draft-ietf-nfsv4-nfs-ulb-v2-01.txt   draft-ietf-nfsv4-nfs-ulb-v2-02.txt 
Network File System Version 4 C. Lever Network File System Version 4 C. Lever
Internet-Draft Oracle Internet-Draft Oracle
Intended status: Standards Track February 3, 2020 Intended status: Standards Track 4 July 2020
Expires: August 6, 2020 Expires: 5 January 2021
Network File System (NFS) Upper-Layer Binding To RPC-Over-RDMA Version 2 Network File System (NFS) Upper-Layer Binding To RPC-Over-RDMA Version 2
draft-ietf-nfsv4-nfs-ulb-v2-01 draft-ietf-nfsv4-nfs-ulb-v2-02
Abstract Abstract
This document specifies Upper-Layer Bindings of Network File System This document specifies Upper-Layer Bindings of Network File System
(NFS) protocol versions to RPC-over-RDMA version 2. (NFS) protocol versions to RPC-over-RDMA version 2.
Note
Discussion of this draft takes place on the NFSv4 working group
mailing list (nfsv4@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/nfsv4/. Working Group
information can be found at https://datatracker.ietf.org/wg/nfsv4/
about/.
This note is to be removed before publishing as an RFC.
The source for this draft is maintained in GitHub. Suggested changes
can be submitted as pull requests at https://github.com/chucklever/
i-d-nfs-ulb-v2. Instructions are on that page as well.
Status of This Memo Status of This Memo
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provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on August 6, 2020. This Internet-Draft will expire on 5 January 2021.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Reply Size Estimation . . . . . . . . . . . . . . . . . . . . 3 3. Reply Size Estimation . . . . . . . . . . . . . . . . . . . . 4
4. Upper-Layer Binding for NFS Versions 2 and 3 . . . . . . . . 3 4. Upper-Layer Binding for NFS Versions 2 and 3 . . . . . . . . 4
4.1. Reply Size Estimation . . . . . . . . . . . . . . . . . . 4 4.1. Reply Size Estimation . . . . . . . . . . . . . . . . . . 4
4.2. RPC Binding Considerations . . . . . . . . . . . . . . . 4 4.2. RPC Binding Considerations . . . . . . . . . . . . . . . 5
4.3. Transport Considerations . . . . . . . . . . . . . . . . 4 4.3. Transport Considerations . . . . . . . . . . . . . . . . 5
5. Upper-Layer Bindings for NFS Version 2 and 3 Auxiliary 5. Upper-Layer Bindings for NFS Version 2 and 3 Auxiliary
Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Protocols . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. MOUNT, NLM, and NSM Protocols . . . . . . . . . . . . . . 6 5.1. MOUNT, NLM, and NSM Protocols . . . . . . . . . . . . . . 6
5.2. NFSACL Protocol . . . . . . . . . . . . . . . . . . . . . 6 5.2. NFSACL Protocol . . . . . . . . . . . . . . . . . . . . . 7
6. Upper-Layer Binding For NFS Version 4 . . . . . . . . . . . . 6 6. Upper-Layer Binding For NFS Version 4 . . . . . . . . . . . . 7
6.1. DDP-Eligibility . . . . . . . . . . . . . . . . . . . . . 7 6.1. DDP-Eligibility . . . . . . . . . . . . . . . . . . . . . 7
6.2. Reply Size Estimation . . . . . . . . . . . . . . . . . . 7 6.2. Reply Size Estimation . . . . . . . . . . . . . . . . . . 8
6.3. RPC Binding Considerations . . . . . . . . . . . . . . . 8 6.3. RPC Binding Considerations . . . . . . . . . . . . . . . 9
6.4. NFS COMPOUND Requests . . . . . . . . . . . . . . . . . . 8 6.4. NFS COMPOUND Requests . . . . . . . . . . . . . . . . . . 9
6.5. NFS Callback Requests . . . . . . . . . . . . . . . . . . 11 6.5. NFS Callback Requests . . . . . . . . . . . . . . . . . . 12
6.6. Session-Related Considerations . . . . . . . . . . . . . 12 6.6. Session-Related Considerations . . . . . . . . . . . . . 13
6.7. Transport Considerations . . . . . . . . . . . . . . . . 12 6.7. Transport Considerations . . . . . . . . . . . . . . . . 14
7. Extending NFS Upper-Layer Bindings . . . . . . . . . . . . . 14 7. Extending NFS Upper-Layer Bindings . . . . . . . . . . . . . 15
8. Security Considerations . . . . . . . . . . . . . . . . . . . 14 8. Security Considerations . . . . . . . . . . . . . . . . . . . 16
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
10.1. Normative References . . . . . . . . . . . . . . . . . . 15 10.1. Normative References . . . . . . . . . . . . . . . . . . 16
10.2. Informative References . . . . . . . . . . . . . . . . . 16 10.2. Informative References . . . . . . . . . . . . . . . . . 17
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 16 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 18
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 16 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction 1. Introduction
The RPC-over-RDMA version 2 transport may employ direct data The RPC-over-RDMA version 2 transport may employ direct data
placement to convey data payloads associated with RPC transactions placement to convey data payloads associated with RPC transactions
[RPCRDMA2]. RPC client and server implementations using RPC-over- [I-D.ietf-nfsv4-rpcrdma-version-two]. RPC client and server
RDMA version 2 must agree which XDR data items and RPC procedures are implementations using RPC-over-RDMA version 2 must agree which XDR
eligible to use direct data placement (DDP) to enable successful data items and RPC procedures are eligible to use direct data
interoperation. placement (DDP) to ensure successful interoperation.
An Upper-Layer Binding specifies this agreement for one or more An Upper-Layer Binding specifies this agreement for one or more
versions of one RPC program. Other operational details, such as RPC versions of one RPC program. Other operational details, such as RPC
binding assignments, pairing Write chunks with result data items, and binding assignments, pairing Write chunks with result data items, and
reply size estimation, are also specified by this Binding. reply size estimation, are also specified by this Binding.
This document contains material required of Upper-Layer Bindings, as This document contains material required of Upper-Layer Bindings, as
specified in [RPCRDMA2], for the following NFS protocol versions: specified in [I-D.ietf-nfsv4-rpcrdma-version-two], for the following
NFS protocol versions:
o NFS version 2 [RFC1094] * NFS version 2 [RFC1094]
o NFS version 3 [RFC1813] * NFS version 3 [RFC1813]
o NFS version 4.0 [RFC7530] * NFS version 4.0 [RFC7530]
o NFS version 4.1 [RFC5661] * NFS version 4.1 [RFC5661]
o NFS version 4.2 [RFC7862] * NFS version 4.2 [RFC7862]
The current document also provides Upper-Layer Bindings for auxiliary The current document also provides Upper-Layer Bindings for auxiliary
protocols used with NFS versions 2 and 3 (see Section 5). protocols used with NFS versions 2 and 3 (see Section 5).
This document assumes the reader is already familiar with concepts This document assumes the reader is already familiar with concepts
and terminology defined in [RPCRDMA2] and the documents it and terminology defined in [I-D.ietf-nfsv4-rpcrdma-version-two] and
references. the documents it references.
2. Requirements Language 2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in
14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
3. Reply Size Estimation 3. Reply Size Estimation
During the construction of each RPC Call message, a Requester is During the construction of each RPC Call message, a Requester is
responsible for allocating appropriate resources for receiving the responsible for allocating appropriate resources for receiving the
corresponding Reply message. If the Requester expects that the RPC corresponding Reply message. If the Requester expects that the RPC
Reply message could be larger than its inline threshold, it MAY Reply message could be larger than its inline threshold, it MAY
provide Write chunks wherein the Responder can place results and provide Write chunks wherein the Responder can place results and
Reply chunks wherein the Responder can place the reply's Payload Reply chunks wherein the Responder can place the reply's Payload
stream. stream. A message continuation facility is also available in RPC-
over-RDMA version 2 to convey RPC messages that are larger than the
transport's inline threshold.
4. Upper-Layer Binding for NFS Versions 2 and 3 4. Upper-Layer Binding for NFS Versions 2 and 3
The Upper-Layer Binding specification in this section applies to NFS The Upper-Layer Binding specification in this section applies to NFS
version 2 [RFC1094] and NFS version 3 [RFC1813]. For brevity, in version 2 [RFC1094] and NFS version 3 [RFC1813]. For brevity, in
this document, a "Legacy NFS client" refers to an NFS client using this document, a "Legacy NFS client" refers to an NFS client using
version 2 or version 3 of the NFS RPC program (100003) to communicate version 2 or version 3 of the NFS RPC program (100003) to communicate
with an NFS server. Likewise, a "Legacy NFS server" is an NFS server with an NFS server. Likewise, a "Legacy NFS server" is an NFS server
communicating with clients using NFS version 2 or NFS version 3. communicating with clients using NFS version 2 or NFS version 3.
The following XDR data items in NFS versions 2 and 3 are DDP- The following XDR data items in NFS versions 2 and 3 are DDP-
eligible: eligible:
o The opaque file data argument in the NFS WRITE procedure * The opaque file data argument in the NFS WRITE procedure
o The pathname argument in the NFS SYMLINK procedure * The pathname argument in the NFS SYMLINK procedure
o The opaque file data result in the NFS READ procedure * The opaque file data result in the NFS READ procedure
o The pathname result in the NFS READLINK procedure * The pathname result in the NFS READLINK procedure
All other argument or result data items in NFS versions 2 and 3 are All other argument or result data items in NFS versions 2 and 3 are
not DDP-eligible. not DDP-eligible.
A transport error does not indicate whether the server has processed Whether or not an NFS operation is considered non-idempotent, a
transport error might not indicate whether the server has processed
the arguments of the RPC Call, or whether the server has accessed or the arguments of the RPC Call, or whether the server has accessed or
modified client memory associated with that RPC. modified client memory associated with that RPC.
4.1. Reply Size Estimation 4.1. Reply Size Estimation
A Legacy NFS client determines the maximum reply size for each A Legacy NFS client determines the maximum reply size for each
operation using the criteria outlined in Section 3. operation using the criteria outlined in Section 3.
4.2. RPC Binding Considerations 4.2. RPC Binding Considerations
Legacy NFS servers traditionally listen for clients on UDP and TCP Legacy NFS servers traditionally listen for clients on UDP and TCP
port 2049. Additionally, they register these ports with a local port 2049. Additionally, they register these ports with a local
portmapper service [RFC1833]. portmapper service [RFC1833].
A Legacy NFS server supporting RPC-over-RDMA version 2 on such a A Legacy NFS server supporting RPC-over-RDMA version 2 and
network and registering itself with the RPC portmapper MAY choose an registering itself with the RPC portmapper MAY choose an arbitrary
arbitrary port, or MAY use the alternative well-known port number for port, or MAY use the alternative well-known port number for its RPC-
its RPC-over-RDMA service (see Section 9). The chosen port MAY be over-RDMA service (see Section 9). The chosen port MAY be registered
registered with the RPC portmapper using the netids assigned in with the RPC portmapper using the netids assigned in
[RPCRDMA2]. [I-D.ietf-nfsv4-rpcrdma-version-two].
4.3. Transport Considerations 4.3. Transport Considerations
Legacy NFS client implementations often rely on a transport-layer Legacy NFS client implementations often rely on a transport-layer
keep-alive mechanism to detect when a legacy server has become keep-alive mechanism to detect when a legacy server has become
unresponsive. When an NFS server is no longer responsive, client- unresponsive. When an NFS server is no longer responsive, client-
side keep-alive terminates the connection, which in turn triggers side keep-alive terminates the connection, which in turn triggers
reconnection and RPC retransmission. reconnection and retransmission of outstanding RPC transactions.
4.3.1. Keep-Alive 4.3.1. Keep-Alive
Some RDMA transports (such as the Reliable Connected QP type on Some RDMA transports (such as the Reliable Connected QP type on
InfiniBand) have no keep-alive mechanism. Without a disconnect or InfiniBand) have no keep-alive mechanism. Without a disconnect or
new RPC traffic, such connections can remain alive long after an NFS new RPC traffic, such connections can remain alive long after an NFS
server has become unresponsive or unreachable. Once an NFS client server has become unresponsive or unreachable. Once an NFS client
has consumed all available RPC-over-RDMA version 2 credits on that has consumed all available RPC-over-RDMA version 2 credits on that
transport connection, it awaits a reply indefinitely before sending transport connection, it awaits a reply indefinitely before sending
another RPC request. another RPC request.
Legacy NFS clients SHOULD reserve one RPC-over-RDMA version 2 credit Legacy NFS clients SHOULD reserve one RPC-over-RDMA version 2 credit
to use for periodic server or connection health assessment. Either to use for periodic server or connection health assessment. Either
peer can use this credit to drive an RPC request on an otherwise idle peer can use this credit to drive an RPC request on an otherwise idle
connection, triggering either an affirmative server response or a connection, triggering either an affirmative server response or a
connection termination. connection termination.
4.3.2. Replay Detection 4.3.2. Replay Detection
Legacy NFS servers can employ request replay detection to reduce the Legacy NFS servers typically employ request replay detection to
risk of data corruption that could result when a client retransmits a reduce the risk of data corruption that could result when an NFS
request. A legacy NFS server can choose to send a cached response client retransmits a non-idempotent NFS request. A legacy NFS server
when a replay is detected, rather than executing the request again. can send a cached response when a replay is detected, rather than
Replay detection is not perfect, but it is usually adequate. executing the request again. Replay detection is not perfect, but it
is usually adequate.
For legacy NFS servers, replay detection commonly utilizes heuristic For legacy NFS servers, replay detection commonly utilizes heuristic
indicators such as the IP address of the NFS client, the source port indicators such as the IP address of the NFS client, the source port
of the connection, the transaction ID of the request, and the of the connection, the transaction ID of the request, and the
contents of the request's RPC and upper-layer protocol headers. In contents of the request's RPC and upper-layer protocol headers. In
short, replay detection is typically based on a connection tuple and short, replay detection is typically based on a connection tuple and
the request's XID. A legacy NFS client is careful to re-use the same the request's XID. A legacy NFS client is careful to re-use the same
source port, if practical, when reconnecting so that legacy NFS source port, if practical, when reconnecting so that legacy NFS
servers are better able to detect retransmissions. servers are better able to detect retransmissions.
However, a legacy NFS client operating over an RDMA transport has no However, a legacy NFS client operating over an RDMA transport has no
control over connection source ports. It is almost certain that an control over connection source ports. It is almost certain that an
RPC request that is retransmitted on a new connection can never be RPC request that is retransmitted on a new connection can never be
detected as a replay if the legacy NFS server includes the connection detected as a replay if the legacy NFS server includes the connection
source port in its replay detection heuristics. source port in its replay detection heuristics.
Therefore a legacy NFS server using an RDMA transport should never Therefore a legacy NFS server using an RDMA transport should never
use a legacy NFS client connection's source port as part of RPC use a legacy NFS client connection's source port as part of its NFS
request replay detection. request replay detection mechanism.
5. Upper-Layer Bindings for NFS Version 2 and 3 Auxiliary Protocols 5. Upper-Layer Bindings for NFS Version 2 and 3 Auxiliary Protocols
Storage administrators typically deploy NFS versions 2 and 3 with Storage administrators typically deploy NFS versions 2 and 3 with
several other protocols, sometimes referred to as "NFS auxiliary several other protocols, sometimes referred to as "NFS auxiliary
protocols." These are distinct RPC programs that define procedures protocols." These are distinct RPC programs that define procedures
that are not part of the NFS RPC program (100003). The Upper-Layer that are not part of the NFS RPC program (100003). The Upper-Layer
Bindings in this section apply to: Bindings in this section apply to:
o Versions 2 and 3 of the MOUNT RPC program (100005) [RFC1813] * Versions 2 and 3 of the MOUNT RPC program (100005) [RFC1813]
o Versions 1, 3, and 4 of the NLM RPC program (100021) [RFC1813] * Versions 1, 3, and 4 of the NLM RPC program (100021) [RFC1813]
o Version 1 of the NSM RPC program (100024), described in Chapter 11 * Version 1 of the NSM RPC program (100024), described in Chapter 11
of [XNFS] of [XNFS]
o Version 1 of the NFSACL RPC program (100227), which does not have * Version 1 of the NFSACL RPC program (100227), which does not have
a public definition. NFSACL is treated in this document as a de a public definition. NFSACL is treated in this document as a de
facto standard, as there are several interoperating facto standard, as there are several interoperating
implementations. implementations.
5.1. MOUNT, NLM, and NSM Protocols 5.1. MOUNT, NLM, and NSM Protocols
Historically, NFS/RDMA implementations have chosen to convey the Historically, NFS/RDMA implementations have chosen to convey the
MOUNT, NLM, and NSM protocols via TCP. A legacy NFS server MOUNT, NLM, and NSM protocols via TCP. A legacy NFS server
implementation MUST provide support for these protocols via TCP to implementation MUST provide support for these protocols via TCP to
enable interoperation of these protocols when NFS/RDMA is in use. enable interoperation of these protocols when NFS/RDMA is in use.
5.2. NFSACL Protocol 5.2. NFSACL Protocol
Often legacy clients and servers that support the NFSACL RPC program Often legacy clients and servers that support the NFSACL RPC program
convey NFSACL procedures on the same connection as the NFS RPC convey NFSACL procedures on the same connection as the NFS RPC
program (100003). Utilizing the same connection obviates the need program (100003). Utilizing the same connection obviates the need
for separate rpcbind queries to discover server support for this RPC 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 ACLs are typically small, but even large ACLs must be encoded and
decoded to some degree. Thus no data item in this Upper-Layer decoded to some degree before being made available to users. Thus no
Protocol is DDP-eligible. data item in this Upper-Layer Protocol is DDP-eligible.
For procedures whose replies do not include an ACL object, the size For procedures whose replies do not include an ACL object, the size
of a reply is determined directly from the NFSACL RPC program's XDR of a reply is determined directly from the NFSACL RPC program's XDR
definition. Legacy client implementations should choose a maximum definition. Legacy client implementations should choose a maximum
size for ACLs based on internal limits. size for ACLs based on internal limits.
6. Upper-Layer Binding For NFS Version 4 6. Upper-Layer Binding For NFS Version 4
The Upper-Layer Binding specification in this section applies to The Upper-Layer Binding specification in this section applies to
versions of the NFS RPC program defined in NFS version 4.0 [RFC7530] versions of the NFS RPC program defined in NFS version 4.0 [RFC7530]
NFS version 4.1 [RFC5661] and NFS version 4.2 [RFC7862]. NFS version 4.1 [RFC5661] and NFS version 4.2 [RFC7862].
6.1. DDP-Eligibility 6.1. DDP-Eligibility
Only the following XDR data items in the COMPOUND procedure of all Only the following XDR data items in the COMPOUND procedure of all
NFS version 4 minor versions are DDP-eligible: NFS version 4 minor versions are DDP-eligible:
o The opaque data field in the WRITE4args structure * The opaque data field in the WRITE4args structure
o The linkdata field of the NF4LNK arm in the createtype4 union * The linkdata field of the NF4LNK arm in the createtype4 union
o The opaque data field in the READ4resok structure * The opaque data field in the READ4resok structure
o The linkdata field in the READLINK4resok structure * The linkdata field in the READLINK4resok structure
6.1.1. The NFSv4.2 READ_PLUS operation
NFS version 4.2 introduces an enhanced READ operation called
READ_PLUS [RFC7862]. READ_PLUS enables an NFS server to perform
inline data reduction of READ results so that the returned READ data
is more compact.
In a READ_PLUS result, returned file content appears as a list of one
or more of the following items:
* Regular data content: the same as the result of a traditional READ
operation.
* Unallocated space in a file: where no data has yet been written or
previously-written data has been removed via a hole-punch
operation.
* A counted pattern.
Upon receipt of a READ_PLUS result, an NFSv4.2 client expands the
returned list into a preferred local representation of the original
file content.
Before receiving that result, an NFSv4.2 client typically does not
know how the file's content is organized on the NFS server. Thus it
is not possible to predict the size or structure of a READ_PLUS Reply
in advance. The use of direct data placement is therefore
challenging.
A READ_PLUS content list containing more than one segment of regular
file data could be conveyed using multiple Write chunks, but only if
the client knows in advance where those chunks appear in the Reply
Payload stream. Moreover, the usual benefits of hardware-assisted
data placement are entirely waived if the client-side transport must
parse the result of each read I/O.
Therefore this Upper Layer Binding does not make any element of an
NFSv4.2 READ_PLUS Reply DDP-eligible. Further, this Upper Layer
Binding recommends that implementers disable the use of the READ_PLUS
operation on NFS/RDMA mount points.
6.2. Reply Size Estimation 6.2. Reply Size Estimation
Within NFS version 4, there are certain variable-length result data Within NFS version 4, there are certain variable-length result data
items whose maximum size cannot be estimated by clients reliably items whose maximum size cannot be estimated by clients reliably
because there is no protocol-specified size limit on these result because there is no protocol-specified size limit on these result
arrays. These include: arrays. These include:
o The attrlist4 field * The attrlist4 field
o Fields containing ACLs such as fattr4_acl, fattr4_dacl, and * Fields containing ACLs such as fattr4_acl, fattr4_dacl, and
fattr4_sacl fattr4_sacl
o Fields in the fs_locations4 and fs_locations_info4 data structures * Fields in the fs_locations4 and fs_locations_info4 data structures
o Fields which pertain to pNFS layout metadata, such as loc_body, * Fields which pertain to pNFS layout metadata, such as loc_body,
loh_body, da_addr_body, lou_body, lrf_body, fattr_layout_types, loh_body, da_addr_body, lou_body, lrf_body, fattr_layout_types,
and fs_layout_types and fs_layout_types
6.2.1. Reply Size Estimation for Minor Version 0 6.2.1. Reply Size Estimation for Minor Version 0
The NFS version 4.0 protocol itself does not impose any bound on the The NFS version 4.0 protocol itself does not impose any bound on the
size of NFS calls or responses. size of NFS calls or replies.
Some of the data items enumerated in Section 6.2 (in particular, the Some of the data items enumerated in Section 6.2 (in particular, the
items related to ACLs and fs_locations) make it difficult to predict items related to ACLs and fs_locations) make it difficult to predict
the maximum size of NFS version 4.0 replies that interrogate the maximum size of NFS version 4.0 replies that interrogate
variable-length fattr4 attributes. Client implementations might rely variable-length fattr4 attributes. Client implementations might rely
upon internal architectural limits to constrain the reply size, but upon internal architectural limits to constrain the reply size, but
such limits are not always guaranteed to be reliable. such limits are not always guaranteed to be reliable.
When an NFS version 4.0 client expects an especially sizeable fattr4 When an NFS version 4.0 client expects an especially sizeable fattr4
result, it can provide a Reply chunk to enable that server to return result, it can provide a Reply chunk to enable that server to return
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operation encounters a transport error. operation encounters a transport error.
6.2.2. Reply Size Estimation for Minor Version 1 and Newer 6.2.2. Reply Size Estimation for Minor Version 1 and Newer
In NFS version 4.1 and newer minor versions, the csa_fore_chan_attrs In NFS version 4.1 and newer minor versions, the csa_fore_chan_attrs
argument of the CREATE_SESSION operation contains a argument of the CREATE_SESSION operation contains a
ca_maxresponsesize field. The value in this field can be taken as ca_maxresponsesize field. The value in this field can be taken as
the absolute maximum size of replies generated by an NFS version 4.1 the absolute maximum size of replies generated by an NFS version 4.1
server. server.
A client can use this value in cases where it is not possible to An NFS version 4 client can use this value in cases where it is not
estimate a reply size upper bound precisely. In practice, objects possible to estimate a reply size upper bound precisely. In
such as ACLs, named attributes, layout bodies, and security labels practice, objects such as ACLs, named attributes, layout bodies, and
are much smaller than this maximum. security labels are much smaller than this maximum.
6.3. RPC Binding Considerations 6.3. RPC Binding Considerations
NFS version 4 servers are required to listen on TCP port 2049, and NFS version 4 servers are required to listen on TCP port 2049, and
they are not required to register with a rpcbind service [RFC7530]. they are not required to register with a rpcbind service [RFC7530].
Therefore, an NFS version 4 server supporting RPC-over-RDMA version 2 Therefore, an NFS version 4 server supporting RPC-over-RDMA version 2
MUST use the alternative well-known port number for its RPC-over-RDMA MUST use the alternative well-known port number for its RPC-over-RDMA
service (see Section 9 Clients SHOULD connect to this well-known port service (see Section 9 Clients SHOULD connect to this well-known port
without consulting the RPC portmapper (as for NFS version 4 on TCP without consulting the RPC portmapper (as for NFS version 4 on TCP
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operation that carries a DDP-eligible data item. An NFS version 4 operation that carries a DDP-eligible data item. An NFS version 4
client provides XDR Position values in each Read chunk to client provides XDR Position values in each Read chunk to
disambiguate which chunk is associated with which argument data item. disambiguate which chunk is associated with which argument data item.
However, NFS version 4 server and client implementations must agree However, NFS version 4 server and client implementations must agree
in advance on how to pair Write chunks with returned result data in advance on how to pair Write chunks with returned result data
items. items.
In the following lists, a "READ operation" refers to any NFS version In the following lists, a "READ operation" refers to any NFS version
4 operation that has a DDP-eligible result data item. An NFS version 4 operation that has a DDP-eligible result data item. An NFS version
4 client applies the mechanism specified in Section 4.3.2 of 4 client applies the mechanism specified in Section 4.3.2 of
[RPCRDMA2] is applied to this class of operations as follows: [I-D.ietf-nfsv4-rpcrdma-version-two] is applied to this class of
operations as follows:
o If an NFS version 4 client wishes all DDP-eligible items in an NFS * 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. reply to be conveyed inline, it leaves the Write list empty.
An NFS version 4 server applies that mechanism as follows: An NFS version 4 server applies that mechanism as follows:
o The first chunk in the Write list MUST be used by the first READ * 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 operation in an NFS version 4 COMPOUND procedure. The next Write
chunk is used by the next READ operation, and so on. 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 * If an NFS version 4 client has provided a matching non-empty Write
chunk, then the corresponding READ operation MUST return its DDP- chunk, then the corresponding READ operation MUST return its DDP-
eligible data item using that chunk. eligible data item using that chunk.
o If an NFS version 4 client has provided an empty matching Write * If an NFS version 4 client has provided an empty matching Write
chunk, then the corresponding READ operation MUST return all of chunk, then the corresponding READ operation MUST return all of
its result data items inline. its result data items inline.
o If a READ operation returns a union arm which does not contain a * 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 DDP-eligible result, and the NFS version 4 client has provided a
matching non-empty Write chunk, an NFS version 4 server MUST matching non-empty Write chunk, an NFS version 4 server MUST
return an empty Write chunk in that Write list position. return an empty Write chunk in that Write list position.
o If there are more READ operations than Write chunks, then * If there are more READ operations than Write chunks, then
remaining NFS Read operations in an NFS version 4 COMPOUND that remaining NFS Read operations in an NFS version 4 COMPOUND that
have no matching Write chunk MUST return their results inline. have no matching Write chunk MUST return their results inline.
6.4.2. Chunk List Complexity 6.4.2. Chunk List Complexity
The RPC-over-RDMA version 2 protocol does not place any limit on the The RPC-over-RDMA version 2 protocol does not place any limit on the
number of chunks or segments that may appear in Read or Write lists. number of chunks or segments that may appear in Read or Write lists.
However, for various reasons, NFS version 4 server implementations However, for various reasons, NFS version 4 server implementations
often have practical limits on the number of chunks or segments they often have practical limits on the number of chunks or segments they
can process in a single RPC transaction conveyed via RPC-over-RDMA can process in a single RPC transaction conveyed via RPC-over-RDMA
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integrity or privacy is in use [RFC7861]. GSS services increase the integrity or privacy is in use [RFC7861]. GSS services increase the
size of credential material in RPC headers, potentially requiring the size of credential material in RPC headers, potentially requiring the
use of a Long message, which increases the complexity of chunk lists use of a Long message, which increases the complexity of chunk lists
independent of the particular NFS version 4 COMPOUND being conveyed. independent of the particular NFS version 4 COMPOUND being conveyed.
In the absence of explicit knowledge of the server's limits, NFS In the absence of explicit knowledge of the server's limits, NFS
version 4 clients SHOULD follow the prescriptions listed below when version 4 clients SHOULD follow the prescriptions listed below when
constructing RPC-over-RDMA version 2 messages. NFS version 4 servers constructing RPC-over-RDMA version 2 messages. NFS version 4 servers
MUST accept and process all such requests. MUST accept and process all such requests.
o The Read list can contain either a Position-Zero Read chunk, one * The Read list can contain either a Position-Zero Read chunk, one
Read chunk with a non-zero Position, or both. Read chunk with a non-zero Position, or both.
o The Write list can contain no more than one Write chunk. * The Write list can contain no more than one Write chunk.
o Any chunk can contain up to sixteen RDMA segments. * Any chunk can contain up to sixteen RDMA segments.
NFS version 4 clients wishing to send more complex chunk lists can NFS version 4 clients wishing to send more complex chunk lists can
provide configuration interfaces to bound the complexity of NFS provide configuration interfaces to bound the complexity of NFS
version 4 COMPOUNDs, limit the number of elements in scatter-gather version 4 COMPOUNDs, limit the number of elements in scatter-gather
operations, and avoid other sources of chunk overruns at the operations, and avoid other sources of chunk overruns at the
receiving peer. receiving peer.
If an NFS version 4 server receives an RPC request via RPC-over-RDMA If an NFS version 4 server receives an RPC request via RPC-over-RDMA
version 2 that it cannot process due to chunk list complexity limits, version 2 that it cannot process due to chunk list complexity limits,
it SHOULD return one of the following responses to the client: it SHOULD return one of the following responses to the client:
o A problem is detected by the transport layer while parsing the * A problem is detected by the transport layer while parsing the
transport header in an RPC Call message. The server responds with transport header in an RPC Call message. The server responds with
an RDMA2_ERROR message with the err field set to ERR_CHUNK. an RDMA2_ERROR message with the err field set to ERR_CHUNK.
o A problem is detected during XDR decoding of the RPC Call message * A problem is detected during XDR decoding of the RPC Call message
while the RPC layer reassembles the call's XDR stream. The server while the RPC layer reassembles the call's XDR stream. The server
responds with an RPC reply with its "reply_stat" field set to responds with an RPC reply with its "reply_stat" field set to
MSG_ACCEPTED and its "accept_stat" field set to GARBAGE_ARGS. MSG_ACCEPTED and its "accept_stat" field set to GARBAGE_ARGS.
After receiving one of these errors, an NFS version 4 client SHOULD After receiving one of these errors, an NFS version 4 client SHOULD
NOT retransmit the failing request, as the result would be the same NOT retransmit the failing request, as the result would be the same
error. It SHOULD immediately terminate the RPC transaction error. It SHOULD immediately terminate the RPC transaction
associated with the XID in the reply. associated with the XID in the reply.
6.4.3. NFS Version 4 COMPOUND Example 6.4.3. NFS Version 4 COMPOUND Example
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Even if NFS version 4.1 is used over a non-IP network protocol, it Even if NFS version 4.1 is used over a non-IP network protocol, it
is RECOMMENDED that the transport support congestion control. is RECOMMENDED that the transport support congestion control.
It is permissible for a connectionless transport to be used under It is permissible for a connectionless transport to be used under
NFS version 4.1; however, reliable and in-order delivery of data NFS version 4.1; however, reliable and in-order delivery of data
combined with congestion control by the connectionless transport combined with congestion control by the connectionless transport
is REQUIRED. As a consequence, UDP by itself MUST NOT be used as is REQUIRED. As a consequence, UDP by itself MUST NOT be used as
an NFS version 4.1 transport. an NFS version 4.1 transport.
RPC-over-RDMA version 2 utilizes only RDMA Reliable Connected QP type RPC-over-RDMA version 2 utilizes only RDMA Reliable Connected QP type
connections [RPCRDMA2]. RDMA Reliable Connected QPs are reliable, connections [I-D.ietf-nfsv4-rpcrdma-version-two]. RDMA Reliable
connection-oriented transports that guarantee in-order delivery, Connected QPs are reliable, connection-oriented transports that
meeting all the above requirements. guarantee in-order delivery, meeting all the above requirements.
6.7.2. Retransmission and Keep-alive 6.7.2. Retransmission and Keep-alive
NFS version 4 client implementations often rely on a transport-layer NFS version 4 client implementations often rely on a transport-layer
keep-alive mechanism to detect when an NFS version 4 server has keep-alive mechanism to detect when an NFS version 4 server has
become unresponsive. When an NFS server is no longer responsive, become unresponsive. When an NFS server is no longer responsive,
client-side keep-alive terminates the connection, which in turn client-side keep-alive terminates the connection, which in turn
triggers reconnection and RPC retransmission. triggers reconnection and RPC retransmission.
Some RDMA transports (such as the Reliable Connected QP type on Some RDMA transports (such as the Reliable Connected QP type on
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Either peer can use this credit to drive an RPC request on an Either peer can use this credit to drive an RPC request on an
otherwise idle connection, triggering either a quick affirmative otherwise idle connection, triggering either a quick affirmative
server response or immediate connection termination. server response or immediate connection termination.
In addition to network partition and request loss scenarios, RPC- In addition to network partition and request loss scenarios, RPC-
over-RDMA version 2 transport connections can be terminated when a over-RDMA version 2 transport connections can be terminated when a
Transport header is malformed, Reply messages exceed receive Transport header is malformed, Reply messages exceed receive
resources, or when too many RPC-over-RDMA messages are sent at once. resources, or when too many RPC-over-RDMA messages are sent at once.
In such cases: In such cases:
o If a transport error occurs (e.g., an RDMA2_ERROR type message is * If a transport error occurs (e.g., an RDMA2_ERROR type message is
received) before the disconnect or instead of a disconnect, the received) before the disconnect or instead of a disconnect, the
Requester MUST respond to that error as prescribed by the Requester MUST respond to that error as prescribed by the
specification of the RPC transport. Then the NFS version 4 rules specification of the RPC transport. Then the NFS version 4 rules
for handling retransmission apply. for handling retransmission apply.
o If there is a transport disconnect and the Responder has provided * If there is a transport disconnect and the Responder has provided
no other response for a request, then only the NFS version 4 rules no other response for a request, then only the NFS version 4 rules
for handling retransmission apply. for handling retransmission apply.
7. Extending NFS Upper-Layer Bindings 7. Extending NFS Upper-Layer Bindings
RPC programs such as NFS are required to have an Upper-Layer Binding RPC programs such as NFS are required to have an Upper-Layer Binding
specification to interoperate on RPC-over-RDMA version 2 transports specification to interoperate on RPC-over-RDMA version 2 transports
[RPCRDMA2]. Via standards action, the Upper-Layer Binding specified [I-D.ietf-nfsv4-rpcrdma-version-two]. Via standards action, the
in this document can be extended to cover versions of the NFS version Upper-Layer Binding specified in this document can be extended to
4 protocol specified after NFS version 4 minor version 2, or to cover cover versions of the NFS version 4 protocol specified after NFS
separately published extensions to an existing NFS version 4 minor version 4 minor version 2, or to cover separately published
version, as described in [RFC8178]. extensions to an existing NFS version 4 minor version, as described
in [RFC8178].
8. Security Considerations 8. Security Considerations
RPC-over-RDMA version 2 supports all RPC security models, including RPC-over-RDMA version 2 supports all RPC security models, including
RPCSEC_GSS security and transport-level security [RFC7861]. The RPCSEC_GSS security and transport-level security [RFC7861]. The
choice of what Direct Data Placement mechanism to convey RPC argument choice of what Direct Data Placement mechanism to convey RPC argument
and results does not affect this since it changes only the method of and results does not affect this since it changes only the method of
data transfer. Because the current document defines only the binding data transfer. Because the current document defines only the binding
of the NFS protocols atop [RPCRDMA2], all relevant security of the NFS protocols atop [I-D.ietf-nfsv4-rpcrdma-version-two], all
considerations are, therefore, described at that layer. relevant security considerations are, therefore, described at that
layer.
9. IANA Considerations 9. IANA Considerations
The use of direct data placement in NFS introduces a need for an The use of direct data placement in NFS introduces a need for an
additional port number assignment for networks that share traditional additional port number assignment for networks that share traditional
UDP and TCP port spaces with RDMA services. The iWARP protocol is UDP and TCP port spaces with RDMA services. The iWARP protocol is
such an example [RFC5040] [RFC5041]. such an example [RFC5040] [RFC5041].
For this purpose, the current document specifies a set of transport For this purpose, the current document specifies a set of transport
protocol port number assignments. IANA has assigned the following protocol port number assignments. IANA has assigned the following
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nfsrdma 20049/tcp Network File System (NFS) over RDMA nfsrdma 20049/tcp Network File System (NFS) over RDMA
nfsrdma 20049/udp Network File System (NFS) over RDMA nfsrdma 20049/udp Network File System (NFS) over RDMA
nfsrdma 20049/sctp Network File System (NFS) over RDMA nfsrdma 20049/sctp Network File System (NFS) over RDMA
The current document should be added as a reference for the nfsrdma The current document should be added as a reference for the nfsrdma
port assignments. The current document does not alter these port assignments. The current document does not alter these
assignments. assignments.
10. References 10. References
10.1. Normative References 10.1. Normative References
[I-D.ietf-nfsv4-rpcrdma-version-two]
Lever, C. and D. Noveck, "RPC-over-RDMA Version 2
Protocol", Work in Progress, Internet-Draft, draft-ietf-
nfsv4-rpcrdma-version-two-02, 3 July 2020,
<https://tools.ietf.org/html/draft-ietf-nfsv4-rpcrdma-
version-two-02>.
[RFC1833] Srinivasan, R., "Binding Protocols for ONC RPC Version 2", [RFC1833] Srinivasan, R., "Binding Protocols for ONC RPC Version 2",
RFC 1833, DOI 10.17487/RFC1833, August 1995, RFC 1833, DOI 10.17487/RFC1833, August 1995,
<https://www.rfc-editor.org/info/rfc1833>. <https://www.rfc-editor.org/info/rfc1833>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC5661] Shepler, S., Ed., Eisler, M., Ed., and D. Noveck, Ed., [RFC5661] Shepler, S., Ed., Eisler, M., Ed., and D. Noveck, Ed.,
skipping to change at page 15, line 47 skipping to change at page 17, line 42
November 2016, <https://www.rfc-editor.org/info/rfc7862>. November 2016, <https://www.rfc-editor.org/info/rfc7862>.
[RFC8167] Lever, C., "Bidirectional Remote Procedure Call on RPC- [RFC8167] Lever, C., "Bidirectional Remote Procedure Call on RPC-
over-RDMA Transports", RFC 8167, DOI 10.17487/RFC8167, over-RDMA Transports", RFC 8167, DOI 10.17487/RFC8167,
June 2017, <https://www.rfc-editor.org/info/rfc8167>. June 2017, <https://www.rfc-editor.org/info/rfc8167>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RPCRDMA2]
Lever, C. and D. Noveck, "RPC-over-RDMA Version 2
Protocol", draft-ietf-nfsv4-rpcrdma-version-two-01 (work
in progress), Jan 2020.
10.2. Informative References 10.2. Informative References
[RFC1094] Nowicki, B., "NFS: Network File System Protocol [RFC1094] Nowicki, B., "NFS: Network File System Protocol
specification", RFC 1094, DOI 10.17487/RFC1094, March specification", RFC 1094, DOI 10.17487/RFC1094, March
1989, <https://www.rfc-editor.org/info/rfc1094>. 1989, <https://www.rfc-editor.org/info/rfc1094>.
[RFC1813] Callaghan, B., Pawlowski, B., and P. Staubach, "NFS [RFC1813] Callaghan, B., Pawlowski, B., and P. Staubach, "NFS
Version 3 Protocol Specification", RFC 1813, Version 3 Protocol Specification", RFC 1813,
DOI 10.17487/RFC1813, June 1995, DOI 10.17487/RFC1813, June 1995,
<https://www.rfc-editor.org/info/rfc1813>. <https://www.rfc-editor.org/info/rfc1813>.
skipping to change at page 16, line 36 skipping to change at page 18, line 25
[RFC8178] Noveck, D., "Rules for NFSv4 Extensions and Minor [RFC8178] Noveck, D., "Rules for NFSv4 Extensions and Minor
Versions", RFC 8178, DOI 10.17487/RFC8178, July 2017, Versions", RFC 8178, DOI 10.17487/RFC8178, July 2017,
<https://www.rfc-editor.org/info/rfc8178>. <https://www.rfc-editor.org/info/rfc8178>.
[XNFS] The Open Group, "Protocols for Interworking: XNFS, Version [XNFS] The Open Group, "Protocols for Interworking: XNFS, Version
3W", February 1998. 3W", February 1998.
Acknowledgments Acknowledgments
Thanks to Tom Talpey, who contributed the text of Section 6.4.2. Thanks to Tom Talpey, who contributed the text of Section 6.4.2.
Dave Noveck contributed the text of Section 6.6 and Section 7. The David Noveck contributed the text of Section 6.6 and Section 7. The
author also wishes to thank Bill Baker and Greg Marsden for their author also wishes to thank Bill Baker and Greg Marsden for their
support of this work. support of this work.
Special thanks go to Transport Area Director Magnus Westerlund, NFSV4 Special thanks go to Transport Area Director Magnus Westerlund, NFSV4
Working Group Chairs Spencer Shepler, Brian Pawlowski, and Dave Working Group Chairs Spencer Shepler, Brian Pawlowski, and David
Noveck, and NFSV4 Working Group Secretary Thomas Haynes for their Noveck, and NFSV4 Working Group Secretary Thomas Haynes for their
support. support.
Author's Address Author's Address
Charles Lever Charles Lever
Oracle Corporation Oracle Corporation
United States of America United States of America
Email: chuck.lever@oracle.com Email: chuck.lever@oracle.com
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