wdiff draft-ietf-nfsv4-rfc5667bis-05.txt draft-ietf-nfsv4-rfc5667bis-06.txt

Network File System Version 4 C. Lever, Ed.
Internet-Draft Oracle
Obsoletes: 5667 (if approved) February 3, 24, 2017
Intended status: Standards Track
Expires: August 7, 28, 2017

Network File System (NFS) Upper Layer Binding To RPC-Over-RDMA
draft-ietf-nfsv4-rfc5667bis-05 Version
One
draft-ietf-nfsv4-rfc5667bis-06

Abstract

This document specifies Upper Layer Bindings of Network File System
(NFS) protocol versions to RPC-over-RDMA. RPC-over-RDMA Version One. Upper Layer
Bindings are required in order to enable RPC-based protocols, protocols such as NFS,
NFS to use Direct Data Placement on RPC-over-RDMA. RPC-over-RDMA Version One. 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
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."

This Internet-Draft will expire on August 7, 28, 2017.

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.

This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this
material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 3
2. Conveying NFS Operations On RPC-Over-RDMA Reply Size Estimation . . . . . . . . . . . . . . . . . . . . 3
2.1. Short Reply Chunk Retry . . . . . . . . . . . . . . . . . 4
3. Upper Layer Binding For for NFS Versions 2 And and 3 . . . . . . . . 4 5
3.1. Reply Size Estimation . . . . . . . . . . . . . . . . . . 5
3.2. RPC Binding Considerations . . . . . . . . . . . . . . . 5
4. Upper Layer Binding For Bindings for NFS Version 4 2 and 3 Auxiliary
Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. MOUNT, NLM, and NSM Protocols . . . . . . . . . . . . . . 6
4.2. NFSACL Protocol . . . . . . . . . . . . . . . . . . . . . 7
5. Extending NFS Upper Layer Bindings Binding For NFS Version 4 . . . . . . . . . . . . 7
5.1. DDP-Eligibility . 12
6. IANA . . . . . . . . . . . . . . . . . . . . 7
5.2. Reply Size Estimation . . . . . . . . . . . . . . . . . . 8
5.3. RPC Binding Considerations . . . . . . . . . . . . . . . 9
5.4. NFS COMPOUND Requests . . . . . . . . . . . . . . . . . . 10
5.5. NFS Callback Requests . . . . . . . . . . . . . . . . . . 11
5.6. Session-Related Considerations . . . . . . . . . . . . . 12
5.7. Transport Considerations . . . . . . . . . . . . . . . . 13
6. Extending NFS Upper Layer Bindings . . . . . . . . . . . . . 14
7. Security Considerations . . . . . . . . . . . . . . . . . . . 13 14
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 15
9.1. Normative References . . . . . . . . . . . . . . . . . . 15
9.2. Informative References . . . . . . . . . . . . . . . . . 16

Appendix A. Changes Since RFC 5667 . . . . . . . . . . . . . . . 15 17
Appendix B. Acknowledgments . . . . . . . . . . . . . . . . . . 17 18
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 17 19

1. Introduction

An RPC-over-RDMA transport, such as the one defined in
[I-D.ietf-nfsv4-rfc5666bis], Version One transport may employ direct data
placement to convey certain data payloads associated with RPC transactions.
transactions [I-D.ietf-nfsv4-rfc5666bis]. To enable successful
interoperation, RPC client and server implementations of RPC Programs running on RPC-over-
RDMA must agree as to which XDR data items in what particular RPC
procedures are eligible for direct data placement (DDP). This
agreement is specified in an Upper Layer Binding.

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 [RFC7862]

Upper Layer Bindings specified in this

This document apply to all versions
of RPC-over-RDMA.

2. Conveying NFS Operations On RPC-Over-RDMA

Definitions of terminology and a general discussion of how RPC-over-
RDMA is used to convey RPC transactions can be found in
[I-D.ietf-nfsv4-rfc5666bis]. In this section, these general
principles are applied in assumes the context of conveying NFS procedures on
RPC-over-RDMA. Some issues common to all NFS protocol versions are
introduced.

2.1. DDP Eligibility Violations

To report a DDP-eligibity violation, an NFS server MUST return one
of:

o An RPC-over-RDMA message of type RDMA_ERROR, reader is already familiar with the rdma_xid
field set to the XID of the matching NFS Call, concepts
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, terminology defined in [I-D.ietf-nfsv4-rfc5666bis] and the accept_stat field set
to GARBAGE_ARGS.

Subsequent sections of this document describe further considerations
particular to specific NFS protocols or procedures.

2.2.
documents it references.

2. Reply Size Estimation

During

On an RPC-over-RDMA Version One transport, during the construction of
each RPC Call message, an NFS client a requester is responsible for allocating
appropriate resources for receiving the matching Reply message. A Reply buffer

An overrun of these resources can result in corruption of the Reply
message or termination of the transport connection. Therefore
reliable reply size estimation is necessary to ensure successful
interoperation. This is particularly critical, for example, when
allocating a Reply chunk.

In many cases most cases, the Upper Layer Protocol's NFS protocol's XDR definition provides enough
information to enable the an NFS client to make a reliable prediction
of predict the maximum size of
the expected Reply message. If there are variable-size data items in
the result, the maximum size of the RPC Reply message can be reliably
estimated in most cases: as follows:

o The client requests only a specific portion of an object (for
example, using the "count" and "offset" fields in an NFS READ).

o The client has already cached the size of the whole object it is
about to request (say, via a previous NFS GETATTR request).

o The client and server have negotiated a maximum size for all calls
and responses.

Subsequent sections responses (using a CREATE_SESSION operation, for instance).

2.1. Short Reply Chunk Retry

In a few cases, either the size of this document describe considerations
particular one or more returned data items or
the number of returned data items cannot be known in advance of
forming an RPC Call.

A requester uses a Reply chunk to specific handle an RPC transaction where the
expected RPC Reply message might be larger than the requester's
inline threshold. If an actual RPC Reply message does not fit in a
client-provided Reply chunk, the NFS procedures server responds with an
RDMA_ERROR message with the rdma_err field set to ERR_CHUNK, or it
could even break the transport connection.

In response, an NFS client can choose to:

o Terminate the RPC transaction with an error, or

o Allocate a larger Reply chunk and send the same request as a new
RPC transaction (to avoid hitting in a Duplicate Reply Cache).
The NFS client should avoid retrying the request indefinitely
because a responder may return ERR_CHUNK for a variety of reasons.

The latter choice is considered heroic recovery, and is only a real
choice for the few operations where it is not possible for an NFS
client to
determine predict the size of the maximum Reply message in advance.

Subsequent sections of this document discuss exactly which operations
might have ultimate difficulty with Reply size based solely on the above
criteria. estimation. These
operations are eligible for "short Reply chunk retry." Unless
explicitly mentioned as applicable, short Reply chunk retry should
not be used.

3. Upper Layer Binding For for NFS Versions 2 And and 3

This

The Upper Layer Binding specification in this section applies to NFS
Version 2 [RFC1094] and NFS Version 3 [RFC1813]. For brevity, in
this section document a "legacy "Legacy NFS client" refers to an NFS client using the
NFS version 2 or NFS version 3 RPC Programs (100003) to communicate
with an NFS server. Likewise, a "legacy "Legacy NFS server" is an NFS server
communicating with clients using NFS version 2 or NFS version 3.

The following XDR data items in NFS versions 2 and 3 are DDP-
eligible:

o The opaque file data argument in the NFS WRITE procedure

o The pathname argument in the NFS SYMLINK procedure

o The opaque file data result in the NFS READ procedure

o The pathname result in the NFS READLINK procedure

All other argument or result data items in NFS versions 2 and 3 are
not DDP-eligible.

A legacy Legacy NFS client MUST NOT send a reduced Payload stream in a Long
Call. A Legacy NFS client MUST NOT enable a Legacy NFS server to
send a reduced Payload stream in a Long Reply.

A Legacy server's response to a DDP-eligibility violation (described
in Section 2.1) does not
give an indication to legacy Legacy clients of whether the server has
processed the arguments of the RPC Call, or whether the server has
accessed or modified client memory associated with that RPC.

3.1. Reply Size Estimation

A legacy Legacy NFS client determines the maximum reply size for each
operation using the basic criteria outlined in Section 2.2.

3.1. 2. There are no
operations in NFS version 2 or 3 that benefit from short Reply chunk
retry.

3.2. RPC Binding Considerations

Legacy NFS servers traditionally listen for clients on UDP and TCP
port 2049. Additionally, they register these ports with a local
portmapper [RFC1833] service.

A Legacy NFS server supporting RPC-over-RDMA Version One 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 (see Section 8). The chosen port MAY be
registered with the RPC portmapper under the netids assigned in
[I-D.ietf-nfsv4-rfc5666bis].

4. Upper Layer Bindings for NFS Version 2 and 3 Auxiliary Protocols

NFS versions 2 and 3 are typically deployed with several other
protocols, sometimes referred to as "NFS auxiliary protocols." These
are separate distinct RPC programs Programs that define procedures which are not part
of the NFS version 2 or version 3 RPC programs. These include: Programs. The Upper Layer
Bindings in this section apply to:

o The MOUNT and NLM protocols, introduced in an appendix of
[RFC1813]

o The NSM protocol, described in Chapter 11 of [NSM]

o The NFSACL protocol, which does not have a public definition
(NFSACL here definition.
NFSACL is treated in this document as a de facto standard standard, as
there are several interoperating implementations). implementations.

RPC-over-RDMA Version One considers these programs RPC Programs as distinct separate
Upper Layer Protocols [I-D.ietf-nfsv4-rfc5666bis]. To enable the use of these
ULPs on an RPC-over-RDMA transport, an Therefore a
separate Upper Layer Binding
specification is Binding, provided here here, is required for each.

3.1.1. each of
these.

4.1. MOUNT, NLM, And and NSM Protocols

Typically MOUNT, NLM, and NSM are conveyed via TCP, even in
deployments where the NFS operations RPC Program operates on RPC-over-RDMA. RPC-over-RDMA
Version One. When a legacy Legacy server supports these programs RPC Programs on RPC-over-RDMA,
RPC-over-RDMA Version One, it advertises the port address via the
usual rpcbind service [RFC1833].

No operation in these protocols conveys a significant data payload,
and the size of RPC messages in these protocols is uniformly small.
Therefore, no XDR data items in these protocols are DDP-eligible.

The largest variable-length XDR data item is an xdr_netobj. In most
implementations this data item is not never larger than 1024 bytes,
making reliable reply size estimation straightforward using the
criteria outlined in Section 2.2.

3.1.2. 2. There are no operations in these
protocols that benefit from short Reply chunk retry.

4.2. NFSACL Protocol

Legacy clients and servers that support the NFSACL RPC program Program
typically convey NFSACL procedures on the same connection as the NFS RPC program.
Programs. This obviates the need for separate rpcbind queries to
discover server support for this RPC program. Program.

ACLs are typically small, but even large ACLs must be encoded and
decoded to some degree. Thus no data item in this Upper Layer
Protocol is DDP-eligible.

For procedures whose replies do not include an ACL object, the size
of a reply is determined directly from the NFSACL program's RPC Program's XDR
definition.

There is no protocol-wide protocol-specified size limit for NFS version 3 ACLs, and
there is no mechanism in either the NFSACL or NFS programs RPC Programs for a
legacy
Legacy client to ascertain the largest ACL a legacy Legacy server can store.
return. Legacy client implementations should choose a maximum size
for ACLs based on their own internal limits. A recommended lower bound for
this maximum is 32,768 bytes.

When an especially large ACL is expected, a Reply chunk might be
required. If a legacy NFS server indicates that it cannot return

Because an NFSACL GETACL response because the legacy NFS client has not provided
a cannot know in advance how large enough Reply chunk to receive that response, the legacy NFS
client can choose to

o Terminate the NFSACL GETACL with an error, or

o Allocate a larger returned
ACL will be, it can use short Reply chunk and send the same retry when an NFSACL GETACL
request as
operation encounters a new RPC transaction. The NFS client should avoid
retrying the request indefinitely.

4. transport error.

5. Upper Layer Binding For NFS Version 4

This

The Upper Layer Binding specification in this section applies to all protocols RPC
Programs defined in NFS Version 4.0 [RFC7530], NFS Version 4.1
[RFC5661], and NFS Version 4.2 [RFC7862].

4.1.

5.1. DDP-Eligibility

Only the following XDR data items in the COMPOUND procedure of all
NFS version 4 minor versions are DDP-eligible:

o The opaque data field in the WRITE4args structure

o The linkdata field of the NF4LNK arm in the createtype4 union

o The opaque data field in the READ4resok structure

o The linkdata field in the READLINK4resok structure

o In minor version 2 and newer, the rpc_data field of the
read_plus_content union (further restrictions on the use of this
data item follow below).

4.1.1.

5.1.1. READ_PLUS Replies

The NFS version 4.2 READ_PLUS operation returns a complex data type
[RFC7862]. The rpr_contents field in the result of this operation is
an array of read_plus_content unions, one arm of which contains an
opaque byte stream (d_data).

The size of d_data is 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 version 4.2 clients, the
following restrictions are placed on the use of the READ_PLUS
operation on an RPC-over-RDMA transports: Version One transport:

o An NFS 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 4.2 client MUST provide
a Write chunk that is either empty (which forces all result data
items for this operation to be returned inline) or large enough to
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 4.2 client is not empty, an NFS version 4.2 server MUST
use that chunk for the first element of the rpr_contents array
that has an rpc_data arm.

o An NFS version 4.2 server MUST NOT return more than two elements
in the 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 NFS version 4.2 server has not asserted rpr_eof
in the reply, the NFS version 4.2 client SHOULD send additional
READ_PLUS requests for any remaining bytes.

4.2. NFS Version 4

5.2. Reply Size Estimation

Within NFS version 4, there are certain variable-length result data
items whose maximum size cannot be estimated by clients reliably
because there is no protocol-specified size limit on these arrays.
These include:

o The attrlist4 field

o Fields containing ACLs such as fattr4_acl, fattr4_dacl,
fattr4_sacl

o Fields in the fs_locations4 and fs_locations_info4 data structures
o Fields opaque to the NFS version 4 protocol 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,

4.2.1.

5.2.1. Reply Size Estimation For for Minor Version 0

The NFSv4.0 NFS version 4.0 protocol itself does not impose any bound on the
size of NFS calls or responses.

Some of the data items enumerated in Section 4.2 5.2 (in particular, the
items related to ACLs and fs_locations) make it difficult to predict
the maximum size of NFSv4.0 GETATTR NFS version 4.0 replies that interrogate
variable-length fattr4 attributes. As discussed in Section 2.2, 2, client
implementations can rely on their own internal architectural limits
to bound constrain the reply size, but such limits are not always
guaranteed to be reliable.

When an especially large NFSv4.0 GETATTR fattr4 result is expected, a Reply chunk
might be required. If an NFSv4.0 server indicates that it
cannot return an NFSv4.0 GETATTR response because the requesting
NFSv4.0 An NFS version 4.0 client has not provided a large enough can use short Reply
chunk to receive
that response, the NFSv4.0 client can choose to

o Terminate the NFSv4.0 GETATTR with retry when an error, or

o Allocate NFS COMPOUND containing a larger Reply chunk and send the same NFSv4.0 GETATTR
request as operation
encounters a new RPC transaction. The NFS client should avoid
retrying the request indefinitely. transport error.

The use of NFS COMPOUND operations raises the possibility of requests
that combine a non-idempotent operation (eg. NFS (e.g. WRITE) with an
NFSv4.0 a GETATTR
operation that requests one or more variable length variable-length results. This
combination should be avoided by ensuring that any NFSv4.0 GETATTR operation
that might return requests a result of unpredictable length is sent in an NFS
COMPOUND by itself.

4.2.2.

5.2.2. Reply Size Estimation For for Minor Version 1 And and Newer

In NFS version 4.1 and newer minor versions, the csa_fore_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 replies generated by a replying an NFS version 4 4.1
server.

This value can be used in cases where it is not possible to estimate
a reply size upper bound precisely. In practice, objects such as
ACLs, named attributes, layout bodies, and security labels are much
smaller than this maximum.

4.3.

5.3. RPC Binding Considerations

NFS version 4 servers are required to listen on TCP port 2049, and
they are not required to register with an rpcbind service [RFC7530].

Therefore, an NFS version 4 server supporting RPC-over-RDMA Version
One MUST use the alternative well-known port number for its RPC-over-
RDMA service (see Section 8). Clients SHOULD connect to this well-
known port without consulting the RPC portmapper (as for NFS version
4 on TCP transports).

5.4. NFS COMPOUND Requests

5.4.1. Long Calls and Replies

Each NFS version 4 COMPOUND procedure contains an array of operations
which may be larger than a connection's inline thresholds, even after
reduction of DDP-elibible payloads. Therefore, an NFS version 4
client MAY send a reduced Payload stream in a Long Call. An NFS
version 4 client MAY enable an NFS version 4 server to send a reduced
Payload stream in a Long Reply.

5.4.2. Multiple DDP-eligible Data Items

The NFS version 4 COMPOUND procedure allows the transmission of more
than one DDP-eligible data item per Call and Reply message. An NFS
version 4 client provides XDR Position values in each Read chunk to
disambiguate which chunk is associated with which argument data item.

However NFS version 4 server and client implementations must agree in
advance on how to pair Write chunks with returned result data items.
The mechanism specified in Section 4.3.2 of
[I-D.ietf-nfsv4-rfc5666bis]) is applied here, with additional
restrictions that appear below.

In the following list, an "NFS Read" operation refers to any NFS
Version 4 operation which has a DDP-
eligible 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 an NFS
reply to be conveyed inline, it leaves the Write list empty.

o The first chunk in the Write list MUST be used by the first READ
operation in an NFS version 4 COMPOUND procedure. The next Write
chunk is used by the next READ operation, and so on.

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

o If a READ operation returns a union arm which does not contain a
DDP-eligible result, and the NFS version 4 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 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.

5.4.3. NFS Version 4 COMPOUND Example

The following example shows a Write list with three Write chunks, A,
B, and C. The NFS version 4 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.

5.5. NFS Version 4 Callback Requests

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

4.4.1.

5.5.1. 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 an RPC-over-RDMA Version One transport.

No operation in the NFS version 4.0 callback RPC program Program conveys a
significant data payload. Therefore, no XDR data items in this RPC
program
Program is DDP-eligible.

A CB_RECALL reply is small and fixed in size. The CB_GETATTR reply
contains a variable-length fattr4 data item. See Section 4.2.1 5.2.1 for a
discussion of reply size prediction for this data item.

An NFS version 4.0 client advertises netids and ad hoc port addresses
for contacting its NFS version 4.0 callback service using the
SETCLIENTID operation.

4.4.2.

5.5.2. NFS Version 4.1 Callback

In NFS version 4.1 and newer 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 Version One
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 procedures defined
in NFS version 4.1 or NFS version 4.2. However, some callback
operations, such as messages that convey device ID information, can
be large, in which case a Long Call or Reply might be required.

When an NFS version 4.1 client can support Long Calls in its
backchannel, it reports a backchannel ca_maxrequestsize that is
larger than the connection's inline thresholds. Otherwise an NFS
version 4 server MUST use only Short messages to convey backchannel
operations.

4.5.

5.6. Session-Related Considerations

Typically the

The presence of an NFS session [RFC5661] (defined in [RFC5661]) has no effect
on the operation of RPC-over-RDMA. RPC-over-RDMA Version One. None of the
operations introduced to support NFS sessions (eg. SEQUENCE) (e.g. the SEQUENCE
operation) contain DDP-eligible data items. There is no need to
match the number of session slots with the number of available RPC-over-RDMA RPC-
over-RDMA credits.

When an NFS session operates on an RPC-over-RDMA transport,

However, there are a few additional new cases where an RPC transaction can fail.
For example, a requester might receive, in response to an RPC
request, an RDMA_ERROR message with an rdma_err value of ERR_CHUNK,
or an RDMA_MSG containing an RPC_GARBAGEARGS reply. These situations
are no different from existing RPC errors which an NFS session
implementation is already prepared to handle for other transports.

And as with other transports during such a failure, there might be no
SEQUENCE result available to the requester to distinguish whether
failure occurred before or after the requested operations were
executed on the responder.

When a transport error occurs (eg. (e.g. RDMA_ERROR), the requester
proceeds as usual to match the incoming XID value to a waiting RPC
Call. The RPC transaction is terminated, and the result status is
reported to the Upper Layer Protocol. The requester's session
implementation then determines the session ID and slot for the failed
request, and performs slot recovery to make that slot usable again.
If this is not done, that slot could be rendered permanently
unavailable.

4.6.

5.7. Transport Considerations

5.7.1. Congestion Avoidance

Section 3.1 of [RFC7530] states:

Where an NFSv4 implementation supports operation over the IP
network protocol, the supported transport layer between NFS and IP
MUST be an IETF standardized transport protocol that is specified
to avoid network congestion; such transports include TCP and the
Stream Control Transmission Protocol (SCTP).

Section 2.9.1 of [RFC5661] further states:

Even if NFSv4.1 is used over a non-IP network protocol, it is
RECOMMENDED that the transport support congestion control.

It is permissible for a connectionless transport to be used under
NFSv4.1; however, reliable and in-order delivery of data combined
with congestion control by the connectionless transport is
REQUIRED. As a consequence, UDP by itself MUST NOT be used as an
NFSv4.1 transport.

RPC-over-RDMA Version One is constructed on a platform of RDMA
Reliable Connections [I-D.ietf-nfsv4-rfc5666bis] [RFC5041]. RDMA
Reliable Connections are reliable, connection-oriented transports
that guarantee in-order delivery, meeting all above requirements for
NFS version 4 transports.

5.7.2. Retransmission And Keep-Alive and 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.

Some RDMA transports (such as Reliable Connections on InfiniBand)
have no keep-alive mechanism. Without a disconnect or new RPC
traffic, such 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.

In addition to network partition and request loss scenarios, RPC-
over-RDMA transport connections can be terminated when a Transport
header is malformed, Reply messages are larger than receive
resources, or when too many RPC-over-RDMA messages are sent at once.
In such cases:

o If there is a transport error indicated (ie, RDMA_ERROR) before
the disconnect or instead of a disconnect, the requester MUST
respond to that error as prescribed by the specification of the
RPC transport. Then the NFS version 4 rules for handling
retransmission apply.

o If there is a transport disconnect and the responder has provided
no other response for a request, then only the NFS version 4 rules
for handling retransmission apply.

6. Extending NFS Upper Layer Bindings

RPC programs Programs such as NFS are required to have an Upper Layer Binding
specification to interoperate on RPC-over-RDMA Version One 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, or separately published extensions to an existing NFS
version 4 minor version, as described in [I-D.ietf-nfsv4-versioning].

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 Version One supports all RPC security models, including
RPCSEC_GSS security and transport-level security [RFC2203]. The
choice of what Direct Data Placement mechanism 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. IANA Considerations

The use of direct data placement in NFS introduces a need for an
additional port number assignment for networks that share traditional
UDP and TCP port spaces with RDMA services. The iWARP protocol is
such an example [RFC5041] [RFC5040].

For this purpose, a set of transport protocol port number assignments
is specified by this document. IANA has assigned the following ports
for NFS/RDMA in the IANA port registry, according to the guidelines
described in [RFC6335].

nfsrdma 20049/tcp Network File System (NFS) over RDMA
nfsrdma 20049/udp Network File System (NFS) over RDMA
nfsrdma 20049/sctp Network File System (NFS) over RDMA

This document should be listed as the reference for the nfsrdma port
assignments. This document does not alter these assignments.

9. References

8.1.

9.1. Normative References

[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-09 draft-ietf-nfsv4-rfc5666bis-10 (work in progress),
January
February 2017.

[I-D.ietf-nfsv4-rpcrdma-bidirection]
Lever, C., "Bi-directional Remote Procedure Call On RPC-
over-RDMA Transports", draft-ietf-nfsv4-rpcrdma-
bidirection-06
bidirection-07 (work in progress), January February 2017.

[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>.

[RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
Cheshire, "Internet Assigned Numbers Authority (IANA)
Procedures for the Management of the Service Name and
Transport Protocol Port Number Registry", BCP 165,
RFC 6335, DOI 10.17487/RFC6335, August 2011,
<http://www.rfc-editor.org/info/rfc6335>.

[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>.

[RFC7862] Haynes, T., "Network File System (NFS) Version 4 Minor
Version 2 Protocol", RFC 7862, DOI 10.17487/RFC7862,
November 2016, <http://www.rfc-editor.org/info/rfc7862>.

8.2.

9.2. Informative References

[I-D.ietf-nfsv4-versioning]
Noveck, D., "Rules for NFSv4 Extensions and Minor
Versions", draft-ietf-nfsv4-versioning-09 (work in
progress), December 2016.

[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>.

[RFC5666] Talpey, T. and B. Callaghan, "Remote Direct Memory Access
Transport for Remote Procedure Call", RFC 5666,
DOI 10.17487/RFC5666, January 2010,
<http://www.rfc-editor.org/info/rfc5666>.

[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). replaced.

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.

Requirements to ignore extra Read or Write chunks have been removed
from the NFS version 2 and 3 Upper Layer Binding, as they conflict
with [I-D.ietf-nfsv4-rfc5666bis].

A complete discussion of reply size estimation has been introduced
for all protocols covered by the Upper Layer Bindings in this
document.

A section discussing NFS version 4 retransmission and connection loss
has been added.

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 to obsolete RFCs have been updated.

o An IANA Considerations Section has replaced been added, which specifies the "Port Usage
Considerations" Section.
port assignments for NFS/RDMA. This replaces the example
assignment that appeared in [RFC5666].

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

Appendix B. Acknowledgments

The author gratefully acknowledges the work of Brent Callaghan and
Tom Talpey on the original NFS Direct Data Placement specification
[RFC5667]. The author also wishes to thank Bill Baker and 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 4.5 5.6 and
Section 6, and insisted on precise discussion of reply size
estimation.

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

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: +1 248 816 6463
Email: chuck.lever@oracle.com