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PROPOSED STANDARD

Internet Engineering Task Force (IETF)                           H. Shah
Request for Comments: 7306                          Broadcom Corporation
Category: Standards Track                                       F. Marti
ISSN: 2070-1721                                            W. Noureddine
                                                            A. Eiriksson
                                            Chelsio Communications, Inc.
                                                                R. Sharp
                                                       Intel Corporation
                                                               June 2014


         Remote Direct Memory Access (RDMA) Protocol Extensions

Abstract

   This document specifies extensions to the IETF Remote Direct Memory
   Access Protocol (RDMAP) as specified in RFC 5040.  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.  The extensions specified in this
   document provide the following capabilities and/or improvements:
   Atomic Operations and Immediate Data.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7306.















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Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.





































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Table of Contents

   1. Introduction ....................................................4
      1.1. Discovery of RDMAP Extensions ..............................5
   2. Requirements Language ...........................................5
   3. Glossary ........................................................6
   4. Header Format Extensions ........................................7
      4.1. RDMAP Control and Invalidate STag Fields ...................7
      4.2. RDMA Message Definitions ...................................9
   5. Atomic Operations ...............................................9
      5.1. Atomic Operation Details ..................................10
           5.1.1. FetchAdd ...........................................10
           5.1.2. CmpSwap ............................................12
      5.2. Atomic Operations .........................................13
           5.2.1. Atomic Operation Request Message ...................14
           5.2.2. Atomic Operation Response Message ..................17
      5.3. Atomicity Guarantees ......................................18
      5.4. Atomic Operations Ordering and Completion Rules ...........18
   6. Immediate Data .................................................20
      6.1. RDMAP Interactions with ULP for Immediate Data ............20
      6.2. Immediate Data Header Format ..............................21
      6.3. Immediate Data or Immediate Data with SE Message ..........21
      6.4. Ordering and Completions ..................................22
   7. Ordering and Completions Table .................................22
   8. Error Processing ...............................................25
      8.1. Errors Detected at the Local Peer .........................25
      8.2. Errors Detected at the Remote Peer ........................26
   9. Security Considerations ........................................26
   10. IANA Considerations ...........................................27
      10.1. RDMAP Message Atomic Operation Subcodes ..................27
      10.2. RDMAP Queue Numbers ......................................28
   11. References ....................................................29
      11.1. Normative References .....................................29
      11.2. Informative References ...................................29
   12. Acknowledgments ...............................................30
   Appendix A. DDP Segment Formats for RDMA Messages .................31
      A.1. DDP Segment for Atomic Operation Request ..................32
      A.2. DDP Segment for Atomic Response ...........................33
      A.3. DDP Segment for Immediate Data and Immediate Data with SE .33












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1.  Introduction

   The RDMA Protocol [RFC5040] provides capabilities for zero-copy data
   communications that preserve memory protection semantics, enabling
   more efficient network protocol implementations.  The RDMA Protocol
   is part of the iWARP family of specifications which also include RFC
   5041 [RFC5041], RFC 5044 [RFC5044], and RFC 6581 [RFC6581].  This
   document specifies the following extensions to the RDMA Protocol
   (RDMAP):

   o  Atomic Operations can be performed on remote memory locations.
      Support for Atomic Operations enhances the usability of RDMAP in
      distributed shared-memory environments.

   o  Immediate Data messages allow the ULP at the sender to provide a
      small amount of data.  When an Immediate Data message is sent
      following an RDMA Write Message, the combination of the two
      messages is an implementation of RDMA Write with Immediate message
      that is found in other RDMA transport protocols.

   Other RDMA transport protocols define the functionality added by
   these extensions leading to differences in RDMA applications and/or
   Upper-Layer Protocols.  Removing these differences in the transport
   protocols simplifies these applications and ULPs, and that is the
   main motivation for the extensions specified in this document.

   RSockets [RSOCKETS] is an example of RDMA-enabled middleware that
   provides a socket interface as the upper-edge interface and utilizes
   RDMA to provide more efficient networking for socket-based
   applications.  RSockets is aware of Immediate Data support in
   InfiniBand [IB].  RSockets cannot utilize the RDMA Write with
   Immediate Data operation from InfiniBand.  The addition of the
   Immediate Data operation specified in this document will alleviate
   this difference in RSockets when running on InfiniBand and iWARP.

   Structured high-performance computing applications based on the
   Message-Passing Interface [MPI] may use Atomic Operations defined in
   this specification.  DAT Atomics [DAT_ATOMICS] is an example of RDMA-
   enabled middleware that provides a portable RDMA programming
   interface for various RDMA transport protocols.  DAT Atomics includes
   a primitive for InfiniBand that is not supported by iWARP RDMA-
   enabled Network Interface Controllers or RNICs.  The addition of
   Atomic Operations as specified in this document will allow Atomic
   Operations in DAT Atomics to work for both InfiniBand and RNICs
   interchangeably.






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   For more background on RDMA Protocol applicability, see
   "Applicability of Remote Direct Memory Access Protocol (RDMA) and
   Direct Data Placement Protocol (DDP)" [RFC5045].

1.1.  Discovery of RDMAP Extensions

   Today there are RDMA applications and/or ULPs that are aware of the
   existence of Atomic and Immediate Data operations for RDMA transports
   such as InfiniBand and application programming interfaces such as
   Open Fabrics Verbs [OFAVERBS].  Today, these applications need to be
   aware that RDMAP does not support certain of these operations.
   Typically, the availability of these capabilities is exposed to the
   applications through adapter query interfaces in software.
   Applications then have to decide to use or not use Immediate Data or
   Atomic Operations based on the results of the query interfaces.  Such
   query interfaces typically return the scope of atomicity guarantees,
   not the individual Atomic Operations supported.  Therefore, this
   specification requires all Atomic Operations defined within to be
   supported if an RNIC supports any Atomic Operations.

   In cases where heterogeneous hardware, with differing support for
   Atomic Operations and Immediate Data Operations, is deployed for use
   by RDMA applications and/or ULPs, applications are either statically
   configured to use or not use optional features or use application-
   specific negotiation mechanisms.  For the extensions covered by this
   document, it is RECOMMENDED that RDMA applications and/or ULPs
   negotiate at the application or ULP level the usage of these
   extensions.  The definition of such application-specific mechanisms
   is outside the scope of this specification.  For backward
   compatibility, existing applications and/or ULPs should not assume
   that these extensions are supported.

   In the absence of application-specific negotiation of the features
   defined within this specification, the new operations can be
   attempted, and reported errors can be used to determine a remote
   peer's capabilities.  In the case of Atomics, a FetchAdd operation
   with "Add Data" set to 0 can safely be used to determine the
   existence of Atomic Operations without modifying the content of a
   remote peer's memory.  A Remote Operation Error or Unexpected OpCode
   error will be reported by the remote peer if there is an Immediate
   Data or Atomic Operation that is not supported by the remote peer.

2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].




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3.  Glossary

   This document is an extension of RFC 5040, and key words are defined
   in the glossary of that document.

   Atomic Operation - an operation that results in an execution of a
      memory operation at a specific ULP Buffer address on a remote node
      using the Tagged Buffer data transfer model.  The consumer can use
      Atomic Operations to read, modify, and write memory at the
      destination ULP Buffer address, while at the same time
      guaranteeing that no other Atomic Operation read or write accesses
      to the ULP Buffer address targeted by the Atomic Operation will
      occur across any other RDMAP Streams on an RNIC at the Responder.

   Atomic Operation Request - an RDMA Message used by the Data Source to
      perform an Atomic Operation at the Responder.

   Atomic Operation Response - an RDMA Message used by the Responder to
      describe the completion of an Atomic Operation at the Responder.

   CmpSwap - an Atomic Operation that is used to compare and swap a
      value at a specific address on a remote node.

   FetchAdd - an Atomic Operation that is used to atomically increment a
      value at a specific ULP Buffer address on a remote node.

   Immediate Data - a small fixed-size portion of data sent from the
      Data Source to a Data Sink.

   Immediate Data Message - an RDMA Message used by the Data Source to
      send Immediate Data to the Data Sink.

   Immediate Data with Solicited Event (SE) Message - an RDMA Message
      used by the Data Source to send Immediate Data with Solicited
      Event to the Data Sink.

   iWARP - a suite of wire protocols comprised of RFC 5040, RFC 5041,
      RFC 5044, and RFC 6581.

   Requester - the sender of an RDMA Atomic Operation request.

   Responder - the receiver of an RDMA Atomic Operation request.

   RNIC - RDMA-enabled Network Interface Controller.  In this context,
      this would be a network I/O adapter or embedded controller with
      iWARP functionality.





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   ULP - Upper-Layer Protocol.  The protocol layer above the one
      currently being referenced.  The ULP for RFC 5040 / RFC 5041 is
      expected to be an OS, Application, adaptation layer, or
      proprietary device.  The RFC 5040 / RFC 5041 documents do not
      specify a ULP -- they provide a set of semantics that allow a ULP
      to be designed to utilize RFC 5040 / RFC 5041.

4.  Header Format Extensions

   The control information of RDMA Messages is included in header fields
   defined in RFC 5041, the Direct Data Placement (DDP) protocol.  RFC
   5040 defines the RDMAP header formats layered on the DDP header
   definition.  This specification extends RFC 5040 with the following
   new formats:

   o  Four new RDMA Messages carry additional RDMAP headers.  The
      Immediate Data operation and Immediate Data with Solicited Event
      operation each include 8 bytes of data following the RDMAP header.
      Atomic Operations include Atomic Request or Atomic Response
      headers following the RDMAP header.  The RDMAP header for Atomic
      Request messages is 52 bytes long as specified in Figure 4.  The
      RDMAP header for Atomic Response Messages is 32 bytes long as
      specified in Figure 5.

   o  Introduction of a new queue for untagged Buffers (QN=3) used for
      Atomic Response tracking.

4.1.  RDMAP Control and Invalidate STag Fields

   For reference, Figure 1 depicts the format of the DDP Control and
   RDMAP Control Fields, in the style and convention of RFC 5040:

   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 1: DDP Control and RDMAP Control Fields

   The DDP Control Field consists of the T (Tagged), L (Last), Resrv,
   and DV (DDP protocol Version) fields [RFC5041].  The RDMAP Control
   Field consists of the RV (RDMA Version), Rsv, and Opcode fields
   [RFC5040].





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   This specification adds values for the RDMA Opcode field to those
   specified in RFC 5040.  Figure 2 defines the new values of the RDMA
   Opcode field that are used for the RDMA Messages defined in this
   specification.

   As shown in Figure 2, STag (Steering Tag) and Tagged Offset are not
   applicable for the RDMA Messages defined in this specification.
   Figure 2 also shows the appropriate Queue Number for each Opcode.

   All RDMA Messages defined in this specification MUST have:

   The RDMA Version (RV) field: 01b.

   Opcode field: Set to one of the values in Figure 2.

   Invalidate STag: Set to zero by the sender, ignored by the receiver.

   -------+-----------+-------+------+-------+---------+-------------
   RDMA   | Message   | Tagged| STag | Queue | In-     | Message
   Opcode | Type      | Flag  | and  | Number| validate| Length
          |           |       | TO   |       | STag    | Communicated
          |           |       |      |       |         | between DDP
          |           |       |      |       |         | and RDMAP
   -------+-----------+-------+------+-------+---------+-------------
   1000b  | Immediate | 0     | N/A  | 0     | N/A     | Yes
          | Data      |       |      |       |         |
   -------+-----------+----------------------------------------------
   1001b  | Immediate | 0     | N/A  | 0     | N/A     | Yes
          | Data with |       |      |       |         |
          | SE        |       |      |       |         |
   -------+-----------+----------------------------------------------
   1010b  | Atomic    | 0     | N/A  | 1     | N/A     | Yes
          | Request   |       |      |       |         |
   -------+-----------+----------------------------------------------
   1011b  | Atomic    | 0     | N/A  | 3     | N/A     | Yes
          | Response  |       |      |       |         |
   -------+-----------+----------------------------------------------

              Figure 2: Additional RDMA Usage of DDP Fields

   Note:  N/A means Not Applicable.

   This extension defines RDMAP use of Queue Number 3 for Untagged
   Buffers for Atomic Responses.  This queue is used for tracking
   outstanding Atomic Requests.

   All other DDP and RDMAP Control Fields are set as described in RFC
   5040.



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4.2.  RDMA Message Definitions

   The following figure defines which RDMA Headers are used on each new
   RDMA Message and which new RDMA Messages are allowed to carry ULP
   payload.

   -------+-----------+-------------------+-------------------------
   RDMA   | Message   | RDMA Header Used  | ULP Message allowed in
   Message| Type      |                   | the RDMA Message
   OpCode |           |                   |
          |           |                   |
   -------+-----------+-------------------+-------------------------
   1000b  | Immediate | Immediate Data    | No
          | Data      | Header            |
   -------+-----------+-------------------+-------------------------
   1001b  | Immediate | Immediate Data    | No
          | Data with | Header            |
          | SE        |                   |
   -------+-----------+-------------------+-------------------------
   1010b  | Atomic    | Atomic Request    | No
          | Request   | Header            |
   -------+-----------+-------------------+-------------------------
   1011b  | Atomic    | Atomic Response   | No
          | Response  | Header            |
   -------+-----------+-------------------+-------------------------

                     Figure 3: RDMA Message Definitions

5.  Atomic Operations

   The RDMA Protocol Specification in RFC 5040 does not include support
   for Atomic Operations, which are an important building block for
   implementing distributed shared memory.

   This document extends the RDMA Protocol specification with a set of
   basic Atomic Operations and specifies their resource and ordering
   rules.  The Atomic Operations specified in this document provide
   equivalent functionality to the InfiniBand RDMA transport as well as
   extended Atomic Operations defined in Open Fabrics Verbs, to allow
   applications that use these primitives to work interchangeably over
   iWARP.  Other operations are left for future consideration.

   Atomic Operations as specified in this document execute a 64-bit
   memory operation at a specified destination ULP Buffer address on a
   Responder node using the Tagged Buffer data transfer model.  The
   operations atomically read, modify, and write back the contents of
   the destination ULP Buffer address and guarantee that Atomic
   Operations on this ULP Buffer address by other RDMAP Streams on the



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   same RNIC do not occur between the read and the write caused by the
   Atomic Operation.  Therefore, the Responder RNIC MUST implement
   mechanisms to prevent Atomic Operations to a memory registered for
   Atomic Operations while an Atomic Operation targeting the memory is
   in progress.  The Requester of an Atomic Operation cannot rely on
   Atomic Operation behavior at the Responder across multiple RNICs or
   with respect to other applications/ULPs running at the Responder that
   can access the ULP Buffer.  It is OPTIONAL for an RNIC to provide
   such behavior when implementing the Atomic Operations specified in
   this document.  An RNIC that supports Atomic Operations as specified
   in this document MUST implement both the FetchAdd operation as
   specified in Section 5.1.1 and the CmpSwap operation as specified in
   Section 5.1.2.  The advertisement of Tagged Buffer information for
   Atomic Operations is outside the scope of this specification and is
   handled by the ULPs.

   Implementation note: It is RECOMMENDED that the applications do not
   use the ULP Buffer addresses used for Atomic Operations for other
   RDMA operations due to the lack of atomicity guarantees between
   operations other than Atomic Operations.

   Implementation note: Errors related to the alignment in the following
   sections cover Atomic Operations targeted at a ULP Buffer address
   that is not aligned to a 64-bit boundary.

   Atomic Operation Request Messages use the same remote addressing
   mechanism as RDMA Reads and Writes.  The ULP Buffer address specified
   in the request is in the address space of the Remote Peer to which
   the Atomic Operation is targeted.

   Atomic Operation Response Messages MUST use the Untagged Buffer model
   with QN=3.  Queue number 3 will be used to track outstanding Atomic
   Operation Request messages at the Requester.  When the Atomic
   Operation Response message is received, the Message Sequence Number
   (MSN) will be used to locate the corresponding Atomic Operation
   request in order to complete the Atomic Operation request.

5.1.  Atomic Operation Details

   The following subsections describe the Atomic Operations in more
   detail.

5.1.1.  FetchAdd

   The FetchAdd Atomic Operation requests the Responder to read a 64-bit
   Original Remote Data Value at a 64-bit aligned ULP Buffer address in
   the Responder's memory, perform the FetchAdd operation on multiple
   fields of selectable length specified by 64-bit "Add Mask", and write



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   the result back to the same ULP Buffer address.  The Atomic addition
   is performed independently on each one of these fields.  A bit set in
   the Add Mask field specifies the field boundary; for each field, a
   bit is set at the most significant bit position for each field,
   causing any carry out of that bit position to be discarded when the
   addition is performed.

   FetchAdd Atomic Operations MUST target ULP Buffer addresses that are
   64-bit aligned.  FetchAdd Atomic Operations that target ULP Buffer
   addresses that are not 64-bit aligned MUST be surfaced as errors, and
   the Responder's memory MUST NOT be modified in such cases.
   Additionally, an error MUST be surfaced and a terminate message MUST
   be generated.  The setting of the Add Mask field to
   0x0000000000000000 results in Atomic Add of 64-bit Original Remote
   Data Value and 64-bit "Add Data".

   The pseudocode below describes a masked FetchAdd Atomic Operation.

   bit_location = 1

   carry = 0

   Remote Data Value = 0

   for bit = 0 to 63

   {

      if (bit != 0 ) bit_location = bit_location << 1

      val1 = (Original Remote Data Value & bit_location) >> bit

      val2 = (Add Data & bit_location) >> bit
      sum = carry + val1 + val2

      carry = (sum & 2) >> 1

      sum = sum & 1

      if (sum)

         Remote Data Value |= bit_location

      carry = ((carry) && (!(Add Mask & bit_location)))

   }





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   The FetchAdd operation is performed in the endian format of the
   target memory.  The "Original Remote Data Value" is converted from
   the endian format of the target memory for return and returned to the
   Requester.  The fields are in big-endian format on the wire.

   The Requester specifies:

   o  Remote STag

   o  Remote Tagged Offset

   o  Add Data

   o  Add Mask

   The Responder returns:

   o  Original Remote Data

5.1.2.  CmpSwap

   The CmpSwap Atomic Operation requires the Responder to read a 64-bit
   value at a ULP Buffer address that is 64-bit aligned in the
   Responder's memory, to perform an AND logical operation using the
   64-bit Compare Mask field in the Atomic Operation Request header,
   then to compare it with the result of a logical AND operation of the
   Compare Mask and the Compare Data fields in the header.  If the two
   values are equal, the Responder is required to swap masked bits in
   the same ULP Buffer address with the masked Swap Data.  If the two
   masked compare values are not equal, the contents of the Responder's
   memory are not changed.  In either case, the original value read from
   the ULP Buffer address is converted from the endian format of the
   target memory for return and returned to the Requester.  The fields
   are in big-endian format on the wire.

   The Requester specifies:

   o  Remote STag

   o  Remote Tagged Offset

   o  Swap Data

   o  Swap Mask

   o  Compare Data

   o  Compare Mask



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   The Responder returns:

   o  Original Remote Data Value

   The following pseudocode describes the masked CmpSwap operation
   result.

      if (!((Compare Data ^ Original Remote Data Value) &

            Compare Mask))

      then

         Remote Data Value =

           (Original Remote Data Value & ~(Swap Mask))

                             | (Swap Data & Swap Mask)

      else

         Remote Data Value = Original Remote Data Value

   After the operation, the remote data Buffer MUST contain the
   "Original Remote Data Value" (if comparison did not match) or the
   masked "Swap Data" (if the comparison did match).  CmpSwap Atomic
   Operations MUST target ULP Buffer addresses that are 64-bit aligned.

   If a CmpSwap Atomic Operation is attempted on a target ULP Buffer
   address that is not 64-bit aligned:

   o  The operation MUST NOT be performed,

   o  The Responder's memory MUST NOT be modified,

   o  The result MUST be surfaced as an error, and

   o  A terminate message MUST be generated.  (See Section 8.2 for the
      contents of the terminate message.)

5.2.  Atomic Operations

   The Atomic Operation Request and Response are RDMA Messages.  An
   Atomic Operation makes use of the DDP Untagged Buffer Model.  Atomic
   Operation Request messages MUST use the same Queue Number as RDMA
   Read Requests (QN=1).  Reusing the same Queue Number for Atomic
   Request messages allows the Atomic Operations to reuse the same
   infrastructure (e.g., Outbound and Inbound RDMA Read Queue Depth



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   (ORD/IRD) flow control) as defined for RDMA Read Requests.  Atomic
   Operation Response messages MUST set Queue Number (QN) to 3 in the
   DDP header.

   The RDMA Message OpCode for an Atomic Request Message is 1010b.  The
   RDMA Message OpCode for an Atomic Response Message is 1011b.

5.2.1.  Atomic Operation Request Message

   The Atomic Operation Request Message carries an Atomic Operation
   Header that describes the ULP Buffer address in the Responder's
   memory.  The Atomic Operation Request header immediately follows the
   DDP header.  The RDMAP layer passes to the DDP layer a RDMAP Control
   Field.  The following figure depicts the Atomic Operation Request
   Header that is used for all Atomic Operation 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Reserved (Not Used)              |AOpCode|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Request Identifier                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Remote STag                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Remote Tagged Offset                     |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Add or Swap Data                        |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Add or Swap Mask                        |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Compare Data                          |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Compare Mask                          |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 4: Atomic Operation Request Header




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      Reserved (Not Used): 28 bits

         This field is set to zero on transmit, ignored on receive.

      Atomic Operation Code (AOpCode): 4 bits.

         See Figure 5.  All Atomic Operation Codes from Figure 5 MUST be
         implemented by an RNIC that supports Atomic Operations.

      Request Identifier: 32 bits.

         The Request Identifier specifies a number that is used to
         identify the Atomic Operation Request Message.  The value used
         in this field is selected by the RNIC that sends the message,
         and it is reflected back to the Local Peer in the Atomic
         Operation Response message.

      Remote STag: 32 bits.

         The Remote STag identifies the Remote Peer's Tagged Buffer
         targeted by the Atomic Operation.  The Remote STag is
         associated with the RDMAP Stream through a mechanism that is
         outside the scope of the RDMAP specification.

      Remote Tagged Offset: 64 bits.

         The Remote Tagged Offset specifies the starting offset, in
         octets, from the base of the Remote Peer's Tagged Buffer
         targeted by the Atomic Operation.  The Remote Tagged Offset MAY
         start at an arbitrary offset but MUST represent a ULP Buffer
         address that is 64-bit aligned.

      Add or Swap Data: 64 bits.

         The Add or Swap Data field specifies the 64-bit "Add Data"
         value in an Atomic FetchAdd Operation or the 64-bit "Swap Data"
         value in an Atomic Swap or CmpSwap Operation.

      Add or Swap Mask: 64 bits

         This field is used in masked Atomic Operations (FetchAdd and
         CmpSwap) to perform a bitwise logical AND operation as
         specified in the definition of these operations.  For non-
         masked Atomic Operations (Swap), this field is set to
         ffffffffffffffffh on transmit and ignored by the receiver.






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      Compare Data: 64 bits.

         The Compare Data field specifies the 64-bit "Compare Data"
         value in an Atomic CmpSwap Operation.  For Atomic Operations
         FetchAdd and Atomic Swap, the Compare Data field is set to zero
         on transmit and ignored by the receiver.

      Compare Mask: 64 bits

         This field is used in masked Atomic Operation CmpSwap to
         perform a bitwise logical AND operation as specified in the
         definition of these operations.  For Atomic Operations FetchAdd
         and Swap, this field is set to ffffffffffffffffh on transmit
         and ignored by the receiver.

   ---------+-----------+----------+----------+---------+---------
   Atomic   | Atomic    | Add or   | Add or   | Compare | Compare
   Operation| Operation | Swap     | Swap     | Data    | Mask
   Code     |           | Data     | Mask     |         |
   ---------+-----------+----------+----------+---------+---------
   0000b    | FetchAdd  | Add Data | Add Mask | N/A     | N/A
   ---------+-----------+----------+----------+---------+---------
   0010b    | CmpSwap   | Swap Data| Swap Mask| Valid   | Valid
   ---------+-----------+-----------------------------------------

            Figure 5: Atomic Operation Message Definitions

   The Atomic Operation Request Message has the following semantics:

   1. An Atomic Operation 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.

   2. One Atomic Operation Request Message MUST consume one Untagged
      Buffer.

   3. The Responder's RDMAP layer MUST process an Atomic Operation
      Request Message.  A valid Atomic Operation Request Message MUST
      NOT be delivered to the Responder's ULP (i.e., it is processed by
      the RDMAP layer).

   4. At the Responder, an error MUST be surfaced in response to
      delivery to the Remote Peer's RDMAP layer of an Atomic Operation
      Request Message with an Atomic Operation Code that the RNIC does
      not support.






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   5. An Atomic Operation Request Message MUST reference the RDMA Read
      Request Queue.  That is, the Requester's RDMAP layer MUST request
      that the DDP layer set the Queue Number field to one.

   6. The Requester MUST pass to the DDP layer Atomic Operation Request
      Messages in the order they were submitted by the ULP.

   7. The Responder MUST process the Atomic Operation Request Messages
      in the order they were sent.

   8. If the Responder receives a valid Atomic Operation Request
      Message, it MUST respond with a valid Atomic Operation Response
      Message.

5.2.2.  Atomic Operation Response Message

   The Atomic Operation Response Message carries an Atomic Operation
   Response Header that contains the "Original Request Identifier" and
   "Original Remote Data Value".  The Atomic Operation Response Header
   immediately follows the DDP header.  The RDMAP layer passes to the
   DDP layer a RDMAP Control Field.  The following figure depicts the
   Atomic Operation Response header that is used for all Atomic
   Operation Response 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Original Request Identifier                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Original Remote Data Value                 |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 6: Atomic Operation Response Header

   Original Request Identifier: 32 bits.

      The Original Request Identifier is set to the value specified in
      the Request Identifier field that was originally provided in the
      corresponding Atomic Operation Request Message.

   Original Remote Data Value: 64 bits.

      The Original Remote Value specifies the original 64-bit value
      stored at the ULP Buffer address targeted by the Atomic Operation.





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   The Atomic Operation Response Message has the following semantics:

   1. The Atomic Operation Response Message for the associated Atomic
      Operation Request Message travels in the opposite direction.

   2. An Atomic Operation Response Message MUST consume an Untagged
      Buffer.  That is, the Responder RDMAP layer MUST request that the
      DDP mark the Message as Untagged.

   3. An Atomic Operation Response Message MUST reference the Queue
      Number 3.  That is, the Responder's RDMAP layer MUST request that
      the DDP layer set the Queue Number field to 3.

   4. The Responder 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 Atomic
      Operation Requests negotiated by the ULP in addition to the
      maximum number of RDMA Read Requests negotiated by the ULP.

   5. The Requester MUST ensure that a sufficient number of Untagged
      Buffers are available on the RDMA Atomic Response Queue (Queue
      with DDP Queue Number 3) to support the maximum number of Atomic
      Operation Requests negotiated by the ULP.

   6. The RDMAP layer MUST Deliver the Atomic Operation Response Message
      to the ULP.

   7. At the Requester, when an invalid Atomic Operation Response
      Message is delivered to the Remote Peer's RDMAP layer, an error is
      surfaced.

   8. When the Responder receives Atomic Operation Request messages, the
      Responder RDMAP layer MUST pass Atomic Operation Response Messages
      to the DDP layer, in the order that the Atomic Operation Request
      Messages were received by the RDMAP layer, at the Responder.

5.3.  Atomicity Guarantees

   Atomicity of the Read-Modify-Write (RMW) on the Responder's node by
   the Atomic Operation MUST be assured in the context of concurrent
   atomic accesses by other RDMAP Streams on the same RNIC.

5.4.  Atomic Operations Ordering and Completion Rules

   In addition to the ordering and completion rules described in RFC
   5040, the following rules apply to implementations of the Atomic
   Operations.




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   1. For an Atomic Operation, the Requester MUST NOT consider the
      contents of the Tagged Buffer at the Responder to be modified by
      that specific Atomic Operation until the Atomic Operation Response
      Message has been Delivered to RDMAP at the Requester.

   2. Atomicity guarantees MUST be provided within the scope of a single
      RNIC.

      Implementation Note: This requirement for atomicity among
      operations is limited to the scope of a single RNIC.  Atomicity
      guarantees are OPTIONAL with respect to access to the Tagged
      Buffer by any other method than an Atomic Operation via the same
      RNIC.  Examples of such accesses that may not be atomic with
      respect to an Atomic Operation include accesses via other RNICs
      and local processor memory access to the Tagged Buffer.

   3. Atomic Operation Request Messages MUST NOT start processing at the
      Responder until they have been Delivered to RDMAP by DDP.

   4. Atomic Operation Response Messages MAY be generated at the
      Responder after subsequent RDMA Write Messages or Send Messages
      have been Placed or Delivered.

   5. Atomic Operation Response Message processing at the Responder MUST
      be started only after the Atomic Operation Request Message has
      been Delivered by the DDP layer (thus, all previous RDMA Messages
      on that DDP Stream have been Delivered).

   6. Send Messages MAY be Completed at the Responder before prior
      incoming Atomic Operation Request Messages have completed their
      response processing.

   7. An Atomic Operation MUST NOT be Completed at the Requester until
      the DDP layer Delivers the associated incoming Atomic Operation
      Response Message.

   8. If more than one outstanding Atomic Request Message is supported
      by both peers, the Atomic Operation Request Messages MUST be
      processed in the order they were delivered by the DDP layer on the
      Responder.  Atomic Operation Response Messages MUST be submitted
      to the DDP layer on the Responder in the order the Atomic
      Operation Request Messages were Delivered by DDP.









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6.  Immediate Data

   The Immediate Data operation is typically used in conjunction with an
   RDMA Write Operation to improve ULP processing efficiency.  The
   efficiency is gained by causing an RDMA Completion to be generated
   immediately following the RDMA Write operation.  This RDMA Completion
   delivers 8 bytes of Immediate Data at the Remote Peer.  The
   combination of an RDMA Write Message followed by an Immediate Data
   Operation has the same behavior as the RDMA Write with Immediate Data
   operation found in InfiniBand.  An Immediate Data operation that is
   not preceded by an RDMA Write operation causes an RDMA Completion.

6.1.  RDMAP Interactions with ULP for Immediate Data

   For Immediate Data operations, the following are the interactions
   between the RDMAP Layer and the ULP:

   o  At the Data Source:

      -  The ULP passes to the RDMAP Layer the following:

         *  8 bytes of ULP Immediate Data

      -  When the Immediate Data operation Completes, an indication of
         the Completion results.

   o  At the Data Sink:

      -  If the Immediate Data operation is Completed successfully, the
         RDMAP Layer passes the following information to the ULP Layer:

         *  8 bytes of Immediate Data

         *  An Event, if the Data Sink is configured to generate an
            Event.

      -  If the Immediate Data operation is 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.










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6.2.  Immediate Data Header Format

   The Immediate Data and Immediate Data with SE Messages carry
   Immediate Data as shown in Figure 7.  The RDMAP layer passes to the
   DDP layer an RDMAP Control Field and 8 bytes of Immediate Data.  The
   first 8 bytes of the data following the DDP header contains the
   Immediate Data.  See Appendix A.3 for the DDP segment format of an
   Immediate Data or Immediate Data with SE Message.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Immediate Data                         |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure 7: Immediate Data or Immediate Data with SE Message Header

   Immediate Data: 64 bits.
      8 bytes of data transferred from the Data Source to an untagged
      Buffer at the Data Sink.

6.3.  Immediate Data or Immediate Data with SE Message

   The Immediate Data or Immediate Data with SE Message uses the DDP
   Untagged Buffer Model to transfer Immediate Data from the Data Source
   to the Data Sink.

   o  An Immediate Data or Immediate Data with SE 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.

   o  One Immediate Data or Immediate Data with SE Message MUST consume
      one Untagged Buffer.

   o  At the Remote Peer, the Immediate Data and Immediate Data with SE
      Messages MUST be Delivered to the Remote Peer's ULP in the order
      they were sent.

   o  For an Immediate Data or Immediate Data with SE Message, the Local
      Peer's RDMAP Layer MUST request that the DDP layer set the Queue
      Number field to zero.

   o  For an Immediate Data or Immediate Data with SE Message, the Local
      Peer's RDMAP Layer MUST request that the DDP layer transmit 8
      bytes of data.




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   o  The Local Peer MUST issue Immediate Data and Immediate Data with
      SE Messages in the order they were submitted by the ULP.

   o  The Remote Peer MUST check that Immediate Data and Immediate Data
      with SE Messages include exactly 8 bytes of data from the DDP
      layer.  The DDP header carries the length field that is reported
      by the DDP layer.

6.4.  Ordering and Completions

   Ordering and completion rules for Immediate Data are the same as
   those for a Send operation as described in Section 5.5 of RFC 5040.

7.  Ordering and Completions Table

   The following table summarizes the ordering relationships for Atomic
   and Immediate Data operations from the standpoint of the Local Peer
   issuing the 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.  Also note that in the
   table below, Immediate Data includes Immediate Data and Immediate
   Data with Solicited Event.

   ---------+----------+-------------+-------------+------------------
   First    | Second   | Placement   | Placement   | Ordering
   Operation| Operation| Guarantee at| Guarantee at| Guarantee at
            |          | Remote Peer | Local Peer  | Remote Peer
   ---------+----------+-------------+-------------+------------------
   Immediate| Send     | No Placement| Not         | Completed in
   Data     |          | Guarantee   | Applicable  | Order
            |          | between Send|             |
            |          | Payload and |             |
            |          | Immediate   |             |
            |          | Data        |             |
   ---------+----------+-------------+-------------+------------------
   Immediate| RDMA     | No Placement| Not         | Not
   Data     | Write    | Guarantee   | Applicable  | Applicable
            |          | between RDMA|             |
            |          | Write       |             |
            |          | Payload and |             |
            |          | Immediate   |             |
            |          | Data        |             |









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   ---------+----------+-------------+-------------+------------------
   Immediate| RDMA     | No Placement| RDMA Read   | RDMA Read
   Data     | Read     | Guarantee   | Response    | Response
            |          | between     | will not be | Message will
            |          | Immediate   | Placed until| not be
            |          | Data and    | Immediate   | generated
            |          | RDMA Read   | Data is     | until
            |          | Request     | Placed at   | Immediate Data
            |          |             | Remote Peer | has been
            |          |             |             | Completed
   ---------+----------+-------------+-------------+------------------
   Immediate| Atomic   | No Placement| Atomic      | Atomic
   Data     |          | Guarantee   | Response    | Response
            |          | between     | will not be | Message will
            |          | Immediate   | Placed until| not be
            |          | Data and    | Immediate   | generated
            |          | Atomic      | Data is     | until
            |          | Request     | Placed at   | Immediate Data
            |          |             | Remote Peer | has been
            |          |             |             | Completed
   ---------+----------+-------------+-------------+------------------
   Immediate| Immediate| No Placement| Not         | Completed in
   Data or  | Data     | Guarantee   | Applicable  | Order
   Send     |          |             |             |
   ---------+----------+-------------+-------------+------------------
   RDMA     | Immediate| No Placement| Not         | Immediate Data
   Write    | Data     | Guarantee   | Applicable  | is Completed
            |          |             |             | after RDMA
            |          |             |             | Write is Placed
            |          |             |             | and Delivered
   ---------+----------+-------------+-------------+------------------
   RDMA Read| Immediate| No Placement| Immediate   | Not Applicable
            | Data     | Guarantee   | Data MAY be |
            |          | between     | Placed      |
            |          | Immediate   | before      |
            |          | Data and    | RDMA Read   |
            |          | RDMA Read   | Response is |
            |          | Request     | generated   |
   ---------+----------+-------------+-------------+------------------
   Atomic   | Immediate| No Placement| Immediate   | Not Applicable
            | Data     | Guarantee   | Data MAY be |
            |          | between     | Placed      |
            |          | Immediate   | before      |
            |          | Data and    | Atomic      |
            |          | Atomic      | Response is |
            |          | Request     | generated   |





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   ---------+----------+-------------+-------------+------------------
   Atomic   | Send     | No Placement| Send Payload| Not Applicable
            |          | Guarantee   | MAY be      |
            |          | between Send| Placed      |
            |          | Payload and | before      |
            |          | Atomic      | Atomic      |
            |          | Request     | Response is |
            |          |             | generated   |
   ---------+----------+-------------+-------------+------------------
   Atomic   | RDMA     | No Placement| RDMA Write  | Not
            | Write    | Guarantee   | Payload MAY | Applicable
            |          | between RDMA| be Placed   |
            |          | Write       | before      |
            |          | Payload and | Atomic      |
            |          | Atomic      | Response is |
            |          | Request     | generated   |
   ---------+----------+-------------+-------------+------------------
   Atomic   | RDMA     | No Placement| No Placement| RDMA Read
            | Read     | Guarantee   | Guarantee   | Response
            |          | between     | between     | Message will
            |          | Atomic      | Atomic      | not be
            |          | Request and | Response    | generated
            |          | RDMA Read   | and RDMA    | until Atomic
            |          | Request     | Read        | Response Message
            |          |             | Response    | has been
            |          |             |             | generated
   ---------+----------+-------------+-------------+------------------
   Atomic   | Atomic   | Placed in   | No Placement| Second Atomic
            |          | order       | Guarantee   | Request
            |          |             | between two | Message will
            |          |             | Atomic      | not be
            |          |             | Responses   | processed
            |          |             |             | until first
            |          |             |             | Atomic Response
            |          |             |             | has been
            |          |             |             | generated
   ---------+----------+-------------+-------------+------------------
   Send     | Atomic   | No Placement| Atomic      | Atomic Response
            |          | Guarantee   | Response    | Message will not
            |          | between Send| will not be | be generated
            |          | Payload and | Placed at   | until Send has
            |          | Atomic      | the Local   | been Completed
            |          | Request     | Peer until  |
            |          |             | Send Payload|
            |          |             | is Placed   |
            |          |             | at the      |
            |          |             | Remote Peer |




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   ---------+----------+-------------+-------------+------------------
   RDMA     | Atomic   | No Placement| Atomic      | Not
   Write    |          | Guarantee   | Response    | Applicable
            |          | between RDMA| will not be |
            |          | Write       | Placed at   |
            |          | Payload and | the Local   |
            |          | Atomic      | Peer until  |
            |          | Request     | RDMA Write  |
            |          |             | Payload     |
            |          |             | is Placed   |
            |          |             | at the      |
            |          |             | Remote Peer |
   ---------+----------+-------------+-------------+------------------
   RDMA     | Atomic   | No Placement| No Placement| Atomic Response
   Read     |          | Guarantee   | Guarantee   | Message will
            |          | between     | between     | not be generated
            |          | Atomic      | Atomic      | until RDMA
            |          | Request and | Response    | Read Response
            |          | RDMA Read   | and RDMA    | has been
            |          | Request     | Read        | generated
            |          |             | Response    |
   ---------+----------+-------------+-------------+------------------

8.  Error Processing

   In addition to the error processing described in Section 7 of RFC
   5040, the following rules apply for the new RDMA Messages defined in
   this specification.

8.1.  Errors Detected at the Local Peer

   The Local Peer MUST send a Terminate Message for each of the
   following cases:

   1. For errors detected while creating an Atomic Request, Atomic
      Response, Immediate Data, or Immediate Data with SE Message, or
      other reasons not directly associated with an incoming Message,
      the Terminate Message and Error code are sent instead of the
      Message.  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 Atomic Request, Atomic
      Response, Immediate Data, or Immediate Data with SE (after the
      Message has been Delivered by DDP), the Terminate Message is sent
      at the earliest possible opportunity, preferably in the next





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RFC 7306                RDMA Protocol Extensions               June 2014


      outgoing RDMA Message.  In this case, the Error Type, Error Code,
      and Terminated DDP Header fields are included in the Terminate
      Message, but the Terminated RDMA Header field is set to zero.

8.2.  Errors Detected at the Remote Peer

   On incoming Atomic Requests, Atomic Responses, Immediate Data, and
   Immediate Data with Solicited Event, the following MUST be validated:

   o  The DDP layer MUST validate all DDP Segment fields.

   o  The RDMA OpCode MUST be valid.

   o  The RDMA Version MUST be valid.

   On incoming Atomic requests the following additional validation MUST
   be performed:

   o  The RDMAP layer MUST validate that the Remote Peer's Tagged ULP
      Buffer address references a ULP Buffer address that is 64-bit
      aligned.  In the case of an error, the RDMAP layer MUST generate a
      Terminate Message indicating RDMA Layer Remote Operation Error
      with Error Code Name "Catastrophic error, localized to RDMAP
      Stream" as described in Section 4.8 of RFC 5040.  Implementation
      Note: A ULP implementation can avoid this error by having the
      target ULP Buffer of an Atomic Operation 64-bit aligned.

9.  Security Considerations

   This document specifies extensions to the RDMA Protocol specification
   in RFC 5040, and as such the Security Considerations discussed in
   Section 8 of RFC 5040 apply.  In particular, Atomic Operations use
   ULP Buffer addresses for the Remote Peer Buffer addressing used in
   RFC 5040 as required by the security model described in RFC 5042
   [RFC5042].

   RDMAP and related protocols may be used by applications that exhibit
   distinctive traffic characteristics such as message timing, source,
   destination, and size patterns.  Examples include structured high-
   performance computing applications based on the MPI interface.  For
   such applications, analysis of encrypted traffic could reveal
   sensitive information, e.g., the nature of the application, size of
   data set being used, and information about the application's rate of
   progress.  Such information can be hidden from passive observation
   via use of Encapsulating Security Payload version 3 (ESPv3) Traffic
   Flow Confidentiality [RFC4303] to obfuscate the encrypted traffic's
   characteristics.  ESPv3 implementation requirements for RDMAP are
   specified in [RFC7146].



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10.  IANA Considerations

   IANA has added the following entries to the "RDMAP Message Operation
   Codes" registry of "Remote Direct Data Placement (RDDP)" registry:

   0x8, Immediate Data, this specification

   0x9, Immediate Data with Solicited Event, this specification

   0xA, Atomic Request, this specification

   0xB, Atomic Response, this specification

   In addition, the following registry has been added to the "Remote
   Direct Data Placement (RDDP)" registry.  The following section
   specifies the registry, its initial contents, and the administration
   policy in more detail.

10.1.  RDMAP Message Atomic Operation Subcodes

   Name of the registry: "RDMAP Message Atomic Operation Subcodes"

   Namespace details: RDMAP Message Atomic Operation Subcodes are 4-bit
   values.

   Information that must be provided to assign a new value: An IESG-
   approved Standards Track specification defining the semantics and
   interoperability requirements of the proposed new value and the
   fields to be recorded in the registry.

   Fields to record in the registry: RDMAP Message Atomic Operation
   Subcode, Atomic Operation, RFC Reference.

   Initial registry contents:

   0x0, FetchAdd, this specification

   0x1, Reserved, this specification

   0x2, CmpSwap, this specification

   Note: An experimental RDMAP Message Operation Code has already been
   allocated; hence, there is no need for an experimental RDMAP Message
   Atomic Operation Subcode.







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RFC 7306                RDMA Protocol Extensions               June 2014


   All other values are Unassigned and available to IANA for assignment.
   New RDMAP Message Atomic Operation Subcodes should be assigned
   sequentially in order to better support implementations that process
   RDMAP Message Atomic Operations in hardware.

   Allocation Policy: Standards Action [RFC5226]

10.2.  RDMAP Queue Numbers

   Name of the registry: "RDMAP DDP Untagged Queue Numbers"

   Namespace details: RDMAP DDP Untagged Queue numbers are 32-bit
   values.

   Information that must be provided to assign a new value: An IESG-
   approved Standards Track specification defining the semantics and
   interoperability requirements of the proposed new value and the
   fields to be recorded in the registry.

   Fields to record in the registry: RDMAP DDP Untagged Queue Numbers,
   Queue Usage Description, RFC Reference.

   Initial registry contents:

   0x00000000, Queue 0 (Send operation Variants), [RFC5040]

   0x00000001, Queue 1 (RDMA Read Request operations), [RFC5040]

   0x00000002, Queue 2 (Terminate operations), [RFC5040]

   0x00000003, Queue 3 (Atomic Response operations), this specification

   Note: An experimental RDMAP Message Operation Code has already been
   allocated; hence, there is no need for an experimental RDMAP DDP
   Untagged Queue Number.

   All other values are Unassigned and available to IANA for assignment.
   New RDMAP queue numbers should be assigned sequentially in order to
   better support implementations that perform RDMAP queue selection in
   hardware.

   Allocation Policy: Standards Action [RFC5226]









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11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4303]  Kent, S., "IP Encapsulating Security Payload (ESP)", RFC
              4303, December 2005.

   [RFC5040]  Recio, R., Metzler, B., Culley, P., Hilland, J., and D.
              Garcia, "A Remote Direct Memory Access Protocol
              Specification", RFC 5040, October 2007.

   [RFC5041]  Shah, H., Pinkerton, J., Recio, R., and P. Culley, "Direct
              Data Placement over Reliable Transports", RFC 5041,
              October 2007.

   [RFC5042]  Pinkerton, J. and E. Deleganes, "Direct Data Placement
              Protocol (DDP) / Remote Direct Memory Access Protocol
              (RDMAP) Security", RFC 5042, October 2007.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [RFC7146]  Black, D. and P. Koning, "Securing Block Storage Protocols
              over IP: RFC 3723 Requirements Update for IPsec v3", RFC
              7146, April 2014.

11.2.  Informative References

   [DAT_ATOMICS]
              DAT Collaborative, "IB Transport Specific Extensions for
              DAT 2.0", User Direct Access Programming Library,
              <http://www.datcollaborative.org/DAT_IB_Extensions.pdf>.

   [IB]       InfiniBand Trade Association, "InfiniBand Architecture
              Specification Volumes 1 and 2", Release 1.1, November
              2002, <http://www.infinibandta.org/specs>.

   [MPI]      Message Passing Interface Forum, "MPI: A Message-Passing
              Interface Standard, Version 3.0", September 2012,
              <http://www.mpi-forum.org/docs/mpi-3.0/mpi30-report.pdf>.







Shah, et al.                 Standards Track                   [Page 29]

RFC 7306                RDMA Protocol Extensions               June 2014


   [OFAVERBS] Rosenstock, H., "Subject: Re: [PATCH 0/2] Add support for
              enhanced atomic operations", message to the linux-rdma
              mailing list,
              <http://www.spinics.net/lists/linux-rdma/msg02405.html>.

   [RFC5044]  Culley, P., Elzur, U., Recio, R., Bailey, S., and J.
              Carrier, "Marker PDU Aligned Framing for TCP
              Specification", RFC 5044, October 2007.

   [RFC5045]  Bestler, C., Ed., and L. Coene, "Applicability of Remote
              Direct Memory Access Protocol (RDMA) and Direct Data
              Placement (DDP)", RFC 5045, October 2007.

   [RFC6581]  Kanevsky, A., Ed., Bestler, C., Ed., Sharp, R., and S.
              Wise, "Enhanced Remote Direct Memory Access (RDMA)
              Connection Establishment", RFC 6581, April 2012.

   [RSOCKETS] Hefty, S., "RDMA CM - RDMA enabled Sockets library for
              Open Fabrics", <http://git.openfabrics.org/?p=~shefty/
              librdmacm.git;a=summary>.

12.  Acknowledgments

   The authors would like to acknowledge the following individuals who
   provided valuable comments and suggestions.

   o  David Black

   o  Arkady Kanevsky

   o  Bernard Metzler

   o  Jim Pinkerton

   o  Tom Talpey

   o  Steve Wise

   o  Don Wood












Shah, et al.                 Standards Track                   [Page 30]

RFC 7306                RDMA Protocol Extensions               June 2014


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.














































Shah, et al.                 Standards Track                   [Page 31]

RFC 7306                RDMA Protocol Extensions               June 2014


A.1.  DDP Segment for Atomic Operation Request

   The following figure depicts an Atomic Operation 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 (Atomic Operation Request) Queue Number      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        DDP (Atomic Operation Request) Message Sequence Number |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             DDP (Atomic Operation Request) Message Offset     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Reserved (Not Used)              |AOpCode|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Request Identifier                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Remote STag                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Remote Tagged Offset                     |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Add or Swap Data                        |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Add or Swap Mask                        |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Compare Data                          |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Compare Mask                          |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+







Shah, et al.                 Standards Track                   [Page 32]

RFC 7306                RDMA Protocol Extensions               June 2014


A.2.  DDP Segment for Atomic Response

   The following figure depicts an Atomic Operation 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  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Reserved (Not Used)                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              DDP (Atomic Operation Request) Queue Number      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        DDP (Atomic Operation Request) Message Sequence Number |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             DDP (Atomic Operation Request) Message Offset     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Original Request Identifier                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Original Remote Value                   |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

A.3.  DDP Segment for Immediate Data and Immediate Data with SE

   The following figure depicts an Immediate Data or Immediate Data with
   SE, 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 (Send) Queue Number                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                DDP (Send) Message Sequence Number             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       DDP Message Offset                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Immediate Data                         |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




Shah, et al.                 Standards Track                   [Page 33]

RFC 7306                RDMA Protocol Extensions               June 2014


Authors' Addresses

   Hemal Shah
   Broadcom Corporation
   5300 California Avenue
   Irvine, CA 92617
   US
   Phone: 1-949-926-6941
   EMail: hemal@broadcom.com


   Felix Marti
   Chelsio Communications, Inc.
   370 San Aleso Ave.
   Sunnyvale, CA 94085
   US
   Phone: 1-408-962-3600
   EMail: felix@chelsio.com


   Asgeir Eiriksson
   Chelsio Communications, Inc.
   370 San Aleso Ave.
   Sunnyvale, CA 94085
   US
   Phone: 1-408-962-3600
   EMail: asgeir@chelsio.com


   Wael Noureddine
   Chelsio Communications, Inc.
   370 San Aleso Ave.
   Sunnyvale, CA 94085
   US
   Phone: 1-408-962-3600
   EMail: wael@chelsio.com


   Robert Sharp
   Intel Corporation
   1300 South Mopac Expy, Mailstop: AN4-4B
   Austin, TX  78746
   US
   Phone: 1-512-362-1407
   EMail: robert.o.sharp@intel.com






Shah, et al.                 Standards Track                   [Page 34]


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