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rfc:rfc5040

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

  1. ——+———–+——-+——+——-+———–+————–

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:
  1. ——+———–+——————-+————————-

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

  1. ——+———–+——-+————-+——+——————–

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

  1. ——+———–+——-+————-+——+——————–

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

  1. ——–+————-+————+————+—————–

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.
  1. —–+——-+—————-+—————-+—————-

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

  1. —–+——-+—————-+—————-+—————-

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

  1. —–+——-+—————-+—————-+—————-

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

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Recio, et al. Standards Track [Page 66]

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