Network File System Version 4                              C. Lever, Ed.
Internet-Draft                                                    Oracle
Obsoletes: 5667 (if approved)                            August 25,                         September 28, 2016
Intended status: Standards Track
Expires: February 26, April 1, 2017

     Network File System (NFS) Upper Layer Binding To RPC-Over-RDMA
                     draft-ietf-nfsv4-rfc5667bis-02
                     draft-ietf-nfsv4-rfc5667bis-03

Abstract

   This document specifies Upper Layer Bindings of Network File System
   (NFS) protocol versions to RPC-over-RDMA transports.  These bindings
   are required to enable RPC-based protocols such as NFS to use direct
   data placement on RPC-over-RDMA transports.  This document obsoletes
   RFC 5667.

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on February 26, April 1, 2017.

Copyright Notice

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

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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Changes Since RFC 5667  . . . . . . . . . . . . . . . . .   3
     1.2.  Extending This Upper Layer Binding  . . . . . . . . . . .   4
     1.3.  Requirements Language . . . . . . . . . . . . . . . . . .   4
   2.  Conveying NFS Operations On RPC-Over-RDMA Transports  . . . .   4
     2.1.  Use Of The Read List  . . . . . . . . . . . . . . . . . .   4
     2.2.  Use Of The Write List . . . . . . . . . . . . . . . . . .   4
     2.3.  Construction Of Individual Chunks . . . . . . . . . . . .   5
     2.4.  Use Of Long Calls And Replies . . . . . . . . . . . . . .   5   3
   3.  NFS Versions 2 And 3 Upper Layer Binding  . . . . . . . . . .   5   4
   4.  NFS Version 4 Upper Layer Binding . . . . . . . . . . . . . .   6
     4.1.  DDP-Eligibility . . . . .
   5.  Extending NFS Upper Layer Bindings  . . . . . . . . . . . . .  13
   6.  IANA Considerations . . .   6
     4.2.  Reply Size Estimation . . . . . . . . . . . . . . . . . .   7
     4.3.  NFS Version 4 COMPOUND  13
   7.  Security Considerations . . . . . . . . . .   7
     4.4.  NFS Version 4 Callback  . . . . . . . . . . . . . . . . .   9
   5.  IANA Considerations  13
   8.  References  . . . . . . . . . . . . . . . . . . . . .   9
   6.  Security Considerations . . . .  14
   Appendix A.  Changes Since RFC 5667 . . . . . . . . . . . . . . .  10
   7.  15
   Appendix B.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . .  10
   8.  References  . . .  16
   Author's Address  . . . . . . . . . . . . . . . . . . . . . .  10
     8.1.  Normative References . . . . . . . . . . . . . . . . . .  10
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  12  17

1.  Introduction

   An RPC-over-RDMA transport, such as defined in
   [I-D.ietf-nfsv4-rfc5666bis], may employ direct data placement to
   transmit large
   convey data payloads associated with RPC transactions.  Each
   RPC-over-RDMA RPC-
   over-RDMA transport header conveys lists of memory locations
   corresponding to XDR data items defined in an Upper Layer Protocol
   (such as NFS).

   To facilitate interoperation, RPC client and server implementations
   must agree in advance on what XDR data items in which RPC procedures
   are eligible for direct data placement (DDP).  This document contains
   material required of Upper Layer Bindings, as specified in
   [I-D.ietf-nfsv4-rfc5666bis], for the following NFS protocol versions:

   o  NFS Version 2 [RFC1094]

   o  NFS Version 3 [RFC1813]

   o  NFS Version 4.0 [RFC7530]

   o  NFS Version 4.1 [RFC5661]

   o  NFS Version 4.2 [I-D.ietf-nfsv4-minorversion2]

1.1.  Changes Since RFC 5667

   Corrections

2.  Conveying NFS Operations On RPC-Over-RDMA Transports

   Definitions of terminology and updates made necessary by new language a general discussion of how RPC-over-
   RDMA is used to convey RPC transactions can be found in
   [I-D.ietf-nfsv4-rfc5666bis] have been introduced.  For example,
   references
   [I-D.ietf-nfsv4-rfc5666bis].  In this section, these general
   principals are applied to deprecated features the specifics of the NFS protocol.

2.1.  Use Of The Read List

   The Read list in each RPC-over-RDMA Version One, transport header represents a set
   of memory regions containing DDP-eligible NFS argument data.  Large
   data items, such as RDMA_MSGP, and the use data payload of an NFS version 3 WRITE
   procedure, are referenced by the Read list for handling RPC replies,
   has been removed. list.  The term "mapping" has been replaced with NFS server pulls
   such payloads from the term
   "binding" or "Upper Layer Binding" throughout client and places them directly into its own
   memory.

   XDR unmarshaling code on the document.  Material
   that duplicates what is in [I-D.ietf-nfsv4-rfc5666bis] has been
   deleted.

   Material required by [I-D.ietf-nfsv4-rfc5666bis] for Upper Layer
   Bindings that was not present in [RFC5667] has been added, including
   discussion of how each NFS version properly estimates server identifies the maximum
   size of RPC replies.

   The following changes have been made, relative to [RFC5667]:

   o  Ambiguous or erroneous uses of RFC2119 terms have been corrected.

   o  References to specific data movement mechanisms have been made
      generic or removed.

   o  References to obsolete RFCs have been replaced.

   o  Technical corrections have been made.  For example, the mention of
      12KB correspondence
   between Read chunks and 36KB inline thresholds have been removed. particular NFS arguments via the chunk
   Position value encoded in each Read segment.

2.2.  Use Of The reference
      to Write List

   The Write list in each RPC-over-RDMA transport header represents a non-existant
   set of memory regions that can receive DDP-eligible NFS version 4 SYMLINK operation has been
      replaced with result data.
   Large data items, such as the payload of an NFS version 4 CREATE(NF4LNK). 3 READ
   procedure, are referenced by the Write list.  The discussion of NFS
      version 4 COMPOUND handling has been completed.

   o  An IANA Considerations Section has replaced server pushes
   such payloads to the "Port Usage
      Considerations" Section.

   o  Code excerpts have been removed, and figures have been modernized.

   o  Language inconsistent with or contradictory client, placing them directly into the client's
   memory.

   Each Write chunk corresponds to
      [I-D.ietf-nfsv4-rfc5666bis] has been removed from Sections 2 a specific XDR data item in an NFS
   reply.  This document specifies how NFS client and
      3, server
   implementations identify the correspondence between Write chunks and both Sections have been combined into
   XDR results.

2.2.1.  Empty Write Chunks

   Section 2 in the
      present document.

   o  An explicit discussion 4.4.6.2 of NFSv4.0 and NFSv4.1 backchannel
      operation will replace [I-D.ietf-nfsv4-rfc5666bis] defines the previous treatment concept of callback
      operations.  No NFSv4.x callback operation
   unused Write chunks.  An unused Write chunk is DDP-eligible.

   o  The binding for NFSv4.1 has been completed.  No DDP-eligible
      operations exist in NFSv4.1 that did not exist a Write chunk with
   either zero segments or where all segments in NFSv4.0.

   o  A binding for NFSv4.2 has been added that includes discussion of
      new data-bearing operations like READ_PLUS.

1.2.  Extending This Upper Layer Binding

   As stated earlier, RPC programs such as NFS are required to the Write chunk have an
   Upper Layer Binding specification to interoperate on RPC-over-RDMA
   transports [I-D.ietf-nfsv4-rfc5666bis].  The Upper Layer Binding
   specified in
   zero length.  In this document can be extended these are referred to cover versions as "empty" Write
   chunks.  A "non-empty" Write chunk has at least one segment of the non-
   zero length.

   An NFS version 4 protocol specified after client might wish an NFS version 4 minor version 2
   via standards action.  This includes NFSv4 extensions that are
   documented separately from a new minor version.

1.3.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are server to be interpreted as described in [RFC2119].

2.  Conveying NFS Operations On RPC-Over-RDMA Transports

   Definitions of terminology and return a general discussion of how RPC-over-
   RDMA DDP-eligible
   result inline.  If there is used to convey RPC transactions can be found only one DDP-eligible result item in
   [I-D.ietf-nfsv4-rfc5666bis].  In this section, these general
   principals are applied to the specifics of
   reply, the NFS protocol.

2.1.  Use Of The Read List

   The Read client simply specifies an empty Write list in each RPC-over-RDMA transport header represents a set
   of memory regions containing DDP-eligible NFS argument data.  Large
   data items, such as to force
   the data payload of an NFS WRITE request, are
   referenced by the Read list.  The server places these directly into
   its memory.

   XDR unmarshaling code on to return that result inline.  If there are multiple
   DDP-eligible results, the NFS server identifies the correspondence
   between Read chunks and particular NFS arguments via the chunk
   Position value encoded in each Read chunk.

2.2.  Use Of The Write List

   The client specifies empty Write list in chunks for
   each RPC-over-RDMA transport header represents a
   set of memory regions that can receive DDP-eligible NFS result data.
   Large data items such as the payload of an item that it wishes to be returned inline.

   An NFS READ request server might encounter an XDR union result where there are
   referenced by
   arms that have a DDP-eligible result, and arms that do not.  If the Write list.  The server places these directly into
   NFS client memory.

   Each has provided a non-empty Write chunk corresponds to that matches with a specific XDR data item in an NFS
   reply.  This document specifies how
   DDP-eligible result, but the response does not contain that result,
   the NFS client and server
   implementations identify the correspondence between MUST return an empty Write chunks and
   XDR results.

2.3.  Construction Of Individual Chunks

   Each Read chunk is represented as a list of segments at in that position in
   the same XDR
   Position, and each Write chunk is represented as an array of
   segments.  An NFS client thus has the flexibility to advertise a set
   of discontiguous memory regions in which to send or receive a single
   DDP-eligible data item.

2.4. list.

2.3.  Use Of Long Calls And Replies

   Small RPC messages are conveyed using RDMA Send operations which are
   of limited size.  If an NFS request is too large to be conveyed via
   an RDMA Send,
   within the NFS server's responder inline threshold, and there are no
   DDP-eligible data items that can be removed, an NFS client must send
   the request using a Long Call.  The entire NFS request is sent in a
   special Read chunk called a Position-
   Zero Position-Zero Read chunk.

   If a an NFS client predicts that the maximum size of an NFS reply is could
   be too large to be conveyed via an RDMA Send, within it's own responder inline
   threshold, it provides a Reply chunk in the RPC-over-RDMA transport
   header conveying the NFS request.  The server can place places the entire NFS
   reply in the Reply chunk.

   These special chunks are described in more detail in
   [I-D.ietf-nfsv4-rfc5666bis].

3.  NFS Versions 2 And 3 Upper Layer Binding

2.4.  Scatter-Gather Considerations

   A chunk comprises exactly one XDR data item.  Each Read chunk is
   represented as a list of segments at the same XDR Position.  Each
   Write chunk is represented as an array of segments.  An NFS client MAY send a single Read chunk
   thus has the flexibility to advertise a set of discontiguous memory
   regions in which to send or receive a single DDP-eligible XDR data
   item.

3.  NFS Versions 2 And 3 Upper Layer Binding

   An NFS version 2 or version 3 client MAY send a single Read chunk to
   supply the opaque file data for an NFS WRITE procedure, or the
   pathname for an NFS SYMLINK procedure.  For these procedures, NFS
   version 2 or 3 servers MUST ignore Read chunks beyond the first in
   the Read list.  For all other NFS procedures, NFS version 2 or 3
   servers MUST ignore Read chunks that have a non-zero value in their
   Position fields, and
   Read chunks beyond the first in the Read list. fields.

   Similarly, an NFS version 2 or version 3 client MAY provide a single
   Write chunk to receive either the opaque file data from an NFS READ
   procedure, or the pathname from an NFS READLINK procedure.  For these
   procedures, NFS version 2 or 3 servers MUST ignore the Write
   list for any other NFS procedure, and any Write chunks
   beyond the first in the Write list.  For all other NFS procedures,
   NFS version 2 or 3 servers MUST ignore the Write list.

   There are no NFS version 2 or 3 procedures that have DDP-eligible
   data items in both their Call and Reply.  However, when an NFS
   version 2 or version 3 client sends a Long Call or Reply, it MAY
   provide a combination of a Read list, a Write list, and/or a Reply
   chunk in the same RPC-over-RDMA header.

   If an NFS version 2 or version 3 client has not provided enough bytes
   in a Read list to match the size of a DDP-eligible NFS argument data
   item, or if an NFS version 2 or version 3 client has not provided
   enough Write list resources to handle an NFS
   WRITE READ or READLINK reply,
   or if the client has not provided a large enough Reply chunk to
   convey an NFS reply, the server MUST return one of:

   o  An RPC-over-RDMA message of type RDMA_ERROR, with the rdma_xid
      field set to the XID of the matching NFS Call, and the rdma_error
      field set to ERR_CHUNK; or

   o  An RPC message (via an RDMA_MSG message) with the xid field set to
      the XID of the matching NFS Call, the mtype field set to REPLY,
      the stat field set to MSG_ACCEPTED, and the accept_stat field set
      to GARBAGE_ARGS.

   These replies do not give any indication to NFS version 2 or version
   3 clients of whether an NFS version 2 or 3 server has processed the
   arguments of the RPC Call, or whether the NFS version 2 or 3 server
   has accessed NFS client memory associated with that RPC.

   NFS version 2 or version 3 clients already successfully estimate the
   maximum reply size of each operation in order to provide an adequate
   set of buffers to receive each NFS reply.  An NFS version 2 or
   version 3 client provides a Reply chunk when the maximum possible
   reply size is larger than the client's responder inline threshold.

4.  NFS Version 4 Upper Layer Binding

   This specification applies to NFS Version 4.0 [RFC7530],

3.1.  Auxiliary Protocols

   NFS Version
   4.1 [RFC5661], versions 2 and NFS Version 4.2 [I-D.ietf-nfsv4-minorversion2].
   It also applies to the callback protocols associated 3 are typically deployed with each several other
   protocols, referred to as "auxiliary" protocols.  These are separate
   RPC protcols which handle operations that are not part of
   these minor versions.

4.1.  DDP-Eligibility

   An the main
   NFS client MAY send protocol.  These include the MOUNT and NLM protocols, introduced
   in an appendix of [RFC1813]; the NSM protocol, described in Chapter
   11 of [NSM]; and the NFSACL protocol, which does not have a Read chunk to supply opaque file data for public
   definition.  However NFSACL is treated as a
   WRITE operation or the pathname de facto standard and
   there are several interoperating implementations.

   RPC-over-RDMA considers these as individual Upper Layer Protocols
   [I-D.ietf-nfsv4-rfc5666bis].  Therefore to operate on an RPC-over-
   RDMA transport, an Upper Layer Binding must be provided for a CREATE(NF4LNK) operation each of
   these.

   Typically MOUNT, NLM, and NSM are conveyed via TCP rather than RPC-
   over-RDMA.  Note that only metadata is conveyed in these protocols,
   thus direct data placement is never necessary, and the size of RPC
   messages is uniformly small.  The maximum size of replies is easily
   determined by examining the XDR definitions of these protocols.

   Implementations that support the NFSACL protocol typically send
   NFSACL procedures on the same connection as the main NFS protocol.
   Thus NFSACL does require an Upper Layer Binding.

   No data item in this protocol is DDP-eligible.  There is no protocol
   size limit for NFS version 4 COMPOUND procedure.  An NFS 3 ACL objects.  The client MUST NOT send can have some
   difficulty ascertaining the size of ACLs to be read from servers.
   Practically speaking, ACLs are not large (less than 4KB in most
   cases), but a Read large Reply chunk that corresponds with any other XDR data item may be provided when the client is in any other
   doubt.  The usual rules apply to the use of Long Messages when the
   size of an NFSACL RPC exceeds a connection's inline thresholds.

4.  NFS
   version Version 4 Upper Layer Binding

   This specification applies to NFS Version 4.0 [RFC7530], NFS Version
   4.1 [RFC5661], and NFS Version 4.2 [I-D.ietf-nfsv4-minorversion2].
   It also applies to the callback protocols associated with each of
   these minor versions defined in the same documents.

4.1.  DDP-Eligibility

   For each WRITE operation in an NFS version 4 COMPOUND procedure, or in an
   NFS version 4 NULL procedure.

   Similarly, an NFS client MAY provide a Write single Read chunk to receive either supply the
   opaque file data from a READ operation, NFS4_CONTENT_DATA from argument.  For each CREATE(NF4LNK) operation in an
   NFS version 4 COMPOUND procedure, An NFS version 4 client MAY provide
   a
   READ_PLUS operation, or single Read chunk to supply the pathname from argument.

   Similarly, for each READ operation in an NFS version 4 COMPOUND
   procedure, an NFS version 4 client MAY provide a single Write chunk
   to receive the opaque file data argument.  For each READ_PLUS
   operation in an NFS version 4 COMPOUND procedure, an NFS version 4
   client MAY provide a single Write chunk to receive NFS4_CONTENT_DATA.
   For each READLINK operation in an NFS version 4 COMPOUND procedure. procedure,
   an NFS version 4 client MAY provide a single Write chunk to receive
   the pathname argument.

   An NFS version 4 client MUST NOT provide a Read or Write chunk that
   corresponds with any other XDR data item in any other NFS version 4
   operation in an NFS version 4 COMPOUND procedure, or in an NFS
   version 4 NULL procedure.

   There is no prohibition against an NFS version 4 COMPOUND procedure
   constructed with both a READ and WRITE operation, say.  Thus it

   It is possible for NFS version 4 COMPOUND procedures to use both the
   Read list and Write list simultaneously.  An NFS version 4 client MAY
   provide a Read list and a Write list in the same transaction if it is
   sending a Long Call or Reply.

   If an NFS version 4 client has not provided enough bytes in a Read
   list to match the size of a DDP-eligible NFS argument data item, or
   if an NFS version 4 client has not provided enough Write list
   resources to handle a WRITE or READLINK operation, or if the client
   has not provided a large enough Reply chunk to convey an NFS reply,
   the server MUST return one of:

   o  An RPC-over-RDMA message of type RDMA_ERROR, with the rdma_xid
      field set to the XID of the matching NFS Call, and the rdma_error
      field set to ERR_CHUNK; or

   o  An RPC message (via an RDMA_MSG message) with the mtype xid field set to REPLY,
      the XID of the matching NFS Call, the stat field set to
      MSG_ACCEPTED, and the accept_stat field set to GARBAGE_ARGS.

4.2.  Reply Size Estimation

   An NFS client provides a Reply chunk when

   Such error replies are permanent errors, and constitute both
   completion of the maximum possible reply
   size RPC transaction, and a valid server response.  It
   is larger than the client's responder inline threshold. not necessary for an NFS
   clients successfully estimate version 4 server to drop the maximum reply size of most
   operations transport
   connection in order to provide this case.

4.1.1.  Session-Related Considerations

   In most cases, the presence of an adequate set NFS session [RFC5661] has no effect
   on the operation of buffers RPC-over-RDMA.  None of the operations introduced
   to receive
   each support NFS reply.

   There are certain NFSv4 sessions contain DDP-eligible data items whose size cannot be reliably
   estimated by clients, however, because there items.  There is no protocol-specified
   size limit on these structures.  These include but are not limited
   need to
   opaque types such as match the attrlist4 field; fields containing ACLs such
   as fattr4_acl, fattr4_dacl, fattr4_sacl; fields in number of session slots with the fs_locations4
   and fs_locations_info4 data structures; and opaque fields loc_body,
   loh_body, da_addr_body, lou_body, lrf_body, fattr_layout_types and
   fs_layout_types, which pertain to pNFS layout metadata.

4.3.  NFS Version 4 COMPOUND Considerations

   An NFS version 4 COMPOUND procedure supplies arguments for a sequence number of operations, and returns results from that sequence.  A client MAY
   construct
   available RPC-over-RDMA credits.

   However, there are some rare error conditions which require special
   handling when an NFS version 4 COMPOUND procedure that uses more than one
   chunk session is operating on an RPC-over-RDMA
   transport.  For example, a requester might receive, in either the Read list response to an
   RPC request, an RDMA_ERROR message with an rdma_err value of
   ERR_CHUNK, or Write list.  The NFS client provides an RDMA_MSG containing an RPC_GARBAGEARGS reply.
   Within RPC-over-RDMA Version One, this class of error can be
   generated for two different reasons:

   o  There was an XDR Position values in each Read chunk to disambiguate which error detected parsing the RPC-over-RDMA headers.

   o  There was an error sending the response, because, for example, a
      necessary reply chunk was not provided or the one provided is
   associated with of
      insufficient length.

   These two situations, which arise only due to incorrect
   implementations, have different implications with regard to Exactly-
   Once Semantics.  An XDR data item.

   However NFS server and client implementations must agree error in advance decoding the request precludes the
   execution of the request on how the responder, but failure to pair Write chunks with returned result data items.  The
   mechanism specified in [I-D.ietf-nfsv4-rfc5666bis]) send a
   reply indicates that some or all of the operations were executed.

   In both instances, the client SHOULD NOT retry the operation.  A
   retry is applied here:

   o  The first chunk liable to result in the Write list MUST be used by same sort of error seen previously.
   Instead, it is best to consider the first READ
      or READLINK operation in as completed
   unsuccessfully and report an NFS version 4 COMPOUND procedure.  The
      next Write chunk is used by error to the next READ or READLINK, and so on.

   o  If there are more READ or READLINK operations than Write chunks,
      then any remaining operations MUST return their results inline.

   o  If an NFS client presents a Write chunk, then consumer who requested the corresponding
      READ or READLINK operation MUST return its data by placing data
      into that chunk.

   o  If
   RPC.

   In addition, within the Write chunk has zero RDMA segments, or if error response, the total size requester does not have
   the result of the segments is zero, then execution of the corresponding READ or READLINK
      operation MUST return its result inline.

   The following example shows a Write list with three Write chunks, A,
   B, SEQUENCE operation, which
   identifies the session, slot, and C. sequence id for the request which
   has failed.  The server consumes xid associated with the provided Write chunks by writing request, obtained from the results
   rdma_xid field of the designated operations in RDMA_ERROR or RDMA_MSG message, must be used to
   determine the compound request,
   READ session and READLINK, back to each chunk.

      Write list:

         A --> B --> C slot for the request which failed, and the
   slot must be properly retired.  If this is not done, the slot could
   be rendered permanently unavailable.

4.2.  Reply Size Estimation

   An NFS version 4 COMPOUND request:

         PUTFH LOOKUP READ PUTFH LOOKUP READLINK PUTFH LOOKUP READ
                       |                   |                   |
                       v                   v                   v
                       A                   B                   C

   If the client does not want to have the READLINK result returned
   directly, it provides a zero-length array of segment triplets for
   buffer B or sets the values in Reply chunk when the segment triplet for buffer B to
   zeros to indicate that maximum
   possible reply size is larger than the READLINK result must be returned inline.

   Unlike client's responder inline
   threshold.  NFS versions 2 and 3, version 4 clients already successfully estimate the
   maximum reply size of most operations in order to provide an adequate
   set of buffers to receive each NFS version 4
   COMPOUND is not bounded.  However, typical NFS version 4 clients
   rarely issue such problematic requests.  In practice, reply.

   There are certain NFS version 4 data items whose size cannot be
   estimated by clients behave in much more predictable ways.  Rsize and wsize apply reliably, however, because there is no protocol-
   specified size limit on these structures.  These include but are not
   limited to COMPOUND operations by capping opaque types, such as:

   o  The attrlist4 field

   o  Fields containing ACLs such as fattr4_acl, fattr4_dacl,
      fattr4_sacl

   o  Fields in the total amount of fs_locations4 and fs_locations_info4 data payload
   allowed in each COMPOUND.  An extension structures
   o  Opaque fields which pertain to pNFS layout metadata, such as
      loc_body, loh_body, da_addr_body, lou_body, lrf_body,
      fattr_layout_types and fs_layout_types,

   In NFS version 4 supporting a
   comprehensive exchange 4.1 and later minor versions, the csa_fore_chan_attrs
   argument of upper-layer message the CREATE_SESSION operation contains a
   ca_maxresponsesize field.  The value in this field can be taken as
   the absolute maximum size parameters is part of [RFC5661].

4.4.  NFS Version 4 Callback

   The replies generated by a replying NFS
   version 4 protocols support server-initiated callbacks server.  This value can be used in cases where it is not
   possible to
   notify clients of events estimate a reply size upper bound precisely.  In
   practice, objects such as recalled delegations.  There ACLs, named attributes, layout bodies, and
   security labels are no
   DDP-eligible data items in callback protocols associated with
   NFSv4.0, NFSv4.1, or NFSv4.2.

   In much smaller than this maximum.

   With regard to NFS version 4.1 and 4.2, callback operations may appear on the
   same connection as one used for 4.0, things are more troublesome.
   Typically NFS version 4 4.0 client requests. implementations rely on their own
   architectural limits to keep reply buffer sizes reasonable.  For
   instance, although the NFS version 4 clients and servers MUST use the mechanism described protocol is capable of conveying
   a megabyte-sized ACL, nearly all known physical filesystems store
   ACLs in
   [I-D.ietf-nfsv4-rpcrdma-bidirection] when backchannel operations on-disk containers which are
   conveyed on RPC-over-RDMA transports.

5.  IANA Considerations small in size.

4.2.1.  Managing READ_PLUS Replies

   The NFS use of direct data placement introduces version 4.2 READ_PLUS operation returns a need for an additional
   NFS port number assignment for networks that share traditional UDP
   and TCP port spaces with RDMA services. complex data type
   [I-D.ietf-nfsv4-minorversion2].  The iWARP [RFC5041]
   [RFC5040] protocol rpr_contents field in the result
   of this operation is such an example (InfiniBand array of read_plus_content unions, one arm of
   which contains an opaque byte stream (d_data).

   The size of d_data is not). limited to the value of the rpa_count field,
   but the protocol does not bound the number of elements which can be
   returned in the rpr_contents array.  In order to make the size of
   READ_PLUS replies predictable by NFS servers for versions 2 and 3 [RFC1094] [RFC1813] traditionally
   listen for clients version 4.2 clients, the
   following restrictions are placed on UDP and TCP port 2049, and additionally, they
   register these with the portmapper and/or rpcbind [RFC1833] service.
   However, [RFC7530] requires use of the READ_PLUS
   operation on RPC-over-RDMA transports:

   o  An NFS servers version 4.2 client MUST NOT provide more than one Write
      chunk for any READ_PLUS operation.  When providing a Write chunk
      for a READ_PLUS operation, an NFS version 4 4.2 client MUST provide
      a Write chunk that is either empty (which forces all result data
      items for this operation to listen on
   TCP port 2049, and they are not required be returned inline) or large enough to register.

   An
      receive rpa_count bytes in a single element of the rpr_contents
      array.

   o  If the Write chunk provided for a READ_PLUS operation by an NFS
      version 2 or 4.2 client is not empty, an NFS version 3 4.2 server supporting RPC-over-RDMA on such
   a network and registering itself with the RPC portmapper MAY choose
   an arbitrary port, or MAY MUST
      use the alternative well-known port number that chunk for its RPC-over-RDMA service.  The chosen port MAY be registered
   with the RPC portmapper under the netid assigned by first element of the requirement
   in [I-D.ietf-nfsv4-rfc5666bis]. rpr_contents array
      that has an rpc_data arm.

   o  An NFS version 4 4.2 server supporting RPC-over-RDMA on such a network MUST use NOT return more than two elements
      in the alternative well-known port number for its RPC-over-RDMA
   service.  Clients SHOULD connect to this well-known port without
   consulting rpr_contents array of any READ_PLUS operation.  It returns
      as much of the requested byte range as it can fit within these two
      elements.  If the RPC portmapper (as for NFSv4/TCP).

   The port number assigned to an NFS service over an RPC-over-RDMA
   transport is available from version 4.2 server has not asserted rpr_eof
      in the IANA port registry [RFC3232].

6.  Security Considerations

   The RDMA transport reply, the NFS version 4.2 client SHOULD send additional
      READ_PLUS requests for RPC [I-D.ietf-nfsv4-rfc5666bis] supports all
   RPC [RFC5531] security models, including RPCSEC_GSS [RFC2203]
   security and transport-level security.  The choice any remaining bytes.

4.3.  NFS Version 4 COMPOUND Requests

   A single NFS version 4 COMPOUND procedure supplies arguments for a
   sequence of RDMA Read and
   RDMA Write to convey RPC argument operations, and returns results does not affect this,
   since it only changes the method of data transfer.  Specifically, the
   requirements of [I-D.ietf-nfsv4-rfc5666bis] ensure from that this choice
   does not introduce new vulnerabilities.

   Because this document defines only the binding of the NFS protocols
   atop [I-D.ietf-nfsv4-rfc5666bis], sequence, all relevant security
   considerations are therefore to be described at
   in a single round-trip [RFC7530].  An NFS version 4 client MAY
   construct an NFS version 4 COMPOUND procedure that layer.

7.  Acknowledgments

   The author gratefully acknowledges provides more than
   one chunk in the work of Brent Callaghan and
   Tom Talpey on Read list or Write list as long as it observes the original
   restrictions in Section 4.1.

   An NFS Direct Data Placement specification
   [RFC5667].  The author also wishes version 4 client provides XDR Position values in each Read
   chunk to thank Bill Baker and Greg
   Marsden for their support of this work.

   Dave Noveck provided excellent review, constructive suggestions, disambiguate which chunk is associated with which argument
   data item.  However NFS version 4 server and
   consistent navigational guidance throughout the process of drafting
   this document.

   Special thanks go client implementations
   must agree in advance on how to nfsv4 Working Group Chair Spencer Shepler and
   nfsv4 Working Group Secretary Thomas Haynes for their support.

8.  References

8.1.  Normative References

   [I-D.ietf-nfsv4-minorversion2]
              Haynes, T., pair Write chunks with returned
   result data items.

   The mechanism specified in Section 5.3.2 of
   [I-D.ietf-nfsv4-rfc5666bis]) is applied here, with some additional
   restrictions.  In the following list, an "NFS Read" operation refers
   to any NFS Version 4 Minor Version 2", draft-ietf-
              nfsv4-minorversion2-41 (work in progress), January 2016.

   [I-D.ietf-nfsv4-rfc5666bis]
              Lever, C., Simpson, W., and T. Talpey, "Remote Direct
              Memory Access Transport for Remote Procedure Call, Version
              One", draft-ietf-nfsv4-rfc5666bis-07 (work operation which has a DDP-eligible result data
   item (i.e., either a READ, READ_PLUS, or READLINK operation).

   o  If an NFS version 4 client wishes all DDP-eligible items in progress),
              May 2016.

   [I-D.ietf-nfsv4-rpcrdma-bidirection]
              Lever, C., "Bi-directional Remote Procedure Call On RPC-
              over-RDMA Transports", draft-ietf-nfsv4-rpcrdma-
              bidirection-05 (work an NFS
      reply to be conveyed inline, it leaves the Write list empty.

   o  The first chunk in progress), June 2016.

   [RFC1833]  Srinivasan, R., "Binding Protocols for ONC RPC Version 2",
              RFC 1833, DOI 10.17487/RFC1833, August 1995,
              <http://www.rfc-editor.org/info/rfc1833>.

   [RFC2119]  Bradner, S., "Key words for use the Write list MUST be used by the first NFS
      Read operation in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC2203]  Eisler, M., Chiu, A., an NFS version 4 COMPOUND procedure.  The next
      Write chunk is used by the next NFS Read operation, and L. Ling, "RPCSEC_GSS Protocol
              Specification", RFC 2203, DOI 10.17487/RFC2203, September
              1997, <http://www.rfc-editor.org/info/rfc2203>.

   [RFC5531]  Thurlow, R., "RPC: Remote Procedure Call Protocol
              Specification Version 2", RFC 5531, DOI 10.17487/RFC5531,
              May 2009, <http://www.rfc-editor.org/info/rfc5531>.

   [RFC5661]  Shepler, S., Ed., Eisler, M., Ed., so on.

   o  If an NFS version 4 client has provided a matching non-empty Write
      chunk, then the corresponding NFS Read operation MUST return its
      DDP-eligible data item using that chunk.

   o  If an NFS version 4 client has provided an empty matching Write
      chunk, then the corresponding NFS Read operation MUST return all
      of its result data items inline.

   o  If an NFS Read operation returns a union arm which does not
      contain a DDP-eligible result, and D. Noveck, Ed.,
              "Network File System (NFS) Version the NFS version 4 Minor client has
      provided a matching non-empty Write chunk, an NFS version 4 server
      MUST return an empty Write chunk in that Write list position.

   o  If there are more NFS Read operations than Write chunks, then
      remaining NFS Read operations in an NFS version 4 COMPOUND that
      have no matching Write chunk MUST return their results inline.

4.3.1.  NFS Version 1
              Protocol", RFC 5661, DOI 10.17487/RFC5661, January 2010,
              <http://www.rfc-editor.org/info/rfc5661>.

   [RFC7530]  Haynes, T., Ed. 4 COMPOUND Example

   The following example shows a Write list with three Write chunks, A,
   B, and D. Noveck, Ed., "Network File System
              (NFS) Version C.  The NFS version 4 Protocol", RFC 7530, DOI 10.17487/RFC7530,
              March 2015, <http://www.rfc-editor.org/info/rfc7530>.

8.2.  Informative server consumes the provided Write
   chunks by writing the results of the designated operations in the
   compound request (READ and READLINK) back to each chunk.

      Write list:

         A --> B --> C

      NFS version 4 COMPOUND request:

         PUTFH LOOKUP READ PUTFH LOOKUP READLINK PUTFH LOOKUP READ
                       |                   |                   |
                       v                   v                   v
                       A                   B                   C

   If the NFS version 4 client does not want to have the READLINK result
   returned via RDMA, it provides an empty Write chunk for buffer B to
   indicate that the READLINK result must be returned inline.

4.4.  NFS Version 4 Callback

   The NFS version 4 protocols support server-initiated callbacks to
   notify clients of events such as recalled delegations.

4.4.1.  NFS Version 4.0 Callback

   NFS version 4.0 implementations typically employ a separate TCP
   connection to handle callback operations, even when the forward
   channel uses a RPC-over-RDMA transport.  Therefore no Upper Layer
   Binding for the NFS version 4.0 callback program is provided in this
   document.

4.4.2.  NFS Version 4.1 Callback

   In NFS version 4.1 and later minor versions, callback operations may
   appear on the same connection as is used for NFS version 4 forward
   channel client requests.  NFS version 4 clients and servers MUST use
   the mechanism described in [I-D.ietf-nfsv4-rpcrdma-bidirection] when
   backchannel operations are conveyed on RPC-over-RDMA transports.

   The csa_back_chan_attrs argument of the CREATE_SESSION operation
   contains a ca_maxresponsesize field.  The value in this field can be
   taken as the absolute maximum size of backchannel replies generated
   by a replying NFS version 4 client.

   There are no DDP-eligible data items in callback protocols associated
   with NFS version 4.1 or NFS version 4.2.  However, some callback
   requests, such as messages that convey device ID information, may be
   large, in which case a Long Call or Reply may be appropriate.  When
   the NFS version 4 client reports a backchannel ca_maxresponsesize
   that is larger than the connection's inline thresholds, the NFS
   version 4 client can support Long messages (i.e., Read chunks and
   Reply chunks).  Otherwise an NFS version 4 server MUST use Short
   messages to convey backchannel operations.

   See Section 4.1 for a discussion of how an NFS version 4 server
   handles situations where an NFS version 4 client has provided
   inadequate RDMA resources to convey a backchannel reply.

4.5.  Connection Keep-Alive

   NFS version 4 client implementations often rely on a transport-layer
   keep-alive mechanism to detect when an NFS version 4 server has
   become unresponsive.  When an NFS server is no longer responsive,
   client-side keep-alive terminates the connection, which in turn
   triggers reconnection and RPC retransmission.

   RDMA transports have no keep-alive mechanism.  Without a disconnect
   or new RPC traffic, RDMA transport connections can remain alive long
   after an NFS server has become unresponsive.  Once an NFS client has
   consumed all available RPC-over-RDMA credits on that transport
   connection, it will forever await a reply before sending another RPC
   request.

   NFS version 4 clients SHOULD reserve one RPC-over-RDMA credit to use
   for periodic server or connection health assessment.  This credit can
   be used to drive an RPC request on an otherwise idle connection,
   triggering either a quick affirmative server response or immediate
   connection termination.

   To prevent lease expiry, NFS version 4 clients should use a lease-
   extending operation such as RENEW or SEQUENCE, rather than a NULL
   request, when performing a periodic health assessment.

5.  Extending NFS Upper Layer Bindings

   RPC programs such as NFS are required to have an Upper Layer Binding
   specification to interoperate on RPC-over-RDMA transports
   [I-D.ietf-nfsv4-rfc5666bis].  Via standards action, the Upper Layer
   Binding specified in this document can be extended to cover versions
   of the NFS version 4 protocol specified after NFS version 4 minor
   version 2.  This includes NFS version 4 extensions that are
   documented separately from a new minor version.

6.  IANA Considerations

   NFS use of direct data placement introduces a need for an additional
   NFS port number assignment for networks that share traditional UDP
   and TCP port spaces with RDMA services.  The iWARP [RFC5041]
   [RFC5040] protocol is such an example (InfiniBand is not).

   NFS servers for versions 2 and 3 [RFC1094] [RFC1813] traditionally
   listen for clients on UDP and TCP port 2049, and additionally, they
   register these with the portmapper and/or rpcbind [RFC1833] service.
   However, [RFC7530] requires NFS version 4 servers to listen on TCP
   port 2049, and they are not required to register.

   An NFS version 2 or version 3 server supporting RPC-over-RDMA on such
   a network and registering itself with the RPC portmapper MAY choose
   an arbitrary port, or MAY use the alternative well-known port number
   for its RPC-over-RDMA service.  The chosen port MAY be registered
   with the RPC portmapper under the netid assigned by the requirement
   in [I-D.ietf-nfsv4-rfc5666bis].

   An NFS version 4 server supporting RPC-over-RDMA on such a network
   MUST use the alternative well-known port number for its RPC-over-RDMA
   service.  Clients SHOULD connect to this well-known port without
   consulting the RPC portmapper (as for NFS version 4 on TCP
   transports).

   The port number assigned to an NFS service over an RPC-over-RDMA
   transport is available from the IANA port registry [RFC3232].

7.  Security Considerations

   RPC-over-RDMA supports all RPC security models, including RPCSEC_GSS
   security and transport-level security [RFC2203].  The choice of RDMA
   Read and RDMA Write to convey RPC argument and results does not
   affect this, since it changes only the method of data transfer.
   Specifically, the requirements of [I-D.ietf-nfsv4-rfc5666bis] ensure
   that this choice does not introduce new vulnerabilities.

   Because this document defines only the binding of the NFS protocols
   atop [I-D.ietf-nfsv4-rfc5666bis], all relevant security
   considerations are therefore to be described at that layer.

8.  References

8.1.  Normative References

   [I-D.ietf-nfsv4-minorversion2]
              Haynes, T., "NFS Version 4 Minor Version 2", draft-ietf-
              nfsv4-minorversion2-41 (work in progress), January 2016.

   [I-D.ietf-nfsv4-rfc5666bis]
              Lever, C., Simpson, W., and T. Talpey, "Remote Direct
              Memory Access Transport for Remote Procedure Call, Version
              One", draft-ietf-nfsv4-rfc5666bis-07 (work in progress),
              May 2016.

   [I-D.ietf-nfsv4-rpcrdma-bidirection]
              Lever, C., "Bi-directional Remote Procedure Call On RPC-
              over-RDMA Transports", draft-ietf-nfsv4-rpcrdma-
              bidirection-05 (work in progress), June 2016.

   [RFC1833]  Srinivasan, R., "Binding Protocols for ONC RPC Version 2",
              RFC 1833, DOI 10.17487/RFC1833, August 1995,
              <http://www.rfc-editor.org/info/rfc1833>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC2203]  Eisler, M., Chiu, A., and L. Ling, "RPCSEC_GSS Protocol
              Specification", RFC 2203, DOI 10.17487/RFC2203, September
              1997, <http://www.rfc-editor.org/info/rfc2203>.

   [RFC5661]  Shepler, S., Ed., Eisler, M., Ed., and D. Noveck, Ed.,
              "Network File System (NFS) Version 4 Minor Version 1
              Protocol", RFC 5661, DOI 10.17487/RFC5661, January 2010,
              <http://www.rfc-editor.org/info/rfc5661>.

   [RFC7530]  Haynes, T., Ed. and D. Noveck, Ed., "Network File System
              (NFS) Version 4 Protocol", RFC 7530, DOI 10.17487/RFC7530,
              March 2015, <http://www.rfc-editor.org/info/rfc7530>.

8.2.  Informative References

   [NSM]      The Open Group, "Protocols for Interworking: XNFS, Version
              3W", February 1998.

   [RFC1094]  Nowicki, B., "NFS: Network File System Protocol
              specification", RFC 1094, DOI 10.17487/RFC1094, March
              1989, <http://www.rfc-editor.org/info/rfc1094>.

   [RFC1813]  Callaghan, B., Pawlowski, B., and P. Staubach, "NFS
              Version 3 Protocol Specification", RFC 1813,
              DOI 10.17487/RFC1813, June 1995,
              <http://www.rfc-editor.org/info/rfc1813>.

   [RFC3232]  Reynolds, J., Ed., "Assigned Numbers: RFC 1700 is Replaced
              by an On-line Database", RFC 3232, DOI 10.17487/RFC3232,
              January 2002, <http://www.rfc-editor.org/info/rfc3232>.

   [RFC5040]  Recio, R., Metzler, B., Culley, P., Hilland, J., and D.
              Garcia, "A Remote Direct Memory Access Protocol
              Specification", RFC 5040, DOI 10.17487/RFC5040, October
              2007, <http://www.rfc-editor.org/info/rfc5040>.

   [RFC5041]  Shah, H., Pinkerton, J., Recio, R., and P. Culley, "Direct
              Data Placement over Reliable Transports", RFC 5041,
              DOI 10.17487/RFC5041, October 2007,
              <http://www.rfc-editor.org/info/rfc5041>.

   [RFC5667]  Talpey, T. and B. Callaghan, "Network File System (NFS)
              Direct Data Placement", RFC 5667, DOI 10.17487/RFC5667,
              January 2010, <http://www.rfc-editor.org/info/rfc5667>.

Appendix A.  Changes Since RFC 5667

   Corrections and updates made necessary by new language in
   [I-D.ietf-nfsv4-rfc5666bis] have been introduced.  For example,
   references to deprecated features of RPC-over-RDMA Version One, such
   as RDMA_MSGP, and the use of the Read list for handling RPC replies,
   have been removed.  The term "mapping" has been replaced with the
   term "binding" or "Upper Layer Binding" throughout the document.
   Some material that duplicates what is in [I-D.ietf-nfsv4-rfc5666bis]
   has been deleted.

   Material required by [I-D.ietf-nfsv4-rfc5666bis] for Upper Layer
   Bindings that was not present in [RFC5667] has been added, including
   discussion of how each NFS version properly estimates the maximum
   size of RPC replies.

   Technical corrections have been made.  For example, the mention of
   12KB and 36KB inline thresholds have been removed.  The reference to
   a non-existant NFS version 4 SYMLINK operation has been replaced with
   NFS version 4 CREATE(NF4LNK).

   The discussion of NFS version 4 COMPOUND handling has been completed.
   Some changes were made to the algorithm for matching DDP-eligible
   results to Write chunks.

   The following additional improvements have been made, relative to
   [RFC5667]:

   o  An explicit discussion of NFS version 4.0 and NFS version 4.1
      backchannel operation has replaced the previous treatment of
      callback operations.

   o  A binding for NFS version 4.2 has been added that includes
      discussion of new data-bearing operations like READ_PLUS.

   o  A section suggesting a mechanism for periodically assessing
      connection health has been introduced.

   o  Language inconsistent with or contradictory to
      [I-D.ietf-nfsv4-rfc5666bis] has been removed from Sections 2 and
      3, and both Sections have been combined into Section 2 in the
      present document.

   o  Ambiguous or erroneous uses of RFC2119 terms have been corrected.

   o  References

   [RFC1094]  Nowicki, B., "NFS: Network File System Protocol
              specification", RFC 1094, DOI 10.17487/RFC1094, March
              1989, <http://www.rfc-editor.org/info/rfc1094>.

   [RFC1813]  Callaghan, B., Pawlowski, B., to obsolete RFCs have been updated.

   o  An IANA Considerations Section has replaced the "Port Usage
      Considerations" Section.

   o  Code excerpts have been removed, and P. Staubach, "NFS
              Version 3 Protocol Specification", RFC 1813,
              DOI 10.17487/RFC1813, June 1995,
              <http://www.rfc-editor.org/info/rfc1813>.

   [RFC3232]  Reynolds, J., Ed., "Assigned Numbers: RFC 1700 is Replaced
              by an On-line Database", RFC 3232, DOI 10.17487/RFC3232,
              January 2002, <http://www.rfc-editor.org/info/rfc3232>.

   [RFC5040]  Recio, R., Metzler, B., Culley, P., Hilland, J., figures have been modernized.

Appendix B.  Acknowledgments

   The author gratefully acknowledges the work of Brent Callaghan and D.
              Garcia, "A Remote
   Tom Talpey on the original NFS Direct Memory Access Protocol
              Specification", RFC 5040, DOI 10.17487/RFC5040, October
              2007, <http://www.rfc-editor.org/info/rfc5040>.

   [RFC5041]  Shah, H., Pinkerton, J., Recio, R., and P. Culley, "Direct Data Placement over Reliable Transports", RFC 5041,
              DOI 10.17487/RFC5041, October 2007,
              <http://www.rfc-editor.org/info/rfc5041>.

   [RFC5667]  Talpey, T. specification
   [RFC5667].  The author also wishes to thank Bill Baker and B. Callaghan, "Network File System (NFS)
              Direct Data Placement", RFC 5667, DOI 10.17487/RFC5667,
              January 2010, <http://www.rfc-editor.org/info/rfc5667>. Greg
   Marsden for their support of this work.

   Dave Noveck provided excellent review, constructive suggestions, and
   consistent navigational guidance throughout the process of drafting
   this document.  Dave also contributed the text of Section 4.1.1.

   Thanks to Karen Deitke for her sharp observations about idempotency,
   and the clarity of the discussion of NFS COMPOUNDs.

   Special thanks go to Transport Area Director Spencer Dawkins, nfsv4
   Working Group Chair Spencer Shepler, and nfsv4 Working Group
   Secretary Thomas Haynes for their support.

Author's Address

   Charles Lever (editor)
   Oracle Corporation
   1015 Granger Avenue
   Ann Arbor, MI  48104
   USA

   Phone: +1 734 274 2396
   Email: chuck.lever@oracle.com