draft-ietf-nfsv4-nfs-ulb-v2-00.txt   draft-ietf-nfsv4-nfs-ulb-v2-01.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 November 17, 2019 Intended status: Standards Track February 3, 2020
Expires: May 20, 2020 Expires: August 6, 2020
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-v2-00 draft-ietf-nfsv4-nfs-ulb-v2-01
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.
Status of This Memo Status of This Memo
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Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Reply Size Estimation . . . . . . . . . . . . . . . . . . . . 3 3. Reply Size Estimation . . . . . . . . . . . . . . . . . . . . 3
4. Upper Layer Binding for NFS Versions 2 and 3 . . . . . . . . 3 4. Upper-Layer Binding for NFS Versions 2 and 3 . . . . . . . . 3
4.1. Reply Size Estimation . . . . . . . . . . . . . . . . . . 4 4.1. Reply Size Estimation . . . . . . . . . . . . . . . . . . 4
4.2. RPC Binding Considerations . . . . . . . . . . . . . . . 4 4.2. RPC Binding Considerations . . . . . . . . . . . . . . . 4
5. Upper Layer Bindings for NFS Version 2 and 3 Auxiliary 4.3. Transport Considerations . . . . . . . . . . . . . . . . 4
Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . 4 5. Upper-Layer Bindings for NFS Version 2 and 3 Auxiliary
5.1. MOUNT, NLM, and NSM Protocols . . . . . . . . . . . . . . 5 Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.2. NFSACL Protocol . . . . . . . . . . . . . . . . . . . . . 5 5.1. MOUNT, NLM, and NSM Protocols . . . . . . . . . . . . . . 6
6. Upper Layer Binding For NFS Version 4 . . . . . . . . . . . . 5 5.2. NFSACL Protocol . . . . . . . . . . . . . . . . . . . . . 6
6.1. DDP-Eligibility . . . . . . . . . . . . . . . . . . . . . 5 6. Upper-Layer Binding For NFS Version 4 . . . . . . . . . . . . 6
6.2. Reply Size Estimation . . . . . . . . . . . . . . . . . . 6 6.1. DDP-Eligibility . . . . . . . . . . . . . . . . . . . . . 7
6.3. RPC Binding Considerations . . . . . . . . . . . . . . . 7 6.2. Reply Size Estimation . . . . . . . . . . . . . . . . . . 7
6.4. NFS COMPOUND Requests . . . . . . . . . . . . . . . . . . 7 6.3. RPC Binding Considerations . . . . . . . . . . . . . . . 8
6.5. NFS Callback Requests . . . . . . . . . . . . . . . . . . 9 6.4. NFS COMPOUND Requests . . . . . . . . . . . . . . . . . . 8
6.6. Session-Related Considerations . . . . . . . . . . . . . 10 6.5. NFS Callback Requests . . . . . . . . . . . . . . . . . . 11
6.7. Transport Considerations . . . . . . . . . . . . . . . . 11 6.6. Session-Related Considerations . . . . . . . . . . . . . 12
7. Extending NFS Upper Layer Bindings . . . . . . . . . . . . . 13 6.7. Transport Considerations . . . . . . . . . . . . . . . . 12
8. Security Considerations . . . . . . . . . . . . . . . . . . . 13 7. Extending NFS Upper-Layer Bindings . . . . . . . . . . . . . 14
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 8. Security Considerations . . . . . . . . . . . . . . . . . . . 14
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
10.1. Normative References . . . . . . . . . . . . . . . . . . 14 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
10.2. Informative References . . . . . . . . . . . . . . . . . 15 10.1. Normative References . . . . . . . . . . . . . . . . . . 15
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 15 10.2. Informative References . . . . . . . . . . . . . . . . . 16
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 15 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 16
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 16
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
[I-D.cel-nfsv4-rpcrdma-version-two]. To enable successful [RPCRDMA2]. RPC client and server implementations using RPC-over-
interoperation, RPC client and server implementations using RPC-over-
RDMA version 2 must agree which XDR data items and RPC procedures are RDMA version 2 must agree which XDR data items and RPC procedures are
eligible to use direct data placement (DDP). eligible to use direct data placement (DDP) to enable 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 [I-D.cel-nfsv4-rpcrdma-version-two], for the following specified in [RPCRDMA2], for the following NFS protocol versions:
NFS protocol versions:
o NFS version 2 [RFC1094] o NFS version 2 [RFC1094]
o NFS version 3 [RFC1813] o NFS version 3 [RFC1813]
o NFS version 4.0 [RFC7530] o NFS version 4.0 [RFC7530]
o NFS version 4.1 [RFC5661] o NFS version 4.1 [RFC5661]
o NFS version 4.2 [RFC7862] o NFS version 4.2 [RFC7862]
Upper Layer Bindings are also provided for auxiliary protocols used The current document also provides Upper-Layer Bindings for auxiliary
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 [I-D.cel-nfsv4-rpcrdma-version-two] and and terminology defined in [RPCRDMA2] and the documents it
the documents it references. 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 BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 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 the RPC Reply corresponding Reply message. If the Requester expects that the RPC
message will be larger than its inline threshold, it MAY provide Reply message could be larger than its inline threshold, it MAY
Write and/or Reply chunks wherein the Responder can place results and provide Write chunks wherein the Responder can place results and
the reply's Payload stream. Reply chunks wherein the Responder can place the reply's Payload
stream.
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 o The opaque file data argument in the NFS WRITE procedure
o The pathname argument in the NFS SYMLINK procedure o The pathname argument in the NFS SYMLINK procedure
o The opaque file data result in the NFS READ procedure o The opaque file data result in the NFS READ procedure
o The pathname result in the NFS READLINK procedure o 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 give an indication of whether the server A transport error does not indicate whether the server has processed
has processed the arguments of the RPC Call, or whether the server the arguments of the RPC Call, or whether the server has accessed or
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 on such a
network and registering itself with the RPC portmapper MAY choose an network and registering itself with the RPC portmapper MAY choose an
arbitrary port, or MAY use the alternative well-known port number for arbitrary port, or MAY use the alternative well-known port number for
its RPC-over-RDMA service (see Section 9). The chosen port MAY be its RPC-over-RDMA service (see Section 9). The chosen port MAY be
registered with the RPC portmapper using the netids assigned in registered with the RPC portmapper using the netids assigned in
[I-D.cel-nfsv4-rpcrdma-version-two]. [RPCRDMA2].
5. Upper Layer Bindings for NFS Version 2 and 3 Auxiliary Protocols 4.3. Transport Considerations
NFS versions 2 and 3 are typically deployed with several other Legacy NFS client implementations often rely on a transport-layer
protocols, sometimes referred to as "NFS auxiliary protocols." These keep-alive mechanism to detect when a legacy server has become
are distinct RPC programs that define procedures which are not part unresponsive. When an NFS server is no longer responsive, client-
of the NFS RPC program (100003). The Upper Layer Bindings in this side keep-alive terminates the connection, which in turn triggers
section apply to: reconnection and RPC retransmission.
4.3.1. Keep-Alive
Some RDMA transports (such as the Reliable Connected QP type 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 or unreachable. Once an NFS client
has consumed all available RPC-over-RDMA version 2 credits on that
transport connection, it awaits a reply indefinitely before sending
another RPC request.
Legacy NFS clients SHOULD reserve one RPC-over-RDMA version 2 credit
to use for periodic server or connection health assessment. Either
peer can use this credit to drive an RPC request on an otherwise idle
connection, triggering either an affirmative server response or a
connection termination.
4.3.2. Replay Detection
Legacy NFS servers can employ request replay detection to reduce the
risk of data corruption that could result when a client retransmits a
request. A legacy NFS server can choose to send a cached response
when a replay is detected, rather than executing the request again.
Replay detection is not perfect, but it is usually adequate.
For legacy NFS servers, replay detection commonly utilizes heuristic
indicators such as the IP address of the NFS client, the source port
of the connection, the transaction ID of the request, and the
contents of the request's RPC and upper-layer protocol headers. In
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
source port, if practical, when reconnecting so that legacy NFS
servers are better able to detect retransmissions.
However, a legacy NFS client operating over an RDMA transport has no
control over connection source ports. It is almost certain that an
RPC request that is retransmitted on a new connection can never be
detected as a replay if the legacy NFS server includes the connection
source port in its replay detection heuristics.
Therefore a legacy NFS server using an RDMA transport should never
use a legacy NFS client connection's source port as part of RPC
request replay detection.
5. Upper-Layer Bindings for NFS Version 2 and 3 Auxiliary Protocols
Storage administrators typically deploy NFS versions 2 and 3 with
several other protocols, sometimes referred to as "NFS auxiliary
protocols." These are distinct RPC programs that define procedures
that are not part of the NFS RPC program (100003). The Upper-Layer
Bindings in this section apply to:
o Versions 2 and 3 of the MOUNT RPC program (100005) [RFC1813] o Versions 2 and 3 of the MOUNT RPC program (100005) [RFC1813]
o Versions 1, 3, and 4 of the NLM RPC program (100021) [RFC1813] o 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 o 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 o 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. To enable interoperation of MOUNT, NLM, and NSM protocols via TCP. A legacy NFS server
these protocols when NFS/RDMA is in use, a legacy NFS server MUST implementation MUST provide support for these protocols via TCP to
provide support for these protocols via TCP. enable interoperation of these protocols when NFS/RDMA is in use.
5.2. NFSACL Protocol 5.2. NFSACL Protocol
Legacy clients and servers that support the NFSACL RPC program Often legacy clients and servers that support the NFSACL RPC program
typically convey NFSACL procedures on the same connection as the NFS convey NFSACL procedures on the same connection as the NFS RPC
RPC program (100003). This obviates the need for separate rpcbind program (100003). Utilizing the same connection obviates the need
queries to discover server support for this RPC program. for separate rpcbind queries to discover server support for this RPC
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. Thus no data item in this Upper-Layer
Protocol is DDP-eligible. 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 their own 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 o The opaque data field in the WRITE4args structure
o The linkdata field of the NF4LNK arm in the createtype4 union o The linkdata field of the NF4LNK arm in the createtype4 union
o The opaque data field in the READ4resok structure o The opaque data field in the READ4resok structure
o The linkdata field in the READLINK4resok structure o The linkdata field in the READLINK4resok structure
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
skipping to change at page 6, line 24 skipping to change at page 7, line 32
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 o The attrlist4 field
o Fields containing ACLs such as fattr4_acl, fattr4_dacl, and o 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 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 o Fields which pertain to pNFS layout metadata, such as loc_body,
layout metadata, such as loc_body, loh_body, da_addr_body, loh_body, da_addr_body, lou_body, lrf_body, fattr_layout_types,
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 responses.
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
on their own internal architectural limits to constrain the reply upon internal architectural limits to constrain the reply size, but
size, but such limits are not always guaranteed to be reliable. such limits are not always guaranteed to be reliable.
When an especially large fattr4 result is expected, an NFS version When an NFS version 4.0 client expects an especially sizeable fattr4
4.0 client can provide a Reply chunk to enable a large result to be result, it can provide a Reply chunk to enable that server to return
returned via explicit RDMA. An NFS version 4.0 client can use short that result via explicit RDMA. An NFS version 4.0 client can use
Reply chunk retry when an NFS COMPOUND containing a GETATTR operation short Reply chunk retry when an NFS COMPOUND containing a GETATTR
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.
This value can be used in cases where it is not possible to estimate A client can use this value in cases where it is not possible to
a reply size upper bound precisely. In practice, objects such as estimate a reply size upper bound precisely. In practice, objects
ACLs, named attributes, layout bodies, and security labels are much such as ACLs, named attributes, layout bodies, and security labels
smaller than this maximum. 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 an 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
transports). transports).
6.4. NFS COMPOUND Requests 6.4. NFS COMPOUND Requests
6.4.1. Multiple DDP-eligible Data Items 6.4.1. Multiple DDP-eligible Data Items
An NFS version 4 COMPOUND procedure can contain more than one An NFS version 4 COMPOUND procedure can contain more than one
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 in However, NFS version 4 server and client implementations must agree
advance on how to pair Write chunks with returned result data items. in advance on how to pair Write chunks with returned result data
items.
In the following list, a "READ operation" refers to any NFS version 4 In the following lists, a "READ operation" refers to any NFS version
operation which has a DDP-eligible result data item. The mechanism 4 operation that has a DDP-eligible result data item. An NFS version
specified in Section 4.3.2 of [I-D.cel-nfsv4-rpcrdma-version-two] is 4 client applies the mechanism specified in Section 4.3.2 of
applied to this class of operations: [RPCRDMA2] is applied to this class of operations as follows:
o If an NFS version 4 client wishes all DDP-eligible items in an NFS 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. reply to be conveyed inline, it leaves the Write list empty.
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 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 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 o 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 o 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
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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 o 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
are prepared to process in a single RPC transaction conveyed via RPC- can process in a single RPC transaction conveyed via RPC-over-RDMA
over-RDMA version 2. version 2.
These implementation limits are especially important when Kerberos These implementation limits are especially important when Kerberos
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 Long messages. This can increase the complexity of chunk use of a Long message, which increases the complexity of chunk lists
lists independent of the 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 such requests. MUST accept and process all such requests.
o The Read list can contain either a Position-Zero Read chunk, one o 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. o The Write list can contain no more than one Write chunk.
o Any chunk can contain up to sixteen RDMA segments. o 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.
An NFS version 4 server SHOULD return one of the following responses If an NFS version 4 server receives an RPC request via RPC-over-RDMA
to a client that has sent an RPC transaction via RPC-over-RDMA version 2 that it cannot process due to chunk list complexity limits,
version 2 which cannot be processed due to chunk list complexity it SHOULD return one of the following responses to the client:
limits on the server:
o A problem is detected by the transport layer while parsing the o 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 o 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.
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An NFS version 4.0 client advertises netids and ad hoc port addresses An NFS version 4.0 client advertises netids and ad hoc port addresses
for contacting its NFS version 4.0 callback service using the for contacting its NFS version 4.0 callback service using the
SETCLIENTID operation. SETCLIENTID operation.
6.5.2. NFS Version 4.1 Callback 6.5.2. NFS Version 4.1 Callback
In NFS version 4.1 and newer minor versions, callback operations may 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 appear on the same connection as is used for NFS version 4 forward
channel client requests. NFS version 4 clients and servers MUST use channel client requests. NFS version 4 clients and servers MUST use
the approach described in [RFC8167] when backchannel operations are the approach described in [RFC8167] to convey backchannel operations
conveyed on RPC-over-RDMA version 2 transports. on an RPC-over-RDMA version 2 transport.
The csa_back_chan_attrs argument of the CREATE_SESSION operation The csa_back_chan_attrs argument of the CREATE_SESSION operation
contains a ca_maxresponsesize field. The value in this field can be contains a ca_maxresponsesize field. The value in this field is the
taken as the absolute maximum size of backchannel replies generated absolute maximum size of backchannel replies generated by a replying
by a replying NFS version 4 client. NFS version 4 client.
There are no DDP-eligible data items in callback procedures defined There are no DDP-eligible data items in callback procedures defined
in NFS version 4.1 or NFS version 4.2. However, some callback in NFS version 4.1 or NFS version 4.2. However, some callback
operations, such as messages that convey device ID information, can operations, such as messages that convey device ID information, can
be large. Message Continuation or a Long message might be used in be sizeable. A sender can use Message Continuation or a Long message
this situation. in this situation.
When an NFS version 4.1 client can support Long Calls in its When an NFS version 4.1 client can support Long Calls in its
backchannel, it reports a backchannel ca_maxrequestsize that is backchannel, it reports a backchannel ca_maxrequestsize that is
larger than the connection's inline thresholds. Otherwise an NFS larger than the connection's inline thresholds. Otherwise, an NFS
version 4 server MUST use only Short messages to convey backchannel version 4 server MUST use only Short messages to convey backchannel
operations. operations.
6.6. Session-Related Considerations 6.6. Session-Related Considerations
The presence of an NFS session (defined in [RFC5661] has no effect on The presence of an NFS version 4 session (as defined in [RFC5661])
the operation of RPC-over-RDMA version 2. None of the operations does not effect the operation of RPC-over-RDMA version 2. None of
introduced to support NFS sessions (e.g. the SEQUENCE operation) the operations introduced to support NFS sessions (e.g., the SEQUENCE
contain DDP-eligible data items. There is no need to match the operation) contain DDP-eligible data items. There is no need to
number of session slots with the number of available RPC-over-RDMA match the number of session slots with the number of available RPC-
version 2 credits. over-RDMA version 2 credits.
However, there are a few new cases where an RPC transaction can fail. However, there are a few new cases where an RPC transaction can fail.
For example, a Requester might receive, in response to an RPC For example, a Requester might receive, in response to an RPC
request, an RDMA2_ERROR message with an rdma_err value of ERR_CHUNK. request, an RDMA2_ERROR message with a rdma_err value of ERR_CHUNK.
These situations are not different from existing RPC errors which an These situations are not different from existing RPC errors, which an
NFS session implementation is already prepared to handle for other NFS session implementation can already handle for other transport
transports. And as with other transports during such a failure, types. Moreover, there might be no SEQUENCE result available to the
there might be no SEQUENCE result available to the Requester to Requester to distinguish whether failure occurred before or after the
distinguish whether failure occurred before or after the requested Responder executed the requested operations.
operations were executed on the Responder.
When a transport error occurs (e.g. RDMA2_ERROR), the Requester When a transport error occurs (e.g., an RDMA2_ERROR type message is
proceeds as usual to match the incoming XID value to a waiting RPC received), the Requester proceeds, as usual, to match the incoming
Call. The RPC transaction is terminated, and the result status is XID value to a waiting RPC Call. The Requester terminates the RPC
reported to the Upper Layer Protocol. The Requester's session transaction and reports the result status to the RPC consumer. The
implementation then determines the session ID and slot for the failed Requester's session implementation then determines the session ID and
request, and performs slot recovery to make that slot usable again. slot for the failed request and performs slot recovery to make that
If this were not done, that slot could be rendered permanently slot usable again. Otherwise, that slot could be rendered
unavailable. permanently unavailable.
When an NFS session is not present (for example, when NFS version 4.0 When an NFS session is not present (for example, when NFS version 4.0
is in use), a transport error does not provide an indication of is in use), a transport error does not indicate whether the server
whether the server has processed the arguments of the RPC Call, or has processed the arguments of the RPC Call, or whether the server
whether the server has accessed or modified client memory associated has accessed or modified client memory associated with that RPC.
with that RPC.
6.7. Transport Considerations 6.7. Transport Considerations
6.7.1. Congestion Avoidance 6.7.1. Congestion Avoidance
Section 3.1 of [RFC7530] states: Section 3.1 of [RFC7530] states:
Where an NFS version 4 implementation supports operation over the Where an NFS version 4 implementation supports operation over the
IP network protocol, the supported transport layer between NFS and IP network protocol, the supported transport layer between NFS and
IP MUST be an IETF standardized transport protocol that is IP MUST be an IETF standardized transport protocol that is
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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 is constructed on a platform of RDMA Reliable RPC-over-RDMA version 2 utilizes only RDMA Reliable Connected QP type
Connected QP type connections [I-D.cel-nfsv4-rpcrdma-version-two] connections [RPCRDMA2]. RDMA Reliable Connected QPs are reliable,
[RFC5041]. RDMA Reliable Connected QPs are reliable, connection- connection-oriented transports that guarantee in-order delivery,
oriented transports that guarantee in-order delivery, meeting all meeting all the above requirements.
above requirements for NFS version 4 transports.
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
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. Once an NFS client has consumed all server has become unresponsive. Once an NFS client has consumed all
available RPC-over-RDMA version 2 credits on that transport available RPC-over-RDMA version 2 credits on that transport
connection, it will forever await a reply before sending another RPC connection, it indefinitely awaits a reply before sending another RPC
request. request.
NFS version 4 clients SHOULD reserve one RPC-over-RDMA version 2 NFS version 4 clients SHOULD reserve one RPC-over-RDMA version 2
credit to use for periodic server or connection health assessment. credit to use for periodic server or connection health assessment.
This credit can be used to drive an RPC request on an otherwise idle Either peer can use this credit to drive an RPC request on an
connection, triggering either a quick affirmative server response or otherwise idle connection, triggering either a quick affirmative
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 are larger than 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 there is a transport error indicated (ie, RDMA2_ERROR) before o If a transport error occurs (e.g., an RDMA2_ERROR type message is
the disconnect or instead of a disconnect, the Requester MUST received) before the disconnect or instead of a disconnect, the
respond to that error as prescribed by the specification of the Requester MUST respond to that error as prescribed by the
RPC transport. Then the NFS version 4 rules for handling specification of the RPC transport. Then the NFS version 4 rules
retransmission apply. for handling retransmission apply.
o If there is a transport disconnect and the Responder has provided 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 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
[I-D.cel-nfsv4-rpcrdma-version-two]. Via standards action, the Upper [RPCRDMA2]. Via standards action, the Upper-Layer Binding specified
Layer Binding specified in this document can be extended to cover in this document can be extended to cover versions of the NFS version
versions of the NFS version 4 protocol specified after NFS version 4 4 protocol specified after NFS version 4 minor version 2, or to cover
minor version 2, or to cover separately published extensions to an separately published extensions to an existing NFS version 4 minor
existing NFS version 4 minor version, as described in [RFC8178]. 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 [I-D.cel-nfsv4-rpcrdma-version-two], all of the NFS protocols atop [RPCRDMA2], all relevant security
relevant security considerations are therefore to be described at considerations are, therefore, described at that layer.
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, a set of transport protocol port number assignments For this purpose, the current document specifies a set of transport
is specified by this document. IANA has assigned the following ports protocol port number assignments. IANA has assigned the following
for NFS/RDMA in the IANA port registry, according to the guidelines ports for NFS/RDMA in the IANA port registry, according to the
described in [RFC6335]. guidelines described in [RFC6335].
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
This document should be listed as a reference for the nfsrdma port The current document should be added as a reference for the nfsrdma
assignments. This document does not alter these assignments. port assignments. The current document does not alter these
assignments.
10. References 10. References
10.1. Normative References 10.1. Normative References
[I-D.cel-nfsv4-rpcrdma-version-two]
Lever, C. and D. Noveck, "RPC-over-RDMA Version 2
Protocol", draft-cel-nfsv4-rpcrdma-version-two-09 (work in
progress), May 2019.
[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 5 skipping to change at page 15, line 47
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 15, line 36 skipping to change at page 16, line 36
[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. Dave Noveck contributed the text of Section 6.6 and Section 7. The
author also wishes to thank Bill Baker and Greg Marsden for their
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 and Brian Pawlowski, and NFSV4 Working Group Chairs Spencer Shepler, Brian Pawlowski, and Dave
Working Group Secretary Thomas Haynes for their support. The author Noveck, and NFSV4 Working Group Secretary Thomas Haynes for their
also wishes to thank Bill Baker and Greg Marsden for their support of support.
this work.
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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