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Versions: 00 01 02 03 04 05 06 07 08 09 10 RFC 7306

Storage Maintenance (storm) Working Group                    Hemal Shah
Internet Draft                                     Broadcom Corporation
Intended status: Standards Track                            Felix Marti
Expires: October 2014                                   Wael Noureddine
                                                       Asgeir Eiriksson
                                            Chelsio Communications, Inc.
                                                           Robert Sharp
                                                      Intel Corporation
                                                         April 16, 2014




                         RDMA Protocol Extensions
                     draft-ietf-storm-rdmap-ext-10.txt


Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with
   the provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   Internet-Drafts are draft documents valid for a maximum of six
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   This Internet-Draft will expire on October 16, 2014.

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
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   (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
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   document must include Simplified BSD License text as described in



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   Section 4.e of the Trust Legal Provisions and are provided without
   warranty as described in the Simplified BSD License.



Abstract

   This document specifies extensions to the IETF Remote Direct Memory
   Access Protocol (RDMAP RFC5040). 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.



Table of Contents


   1. Introduction...................................................3
      1.1. Discovery of RDMAP Extensions.............................4
   2. Requirements Language..........................................5
   3. Glossary.......................................................5
   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.................................11
         5.1.1. FetchAdd............................................11
         5.1.2. CmpSwap.............................................12
      5.2. Atomic Operations........................................14
         5.2.1. Atomic Operation Request Message....................14
         5.2.2. Atomic Operation Response Message...................18
      5.3. Atomicity Guarantees.....................................19
      5.4. Atomic Operations Ordering and Completion Rules..........19
   6. Immediate Data................................................21
      6.1. RDMAP Interactions with ULP for Immediate Data...........21
      6.2. Immediate Data Header Format.............................22
      6.3. Immediate Data or Immediate Data with SE Message.........22
      6.4. Ordering and Completions.................................23
   7. Ordering and Completions Table................................23
   8. Error Processing..............................................26
      8.1. Errors Detected at the Local Peer........................26
      8.2. Errors Detected at the Remote Peer.......................27


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   9. Security Considerations.......................................28
   10. IANA Considerations..........................................28
      10.1. RDMAP Message Atomic Operation Subcodes.................28
      10.2. RDMAP Queue Numbers.....................................29
   11. References...................................................30
      11.1. Normative References....................................30
      11.2. Informative References..................................31
   12. Acknowledgments..............................................32
   Appendix A. DDP Segment Formats for RDMA Messages................33
      A.1. DDP Segment for Atomic Operation Request.................33
      A.2. DDP Segment for Atomic Response..........................35
      A.3. DDP Segment for Immediate Data and Immediate Data with SE35


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 on remote memory locations. Support for atomic
      operation 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 sockets based
   applications.  RSockets is aware of Immediate Data support in
   InfiniBand [IB].  RSockets cannot utilize the RDMA Write with


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   Immediate Data operation from InfiniBand .  The addition of the
   Immediate Data operation specified in this draft will alleviate this
   difference in RSockets when running on InfiniBand and iWARP.

   Structured high performance computing applications based on the MPI
   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 Network Interface Controllers or RNICs.  The addition of Atomic
   Operations as specified in this draft will allow atomic operations
   in DAT Atomics to work for both InfiniBand and RNICs
   interchangeably.

   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 to 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 mechanism
   is outside the scope of this specification. For backward


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   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 / Unexpected OpCode error
   will be reported by the remote peer in the case of an Immediate Data
   or Atomic Operation as described if 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].

3. Glossary

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

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

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


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

   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.




















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4. Header Format Extensions

   The control information of RDMA Messages is included in DDP protocol
   RFC 5041 defined header fields. RFC 5040 defines the RDMAP header
   formats layered on the DDP header definition.  This specification
   extends RFC 5040 with the following new formats:
   .  Four new RDMA Messages carry additional RDMAP headers. The
      Immediate Data operation and Immediate Data with Solicited Event
      operation 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.

   .  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,L, Resrv and DV fields RFC
   5041. The RDMAP Control Field consists of the RV, Rsv and Opcode
   fields RFC 5040.

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




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   Figure 2As shown in Figure 2, STag 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.



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   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
   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 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 Requestor.  When the Atomic
   Operation Response message is received, the MSN will be used to
   locate the corresponding Atomic Operation request in order to
   complete the Atomic Operation request.





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5.1. Atomic Operation Details

   The following sub-sections describe the Atomic Operations in more
   details.

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, to perform FetchAdd operation on
   multiple fields of selectable length specified by 64-bit "Add Mask",
   and write 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 "Add Mask" field to 0x0000000000000000
   results in Atomic Add of 64-bit Original Remote Data Value and 64-
   bit "Add Data".

   The pseudo code below describes 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



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      sum = carry + val1 + val2

      carry = (sum & 2) >> 1

      sum = sum & 1

      if (sum)

         Remote Data Value |= bit_location

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

   }

   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 64-bit aligned ULP Buffer address 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, and, if
   the two values are equal, 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


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   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

   The Responder returns:

   o  Original Remote Data Value

   The following pseudo code 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.


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   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
      terminate message contents)



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. 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:











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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      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

     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.



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         The Request Identifier specifies a number that is used to
         identify Atomic Operation Request Message. The value used in
         this field is selected by the RNIC that sends the message, and
         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 64-bit
         aligned ULP Buffer address.

     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.

     Compare Data: 64 bits.

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

     Compare Mask: 64 bits




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         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.

   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.


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   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.

   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.


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   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 Messages are
      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:
   .  At the Data Source:

       .   The ULP passes to the RDMAP Layer the following:

           .   Eight bytes of ULP Immediate Data

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

   .  At the Data Sink:

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

           .   Eight 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 section 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.
        Eight 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.
   .  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.

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

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





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   .  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.

   .  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.

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

   .  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 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        |             |
   ---------+----------+-------------+-------------+------------------



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   Immediate| RDMA     | No Placement| Not         | Not
   Data     | Write    | Guarantee   | Applicable  | Applicable
            |          | between RDMA|             |
            |          | Write       |             |
            |          | Payload and |             |
            |          | Immediate   |             |
            |          | Data        |             |
   ---------+----------+-------------+-------------+------------------
   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   |


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   ---------+----------+-------------+-------------+------------------
   Atomic   | Immediate| No Placement| Immediate   | Not Applicable
            | Data     | Guarantee   | Data MAY be |
            |          | between     | Placed      |
            |          | Immediate   | before      |
            |          | Data and    | Atomic      |
            |          | Atomic      | Response is |
            |          | Request     | generated   |
   ---------+----------+-------------+-------------+------------------
   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
   ---------+----------+-------------+-------------+------------------


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   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 |
   ---------+----------+-------------+-------------+------------------
   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 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:




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   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 Solicited Event
      (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, 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:


   .  The DDP layer MUST validate all DDP Segment fields.

   .  The RDMA OpCode MUST be valid.

   .  The RDMA Version MUST be valid.

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

   .  The RDMAP layer MUST validate that the Remote Peer's Tagged ULP
      Buffer address references a 64-bit aligned ULP Buffer address. 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.






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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 RFC 5042 [RFC5042]
   security model.

   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 ESPv3 Traffic Flow Confidentiality [RFC4303] to obfuscate
   the encrypted traffic's characteristics.  ESPv3 implementation
   requirements for RDMAP are specified in [RFC7146].

10. IANA Considerations

   IANA is requested to add the following entries to the "RDMAP Message
   Operation Codes" registry of "RDDP Registries":

   0x8, Immediate Data, [RFCXXXX]

   0x9, Immediate Data with Solicited Event, [RFCXXXX]

   0xA, Atomic Request, [RFCXXXX]

   0xB, Atomic Response, [RFCXXXX]

   In addition, the following registry is requested to be added to
   "RDDP Registries". The following section specifies the registry, its
   initial contents and the administration policy in more detail.

   RFC Editor: Please replace XXXX in all instances of [RFCXXXX] above
   with the RFC number of this document and remove this note.

10.1. RDMAP Message Atomic Operation Subcodes

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



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

   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, [RFCXXXX]

   0x1, Reserved

   0x2, CmpSwap, [RFCXXXX]

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

   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])

   RFC Editor: Please replace XXXX in all instances of [RFCXXXX] above
   with the RFC number of this document and remove this note.

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 [RFCXXXX].

   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.



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   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), [RFCXXXX]

   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])

   RFC Editor: Please replace XXXX in all instances of [RFCXXXX] above
   with the RFC number of this document and remove this note.



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

   [RFC5040] Recio, R. et al., "A Remote Direct Memory Access Protocol
             Specification", RFC 5040, October 2007.

   [RFC5041] Shah, H. et al., "Direct Data Placement over Reliable
             Transports", RFC 5041, October 2007.



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

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

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

   RFC Editor: Please remove reference to RFC5226 if the associated
   IANA Considerations reference is also removed before publication.

11.2. Informative References

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

   [RSOCKETS]  RSockets, RDMA enabled Sockets library for Open Fabrics,
             available from
             http://git.openfabrics.org/?p=~shefty/librdmacm.git;a=summ
             ary.

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

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

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

   [OFAVERBS]   Open Fabrics Alliance Verbs Enhanced Atomic Operations,
             "[PATCH 0/2] Add support for enhanced atomic operations",
             available from http://www.spinics.net/lists/linux-
             rdma/msg02405.html.

   [DAT_ATOMICS]   DAT Collaborative, User Direct Access Programming
             Library, "Ratified DAT IB extension spec", available from
             http://www.datcollaborative.org/DAT_IB_Extensions.pdf.


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



12. Acknowledgments

   The authors would like to acknowledge the following contributors 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

   This document was prepared using 2-Word-v2.0.template.dot.




















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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 Atomic Operation Request

   The following figure depicts an Atomic Operation Request, DDP
   Segment:





































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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
                                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                   |  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                          |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+








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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:

















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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
                                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                   |  DDP Control  | RDMA Control  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Reserved (Not Used)                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    DDP (Send) Queue Number                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                DDP (Send) Message Sequence Number             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       DDP Message Offset                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Immediate Data                         |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+






























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Authors' Addresses

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

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

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

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

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











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