RPC-over-RDMA Extensions to Reduce Internode Round-trips
draft-dnoveck-nfsv4-rpcrdma-rtrext-00

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Network File System Version 4                                  D. Noveck
Internet-Draft                                                       HPE
Intended status: Standards Track                            June 5, 2016
Expires: December 7, 2016

        RPC-over-RDMA Extensions to Reduce Internode Round-trips
                 draft-dnoveck-nfsv4-rpcrdma-rtrext-00

Abstract

   It is expected that the RPC-over-RDMA transport will, at some point,
   allow protocol extensions to be defined.  This would provide for the
   specification of OPTIONAL features allowing participants who
   implement the OPTIONAL features to cooperate as specified by that
   extension, while still interoperating with participants who do not
   support that extension.

   A particular extension is described herein, whose purpose is to
   reduce the latency due to inter-node round-trips needed to effect
   operations which involve direct data placement or which transfer RPC
   messages longer than the fixed inline buffer size limit.

Status of This Memo

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   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of

Noveck                  Expires December 7, 2016                [Page 1]
Internet-Draft       RPC/RDMA Round-trip Reductions            June 2016

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Table of Contents

   1.  Preliminaries . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
     1.2.  Introduction  . . . . . . . . . . . . . . . . . . . . . .   3
     1.3.  Prerequisites . . . . . . . . . . . . . . . . . . . . . .   3
     1.4.  Role Terminology  . . . . . . . . . . . . . . . . . . . .   4
   2.  Extension Overview  . . . . . . . . . . . . . . . . . . . . .   5
   3.  Direct Data Placement Feature . . . . . . . . . . . . . . . .   5
     3.1.  Current Situation . . . . . . . . . . . . . . . . . . . .   5
     3.2.  RDMA_MSGP . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.3.  Send-based DDP  . . . . . . . . . . . . . . . . . . . . .   7
     3.4.  Other DDP-Related Extensions  . . . . . . . . . . . . . .   7
   4.  Message Continuation Feature  . . . . . . . . . . . . . . . .   8
     4.1.  Current Situation . . . . . . . . . . . . . . . . . . . .   8
     4.2.  Message Continuation Changes  . . . . . . . . . . . . . .   9
     4.3.  Message Continuation and Credits  . . . . . . . . . . . .   9
   5.  Protocol Additions  . . . . . . . . . . . . . . . . . . . . .  10
     5.1.  New Operation Support . . . . . . . . . . . . . . . . . .  10
     5.2.  Message Continuation Support  . . . . . . . . . . . . . .  11
     5.3.  Send-based DDP Support  . . . . . . . . . . . . . . . . .  11
     5.4.  Error Reporting . . . . . . . . . . . . . . . . . . . . .  12
   6.  XDR Preliminaries . . . . . . . . . . . . . . . . . . . . . .  13
     6.1.  Message Continuation Preliminaries  . . . . . . . . . . .  13
     6.2.  Data Placement Preliminaries  . . . . . . . . . . . . . .  14
   7.  Data Placement Structures . . . . . . . . . . . . . . . . . .  17
     7.1.  Data Placement Overview . . . . . . . . . . . . . . . . .  17
     7.2.  Buffer Structure Definition . . . . . . . . . . . . . . .  18
     7.3.  Message DDP Structures  . . . . . . . . . . . . . . . . .  20
     7.4.  Response Direction DDP Structures . . . . . . . . . . . .  21
   8.  Transport Characteristics . . . . . . . . . . . . . . . . . .  24
     8.1.  Characteristics List  . . . . . . . . . . . . . . . . . .  24
     8.2.  RTR Support Characteristic  . . . . . . . . . . . . . . .  25
     8.3.  Receive Buffer Structure Characteristic . . . . . . . . .  25
     8.4.  Request Transmission Receive Limit Characteristic . . . .  26
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