Improving the Performance and Reliability of RPC Replies on RPC-over-RDMA Transports
draft-cel-nfsv4-rpcrdma-reliable-reply-00

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Network File System Version 4                                   C. Lever
Internet-Draft                                                    Oracle
Intended status: Experimental                               May 13, 2017
Expires: November 14, 2017

 Improving the Performance and Reliability of RPC Replies on RPC-over-
                            RDMA Transports
               draft-cel-nfsv4-rpcrdma-reliable-reply-00

Abstract

   RPC transports such as RPC-over-RDMA Version One require reply
   buffers to be in place before an RPC Call is sent.  However, Upper
   Layer Protocols sometimes have difficulty estimating the expected
   maximum size of RPC replies.  This introduces the risk that an RPC
   Reply message can overrun reply resources provided by the requester,
   preventing delivery of the message, through no fault of the
   requester.  This document describes a mechanism that eliminates the
   need for pre-allocation of reply resources for unpredictably large
   replies.

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 [RFC2119].

Status of This Memo

   This Internet-Draft is submitted 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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   This Internet-Draft will expire on November 14, 2017.

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Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Reply Chunk Overrun . . . . . . . . . . . . . . . . . . .   4
     2.2.  Reply Size Calculation  . . . . . . . . . . . . . . . . .   4
     2.3.  Requester Registration Costs  . . . . . . . . . . . . . .   5
     2.4.  Denial of Service . . . . . . . . . . . . . . . . . . . .   5
     2.5.  Estimating Transport Header Size  . . . . . . . . . . . .   6
   3.  Responder-Provided Read Chunks  . . . . . . . . . . . . . . .   6
     3.1.  Specification . . . . . . . . . . . . . . . . . . . . . .   7
   4.  Analysis  . . . . . . . . . . . . . . . . . . . . . . . . . .   9
     4.1.  Benefits  . . . . . . . . . . . . . . . . . . . . . . . .   9
     4.2.  Costs . . . . . . . . . . . . . . . . . . . . . . . . . .  10
     4.3.  Selecting a Reply Mechanism . . . . . . . . . . . . . . .  11
     4.4.  Implementation Complexity . . . . . . . . . . . . . . . .  12
     4.5.  Alternatives  . . . . . . . . . . . . . . . . . . . . . .  13
   5.  Interoperation Considerations . . . . . . . . . . . . . . . .  14
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  15
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  15
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .  16
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  16

1.  Introduction

   One way in which RPC-over-RDMA Version One improves transport
   efficiency is by ensuring resources for RPC replies are available in
   advance of each RPC transaction [I-D.ietf-nfsv4-rfc5666bis].  These
   resources are typically provisioned before a requester sends each RPC

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   Call message.  They are provided to the responder to use for
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