Bidirectional Remote Procedure Call on RPC-over-RDMA Transports
RFC 8167

• Status
• IESG evaluation record
• IESG writeups
• Email expansions
• History

• Versions
• 00
• 01
• 02
• 03
• 04
• 05
• 06
• 07
• 08

Internet Engineering Task Force (IETF)                          C. Lever
Request for Comments: 8167                                        Oracle
Category: Standards Track                                      June 2017
ISSN: 2070-1721

    Bidirectional Remote Procedure Call on RPC-over-RDMA Transports

Abstract

   Minor versions of Network File System (NFS) version 4 newer than
   minor version 0 work best when Remote Procedure Call (RPC) transports
   can send RPC transactions in both directions on the same connection.
   This document describes how RPC transport endpoints capable of Remote
   Direct Memory Access (RDMA) convey RPCs in both directions on a
   single connection.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc8167.

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
   to this document.  Code Components extracted from this document must
   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.

Lever                        Standards Track                    [Page 1]
RFC 8167               Bidirectional RPC-over-RDMA             June 2017

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Understanding RPC Direction . . . . . . . . . . . . . . . . .   3
   3.  Immediate Uses of Bidirectional RPC-over-RDMA . . . . . . . .   5
   4.  Flow Control  . . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Sending and Receiving Operations in the Reverse Direction . .   8
   6.  In the Absence of Support for Reverse-Direction Operation . .  11
   7.  Considerations for ULBs . . . . . . . . . . . . . . . . . . .  11
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   10. Normative References  . . . . . . . . . . . . . . . . . . . .  12
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  13
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   RPC-over-RDMA transports, introduced in [RFC8166], efficiently convey
   Remote Procedure Call (RPC) transactions on transport layers capable
   of Remote Direct Memory Access (RDMA).  The purpose of this document
   is to enable concurrent operation in both directions on a single
   transport connection using RPC-over-RDMA protocol versions that do
   not have specific facilities for reverse-direction operation.

   Reverse-direction RPC transactions are necessary for the operation of
   version 4.1 of the Network File System (NFS), and in particular, of
   Parallel NFS (pNFS) [RFC5661], though any Upper-Layer Protocol (ULP)
   implementation may make use of them.  An Upper-Layer Binding (ULB)
   for NFS version 4.x callback operation is additionally required (see
   Section 7) but is not provided in this document.

   For example, using the approach described herein, RPC transactions
   can be conveyed in both directions on the same RPC-over-RDMA version
   1 connection without changes to the RPC-over-RDMA version 1 protocol.
   This document does not update the protocol specified in [RFC8166].

   The remainder of this document assumes familiarity with the
   terminology and concepts contained in [RFC8166], especially Sections
   2 and 3.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

Lever                        Standards Track                    [Page 2]
RFC 8167               Bidirectional RPC-over-RDMA             June 2017

2.  Understanding RPC Direction

   The Open Network Computing Remote Procedure Call (ONC RPC) protocol
   as described in [RFC5531] is architected as a message-passing
   protocol between one server and one or more clients.  ONC RPC