< draft-ietf-nfsv4-rfc5667bis-03.txt   draft-ietf-nfsv4-rfc5667bis-04.txt >
Network File System Version 4 C. Lever, Ed. Network File System Version 4 C. Lever, Ed.
Internet-Draft Oracle Internet-Draft Oracle
Obsoletes: 5667 (if approved) September 28, 2016 Obsoletes: 5667 (if approved) January 20, 2017
Intended status: Standards Track Intended status: Standards Track
Expires: April 1, 2017 Expires: July 24, 2017
Network File System (NFS) Upper Layer Binding To RPC-Over-RDMA Network File System (NFS) Upper Layer Binding To RPC-Over-RDMA
draft-ietf-nfsv4-rfc5667bis-03 draft-ietf-nfsv4-rfc5667bis-04
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 transports. These bindings (NFS) protocol versions to RPC-over-RDMA. Upper Layer Bindings are
are required to enable RPC-based protocols such as NFS to use direct required to enable RPC-based protocols, such as NFS, to use Direct
data placement on RPC-over-RDMA transports. This document obsoletes Data Placement on RPC-over-RDMA. This document obsoletes RFC 5667.
RFC 5667.
Requirements Language 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", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
skipping to change at page 1, line 41 skipping to change at page 1, line 40
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This Internet-Draft will expire on April 1, 2017. This Internet-Draft will expire on July 24, 2017.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conveying NFS Operations On RPC-Over-RDMA Transports . . . . 3 2. Conveying NFS Operations On RPC-Over-RDMA . . . . . . . . . . 3
3. NFS Versions 2 And 3 Upper Layer Binding . . . . . . . . . . 4 3. Upper Layer Binding For NFS Versions 2 And 3 . . . . . . . . 5
4. NFS Version 4 Upper Layer Binding . . . . . . . . . . . . . . 6 4. Upper Layer Binding For NFS Version 4 . . . . . . . . . . . . 7
5. Extending NFS Upper Layer Bindings . . . . . . . . . . . . . 13 5. Extending NFS Upper Layer Bindings . . . . . . . . . . . . . 13
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
7. Security Considerations . . . . . . . . . . . . . . . . . . . 13 7. Security Considerations . . . . . . . . . . . . . . . . . . . 14
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
Appendix A. Changes Since RFC 5667 . . . . . . . . . . . . . . . 15 Appendix A. Changes Since RFC 5667 . . . . . . . . . . . . . . . 16
Appendix B. Acknowledgments . . . . . . . . . . . . . . . . . . 16 Appendix B. Acknowledgments . . . . . . . . . . . . . . . . . . 17
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 17 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction 1. Introduction
An RPC-over-RDMA transport, such as defined in An RPC-over-RDMA transport, such as the one defined in
[I-D.ietf-nfsv4-rfc5666bis], may employ direct data placement to [I-D.ietf-nfsv4-rfc5666bis], may employ direct data placement to
convey data payloads associated with RPC transactions. Each RPC- convey data payloads associated with RPC transactions. To enable
over-RDMA transport header conveys lists of memory locations successful interoperation, RPC client and server implementations must
corresponding to XDR data items defined in an Upper Layer Protocol agree as to which XDR data items in what particular RPC procedures
(such as NFS). are eligible for direct data placement (DDP).
To facilitate interoperation, RPC client and server implementations This document contains material required of Upper Layer Bindings, as
must agree in advance on what XDR data items in which RPC procedures specified in [I-D.ietf-nfsv4-rfc5666bis], for the following NFS
are eligible for direct data placement (DDP). This document contains protocol versions:
material required of Upper Layer Bindings, as specified in
[I-D.ietf-nfsv4-rfc5666bis], for the following NFS protocol versions:
o NFS Version 2 [RFC1094] o NFS Version 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 [I-D.ietf-nfsv4-minorversion2] o NFS Version 4.2 [RFC7862]
2. Conveying NFS Operations On RPC-Over-RDMA Transports Upper Layer Bindings specified in this document apply to all versions
of RPC-over-RDMA.
2. Conveying NFS Operations On RPC-Over-RDMA
Definitions of terminology and a general discussion of how RPC-over- Definitions of terminology and a general discussion of how RPC-over-
RDMA is used to convey RPC transactions can be found in RDMA is used to convey RPC transactions can be found in
[I-D.ietf-nfsv4-rfc5666bis]. In this section, these general [I-D.ietf-nfsv4-rfc5666bis]. In this section, these general
principals are applied to the specifics of the NFS protocol. principles are applied in the context of conveying NFS procedures on
RPC-over-RDMA. Some issues common to all NFS protocol versions are
introduced.
2.1. Use Of The Read List 2.1. The Read List
The Read list in each RPC-over-RDMA transport header represents a set The Read list in each RPC-over-RDMA transport header represents a set
of memory regions containing DDP-eligible NFS argument data. Large of memory regions containing DDP-eligible NFS argument data. Large
data items, such as the data payload of an NFS version 3 WRITE data items, such as the data payload of an NFS version 3 WRITE
procedure, are referenced by the Read list. The NFS server pulls procedure, can be referenced by the Read list. The NFS server pulls
such payloads from the client and places them directly into its own such payloads from the client and places them directly into its own
memory. memory.
XDR unmarshaling code on the NFS server identifies the correspondence Exactly which XDR data items may be conveyed in this fashion is
between Read chunks and particular NFS arguments via the chunk detailed later in this document.
Position value encoded in each Read segment.
2.2. Use Of The Write List 2.2. The Write List
The Write list in each RPC-over-RDMA transport header represents a The Write list in each RPC-over-RDMA transport header represents a
set of memory regions that can receive DDP-eligible NFS result data. set of memory regions that can receive DDP-eligible NFS result data.
Large data items, such as the payload of an NFS version 3 READ Large data items, such as the payload of an NFS version 3 READ
procedure, are referenced by the Write list. The NFS server pushes procedure, can be referenced by the Write list. The NFS server
such payloads to the client, placing them directly into the client's pushes such payloads to the client, placing them directly into the
memory. client's memory.
Each Write chunk corresponds to a specific XDR data item in an NFS Each Write chunk corresponds to a specific XDR data item in an NFS
reply. This document specifies how NFS client and server reply. This document specifies how NFS client and server
implementations identify the correspondence between Write chunks and implementations identify the correspondence between Write chunks and
XDR results. XDR results.
2.2.1. Empty Write Chunks Exactly which XDR data items may be conveyed in this fashion is
detailed later in this document.
Section 4.4.6.2 of [I-D.ietf-nfsv4-rfc5666bis] defines the concept of
unused Write chunks. An unused Write chunk is a Write chunk with
either zero segments or where all segments in the Write chunk have
zero length. In this document these are referred to as "empty" Write
chunks. A "non-empty" Write chunk has at least one segment of non-
zero length.
An NFS client might wish an NFS server to return a DDP-eligible
result inline. If there is only one DDP-eligible result item in the
reply, the NFS client simply specifies an empty Write list to force
the NFS server to return that result inline. If there are multiple
DDP-eligible results, the NFS client specifies empty Write chunks for
each DDP-eligible data item that it wishes to be returned inline.
An NFS server might encounter an XDR union result where there are
arms that have a DDP-eligible result, and arms that do not. If the
NFS client has provided a non-empty Write chunk that matches with a
DDP-eligible result, but the response does not contain that result,
the NFS server MUST return an empty Write chunk in that position in
the Write list.
2.3. Use Of Long Calls And Replies 2.3. Long Calls And Replies
Small RPC messages are conveyed using RDMA Send operations which are Small RPC messages are conveyed using RDMA Send operations which are
of limited size. If an NFS request is too large to be conveyed of limited size. If an NFS request is too large to be conveyed
within the NFS server's responder inline threshold, and there are no within the NFS server's responder inline threshold, and there are no
DDP-eligible data items that can be removed, an NFS client must send DDP-eligible data items that can be removed, an NFS client must send
the request using a Long Call. The entire NFS request is sent in a the request in the form of a Long Call. The entire NFS request is
special Read chunk called a Position-Zero Read chunk. sent in a special Read chunk called a Position Zero Read chunk.
If an NFS client predicts that the maximum size of an NFS reply could If an NFS client determines that the maximum size of an NFS reply
be too large to be conveyed within it's own responder inline could be too large to be conveyed within it's own responder inline
threshold, it provides a Reply chunk in the RPC-over-RDMA transport threshold, it provides a Reply chunk in the RPC-over-RDMA transport
header conveying the NFS request. The server places the entire NFS header conveying the NFS request. The server places the entire NFS
reply in the Reply chunk. reply in the Reply chunk.
These special chunks are described in more detail in When the RPC authentication flavor requires that DDP-eligible data
items are never removed from RPC messages, an NFS client can provide
both a Position Zero Read chunk and a Reply chunk for the same RPC.
These special chunks are discussed in further detail in
[I-D.ietf-nfsv4-rfc5666bis]. [I-D.ietf-nfsv4-rfc5666bis].
2.4. Scatter-Gather Considerations 2.4. Scatter-Gather Considerations
A chunk comprises exactly one XDR data item. Each Read chunk is A chunk typically corresponds to exactly one XDR data item. Each
represented as a list of segments at the same XDR Position. Each Read chunk is represented as a list of segments at the same XDR
Write chunk is represented as an array of segments. An NFS client Position. Each Write chunk is represented as an array of segments.
thus has the flexibility to advertise a set of discontiguous memory An NFS client thus has the flexibility to advertise a set of
regions in which to send or receive a single DDP-eligible XDR data discontiguous memory regions in which to convey a single DDP-eligible
item. XDR data item.
3. NFS Versions 2 And 3 Upper Layer Binding
An NFS version 2 or version 3 client MAY send a single Read chunk to
supply the opaque file data for an NFS WRITE procedure, or the
pathname for an NFS SYMLINK procedure. For these procedures, NFS
version 2 or 3 servers MUST ignore Read chunks beyond the first in
the Read list. For all other NFS procedures, NFS version 2 or 3
servers MUST ignore Read chunks that have a non-zero value in their
Position fields.
Similarly, an NFS version 2 or version 3 client MAY provide a single
Write chunk to receive either the opaque file data from an NFS READ
procedure, or the pathname from an NFS READLINK procedure. For these
procedures, NFS version 2 or 3 servers MUST ignore Write chunks
beyond the first in the Write list. For all other NFS procedures,
NFS version 2 or 3 servers MUST ignore the Write list.
There are no NFS version 2 or 3 procedures that have DDP-eligible 2.5. DDP Eligibility Violations
data items in both their Call and Reply. However, when an NFS
version 2 or version 3 client sends a Long Call or Reply, it MAY
provide a combination of a Read list, a Write list, and/or a Reply
chunk in the same RPC-over-RDMA header.
If an NFS version 2 or version 3 client has not provided enough bytes To report a DDP-eligibity violation, an NFS server MUST return one
in a Read list to match the size of a DDP-eligible NFS argument data of:
item, or if an NFS version 2 or version 3 client has not provided
enough Write list resources to handle an NFS READ or READLINK reply,
or if the client has not provided a large enough Reply chunk to
convey an NFS reply, the server MUST return one of:
o An RPC-over-RDMA message of type RDMA_ERROR, with the rdma_xid o An RPC-over-RDMA message of type RDMA_ERROR, with the rdma_xid
field set to the XID of the matching NFS Call, and the rdma_error field set to the XID of the matching NFS Call, and the rdma_error
field set to ERR_CHUNK; or field set to ERR_CHUNK; or
o An RPC message (via an RDMA_MSG message) with the xid field set to o An RPC message (via an RDMA_MSG message) with the xid field set to
the XID of the matching NFS Call, the mtype field set to REPLY, the XID of the matching NFS Call, the mtype field set to REPLY,
the stat field set to MSG_ACCEPTED, and the accept_stat field set the stat field set to MSG_ACCEPTED, and the accept_stat field set
to GARBAGE_ARGS. to GARBAGE_ARGS.
These replies do not give any indication to NFS version 2 or version Subsequent sections of this document describe further considerations
3 clients of whether an NFS version 2 or 3 server has processed the particular to specific NFS protocols or procedures.
arguments of the RPC Call, or whether the NFS version 2 or 3 server
has accessed NFS client memory associated with that RPC.
NFS version 2 or version 3 clients already successfully estimate the 2.6. Reply Size Estimation
maximum reply size of each operation in order to provide an adequate
set of buffers to receive each NFS reply. An NFS version 2 or
version 3 client provides a Reply chunk when the maximum possible
reply size is larger than the client's responder inline threshold.
3.1. Auxiliary Protocols During the construction of each RPC Call message, an NFS client is
responsible for allocating appropriate resources for receiving the
matching Reply message. A Reply buffer overrun can result in
corruption of the Reply message or termination of the transport
connection. Therefore reliable reply size estimation is necessary to
ensure successful interoperation.
NFS versions 2 and 3 are typically deployed with several other In many cases the Upper Layer Protocol's XDR definition provides
protocols, referred to as "auxiliary" protocols. These are separate enough information to enable the client to make a reliable prediction
RPC protcols which handle operations that are not part of the main of the maximum size of the expected Reply message. If there are
NFS protocol. These include the MOUNT and NLM protocols, introduced variable-size data items in the result, the maximum size of the RPC
in an appendix of [RFC1813]; the NSM protocol, described in Chapter Reply message can be reliably estimated in most cases:
11 of [NSM]; and the NFSACL protocol, which does not have a public
definition. However NFSACL is treated as a de facto standard and
there are several interoperating implementations.
RPC-over-RDMA considers these as individual Upper Layer Protocols o The client requests only a specific portion of an object (for
[I-D.ietf-nfsv4-rfc5666bis]. Therefore to operate on an RPC-over- example, using the "count" and "offset" fields in an NFS READ).
RDMA transport, an Upper Layer Binding must be provided for each of
these.
Typically MOUNT, NLM, and NSM are conveyed via TCP rather than RPC- o The client has already cached the size of the whole object it is
over-RDMA. Note that only metadata is conveyed in these protocols, about to request (say, via a previous NFS GETATTR request).
thus direct data placement is never necessary, and the size of RPC
messages is uniformly small. The maximum size of replies is easily
determined by examining the XDR definitions of these protocols.
Implementations that support the NFSACL protocol typically send It is occasionally not possible to determine the maximum Reply
NFSACL procedures on the same connection as the main NFS protocol. message size based solely on the above criteria. NFS client
Thus NFSACL does require an Upper Layer Binding. implementers can choose to provide the largest possible Reply buffer
in those cases, based on, for instance, the largest possible NFS READ
or WRITE payload (which is negotiated at mount time).
No data item in this protocol is DDP-eligible. There is no protocol In rare cases, a client may encounter a reply for which no a priori
size limit for NFS version 3 ACL objects. The client can have some determination of reply size bound is possible. The client SHOULD
difficulty ascertaining the size of ACLs to be read from servers. expect a transport error to indicate that it must either terminate
Practically speaking, ACLs are not large (less than 4KB in most that RPC transaction, or retry it with a larger Reply chunk.
cases), but a large Reply chunk may be provided when the client is in
doubt. The usual rules apply to the use of Long Messages when the
size of an NFSACL RPC exceeds a connection's inline thresholds.
4. NFS Version 4 Upper Layer Binding The use of NFS COMPOUND operations raises the possibility of non-
idempotent requests that combine a non-idempotent operation with an
operation whose reply size is uncertain. This causes potential
difficulties with retrying the transaction. Note however that many
operations normally considered non-idempotent (e.g WRITE, SETATTR)
are actually idempotent. Truly non-idempotent operations are quite
unusual in COMPOUNDs that include operations with uncertain reply
sizes.
This specification applies to NFS Version 4.0 [RFC7530], NFS Version 3. Upper Layer Binding For NFS Versions 2 And 3
4.1 [RFC5661], and NFS Version 4.2 [I-D.ietf-nfsv4-minorversion2].
It also applies to the callback protocols associated with each of
these minor versions defined in the same documents.
4.1. DDP-Eligibility This Upper Layer Binding specification applies to NFS Version 2
[RFC1094] and NFS Version 3 [RFC1813]. For brevity, in this section
a "legacy NFS client" refers to an NFS client using NFS version 2 or
NFS version 3 to communicate with an NFS server. Likewise, a "legacy
NFS server" is an NFS server communicating with clients using NFS
version 2 or NFS version 3.
For each WRITE operation in an NFS version 4 COMPOUND procedure, an The following XDR data items in NFS versions 2 and 3 are DDP-
NFS version 4 client MAY provide a single Read chunk to supply the eligible:
opaque file data argument. For each CREATE(NF4LNK) operation in an
NFS version 4 COMPOUND procedure, An NFS version 4 client MAY provide
a single Read chunk to supply the pathname argument.
Similarly, for each READ operation in an NFS version 4 COMPOUND o The opaque file data argument in the NFS WRITE procedure
procedure, an NFS version 4 client MAY provide a single Write chunk
to receive the opaque file data argument. For each READ_PLUS
operation in an NFS version 4 COMPOUND procedure, an NFS version 4
client MAY provide a single Write chunk to receive NFS4_CONTENT_DATA.
For each READLINK operation in an NFS version 4 COMPOUND procedure,
an NFS version 4 client MAY provide a single Write chunk to receive
the pathname argument.
An NFS version 4 client MUST NOT provide a Read or Write chunk that o The pathname argument in the NFS SYMLINK procedure
corresponds with any other XDR data item in any other NFS version 4
operation in an NFS version 4 COMPOUND procedure, or in an NFS
version 4 NULL procedure.
It is possible for NFS version 4 COMPOUND procedures to use both the o The opaque file data result in the NFS READ procedure
Read list and Write list simultaneously. An NFS version 4 client MAY
provide a Read list and a Write list in the same transaction if it is
sending a Long Call or Reply.
If an NFS version 4 client has not provided enough bytes in a Read o The pathname result in the NFS READLINK procedure
list to match the size of a DDP-eligible NFS argument data item, or
if an NFS version 4 client has not provided enough Write list
resources to handle a WRITE or READLINK operation, or if the client
has not provided a large enough Reply chunk to convey an NFS reply,
the server MUST return one of:
o An RPC-over-RDMA message of type RDMA_ERROR, with the rdma_xid All other argument or result data items in NFS versions 2 and 3 are
field set to the XID of the matching NFS Call, and the rdma_error not DDP-eligible.
field set to ERR_CHUNK; or
o An RPC message (via an RDMA_MSG message) with the xid field set to A legacy server's response to a DDP-eligibility violation (described
the XID of the matching NFS Call, the stat field set to in Section 2.5) does not give an indication to legacy clients of
MSG_ACCEPTED, and the accept_stat field set to GARBAGE_ARGS. whether the server has processed the arguments of the RPC Call, or
whether the server has accessed or modified client memory associated
with that RPC.
Such error replies are permanent errors, and constitute both A legacy NFS client determines the maximum reply size for each
completion of the RPC transaction, and a valid server response. It operation using the basic criteria outlined in Section 2.6. Such
is not necessary for an NFS version 4 server to drop the transport clients provide a Reply chunk when the maximum possible reply size,
connection in this case. exclusive of any data items represented by Write chunks, is larger
than the client's responder inline threshold.
4.1.1. Session-Related Considerations 3.1. Auxiliary Protocols
In most cases, the presence of an NFS session [RFC5661] has no effect NFS versions 2 and 3 are typically deployed with several other
on the operation of RPC-over-RDMA. None of the operations introduced protocols, sometimes referred to as "NFS auxiliary protocols." These
to support NFS sessions contain DDP-eligible data items. There is no are separate RPC programs that define procedures which are not part
need to match the number of session slots with the number of of the NFS version 2 or version 3 RPC programs. These include:
available RPC-over-RDMA credits.
However, there are some rare error conditions which require special o The MOUNT and NLM protocols, introduced in an appendix of
handling when an NFS session is operating on an RPC-over-RDMA [RFC1813]
transport. For example, a requester might receive, in response to an
RPC request, an RDMA_ERROR message with an rdma_err value of
ERR_CHUNK, or an RDMA_MSG containing an RPC_GARBAGEARGS reply.
Within RPC-over-RDMA Version One, this class of error can be
generated for two different reasons:
o There was an XDR error detected parsing the RPC-over-RDMA headers. o The NSM protocol, described in Chapter 11 of [NSM]
o There was an error sending the response, because, for example, a o The NFSACL protocol, which does not have a public definition
necessary reply chunk was not provided or the one provided is of (NFSACL here is treated as a de facto standard as there are
insufficient length. several interoperating implementations).
These two situations, which arise only due to incorrect RPC-over-RDMA considers these programs as distinct Upper Layer
implementations, have different implications with regard to Exactly- Protocols [I-D.ietf-nfsv4-rfc5666bis]. To enable the use of these
Once Semantics. An XDR error in decoding the request precludes the ULPs on an RPC-over-RDMA transport, an Upper Layer Binding
execution of the request on the responder, but failure to send a specification is provided here for each.
reply indicates that some or all of the operations were executed.
In both instances, the client SHOULD NOT retry the operation. A 3.1.1. MOUNT, NLM, And NSM Protocols
retry is liable to result in the same sort of error seen previously.
Instead, it is best to consider the operation as completed
unsuccessfully and report an error to the consumer who requested the
RPC.
In addition, within the error response, the requester does not have Typically MOUNT, NLM, and NSM are conveyed via TCP, even in
the result of the execution of the SEQUENCE operation, which deployments where NFS operations on RPC-over-RDMA. When a legacy
identifies the session, slot, and sequence id for the request which server supports these programs on RPC-over-RDMA, it advertises the
has failed. The xid associated with the request, obtained from the port address via the usual rpcbind service [RFC1833].
rdma_xid field of the RDMA_ERROR or RDMA_MSG message, must be used to
determine the session and slot for the request which failed, and the
slot must be properly retired. If this is not done, the slot could
be rendered permanently unavailable.
4.2. Reply Size Estimation No operation in these protocols conveys a significant data payload,
and the size of RPC messages in these protocols is uniformly small.
Therefore, no XDR data items in these protocols are DDP-eligible.
The largest variable-length XDR data item is an xdr_netobj. In most
implementations this data item is not larger than 1024 bytes, making
reliable reply size estimation straightforward using the criteria
outlined in Section 2.6.
An NFS version 4 client provides a Reply chunk when the maximum 3.1.2. NFSACL Protocol
possible reply size is larger than the client's responder inline
threshold. NFS version 4 clients already successfully estimate the
maximum reply size of most operations in order to provide an adequate
set of buffers to receive each NFS reply.
There are certain NFS version 4 data items whose size cannot be Legacy clients and servers that support the NFSACL RPC program
estimated by clients reliably, however, because there is no protocol- typically convey NFSACL procedures on the same connection as the NFS
specified size limit on these structures. These include but are not RPC program. This obviates the need for separate rpcbind queries to
limited to opaque types, such as: discover server support for this RPC program.
o The attrlist4 field ACLs are typically small, but even large ACLs must be encoded and
decoded to some degree. Thus no data item in this Upper Layer
Protocol is DDP-eligible.
o Fields containing ACLs such as fattr4_acl, fattr4_dacl, For procedures whose replies do not include an ACL object, the size
fattr4_sacl of a reply is determined directly from the NFSACL program's XDR
definition.
o Fields in the fs_locations4 and fs_locations_info4 data structures There is no protocol-wide size limit for NFS version 3 ACLs, and
o Opaque fields which pertain to pNFS layout metadata, such as there is no mechanism in either the NFSACL or NFS programs for a
loc_body, loh_body, da_addr_body, lou_body, lrf_body, legacy client to ascertain the largest ACL a legacy server can store.
fattr_layout_types and fs_layout_types, Legacy client implementations should choose a maximum size for ACLs
based on their own internal limits. A recommended lower bound for
this maximum is 32,768 bytes, though a larger Reply chunk (up to the
negotiated rsize setting) can be provided.
In NFS version 4.1 and later minor versions, the csa_fore_chan_attrs 4. Upper Layer Binding For NFS Version 4
argument of the CREATE_SESSION operation contains a
ca_maxresponsesize field. The value in this field can be taken as
the absolute maximum size of replies generated by a replying NFS
version 4 server. This value can be used in cases where it is not
possible to estimate a reply size upper bound precisely. In
practice, objects such as ACLs, named attributes, layout bodies, and
security labels are much smaller than this maximum.
With regard to NFS version 4.0, things are more troublesome. This Upper Layer Binding specification applies to all protocols
Typically NFS version 4.0 client implementations rely on their own defined in NFS Version 4.0 [RFC7530], NFS Version 4.1 [RFC5661], and
architectural limits to keep reply buffer sizes reasonable. For NFS Version 4.2 [RFC7862].
instance, although the NFS version 4 protocol is capable of conveying
a megabyte-sized ACL, nearly all known physical filesystems store
ACLs in on-disk containers which are small in size.
4.2.1. Managing READ_PLUS Replies 4.1. DDP-Eligibility
Only the following XDR data items in the COMPOUND procedure of all
NFS version 4 minor versions are DDP-eligible:
o The opaque data field in the WRITE4args structure
o The linkdata field of the NF4LNK arm in the createtype4 union
o The opaque data field in the READ4resok structure
o The linkdata field in the READLINK4resok structure
o In minor version 2 and newer, the rpc_data field of the
read_plus_content union (further restrictions on the use of this
data item follow below).
4.1.1. READ_PLUS Replies
The NFS version 4.2 READ_PLUS operation returns a complex data type The NFS version 4.2 READ_PLUS operation returns a complex data type
[I-D.ietf-nfsv4-minorversion2]. The rpr_contents field in the result [RFC7862]. The rpr_contents field in the result of this operation is
of this operation is an array of read_plus_content unions, one arm of an array of read_plus_content unions, one arm of which contains an
which contains an opaque byte stream (d_data). opaque byte stream (d_data).
The size of d_data is limited to the value of the rpa_count field, The size of d_data is limited to the value of the rpa_count field,
but the protocol does not bound the number of elements which can be but the protocol does not bound the number of elements which can be
returned in the rpr_contents array. In order to make the size of returned in the rpr_contents array. In order to make the size of
READ_PLUS replies predictable by NFS version 4.2 clients, the READ_PLUS replies predictable by NFS version 4.2 clients, the
following restrictions are placed on the use of the READ_PLUS following restrictions are placed on the use of the READ_PLUS
operation on RPC-over-RDMA transports: operation on RPC-over-RDMA transports:
o An NFS version 4.2 client MUST NOT provide more than one Write o An NFS version 4.2 client MUST NOT provide more than one Write
chunk for any READ_PLUS operation. When providing a Write chunk chunk for any READ_PLUS operation. When providing a Write chunk
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use that chunk for the first element of the rpr_contents array use that chunk for the first element of the rpr_contents array
that has an rpc_data arm. that has an rpc_data arm.
o An NFS version 4.2 server MUST NOT return more than two elements o An NFS version 4.2 server MUST NOT return more than two elements
in the rpr_contents array of any READ_PLUS operation. It returns in the rpr_contents array of any READ_PLUS operation. It returns
as much of the requested byte range as it can fit within these two as much of the requested byte range as it can fit within these two
elements. If the NFS version 4.2 server has not asserted rpr_eof elements. If the NFS version 4.2 server has not asserted rpr_eof
in the reply, the NFS version 4.2 client SHOULD send additional in the reply, the NFS version 4.2 client SHOULD send additional
READ_PLUS requests for any remaining bytes. READ_PLUS requests for any remaining bytes.
4.3. NFS Version 4 COMPOUND Requests 4.2. NFS Version 4 Reply Size Estimation
A single NFS version 4 COMPOUND procedure supplies arguments for a An NFS version 4 client provides a Reply chunk when the maximum
sequence of operations, and returns results from that sequence, all possible reply size is larger than the client's responder inline
in a single round-trip [RFC7530]. An NFS version 4 client MAY threshold.
construct an NFS version 4 COMPOUND procedure that provides more than
one chunk in the Read list or Write list as long as it observes the
restrictions in Section 4.1.
An NFS version 4 client provides XDR Position values in each Read There are certain NFS version 4 data items whose size cannot be
chunk to disambiguate which chunk is associated with which argument estimated by clients reliably, however, because there is no protocol-
data item. However NFS version 4 server and client implementations specified size limit on these structures. These include:
must agree in advance on how to pair Write chunks with returned
result data items.
The mechanism specified in Section 5.3.2 of o The attrlist4 field
[I-D.ietf-nfsv4-rfc5666bis]) is applied here, with some additional
restrictions. In the following list, an "NFS Read" operation refers o Fields containing ACLs such as fattr4_acl, fattr4_dacl,
to any NFS Version 4 operation which has a DDP-eligible result data fattr4_sacl
item (i.e., either a READ, READ_PLUS, or READLINK operation).
o Fields in the fs_locations4 and fs_locations_info4 data structures
o Opaque fields which pertain to pNFS layout metadata, such as
loc_body, loh_body, da_addr_body, lou_body, lrf_body,
fattr_layout_types and fs_layout_types,
4.2.1. Reply Size Estimation For Minor Version 0
The items enumerated above in Section 4.2 make it difficult to
predict the maximum size of GETATTR replies that interrogate
variable-length attributes. As discussed in Section 2.6, client
implementations can rely on their own internal architectural limits
to bound the reply size, but such limits are not guaranteed to be
reliable.
If a client implementation is equipped to recognize that a transport
error could mean that it provisioned an inadequately sized Reply
chunk, it can retry the operation with a larger Reply chunk.
Otherwise, the client must terminate the RPC transaction.
It is best to avoid issuing single COMPOUNDs that contain both non-
idempotent operations and operations where the maximum reply size
cannot be reliably predicted.
4.2.2. Reply Size Estimation For Minor Version 1 And Newer
In NFS version 4.1 and newer minor versions, the csa_fore_chan_attrs
argument of the CREATE_SESSION operation contains a
ca_maxresponsesize field. The value in this field can be taken as
the absolute maximum size of replies generated by a replying NFS
version 4 server.
This value can be used in cases where it is not possible to estimate
a reply size upper bound precisely. In practice, objects such as
ACLs, named attributes, layout bodies, and security labels are much
smaller than this maximum.
4.3. NFS Version 4 COMPOUND Requests
The NFS version 4 COMPOUND procedure allows the transmission of more
than one DDP-eligible data item per Call and Reply message. An NFS
version 4 client provides XDR Position values in each Read chunk to
disambiguate which chunk is associated with which argument data item.
However NFS version 4 server and client implementations must agree in
advance on how to pair Write chunks with returned result data items.
The mechanism specified in Section 4.3.2 of
[I-D.ietf-nfsv4-rfc5666bis]) is applied here, with additional
restrictions that appear below. In the following list, an "NFS Read"
operation refers to any NFS Version 4 operation which has a DDP-
eligible result data item (i.e., either a READ, READ_PLUS, or
READLINK operation).
o If an NFS version 4 client wishes all DDP-eligible items in an NFS 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.
o The first chunk in the Write list MUST be used by the first NFS o The first chunk in the Write list MUST be used by the first READ
Read operation in an NFS version 4 COMPOUND procedure. The next operation in an NFS version 4 COMPOUND procedure. The next Write
Write chunk is used by the next NFS 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 NFS Read operation MUST return its chunk, then the corresponding READ operation MUST return its DDP-
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 NFS Read operation MUST return all chunk, then the corresponding READ operation MUST return all of
of its result data items inline. its result data items inline.
o If an NFS Read operation returns a union arm which does not o If an READ operation returns a union arm which does not contain a
contain a DDP-eligible result, and the NFS version 4 client has DDP-eligible result, and the NFS version 4 client has provided a
provided a matching non-empty Write chunk, an NFS version 4 server matching non-empty Write chunk, an NFS version 4 server MUST
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 NFS 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.
4.3.1. NFS Version 4 COMPOUND Example 4.3.1. NFS Version 4 COMPOUND Example
The following example shows a Write list with three Write chunks, A, The following example shows a Write list with three Write chunks, A,
B, and C. The NFS version 4 server consumes the provided Write B, and C. The NFS version 4 server consumes the provided Write
chunks by writing the results of the designated operations in the chunks by writing the results of the designated operations in the
compound request (READ and READLINK) back to each chunk. compound request (READ and READLINK) back to each chunk.
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4.4. NFS Version 4 Callback 4.4. NFS Version 4 Callback
The NFS version 4 protocols support server-initiated callbacks to The NFS version 4 protocols support server-initiated callbacks to
notify clients of events such as recalled delegations. notify clients of events such as recalled delegations.
4.4.1. NFS Version 4.0 Callback 4.4.1. NFS Version 4.0 Callback
NFS version 4.0 implementations typically employ a separate TCP NFS version 4.0 implementations typically employ a separate TCP
connection to handle callback operations, even when the forward connection to handle callback operations, even when the forward
channel uses a RPC-over-RDMA transport. Therefore no Upper Layer channel uses a RPC-over-RDMA transport.
Binding for the NFS version 4.0 callback program is provided in this
document. No operation in the NFS version 4.0 callback RPC program conveys a
significant data payload. Therefore, no XDR data items in this RPC
program is DDP-eligible.
A CB_RECALL reply is small and fixed in size. The CB_GETATTR reply
contains a variable-length fattr4 data item. See Section 4.2.1 for a
discussion of reply size prediction for this data item.
An NFS version 4.0 client advertises netids and ad hoc port addresses
for contacting its NFS version 4.0 callback service using the
SETCLIENTID operation.
4.4.2. NFS Version 4.1 Callback 4.4.2. NFS Version 4.1 Callback
In NFS version 4.1 and later 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 mechanism described in [I-D.ietf-nfsv4-rpcrdma-bidirection] when the mechanism described in [I-D.ietf-nfsv4-rpcrdma-bidirection] when
backchannel operations are conveyed on RPC-over-RDMA transports. backchannel operations are conveyed on RPC-over-RDMA transports.
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 can be
taken as the absolute maximum size of backchannel replies generated taken as the absolute maximum size of backchannel replies generated
by a replying NFS version 4 client. by a replying NFS version 4 client.
There are no DDP-eligible data items in callback protocols associated There are no DDP-eligible data items in callback procedures defined
with 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
requests, such as messages that convey device ID information, may be operations, such as messages that convey device ID information, can
large, in which case a Long Call or Reply may be appropriate. When be large, in which case a Long Call or Reply might be required.
the NFS version 4 client reports a backchannel ca_maxresponsesize
that is larger than the connection's inline thresholds, the NFS
version 4 client can support Long messages (i.e., Read chunks and
Reply chunks). Otherwise an NFS version 4 server MUST use Short
messages to convey backchannel operations.
See Section 4.1 for a discussion of how an NFS version 4 server When an NFS version 4.1 client reports a backchannel
handles situations where an NFS version 4 client has provided ca_maxrequestsize that is larger than the connection's inline
inadequate RDMA resources to convey a backchannel reply. thresholds, the NFS version 4 client can support Long Calls.
Otherwise an NFS version 4 server MUST use Short messages to convey
backchannel operations.
4.5. Connection Keep-Alive 4.5. Session-Related Considerations
Typically the presence of an NFS session [RFC5661] has no effect on
the operation of RPC-over-RDMA. None of the operations introduced to
support NFS sessions contain DDP-eligible data items. There is no
need to match the number of session slots with the number of
available RPC-over-RDMA credits.
However, there are some rare error conditions which require special
handling when an NFS session is operating on an RPC-over-RDMA
transport. For example, a requester might receive, in response to an
RPC request, an RDMA_ERROR message with an rdma_err value of
ERR_CHUNK, or an RDMA_MSG containing an RPC_GARBAGEARGS reply.
Within RPC-over-RDMA Version One, this class of error can be
generated for two different reasons:
o There was an XDR error detected parsing the RPC-over-RDMA headers.
o There was an error sending the response, because, for example, a
necessary reply chunk was not provided or the one provided is of
insufficient length.
These two situations, which arise due to incorrect implementations or
underestimation of reply size, have different implications with
regard to Exactly-Once Semantics. An XDR error in decoding the
request precludes the execution of the request on the responder, but
failure to send a reply indicates that some or all of the operations
were executed.
In both instances, the client SHOULD NOT retry the operation without
addressing reply resource inadequacy. Such a retry can result in the
same sort of error seen previously. Instead, it is best to consider
the operation as completed unsuccessfully and report an error to the
consumer who requested the RPC.
In addition, within the error response, the requester does not have
the result of the execution of the SEQUENCE operation, which
identifies the session, slot, and sequence id for the request which
has failed. The xid associated with the request, obtained from the
rdma_xid field of the RDMA_ERROR or RDMA_MSG message, must be used to
determine the session and slot for the request which failed, and the
slot must be properly retired. If this is not done, the slot could
be rendered permanently unavailable.
4.6. Connection 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.
RDMA transports have no keep-alive mechanism. Without a disconnect Some RDMA transports (such as Reliable Connections on InfiniBand)
or new RPC traffic, RDMA transport connections can remain alive long have no keep-alive mechanism. Without a disconnect or new RPC
after an NFS server has become unresponsive. Once an NFS client has traffic, such connections can remain alive long after an NFS server
consumed all available RPC-over-RDMA credits on that transport has become unresponsive. Once an NFS client has consumed all
connection, it will forever await a reply before sending another RPC available RPC-over-RDMA credits on that transport connection, it will
request. forever await a reply before sending another RPC request.
NFS version 4 clients SHOULD reserve one RPC-over-RDMA credit to use NFS version 4 clients SHOULD reserve one RPC-over-RDMA credit to use
for periodic server or connection health assessment. This credit can for periodic server or connection health assessment. This credit can
be used to drive an RPC request on an otherwise idle connection, be used to drive an RPC request on an otherwise idle connection,
triggering either a quick affirmative server response or immediate triggering either a quick affirmative server response or immediate
connection termination. connection termination.
To prevent lease expiry, NFS version 4 clients should use a lease-
extending operation such as RENEW or SEQUENCE, rather than a NULL
request, when performing a periodic health assessment.
5. Extending NFS Upper Layer Bindings 5. 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 transports specification to interoperate on RPC-over-RDMA transports
[I-D.ietf-nfsv4-rfc5666bis]. Via standards action, the Upper Layer [I-D.ietf-nfsv4-rfc5666bis]. Via standards action, the Upper Layer
Binding specified in this document can be extended to cover versions Binding specified in this document can be extended to cover versions
of the NFS version 4 protocol specified after NFS version 4 minor of the NFS version 4 protocol specified after NFS version 4 minor
version 2. This includes NFS version 4 extensions that are version 2, or separately published extensions to an existing NFS
documented separately from a new minor version. version 4 minor version, as described in [I-D.ietf-nfsv4-versioning].
6. IANA Considerations 6. IANA Considerations
NFS use of direct data placement introduces a need for an additional NFS use of direct data placement introduces a need for an additional
NFS port number assignment for networks that share traditional UDP NFS port number assignment for networks that share traditional UDP
and TCP port spaces with RDMA services. The iWARP [RFC5041] and TCP port spaces with RDMA services. The iWARP [RFC5041]
[RFC5040] protocol is such an example (InfiniBand is not). [RFC5040] protocol is such an example (InfiniBand is not).
NFS servers for versions 2 and 3 [RFC1094] [RFC1813] traditionally NFS servers for versions 2 and 3 [RFC1094] [RFC1813] traditionally
listen for clients on UDP and TCP port 2049, and additionally, they listen for clients on UDP and TCP port 2049, and additionally, they
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that this choice does not introduce new vulnerabilities. that this choice does not introduce new vulnerabilities.
Because this document defines only the binding of the NFS protocols Because this document defines only the binding of the NFS protocols
atop [I-D.ietf-nfsv4-rfc5666bis], all relevant security atop [I-D.ietf-nfsv4-rfc5666bis], all relevant security
considerations are therefore to be described at that layer. considerations are therefore to be described at that layer.
8. References 8. References
8.1. Normative References 8.1. Normative References
[I-D.ietf-nfsv4-minorversion2]
Haynes, T., "NFS Version 4 Minor Version 2", draft-ietf-
nfsv4-minorversion2-41 (work in progress), January 2016.
[I-D.ietf-nfsv4-rfc5666bis] [I-D.ietf-nfsv4-rfc5666bis]
Lever, C., Simpson, W., and T. Talpey, "Remote Direct Lever, C., Simpson, W., and T. Talpey, "Remote Direct
Memory Access Transport for Remote Procedure Call, Version Memory Access Transport for Remote Procedure Call, Version
One", draft-ietf-nfsv4-rfc5666bis-07 (work in progress), One", draft-ietf-nfsv4-rfc5666bis-09 (work in progress),
May 2016. January 2017.
[I-D.ietf-nfsv4-rpcrdma-bidirection] [I-D.ietf-nfsv4-rpcrdma-bidirection]
Lever, C., "Bi-directional Remote Procedure Call On RPC- Lever, C., "Bi-directional Remote Procedure Call On RPC-
over-RDMA Transports", draft-ietf-nfsv4-rpcrdma- over-RDMA Transports", draft-ietf-nfsv4-rpcrdma-
bidirection-05 (work in progress), June 2016. bidirection-06 (work in progress), January 2017.
[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,
<http://www.rfc-editor.org/info/rfc1833>. <http://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,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
skipping to change at page 15, line 5 skipping to change at page 15, line 42
[RFC5661] Shepler, S., Ed., Eisler, M., Ed., and D. Noveck, Ed., [RFC5661] Shepler, S., Ed., Eisler, M., Ed., and D. Noveck, Ed.,
"Network File System (NFS) Version 4 Minor Version 1 "Network File System (NFS) Version 4 Minor Version 1
Protocol", RFC 5661, DOI 10.17487/RFC5661, January 2010, Protocol", RFC 5661, DOI 10.17487/RFC5661, January 2010,
<http://www.rfc-editor.org/info/rfc5661>. <http://www.rfc-editor.org/info/rfc5661>.
[RFC7530] Haynes, T., Ed. and D. Noveck, Ed., "Network File System [RFC7530] Haynes, T., Ed. and D. Noveck, Ed., "Network File System
(NFS) Version 4 Protocol", RFC 7530, DOI 10.17487/RFC7530, (NFS) Version 4 Protocol", RFC 7530, DOI 10.17487/RFC7530,
March 2015, <http://www.rfc-editor.org/info/rfc7530>. March 2015, <http://www.rfc-editor.org/info/rfc7530>.
[RFC7862] Haynes, T., "Network File System (NFS) Version 4 Minor
Version 2 Protocol", RFC 7862, DOI 10.17487/RFC7862,
November 2016, <http://www.rfc-editor.org/info/rfc7862>.
8.2. Informative References 8.2. Informative References
[I-D.ietf-nfsv4-versioning]
Noveck, D., "Rules for NFSv4 Extensions and Minor
Versions", draft-ietf-nfsv4-versioning-09 (work in
progress), December 2016.
[NSM] The Open Group, "Protocols for Interworking: XNFS, Version [NSM] The Open Group, "Protocols for Interworking: XNFS, Version
3W", February 1998. 3W", February 1998.
[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, <http://www.rfc-editor.org/info/rfc1094>. 1989, <http://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,
skipping to change at page 16, line 14 skipping to change at page 17, line 11
Technical corrections have been made. For example, the mention of Technical corrections have been made. For example, the mention of
12KB and 36KB inline thresholds have been removed. The reference to 12KB and 36KB inline thresholds have been removed. The reference to
a non-existant NFS version 4 SYMLINK operation has been replaced with a non-existant NFS version 4 SYMLINK operation has been replaced with
NFS version 4 CREATE(NF4LNK). NFS version 4 CREATE(NF4LNK).
The discussion of NFS version 4 COMPOUND handling has been completed. The discussion of NFS version 4 COMPOUND handling has been completed.
Some changes were made to the algorithm for matching DDP-eligible Some changes were made to the algorithm for matching DDP-eligible
results to Write chunks. results to Write chunks.
Requirements to ignore extra Read or Write chunks have been removed
from the NFS version 2 and 3 Upper Layer Binding, as they conflict
with [I-D.ietf-nfsv4-rfc5666bis].
A complete discussion of reply size estimation has been introduced
for all protocols covered by the Upper Layer Bindings in this
document.
The following additional improvements have been made, relative to The following additional improvements have been made, relative to
[RFC5667]: [RFC5667]:
o An explicit discussion of NFS version 4.0 and NFS version 4.1 o An explicit discussion of NFS version 4.0 and NFS version 4.1
backchannel operation has replaced the previous treatment of backchannel operation has replaced the previous treatment of
callback operations. callback operations.
o A binding for NFS version 4.2 has been added that includes o A binding for NFS version 4.2 has been added that includes
discussion of new data-bearing operations like READ_PLUS. discussion of new data-bearing operations like READ_PLUS.
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Appendix B. Acknowledgments Appendix B. Acknowledgments
The author gratefully acknowledges the work of Brent Callaghan and The author gratefully acknowledges the work of Brent Callaghan and
Tom Talpey on the original NFS Direct Data Placement specification Tom Talpey on the original NFS Direct Data Placement specification
[RFC5667]. The author also wishes to thank Bill Baker and Greg [RFC5667]. The author also wishes to thank Bill Baker and Greg
Marsden for their support of this work. Marsden for their support of this work.
Dave Noveck provided excellent review, constructive suggestions, and Dave Noveck provided excellent review, constructive suggestions, and
consistent navigational guidance throughout the process of drafting consistent navigational guidance throughout the process of drafting
this document. Dave also contributed the text of Section 4.1.1. this document. Dave also contributed the text of Section 4.5
Thanks to Karen Deitke for her sharp observations about idempotency, Thanks to Karen Deitke for her sharp observations about idempotency,
and the clarity of the discussion of NFS COMPOUNDs. and the clarity of the discussion of NFS COMPOUNDs.
Special thanks go to Transport Area Director Spencer Dawkins, nfsv4 Special thanks go to Transport Area Director Spencer Dawkins, nfsv4
Working Group Chair Spencer Shepler, and nfsv4 Working Group Working Group Chair Spencer Shepler, and nfsv4 Working Group
Secretary Thomas Haynes for their support. Secretary Thomas Haynes for their support.
Author's Address Author's Address
Charles Lever (editor) Charles Lever (editor)
Oracle Corporation Oracle Corporation
1015 Granger Avenue 1015 Granger Avenue
Ann Arbor, MI 48104 Ann Arbor, MI 48104
USA USA
Phone: +1 734 274 2396 Phone: +1 248 816 6463
Email: chuck.lever@oracle.com Email: chuck.lever@oracle.com
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