Direct Data Placement over Reliable Transports
RFC 5041

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• 07

Network Working Group                                            H. Shah
Request for Comments: 5041                          Broadcom Corporation
Category: Standards Track                                   J. Pinkerton
                                                   Microsoft Corporation
                                                                R. Recio
                                                         IBM Corporation
                                                               P. Culley
                                                 Hewlett-Packard Company
                                                            October 2007

            Direct Data Placement over Reliable Transports

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Abstract

   The Direct Data Placement protocol provides information to Place the
   incoming data directly into an upper layer protocol's receive buffer
   without intermediate buffers.  This removes excess CPU and memory
   utilization associated with transferring data through the
   intermediate buffers.

Table of Contents

   1. Introduction ....................................................3
      1.1. Architectural Goals ........................................3
      1.2. Protocol Overview ..........................................4
      1.3. DDP Layering ...............................................6
   2. Glossary ........................................................7
      2.1. General ....................................................7
      2.2. LLP ........................................................9
      2.3. Direct Data Placement (DDP) ................................9
   3. Reliable Delivery LLP Requirements .............................12
   4. Header Format ..................................................13
      4.1. DDP Control Field .........................................13
      4.2. DDP Tagged Buffer Model Header ............................14
      4.3. DDP Untagged Buffer Model Header ..........................16
      4.4. DDP Segment Format ........................................17
   5. Data Transfer ..................................................18
      5.1. DDP Tagged or Untagged Buffer Models ......................18
           5.1.1. Tagged Buffer Model ................................18

Shah, et al.                Standards Track                     [Page 1]
RFC 5041               DDP Protocol Specification           October 2007

           5.1.2. Untagged Buffer Model ..............................18
      5.2. Segmentation and Reassembly of a DDP Message ..............19
      5.3. Ordering Among DDP Messages ...............................21
      5.4. DDP Message Completion and Delivery .......................21
   6. DDP Stream Setup and Teardown ..................................22
      6.1. DDP Stream Setup ..........................................22
      6.2. DDP Stream Teardown .......................................22
           6.2.1. DDP Graceful Teardown ..............................22
           6.2.2. DDP Abortive Teardown ..............................23
   7. Error Semantics ................................................24
      7.1. Errors Detected at the Data Sink ..........................24
      7.2. DDP Error Numbers .........................................25
   8. Security Considerations ........................................26
      8.1. Protocol-Specific Security Considerations .................26
      8.2. Association of an STag and a DDP Stream ...................26
      8.3. Security Requirements .....................................27
           8.3.1. RNIC Requirements ..................................28
           8.3.2. Privileged Resources Manager Requirement ...........29
      8.4. Security Services for DDP .................................30
           8.4.1. Available Security Services ........................30
           8.4.2. Requirements for IPsec Services for DDP ............30
   9. IANA Considerations ............................................31
   10. References ....................................................32
      10.1. Normative References .....................................32
      10.2. Informative References ...................................33
    Appendix A. Receive Window Sizing ................................34
    Appendix B. Contributors .........................................34

Table of Figures

    Figure 1: DDP Layering ............................................6
    Figure 2: MPA, DDP, and RDMAP Header Alignment ....................7
    Figure 3: DDP Control Field ......................................13