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Versions: (draft-stewart-rddp-sctp) 00 01 02 03 04 05 06 07 RFC 5043 Draft is active
In: Proposed Standard
Remote Direct Data Placement                                  R. Stewart
Working Group                                        Cisco Systems, Inc.
Internet-Draft                                                C. Bestler
Expires: February 15, 2006                                      Broadcom
                                                                 H. Shah
                                                       Intel Corporation
                                                              V. Kashyap
                                                                     IBM
                                                              S. Ganguly
                                                              Consultant
                                                         August 14, 2005


Stream Control Transmission Protocol (SCTP) Remote Direct Memory Access
             (RDMA) Direct Data Placement (DDP) Adaptation
                      draft-ietf-rddp-sctp-02.txt

Status of this Memo

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Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract




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   This document describes a method to adapt Direct Data Placement (DDP)
   and Remote Direct Memory Access (RDMA) to Stream Control Transmission
   Protocol (SCTP) RFC2960 [2] using a generic description found in
   [RDMA-Draft] [4] and [DDP-Draft] [3].

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1   Definitions  . . . . . . . . . . . . . . . . . . . . . . .  3
     1.2   Conventions  . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Data Formats . . . . . . . . . . . . . . . . . . . . . . . . .  5
     2.1   Adaptation Layer Indicator . . . . . . . . . . . . . . . .  5
     2.2   Payload Data Chunks  . . . . . . . . . . . . . . . . . . .  5
       2.2.1   DDP Source Sequence Number (DDP-SSN) . . . . . . . . .  6
       2.2.2   DDP Segment Payload Data Chunk . . . . . . . . . . . .  6
       2.2.3   DDP Stream Session Control Data Chunk  . . . . . . . .  7
   3.  DDP Stream Sessions  . . . . . . . . . . . . . . . . . . . . .  8
     3.1   Sequencing . . . . . . . . . . . . . . . . . . . . . . . .  8
     3.2   Legal Sequence: Active/Passive Session Accepted  . . . . .  8
     3.3   Legal Sequence: Active/Passive Session Rejected  . . . . .  9
     3.4   Legal Sequence: Active/Passive Session Non-ULP Rejected  .  9
     3.5   ULP Specific Sequencing  . . . . . . . . . . . . . . . . .  9
     3.6   Other Sequencing Rules . . . . . . . . . . . . . . . . . .  9
   4.  SCTP Endpoints . . . . . . . . . . . . . . . . . . . . . . . . 11
     4.1   Adaptation Layer Indication Restriction  . . . . . . . . . 11
     4.2   Multihoming Implications . . . . . . . . . . . . . . . . . 11
   5.  Number of Streams  . . . . . . . . . . . . . . . . . . . . . . 12
   6.  Fragmentation  . . . . . . . . . . . . . . . . . . . . . . . . 13
   7.  Sequenced Unordered Operation  . . . . . . . . . . . . . . . . 14
   8.  Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     8.1   Association Initialization . . . . . . . . . . . . . . . . 15
     8.2   Chunk Bundling . . . . . . . . . . . . . . . . . . . . . . 15
     8.3   Association Termination  . . . . . . . . . . . . . . . . . 16
   9.  IANA considerations  . . . . . . . . . . . . . . . . . . . . . 17
   10.   Security Considerations  . . . . . . . . . . . . . . . . . . 18
   11.   Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . 19
   12.   Normative References . . . . . . . . . . . . . . . . . . . . 19
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 19
       Intellectual Property and Copyright Statements . . . . . . . . 21












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1.  Introduction

   This document describes a method to adapt Direct Data Placement (DDP)
   and Remote Direct Memory Access (RDMA) to Stream Control Transmission
   Protocol (SCTP) RFC2960 [2] using a generic description found in
   [RDMA-Draft] [4] and [DDP-Draft] [3] This adaption provides a method
   for two peers to know that each side is performing DDP or RDMA thus
   enabling hardware acceleration if available.

   Some implementations may include this adaptation layer within their
   SCTP implementations to obtain maximum performance but the behavior
   of SCTP will be unaffected.  In order to accomplish this we specify
   the use of the new adaptation layer indication as defined in [ADDIP-
   Draft] [6]

1.1  Definitions

   DDP Endpoint - The logical sender/receiver of DDP Segments.  An SCTP
      Stream pair is not assumed to have a DDP Endpoint.  DDP Segments
      may only be sent once a DDP Endpoint has been assigned to an SCTP
      Stream pair by a local interface.

   DDP Source Stream Sequence (DDP-SSN) - A stream specific sequence
      number assigned by the DDP layer for each SCTP Data Chunk sent.
      Use of the SCTP Stream Sequence Number (SSN) could result in
      ordered delivery at the receiving end.  Use of unordered Data
      Chunks indicates that the receiving SCTP layer is to deliver them
      without delay.  The DDP-SSN retains the original order the Data
      Chunks were generated in, no matter what order they were actually
      sent or received.

   DDP Stream - A bi-directional pair of SCTP streams which have the
      same SCTP stream identifier.

   DDP Stream Session - A single pairing of DDP Endpoints over a DDP
      Stream that lasts from a Initiation message through the
      Termination message(s).

   DDP Stream Session Control - DDP Stream Session Control messages are
      used to control the association of the DDP Endpoint with the DDP
      Stream.

   RDMA - Remote Direct Memory Access.

   RNIC - RDMA Network Interface Card.






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   SCTP association - A protocol relationship between two SCTP
      endpoints.  An SCTP association supports multiple SCTP streams.

   SCTP Data Chunk - An SCTP Chunk used to convey Payload Data.  There
      can be multiple Chunks within each SCTP packet.  Other Chunks are
      used to control the SCTP Association.

   SCTP endpoint - The logical sender/receiver of SCTP packets.  On a
      multi-homed host, an SCTP endpoint is represented to its peers as
      a combination of a SCTP port number and a set of eligible
      destination transport addresses to which SCTP packets can be sent.

   SCTP Stream - A uni-directional logical channel established from one
      to another associated SCTP endpoint.  There can be multiple SCTP
      Streams within each SCTP association.  An SCTP Stream is used to
      form one direction of a DDP stream.

   Transmission Sequence Number (TSN) - A 32-bit sequence number used
      internally by SCTP.  One TSN is attached to each chunk containing
      user data to permit the receiving SCTP endpoint to acknowledge its
      receipt and detect duplicate deliveries.


1.2  Conventions

   The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
   SHOULD NOT, RECOMMENDED, NOT RECOMMENDED, MAY, and OPTIONAL, when
   they appear in this document, are to be interpreted as described in
   RFC2119 [1].






















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2.  Data Formats

2.1  Adaptation Layer Indicator

   This mapping places an entire SCTP association into a specific DDP
   mode: DDP or DDP+RDMA.  It is presumed that the handling of incoming
   data chunks for DDP enabled associations is sufficiently different
   than for routine SCTP associations that it is undesirable to mix DDP
   and non-DDP streams in a single association.  An application that
   needs to mix DDP and non-DDP traffic must use use different
   associations with different adaptation indications for the DDP
   traffic and non-DDP traffic.

   We define a adaption indication which MUST appear in the INIT or
   INIT-ACK with the following format as defined in [ADDIP-Draft] [6]

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Type =0xC006           |    Length = Variable          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Adaptation Indication                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Adaptation Indication:

   The following values are defined for DDP in this document:

         DDP                        - 0x00000001
         DDP+RDMA                   - 0x00000002



2.2  Payload Data Chunks

   After the SCTP association has been established, all DDP relevant
   messages are encoded as Payload Data Chunks.  Each includes a SCTP
   Stream identifier, a Transmissions Sequence Number (TSN), a Payload
   Protocol Identifier, the chunk length and the payload data bytes.

   The DDP SCTP adaptation uses two types of Payload Data Chunks,
   differentiated by the Payload Protocol Identifier:

      DDP Segments are use to for messages sent between DDP Endpoints.
      Each DDP Segment is exactly contained in one SCTP payload data
      chunk with the payload protocol identifier 0x00000001





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      DDP Stream Session messages are used to control the binding of DDP
      endpoints with SCTP streams.


   Payload Protocol Identifier:

   The following value are defined for DDP in this document:

         DDP Segment                - 0x00000001
         DDP Stream Session Control - 0x00000002



2.2.1  DDP Source Sequence Number (DDP-SSN)

   All Payload Data Chunks include a DDP Source Sequence Number (DDP-
   SSN) that tracks the sequence the messages were submitted to the SCTP
   layer.  This field MUST be maintained by the adaptation layer.  It is
   initialized to 1 for each stream at the beginning of each DDP Stream
   Session.  DDP-SSN is increased by one (modulo 65536) for each DDP
   segment submitted to the SCTP layer

   The SCTP Stream Sequence Number (SSN) is not suitable for this
   purpose, because all messages defined by this document use unordered
   Payload Data Chunks to ensure prompt delivery from the receiving SCTP
   layer.

   The SCTP Transmission Sequence Number (TSN) is not suitable for
   determine the original order of Data Chunks within a stream.  The
   sending SCTP layer is allowed to optimize the transmission sequence
   of unordered Data Chunks to encourage Chunk Bundling, or other
   purposes.

   DDP requires that an LLP deliver ordering information with each DDP
   Segment.  The SCTP Adaptation presents the DDP-SSN for this purpose.

2.2.2  DDP Segment Payload Data Chunk

   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-SSN              |         DDP Segment           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
   |                                                               |
   |                         ...                                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   DDP Segments are as defined in [DDP-Draft].



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2.2.3  DDP Stream Session Control Data Chunk


   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-SSN              |    Function Code              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Private Data (Dependent on Function Code)          |
   |                         ...                                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The following function code values are defined for DDP in
   this document:


         DDP Stream Session Initiate         - 0x001
         DDP Stream Session Accept           - 0x002
         DDP Stream Session Reject           - 0x003
         DDP Stream Session Terminate        - 0x004


   ULP supplied Private Data MUST be included for DDP Stream Session
   Initiate DDP Stream Session Accept and DDP Stream Session Reject
   messages.  However, the ULP supplied Private DATA MAY be of zero
   length.  Private Data length MUST NOT exceed 512 bytes in any
   message.  Private Data MUST NOT be included for the DDP Stream
   Session Terminate message.

   The length of private data is derived from the length of the Data
   Chunk

   Received DDP Stream Session Control messages SHOULD be reported to
   the ULP.  If reported, any supplied Private Data MUST be available
   for the ULP to examine.

   There MAY be a limit on the rate at which Stream Session Control
   message can be reported to the ULP.  When this rate is exceeded, or
   when other factors prevent the message from being reported to the
   ULP, the session MUST be terminated.











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3.  DDP Stream Sessions

   A DDP Endpoint is the logical sender/receiver of DDP Segments.  A DDP
   Stream connects two DDP Endpoints using a matched pair of SCTP
   Streams.

   A DDP Stream Session defines the sequence of Data Chunks exchanged
   between two DDP Endpoints over a DDP Stream that has a distinct
   beginning and end.  Data Chunks from one DDP Stream Session are never
   carried over to the next session.

   The local interface MAY associate a DDP Endpoint with the DDP Stream
   based upon the initial exchanges of a DDP Session, and terminate that
   association at the session's end.

   A DDP Stream is associated with at most one Protection Domain during
   a single DDP Stream Session.

3.1  Sequencing

   The DDP Source Sequence Number(DDP-SSN) is reset to one at the
   beginning of each DDP Stream Session.

   The Payload Data Chunks for a given session, when sequenced by their
   DDP-SSN, MUST follow one of the patterns defined in this section.

   If the adaptation layer receives a Payload Data Chunk that conforms
   to none of the enumerated legal patterns the DDP Stream Session MUST
   be terminated.

3.2  Legal Sequence: Active/Passive Session Accepted

   In this DDP Stream Session sequence one DDP Endpoint assumes the
   active role in requesting a DDP Stream Session, which the other side
   accepts.

      Active Side sends a DDP Stream Session Initiate message.

      Passive Side sends a DDP Stream Session Accept mesage.

      Each side may then send zero or more DDP Segments with increasing
      DDP-SSNs, subject to various layers of flow control.

      The final User Data Chunk for each side MAY be a DDP Stream
      Terminate.  At least one side MUST send a DDP Stream Terminate.
      Note that this would follow any RDMAP Terminate message, which to
      this layer is simply another Payload Data Chunk.




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3.3  Legal Sequence: Active/Passive Session Rejected

   DDP Stream Sessions allow each party to send a single non-payload
   message before the other end commits specific resources to the
   session.  This allow each end to determine which resources are to be
   used, and how they are to be configured, or even if the session
   should be granted.

   These decision MAY be influenced by the need to assign a specific
   Protection Domain, to determine how many RDMA Read Credits are
   required, or to determine now many receive operations the ULP should
   enable.

   Because of these, or other, factors the Passive side MAY choose to
   reject a DDP Stream Session Request.  This results in the following
   legal sequence:

      Active Side sends a DDP Stream Session Initiate message.

      Passive Side sends a DDP Stream Session Reject mesage.

   An DDP Stream Session Reject message MUST NOT be sent unless the
   rejection is at the direction of the ULP.

3.4  Legal Sequence: Active/Passive Session Non-ULP Rejected

   Acceptance or rejection of DDP Stream Session Initiate messages
   SHOULD be under the control of the ULP.  This MAY require passing an
   event to the ULP.  There MUST be a finite limit on the number of such
   requests that are pending a ULP decision.  When more session requests
   are received the passive side MUST respond to the Initiate message
   with a DDP Stream Terminate Message.

3.5  ULP Specific Sequencing

   An implementation MAY choose to support additional ULP specific
   sequences, but MUST NOT do so unless requested to do so by the ULP.

   A defined ULP MUST be able to operate using only the defined
   mandatory session sequences.  Any additional sequences must be used
   only for optional optimizations.

3.6  Other Sequencing Rules

   A DDP Stream Session Control message MUST NOT be sent if it may be
   received before a prior DDP Stream Session Control message within the
   same DDP Stream Session.




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   An active side of a DDP Stream Session MUST NOT send a DDP Segment
   that might be received before the DDP Stream Session Initiate
   message.

   This MAY be determined by SCTP acking of the Data Chunk used to carry
   the DDP Stream Session Initiate message, or by receipt of a
   responsive DDP Stream Session Control message.

   A DDP Stream MUST NOT be re-used for another DDP Stream Session while
   any Data Chunk from a prior session might be outstanding.









































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4.  SCTP Endpoints

4.1  Adaptation Layer Indication Restriction

   The local interface MUST allow the ULP to specify an SCTP endpoint to
   use a specific Adaptation Indication.  It MAY require the ULP to do
   so.

   Once an endpoint decides on its acceptable Adaptation Indication(s),
   it SHOULD terminate all requests to establish an association with any
   different Adaptation Indication.

   An SCTP implementation MAY choose to accept association requests for
   a given SCTP endpoint only until one association for the endpoint has
   been established.  At that point it MAY choose to restrict all
   further associations for the same endpoint to use the same Adaptation
   Indication.

4.2  Multihoming Implications

   SCTP allows an SCTP endpoint to be associated with multiple IP
   addresses, potentially representing different interface devices.
   Distribution of the logic for a single DDP stream across multiple
   input devices can be very undesirable, resulting in complex cache
   coherency challenges.  Therefore the local interface MAY restrict
   DDP-enabled SCTP endpoints to a single IP address, or to a set of IP
   addresses that are all assigned to the same input device ("RNIC").

   The default binding of a DDP enabled SCTP endpoint SHOULD NOT cover
   more than a single IP address unless doing so results in no
   additional bus traffic or duplication of memory registration
   resources.  This will frequently result in a different default than
   for SCTP endpoints that are not DDP enabled.

   Even when multi-homing is supported, ULPs are cautioned that they
   SHOULD NOT use ULP control of the source address in attempt to load-
   balance a stream across multiple paths.  A receiving DDP/SCTP
   implementation that chooses to support multi-homing SHOULD optimize
   its design on the assumption that multi-homing will be used for
   network fault tolerance, and not to load-balance between paths.  This
   is consistent with recommended SCTP practices.










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5.  Number of Streams

   DDP Streams are bidirectional.  They are always composed by pairing
   the inbound and outbound SCTP streams with the same SCTP Stream
   Identifier.

   DDP should request the maximum number of SCTP stream it will wish to
   use over the lifetime of the association.  SCTP streams must still be
   bound to DDP Endpoints, and a DDP or DDP+RDMA enabled SCTP
   association does not support ordered Data Chunks.  Therefore the mere
   existence of an SCTP stream is unlikely to require signifigant
   supporting resources.

   This mapping uses an SCTP association to carry one or more DDP
   Steams.  Each DDP Stream will be mapped to a pair of SCTP streams
   with the same SCTP stream number.  DDP MUST initialize all of its
   SCTP associations with the same number of inbound and outbound
   streams.

































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6.  Fragmentation

   A DDP/SCTP Receiver already must deal with fragementation at both the
   IP and DDP Layers.  Therefore use of SCTP layer segmenting will be
   avoided for most cases.

   As a Lower Layer Protocol (LLP) for DDP, the SCTP adaptation layer
   MUST inform the DDP layer of the DDP Segment size that will be
   supported.  This should be the largest value that can be supported
   without use of IP or SCTP fragmention, or 516 bytes, whichever is
   larger.

   SCTP Data Chunk fragmentation MUST NOT be used for the cases where IP
   fragmentation is not required.  SCTP data chunk fragmentation MAY be
   used to avoid IP fragmentation

   The SCTP adaptation layer SHOULD set the maximum DDP Segment size
   below the theoretical maximum in order to allow bundling of Control
   Chunks in the same SCTP packet.

   The SCTP adaptation layer MUST reject user messages that are larger
   than the maximum specified.





























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7.  Sequenced Unordered Operation

   DDP MUST use the Unordered option on all Data Chunks (U Flag set to
   one).  The SCTP Layer is expected to deliver Data Chunks to the DDP
   layer without delay.

   Because DDP employs unordered SCTP delivery, the receiver MUST NOT
   rely upon the SCTP Transmission Sequence Number (TSN) to imply
   ordering of DDP Segments.  The fact that the SCTP Data Chunk for a
   DDP Segment is prior the cumulative ack point does not guarantee that
   all prior DDP segments have been placed.  The SCTP sender is not
   obligated to transmit unordered Data Chunks in the order presented.

   The DDP-SSN can be used without special logic to determine the
   submission sequence when the maximum number of in-flight messages is
   less than 32768.  This also applies if the sending SCTP accepts no
   more than 32767 Data Chunks for a single stream without assigning
   TSNs.

   If SCTP does accept more than 32768 Data chunks for a single stream
   without assigning TSNs,  the sending DDP must simply refrain from
   sending more than 32767 Data Chunks for a single stream without
   acknowledgement.  Note that it MUST NOT rely upon ULP flow control
   for this purpose.  Typical ULP flow control will deal exclusively
   with untagged DDP Messages, not with DDP segments.

   The receiving DDP implementation MAY perform a validity check on
   received DDP-SSNs to ensure that any gap could be accounted for by
   unreceived Data Chunks.  Implementations are advised against
   allocating resources on the assumption that DDP-SSNs are valid
   without first performing such a validtity check.  An invalid DDP-SSN
   MAY result in termination of the DDP Stream.



















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8.  Procedures

8.1  Association Initialization

   At the startup of an association, an endpoint wishing to perform DDP,
   RDMA, or DDP+RDMA placement MUST include an adaptation layer
   indication in its INIT or INIT-ACK (as defined in Section 2.1.  After
   the exchange of the initial first two SCTP chunks (INIT and INIT-
   ACK), an endpoint MUST verify and inspect the adaptation indication
   and compare it to the following table to determine proper action.

          Indication |           Action
            type     |

   ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
                     | This indicates that the peer DOES NOT
         NONE        | support ANY DDP or RDMA adaption and thus
                     | RDMA and DDP procedures MUST NOT be
                     | performed upon this association.
   ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
                     | This indicates that the peer DOES support
         DDP         | DDP (but not RDMA). Procedures outlined in
                     | [DDP-Draft] MUST be followed.
   ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
                     | This indicates that the peer supports BOTH
        DDP+RDMA     | RDMA and DDP. If the receiving endpoint
                     | indicated the same, then the procedures in
                     | both [RDMA-Draft] and [DDP-Draft]
                     | MUST be followed. If the local endpoint
                     | only indicated DDP, then ONLY the
                     | procedures in [DDP-Draft] MUST be followed.
   ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
                     | This indicates that the peer DOES NOT
       ANY-OTHER     | support ANY DDP or RDMA adaption and thus
       Indication    | RDMA and DDP procedures MUST NOT be
                     | performed upon this association.

   ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

   An implementation MAY require that all associations for a given SCTP
   endpoint be placed in the same mode.

   The local interface MAY allow the ULP to accept only requests to
   establish an association in a specified mode.

8.2  Chunk Bundling

   SCTP allows multiple Data Chunks to be bundled in a single SCTP



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   packet.  Data chunks containing DDP Segments with untagged messages
   SHOULD NOT be delayed to facilitate bundling.  Data chunks containing
   DDP Segments with tagged messages will generally be full sized, and
   hence not subject to bundling.  However partial size tagged messages
   MAY be delayed, as that they are frequently followed by a short
   untagged message.

8.3  Association Termination

   Termination of an SCTP Association due to errors should be handled at
   the SCTP layer.  The RDMAP defined RDMAP Terminate Message SHOULD NOT
   be sent on each DDP Stream when a determination has been made to
   terminate an SCTP association.  Sending that message on each SCTP
   stream could severely delay the termination of the association.

   The local interface SHOULD notify all consumers of DDP streams when
   the underlying SCTP stream has been terminated.

   Other RDMAP defined Terminate Messages MUST be generated as specified
   when a DDP Stream is terminated.  Note that with the SCTP mapping,
   termination of a DDP Stream does not mandate termination of the
   Association.





























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9.  IANA considerations

   This document defines two new Adaptation Layer Indication codepoints:


         DDP                         - 0x00000001
         DDP+RDMA                    - 0x00000002

   This document also defines two new Payload Protocol Identifier
   (PPIDs):

         DDP Segment                 - 0x00000001
         DDP Stream Session Control  - 0x00000002






































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10.  Security Considerations

   Any direct placement of memory could pose a significant security risk
   if adequate local controls are not provided.  These threats should be
   addressed in the appropriate DDP [DDP-Draft] [3] or RDMA [RDMA-Draft]
   [4] drafts.  This document does not add any additional security risks
   over those found in RFC2960 [2].












































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11.  Acknowledgments

   Special Acknowledgment to Sukanta Ganguly for his extra efforts in
   reading and reviewing this document.

   The authors would like to thank the following people that have
   provided comments and input: Stephen Bailey, David Black, Douglas
   Otis, Allyn Romanow and Jim Williams.

12.  Normative References

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

   [2]  Stewart, R., Xie, Q., Morneault, K., Sharp, C., Schwarzbauer,
        H., Taylor, T., Rytina, I., Kalla, M., Zhang, L., and V. Paxson,
        "Stream Control Transmission Protocol", RFC 2960, October 2000.

   [3]  Shah, H., "Direct Data Placement over Reliable Transports",
        draft-ietf-rddp-ddp-05 (work in progress), July 2005.

   [4]  Recio, R., "An RDMA Protocol Specification",
        draft-ietf-rddp-rdmap-05 (work in progress), July 2005.

   [5]  Stewart, R., "Sockets API Extensions for Stream Control
        Transmission Protocol (SCTP)", draft-ietf-tsvwg-sctpsocket-10
        (work in progress), February 2005.

   [6]  Stewart, R., "Stream Control Transmission Protocol (SCTP)
        Dynamic Address  Reconfiguration",
        draft-ietf-tsvwg-addip-sctp-12 (work in progress), June 2005.


Authors' Addresses

   Randall R. Stewart
   Cisco Systems, Inc.
   Forest Drive
   Columbia, SC  29036
   USA

   Phone:
   Email: rrs@cisco.com








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   Caitlin Bestler
   Broadcom
   49 Discovery
   Irvine, CA  92618
   USA

   Phone:
   Email: caitlinb@siliquent.com


   Hemal V. Shah
   Intel Corporation
   Mailstop: PTL1
   1501 S. Mopac Expressway, #400
   Austin, TX  78746
   USA

   Phone:
   Email: hemal.shah@intel.com


   Vivek Kashyap
   IBM
   15450 SW Koll Parkway
   Beaverton, OR  57006
   USA

   Phone:
   Email: vivk@us.ibm.com


   Sukanta Ganguly
   Consultant

   Phone:
   Email: sganguly@yahoo.com















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