSZ) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Source STag (SrcSTag) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Data Source Tagged Offset (SrcTO) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12: RDMA Read Request, DDP Segment format
Recio, et al. Standards Track [Page 55]
RFC 5040 RDMA Protocol Specification October 2007
A.3. DDP Segment for RDMA Read Response
The following figure depicts an RDMA Read Response, DDP Segment:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP Control | RDMA Control |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Sink STag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Sink Tagged Offset |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RDMA Read Response ULP Payload |
// //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 13: RDMA Read Response, DDP Segment Format
A.4. DDP Segment for Send and Send with Solicited Event
The following figure depicts a Send and Send with Solicited
Request, DDP Segment:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP Control | RDMA Control |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved (Not Used) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Send) Queue Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Send) Message Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Send) Message Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Send ULP Payload |
// //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 14: Send and Send with Solicited Event, DDP Segment Format
Recio, et al. Standards Track [Page 56]
RFC 5040 RDMA Protocol Specification October 2007
A.5. DDP Segment for Send with Invalidate and Send with SE and
Invalidate
The following figure depicts a Send with Invalidate and Send with
Solicited and Invalidate Request, DDP Segment:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP Control | RDMA Control |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Invalidate STag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Send) Queue Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Send) Message Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Send) Message Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Send ULP Payload |
// //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 15: Send with Invalidate and Send with SE and Invalidate,
DDP Segment Format
Recio, et al. Standards Track [Page 57]
RFC 5040 RDMA Protocol Specification October 2007
A.6. DDP Segment for Terminate
The following figure depicts a Terminate, DDP Segment:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP Control | RDMA Control |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved (Not Used) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP (Terminate) Queue Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP (Terminate) Message Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP (Terminate) Message Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Terminate Control | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP Segment Length (if any) | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
+ +
| Terminated DDP Header (if any) |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// //
| Terminated RDMA Header (if any) |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 16: Terminate, DDP Segment Format
Recio, et al. Standards Track [Page 58]
RFC 5040 RDMA Protocol Specification October 2007
Appendix B. Ordering and Completion Table
The following table summarizes the ordering relationships that are
defined in Section 5.5, "Ordering and Completions", from the
standpoint of the local peer issuing the two Operations. Note that
in the table that follows, Send includes Send, Send with Invalidate,
Send with Solicited Event, and Send with Solicited Event and
Invalidate.
------+-------+----------------+----------------+----------------
First | Later | Placement | Placement | Ordering
Op | Op | guarantee at | guarantee at | guarantee at
| | Remote Peer | Local Peer | Remote Peer
| | | |
------+-------+----------------+----------------+----------------
Send | Send | No placement | Not applicable | Completed in
| | guarantee. If | | order.
| | guarantee is | |
| | necessary, see | |
| | footnote 1. | |
------+-------+----------------+----------------+----------------
Send | RDMA | No placement | Not applicable | Not applicable
| Write | guarantee. If | |
| | guarantee is | |
| | necessary, see | |
| | footnote 1. | |
------+-------+----------------+----------------+----------------
Send | RDMA | No placement | RDMA Read | RDMA Read
| Read | guarantee | Response | Response
| | between Send | Payload will | Message will
| | Payload and | not be placed | not be
| | RDMA Read | at the local | generated until
| | Request Header | peer until the | Send has been
| | | Send Payload is| Completed
| | | placed at the |
| | | Remote Peer |
------+-------+----------------+----------------+----------------
RDMA | Send | No placement | Not applicable | Not applicable
Write | | guarantee. If | |
| | guarantee is | |
| | necessary, see | |
| | footnote 1. | |
Recio, et al. Standards Track [Page 59]
RFC 5040 RDMA Protocol Specification October 2007
------+-------+----------------+----------------+----------------
RDMA | RDMA | No placement | Not applicable | Not applicable
Write | Write | guarantee. If | |
| | guarantee is | |
| | necessary, see | |
| | footnote 1. | |
------+-------+----------------+----------------+----------------
RDMA | RDMA | No placement | RDMA Read | Not applicable
Write | Read | guarantee | Response |
| | between RDMA | Payload will |
| | Write Payload | not be placed |
| | and RDMA Read | at the local |
| | Request Header | peer until the |
| | | RDMA Write |
| | | Payload is |
| | | placed at the |
| | | Remote Peer |
------+-------+----------------+----------------+----------------
RDMA | Send | No placement | Send Payload | Not applicable
Read | | guarantee | may be placed |
| | between RDMA | at the remote |
| | Read Request | peer before the|
| | Header and Send| RDMA Read |
| | payload | Response is |
| | | generated. |
| | | If guarantee is|
| | | necessary, see |
| | | footnote 2. |
------+-------+----------------+----------------+----------------
RDMA | RDMA | No placement | RDMA Write | Not applicable
Read | Write | guarantee | Payload may be |
| | between RDMA | placed at the |
| | Read Request | Remote Peer |
| | Header and RDMA| before the RDMA|
| | Write payload | Read Response |
| | | is generated. |
| | | If guarantee is|
| | | necessary, see |
| | | footnote 2. |
Recio, et al. Standards Track [Page 60]
RFC 5040 RDMA Protocol Specification October 2007
------+-------+----------------+----------------+----------------
RDMA | RDMA | No placement | No placement | Second RDMA
Read | Read | guarantee of | guarantee of | Read Response
| | the two RDMA | the two RDMA | will not be
| | Read Request | Read Response | generated until
| | Headers | Payloads. | first RDMA Read
| | Additionally, | | Response is
| | there is no | | generated.
| | guarantee that | |
| | the Tagged | |
| | Buffers | |
| | referenced in | |
| | the RDMA Read | |
| | will be read in| |
| | order | |
Figure 17: Operation Ordering
Footnote 1: If the guarantee is necessary, a ULP may insert an RDMA
Read operation and wait for it to complete to act as a Fence.
Footnote 2: If the guarantee is necessary, a ULP may wait for the
RDMA Read operation to complete before performing the Send.
Appendix C. Contributors
Dwight Barron
Hewlett-Packard Company
20555 SH 249
Houston, TX 77070-2698 USA
Phone: 281-514-2769
EMail: dwight.barron@hp.com
Caitlin Bestler
Broadcom Corporation
16215 Alton Parkway
Irvine, CA 92619-7013 USA
Phone: 949-926-6383
EMail: caitlinb@broadcom.com
John Carrier
Cray, Inc.
411 First Avenue S, Suite 600
Seattle, WA 98104-2860 USA
Phone: 206-701-2090
EMail: carrier@cray.com
Recio, et al. Standards Track [Page 61]
RFC 5040 RDMA Protocol Specification October 2007
Ted Compton
EMC Corporation
Research Triangle Park, NC 27709 USA
Phone: 919-248-6075
EMail: compton_ted@emc.com
Uri Elzur
Broadcom Corporation
16215 Alton Parkway
Irvine, California 92619-7013 USA
Phone: +1 (949) 585-6432
EMail: Uri@Broadcom.com
Hari Ghadia
Gen10 Technology, Inc.
1501 W Shady Grove Road
Grand Prairie, TX 75050
Phone: (972) 301 3630
EMail: hghadia@gen10technology.com
Howard C. Herbert
Intel Corporation
MS CH7-404
5000 West Chandler Blvd.
Chandler, Arizona 85226
Phone: 480-554-3116
EMail: howard.c.herbert@intel.com
Mike Ko
IBM
650 Harry Rd.
San Jose, CA 95120
Phone: (408) 927-2085
EMail: mako@us.ibm.com
Mike Krause
Hewlett-Packard Company
43LN
19410 Homestead Road
Cupertino, CA 95014 USA
Phone: 408-447-3191
EMail: krause@cup.hp.com
Recio, et al. Standards Track [Page 62]
RFC 5040 RDMA Protocol Specification October 2007
Dave Minturn
Intel Corporation
MS JF1-210
5200 North East Elam Young Parkway
Hillsboro, Oregon 97124
Phone: 503-712-4106
EMail: dave.b.minturn@intel.com
Mike Penna
Broadcom Corporation
16215 Alton Parkway
Irvine, California 92619-7013 USA
Phone: +1 (949) 926-7149
EMail: MPenna@Broadcom.com
Jim Pinkerton
Microsoft, Inc.
One Microsoft Way
Redmond, WA 98052 USA
EMail: jpink@microsoft.com
Hemal Shah
Broadcom Corporation
5300 California Avenue
Irvine, CA 92617 USA
Phone: +1 (949) 926-6941
EMail: hemal@broadcom.com
Allyn Romanow
Cisco Systems
170 W Tasman Drive
San Jose, CA 95134 USA
Phone: +1 408 525 8836
EMail: allyn@cisco.com
Tom Talpey
Network Appliance
1601 Trapelo Road #16
Waltham, MA 02451 USA
Phone: +1 (781) 768-5329
EMail: thomas.talpey@netapp.com
Recio, et al. Standards Track [Page 63]
RFC 5040 RDMA Protocol Specification October 2007
Patricia Thaler
Broadcom Corporation
16215 Alton Parkway
Irvine, CA 92619-7013 USA
Phone: +1-916-570-2707
EMail: pthaler@broadcom.com
Jim Wendt
Hewlett-Packard Company
8000 Foothills Boulevard MS 5668
Roseville, CA 95747-5668 USA
Phone: +1 916 785 5198
EMail: jim_wendt@hp.com
Madeline Vega
IBM
11400 Burnet Rd. Bld.45-2L-007
Austin, TX 78758 USA
Phone: 512-838-7739
EMail: mvega1@us.ibm.com
Claudia Salzberg
IBM
11501 Burnet Rd. Bld.902-5B-014
Austin, TX 78758 USA
Phone: 512-838-5156
EMail: salzberg@us.ibm.com
Recio, et al. Standards Track [Page 64]
RFC 5040 RDMA Protocol Specification October 2007
Authors' Addresses
Renato J. Recio
IBM Corp.
11501 Burnett Road
Austin, TX 78758 USA
Phone: 512-838-3685
EMail: recio@us.ibm.com
Bernard Metzler
IBM Research GmbH
Zurich Research Laboratory
Saeumerstrasse 4
CH-8803 Rueschlikon, Switzerland
Phone: +41 44 724 8605
EMail: bmt@zurich.ibm.com
Paul R. Culley
Hewlett-Packard Company
20555 SH 249
Houston, TX 77070-2698 USA
Phone: 281-514-5543
EMail: paul.culley@hp.com
Jeff Hilland
Hewlett-Packard Company
20555 SH 249
Houston, TX 77070-2698 USA
Phone: 281-514-9489
EMail: jeff.hilland@hp.com
Dave Garcia
24100 Hutchinson Rd.
Los Gatos, CA 95033 USA
Phone: +1 (831) 247-4464
Email: Dave.Garcia@StanfordAlumni.org
Recio, et al. Standards Track [Page 65]
RFC 5040 RDMA Protocol Specification October 2007
Full Copyright Statement
Copyright (C) The IETF Trust (2007).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Recio, et al. Standards Track [Page 66]