draft-ietf-nfsv4-versioning-01.txt   draft-ietf-nfsv4-versioning-02.txt 
NFSv4 D. Noveck NFSv4 D. Noveck
Internet-Draft HP Internet-Draft HP
Intended status: Standards Track July 2, 2015 Updates: 5661 (if approved) October 10, 2015
Expires: January 3, 2016 Intended status: Standards Track
Expires: April 12, 2016
NFSv4 Version Management NFSv4 Version Management
draft-ietf-nfsv4-versioning-01 draft-ietf-nfsv4-versioning-02
Abstract Abstract
This document describes the management of versioning within the NFSv4 This document describes the management of versioning within the NFSv4
family of protocols. It covers the creation of minor versions, the family of protocols. It covers the creation of minor versions, the
addition of optional features to existing minor versions, and the addition of optional features to existing minor versions, and the
correction of flaws in features already published as Proposed correction of flaws in features already published as Proposed
Standards. The rules relating to the construction of minor versions Standards. The rules relating to the construction of minor versions
and the interaction of minor version implementations that appear in and the interaction of minor version implementations that appear in
this document supersede the minor versioning rules in RFC5661. this document supersede the minor versioning rules in RFC5661.
skipping to change at page 1, line 36 skipping to change at page 1, line 37
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This Internet-Draft will expire on January 3, 2016. This Internet-Draft will expire on April 12, 2016.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Existing Minor Versions . . . . . . . . . . . . . . . . . 3 1.1. Existing Minor Versions . . . . . . . . . . . . . . . . . 4
1.2. Updated NFSv4 Version Management Framework . . . . . . . 3 1.2. Updated NFSv4 Version Management Framework . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Consolidation of Version Management Rules . . . . . . . . . . 6 2.1. Use of Keywords Defined in RFC2119 . . . . . . . . . . . 6
4. NFSv4 Protocol Changes . . . . . . . . . . . . . . . . . . . 7 2.2. Use of Feature Statuses . . . . . . . . . . . . . . . . . 7
4.1. XDR Extension . . . . . . . . . . . . . . . . . . . . . . 7 2.3. NFSv4 Versions . . . . . . . . . . . . . . . . . . . . . 8
4.1.1. XDR Extension in General . . . . . . . . . . . . . . 8 3. Consolidation of Version Management Rules . . . . . . . . . . 9
4.1.2. Particulars of XDR Extension within NFSv4 . . . . . . 9 4. XDR Considerations . . . . . . . . . . . . . . . . . . . . . 10
4.1.3. Rules for XDR Extension within NFSv4 . . . . . . . . 9 4.1. XDR Extension . . . . . . . . . . . . . . . . . . . . . . 10
4.2. Non-XDR Protocol Changes . . . . . . . . . . . . . . . . 10 4.1.1. XDR Extension in General . . . . . . . . . . . . . . 11
4.2.1. Field Interpretation and Use . . . . . . . . . . . . 10 4.1.2. Particulars of XDR Extension within NFSv4 . . . . . . 12
4.2.2. Behavioral Changes . . . . . . . . . . . . . . . . . 11 4.1.3. Rules for XDR Extension within NFSv4 . . . . . . . . 12
4.2.3. Rules for non-XDR changes . . . . . . . . . . . . . . 11 4.2. Handling of Protocol Elements . . . . . . . . . . . . . . 13
4.3. Specification of Associated Protocols . . . . . . . . . . 12 4.3. Organization of Protocol Elements . . . . . . . . . . . . 14
4.3.1. Associated Protocols via pNFS Mapping Types . . . . . 12 4.4. Inter-version Interoperability . . . . . . . . . . . . . 14
4.3.2. Additional Forms of Associated Protocols . . . . . . 13 4.4.1. Requirements for Knowledge of Protocol Elements . . . 14
5. Documentation Approach . . . . . . . . . . . . . . . . . . . 14 4.4.2. Establishing Interoperability . . . . . . . . . . . . 16
5.1. Indexing material . . . . . . . . . . . . . . . . . . . . 14 4.4.3. Determining Knowledge of Protocol Elements . . . . . 17
6. NFSv4 Features . . . . . . . . . . . . . . . . . . . . . . . 14 4.4.4. Interoperability Between Version Groups . . . . . . . 18
6.1. Rules for Feature Construction . . . . . . . . . . . . . 15 5. Other NFSv4 Protocol Changes . . . . . . . . . . . . . . . . 18
6.2. Feature Statuses . . . . . . . . . . . . . . . . . . . . 15 5.1. Non-XDR Protocol Changes . . . . . . . . . . . . . . . . 19
6.3. Feature Discovery . . . . . . . . . . . . . . . . . . . . 16 5.1.1. Field Interpretation and Use . . . . . . . . . . . . 19
6.4. Feature Specification Documents . . . . . . . . . . . . . 16 5.1.2. Behavioral Changes . . . . . . . . . . . . . . . . . 20
6.5. Feature Incorporation . . . . . . . . . . . . . . . . . . 17 5.1.3. Rules for non-XDR changes . . . . . . . . . . . . . . 20
7. Extensions within Minor Versions . . . . . . . . . . . . . . 18 5.2. Specification of Associated Protocols . . . . . . . . . . 21
8. Adding Features to Extensible Minor Versions . . . . . . . . 18 5.2.1. Associated Protocols via pNFS Mapping Types . . . . . 22
8.1. Use of Feature Specification Documents . . . . . . . . . 18 5.2.2. Additional Forms of Associated Protocols . . . . . . 22
8.2. Compatibility Issues . . . . . . . . . . . . . . . . . . 19 6. NFSv4 Protocol Features . . . . . . . . . . . . . . . . . . . 23
8.2.1. Compatibility Issues for Messages Sent to Servers . . 19 6.1. Previous Uses of the Feature Concept . . . . . . . . . . 24
8.2.2. Compatibility Issues for Messages Sent to Clients . . 21 6.2. Rules for Protocol Feature Construction . . . . . . . . . 25
8.3. Additional Documents to be Produced . . . . . . . . . . . 22 6.3. Statuses of Features . . . . . . . . . . . . . . . . . . 25
8.3.1. Minor Version Indexing Document . . . . . . . . . . . 22 6.4. Statuses of Protocol Elements Within Features . . . . . . 26
8.3.2. Consolidated XDR Document . . . . . . . . . . . . . . 22 6.5. Determining Protocol Element Support . . . . . . . . . . 28
8.3.3. XDR Assignment Document . . . . . . . . . . . . . . . 23 6.6. Feature Discovery . . . . . . . . . . . . . . . . . . . . 29
8.3.4. Transition of Documents to RFC's . . . . . . . . . . 24 7. Documentation of Protocol Changes . . . . . . . . . . . . . . 31
8.4. Relationship Between Minor Versioning and Extensions 7.1. Documentation Approach . . . . . . . . . . . . . . . . . 31
within a Minor Version . . . . . . . . . . . . . . . . . 24 7.2. Indexing material . . . . . . . . . . . . . . . . . . . . 31
9. Minor Versions . . . . . . . . . . . . . . . . . . . . . . . 25 7.3. Feature Specification Documents . . . . . . . . . . . . . 32
9.1. Minor Version Construction . . . . . . . . . . . . . . . 25 7.4. Feature Incorporation . . . . . . . . . . . . . . . . . . 34
9.2. Minor Version Interaction . . . . . . . . . . . . . . . . 26 7.5. XDR File Considerations . . . . . . . . . . . . . . . . . 34
9.2.1. Minor Version Identifier Transfer Issues . . . . . . 26 8. Extensions within Minor Versions . . . . . . . . . . . . . . 35
9.2.2. Minor Version Compatibility Issues . . . . . . . . . 26 9. Adding Features to Extensible Minor Versions . . . . . . . . 36
9.1. Use of Feature Specification Documents . . . . . . . . . 36
9.3. Minor Version Documentation . . . . . . . . . . . . . . . 27 9.2. Compatibility Issues . . . . . . . . . . . . . . . . . . 37
10. Correction of Existing Minor Versions and Features . . . . . 27 9.2.1. Compatibility Issues for Messages Sent to Servers . . 37
10.1. Documentation of XDR Changes . . . . . . . . . . . . . . 29 9.2.2. Compatibility Issues for Messages Sent to Clients . . 38
11. Security Considerations . . . . . . . . . . . . . . . . . . . 30 9.3. Additional Documents to be Produced . . . . . . . . . . . 39
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30 9.3.1. Minor Version Indexing Document . . . . . . . . . . . 39
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 31 9.3.2. Consolidated XDR Document . . . . . . . . . . . . . . 40
13.1. Normative References . . . . . . . . . . . . . . . . . . 31 9.3.3. XDR Assignment Document . . . . . . . . . . . . . . . 40
13.2. Informative References . . . . . . . . . . . . . . . . . 31 9.3.4. Transition of Documents to RFC's . . . . . . . . . . 41
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 32 9.4. Relationship Between Minor Versioning and Extensions
within a Minor Version . . . . . . . . . . . . . . . . . 42
10. Minor Versions . . . . . . . . . . . . . . . . . . . . . . . 43
10.1. Reasons for New Minor Versions . . . . . . . . . . . . . 43
10.1.1. New Minor Versions within an Existing Group . . . . 43
10.1.2. New Minor Version Groups . . . . . . . . . . . . . . 43
10.1.3. Limits on Minor Version Groups . . . . . . . . . . . 46
10.2. Role of Minor Versions . . . . . . . . . . . . . . . . . 47
10.3. Minor Version Interaction Rules . . . . . . . . . . . . 47
10.3.1. Minor Version Identifier Transfer Issues . . . . . . 48
10.3.2. Minor Version Intra-Group Compatibility . . . . . . 48
10.3.3. Minor Version Inter-Group Compatibility . . . . . . 49
10.4. Minor Version Documentation . . . . . . . . . . . . . . 50
11. Correction of Existing Minor Versions and Features . . . . . 50
11.1. XDR Changes to Implement Protocol Corrections . . . . . 51
11.2. Documentation of XDR Changes . . . . . . . . . . . . . . 53
12. Security Considerations . . . . . . . . . . . . . . . . . . . 54
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 54
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 54
14.1. Normative References . . . . . . . . . . . . . . . . . . 54
14.2. Informative References . . . . . . . . . . . . . . . . . 54
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 55
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 55
1. Introduction 1. Introduction
To address the requirement for an NFS protocol that can evolve as the To address the requirement for an NFS protocol that can evolve as the
need arises, the Network File System (NFS) version 4 (NFSv4) protocol need arises, the Network File System (NFS) version 4 (NFSv4) protocol
provides rules and a framework to allow for future changes via the provides a framework to allow for future changes via the creation of
creation of new protocol versions and certain forms of modification new protocol versions including minor versions and certain forms of
of existing versions. These version management rules allow changes modification of existing minor versions. The version management
rules contained in this document allow extensions and other changes
to be implemented in a way that maintains compatibility with existing to be implemented in a way that maintains compatibility with existing
clients and servers. clients and servers.
1.1. Existing Minor Versions 1.1. Existing Minor Versions
Previously, all such changes had been part of new minor versions. Previously, all protocol changes had been part of new minor versions.
The COMPOUND procedure (see Section 14.2 of [RFC7530]) specifies the The COMPOUND procedure (see Section 14.2 of [RFC7530]) specifies the
minor version being used by the client in making requests. The minor version being used by the client in making requests. The
CB_COMPOUND (see Section 15.2 of [RFC7530]) procedure specifies the CB_COMPOUND procedure (see Section 15.2 of [RFC7530]) specifies the
minor version being used by the server on callback requests. minor version being used by the server on callback requests.
Each existing minor version has been specified by one or more Each existing minor version has been specified by one or more
standards track RFCs: standards track RFCs:
o Minor version 0 is specified by [RFC7530] with the XDR description o Minor version 0 (NFSv4.0) is specified by [RFC7530] with the XDR
appearing in [RFC7531]. description appearing in [RFC7531].
o Minor version 1 is specified by [RFC5661]) with the XDR o Minor version 1 (NFSv4.1) is specified by [RFC5661] with the XDR
description appearing in [RFC5662]. description appearing in [RFC5662].
o Minor version 2 is specified by [NFSv42] (in terms of changes from o Minor version 2 (NFSv4.2) is specified by [NFSv42] (in terms of
[RFC5661]). The XDR description appears in [NFSv42-dot-x] changes from [RFC5661]). The XDR description appears in
[NFSv42-dot-x]
Existing minor versions can be divided into two groups, based on
compatibility considerations. NFSv4.0 is one group, while NFSv4.1,
NFSv4.2, and potentially other minor versions form a second group.
The definition of NFSv4 minor version groups is explained in more
detail in Section 2.3, as are the concepts of NFSv4 versions and
version groups.
1.2. Updated NFSv4 Version Management Framework 1.2. Updated NFSv4 Version Management Framework
A number of significant changes from previous version management A number of significant changes from previous version management
practices should be noted here: practices should be noted here:
o Creation of a new minor version is no longer the only way in which o Creation of a new minor version is no longer the only way in which
protocol changes may be made. Many changes can be done within the protocol changes may be made. Added optional features and
context of a single minor version. Creation of new minor versions protocol corrections can be proposed, specified and implemented
remains available to make other sorts of changes. within the context of a single minor version. Creation of new
minor versions remains available to make other sorts of changes.
o Specification of future minor versions in the way that was done o Specification of future minor versions in the way that was done
for NFSv4.0 and NFSv4.1 (i.e. as a single document defining the for NFSv4.0 and NFSv4.1 (i.e. as a single document defining the
entire protocol) is no longer practical and should not be entire protocol) is no longer practical and should not be
attempted. All future minor versions will be documented by attempted. All future minor versions will be documented by
specifying the differences between the minor version being specifying the differences between the minor version being
documented and the previous minor version. The documentation documented and the previous minor version. The documentation
framework discussed in Section 5 should be used. framework discussed in Section 7 should be used.
This document starts by presenting the conceptual framework on which After dealing with some preliminary matters, this document focuses on
NFSv4 versioning is built. presenting the conceptual framework on which NFSv4 versioning is
built.
o First we discuss (in Section 4) the range of protocol changes that o First we discuss (in Section 4) how the XDR descriptions for
NFSv4 versioning is to deal with. various NFSv4 versions can be extended to produce the XDR
descriptions for other versions while allowing clients and servers
using the XDR descriptions associated with different versions to
communicate.
o We then complete the discussion (in Section 5) of the range of
protocol changes that NFSv4 versioning is to deal with.
o Then we discuss (in Section 6) how those changes are organized o Then we discuss (in Section 6) how those changes are organized
into features. into features and feature packages.
Using this framework, we then look at the ways the NFSv4 protocol can Using this framework, we then discuss how changes are documented and
be changed. look at the ways that those changes can be incorporated into the
NFSv4 protocol.
o The addition of new features to existing minor versions is o The addition of new feature packages to existing minor versions is
discussed in Sections 7 and 8. discussed in Sections 8 and 9.
o New Minor versions can be constructed, as described in Section 9. o New Minor versions can be constructed, as described in Section 10.
o Issues relating to the correction of protocol errors in existing o Issues relating to the correction of protocol errors in existing
features and minor versions are discussed in Section 10. features and minor versions are discussed in Section 11.
2. Terminology 2. Terminology
A basic familiarity with the NFSv4 terminology is assumed in this A basic familiarity with NFSv4 terminology is assumed in this
document and the reader is pointed to [RFC7530]. document and the reader is pointed to [RFC7530].
The word "feature" has been used inconsistently in previous In this document, the term "version" is not limited to minor
treatments of NFSv4 versioning. Sometimes it is used to indicate a versions. When minor versions are meant, the term "minor version" is
specific XDR extension, while at other times it has been used to used explicitly. For more discussion of this and related terms, see
indicate a set of multiple such extensions which are either supported Section 2.3
or not supported together.
In this document, we use the word "feature" in the second sense, In this document, the word "feature" is used , except in the case of
while individual protocol extensions which are incorporated in a quotations, to denote a key structuring concept which allows the
feature are referred to as "protocol elements." The term "feature defining RFCs to clearly specify what protocol elements must be
elements" is similar but it differs in that it includes changes in supported together by the server and when a given server must be able
field interpretation and use (Section 4.2.1) and protocol behavior to correctly interpret the corresponding associated protocol
(See Section 4.2.2). See Section 6 for more details. constructs. See Section 6 for more details.
In previous NFSv4 documents, the word "features" has been used in a
number of different senses, as discussed in Section 6.1.
Two important terms related to the feature concept need to be
introduced here:
o A "feature package" is a set of features defined together, either
because they were defined together as part of a minor version or
as part of the same protocol extension.
o A "feature element" is one of the constituent changes which is
part of a given feature. This can include the addition of the
protocol elements described in Section 4.1.3 but also the other
sorts of allowed protocol changes described in Section 5.
We also need to introduce our vocabulary regarding specification of We also need to introduce our vocabulary regarding specification of
features and minor versions. Given the ongoing shift to a finer- features and minor versions. Given the ongoing shift to a finer-
grained documentation model, it is important to be clear here. grained documentation model, it is important to be clear here.
o The term "minor version definition document" denotes the principal o The term "minor version definition document" denotes the principal
document defining a specific NFSv4 minor version. It may be in document defining a specific NFSv4 minor version. It may be in
the form of a complete protocol definition (e.g. [RFC7530], the form of a complete protocol definition (e.g. [RFC7530],
[RFC5661]), a specification of changes relative to the previous [RFC5661]), a specification of changes relative to the previous
minor version (e.g. [NFSv42]), or in a document that specifies minor version (e.g. [NFSv42]), or in a document that specifies
the features to be included, either by referencing their the features to be included, either by referencing their
definition document normatively (see Section 9.3) or implicitly definition document normatively (see Section 10.4) or implicitly
(see Section 8). (see Section 9).
o The term "minor version documentation" includes the minor version o The term "minor version documentation" includes the minor version
definition document but also includes any corresponding XDR definition document but also includes any corresponding XDR
definition documents if they are published separately (e.g. definition documents if they are published separately (e.g.
[RFC7531], [RFC5662]), [NFSv42-dot-x]). Also included are [RFC7531], [RFC5662], [NFSv42-dot-x]). Also included are
documents separately specifying features newly incorporated in the documents separately specifying features newly incorporated in the
minor version and the ancillary documents described in minor version and the ancillary documents described in
Section 8.3. Section 9.3.
o The term "feature definition document" denotes a document o The term "feature definition document" denotes a document
describing a single feature or a set of closely related features. describing a single feature or a set of closely related features,
forming a feature package.
As noted above, the keywords defined by [RFC2119] have special o The term "protocol definition document" denotes a minor version
meanings which this document intends to adhere to. However, due to definition document, a feature definition document or any
the nature of this document and some special circumstances, there are standards-track document updating one of these.
some complexities to take note of:
2.1. Use of Keywords Defined in RFC2119
The keywords defined by [RFC2119] have special meanings which this
document intends to adhere to. However, due to the nature of this
document and some special circumstances, there are some complexities
to take note of:
o Where this document does not directly specify implementation o Where this document does not directly specify implementation
requirements, use of these capitalized term is often not requirements, use of these capitalized terms is often not
appropriate. Instead, what document writers need to do is stated appropriate, since the guidance given in this document does not
without these specialized terms. In any case, one should not directly affect interoperability.
conclude that the normative character of this document is
compromised by this.
o In speaking of the previously existing possible statuses of o In this document, what authors of RFCs defining features and minor
feature elements, the lower-case versions of these terms are used, versions need to do is stated without these specialized terms.
following the practice of [RFC3530]. This is despite the fact Although it is necessary to follow this guidance to provide
that the corresponding uses of these terms in [RFC5661] was successful NFSv4 version management, that sort of necessity is not
switched to upper-case, for no clear reason, and similarly in the of the sort defined as applicable to the use of the keywords
case [RFC7530], presumably due to inertia. defined in [RFC2119].
o In speaking of the potential statuses of features, the words The fact that these capitalized terms are not used should not be
"required" and "non-required" are used. By using the latter term, interpreted as indicating that this guidance does not need to be
we focus on the fact that the feature in question is not required followed or is somehow not important.
to be supported, while treating any potential recommendation for
support as out-of-scope. o In speaking of the possible statuses of features and feature
elements, the terms "OPTIONAL" and "REQUIRED" are used. For
further discussion, see Section 2.2.
o When one of these upper-case keywords defined in [RFC2119] is used o When one of these upper-case keywords defined in [RFC2119] is used
in this document, it is in the context of a rule directed to an in this document, it is in the context of a rule directed to an
implementer of NFSV4 minor versions, or in a quotation, sometimes implementer of NFSv4 minor versions, the status of a feature or
indirect, from another document. protocol element, or in a quotation, sometimes indirect, from
another document.
2.2. Use of Feature Statuses
There has been some confusion, during the history of NFSv4, about the
correct use of these terms, and instances in which the keywords
defined in [RFC2119] were used in ways that appear to be at variance
with the definitions in that document.
o In [RFC3530], the lower-case terms "optional", "recommended", and
"required" were used as feature statuses, Later, in [RFC5661] and
[RFC7530], the corresponding upper-case keywords were used.
However, it is not clear why this change was made.
o In the case of "RECOMMENDED", its use as a feature status is
inconsistent with [RFC2119] and it will not be used for this
purpose in this document.
o The word "RECOMMENDED" to denote the status of attributes in
[RFC3530] and [RFC5661] raises similar issues. This has been
recognized in [RFC7530] with regard to NFSV4.0, although the
situation with regard to NFSv4.1 remains unresolved.
In this document, the keywords "OPTIONAL" and "REQUIRED" and the
phrase "mandatory to not implement" are used to denote the status of
features and individual protocol elements within a given minor
version. In using these terms, RFCs which specify the status of
features or protocol elements inform:
o client implementations whether they need to deal with the absence
of support for the protocol elements
o server implementations whether they need to provide support for
the protocol elements
When the status of a protocol feature is specified, the support
requirements for associated protocol elements are defined by the
status of the protocol elements with regard to the feature in
question as described in Section 6.4.
The fact that such statuses and the organization of protocol features
may change between minor version groups may raise interoperability
issues which the authors of minor version RFCs and the working group
need to carefully consider. See Section 10.1.2 for guidance in this
regard.
2.3. NFSv4 Versions
The term "version" denotes any valid protocol variant constructed
according to the rules in this document. It includes minor versions,
but there are situations which allow multiple versions to be
associated with and co-exist within a single minor version:
o When there are feature specification documents published as
Proposed Standards extending a given minor version, then the
protocol defined by the minor version specification document, when
combined with any subset (not necessarily proper) of the feature
specification documents, is a valid NFSv4 version which is part of
the minor version in question.
o When there are protocol corrections published which update a given
minor version, each set of published updates, up to the date of
publication of the update, is a valid NFSv4 version which is part
of the minor version in question.
A minor version group is defined as a set of minor versions having
exactly the same set of REQUIRED and mandatory to not implement
protocol elements. Clients and servers which implement minor
versions within the same group should be compatible as long as each
takes proper care, as it should, to properly deal with the case in
which the other party does not know of or has no support for OPTIONAL
protocol elements. The associated set of versions is referred to as
a "version group".
3. Consolidation of Version Management Rules 3. Consolidation of Version Management Rules
In the past, the only existing version management rules were the In the past, the only existing version management rules were the
minor versioning rules that had been being maintained and specified minor versioning rules that had been being maintained and specified
in the Standards Track RFCs which defined the individual minor in the Standards Track RFCs which defined the individual minor
versions. As a result, these minor versioning rules were modified on versions. In the past, these minor versioning rules were modified on
an ad hoc basis for each new minor version. an ad hoc basis for each new minor version.
More recently, minor versioning rules were specified in [RFC5661] More recently, minor versioning rules were specified in [RFC5661]
while modifications to those rules were allowed in subsequent minor while modifications to those rules were allowed in subsequent minor
versions. versions.
This document defines a set of version management rules, including This document defines a set of version management rules, including
rules for minor version construction. These rules apply to all rules for minor version construction. These rules apply to all
future changes to the NFSv4 protocol. The rules are subject to future changes to the NFSv4 protocol. The rules are subject to
change but any such change should be part of a standards track RFC change but any such change should be part of a standards track RFC
obsoleting or updating this document. obsoleting or updating this document.
Rather than a single list of minor versioning rules, as in [RFC5661], Rather than a single list of minor versioning rules, as in [RFC5661],
this document defines multiple sets of rules that deal with the this document defines multiple sets of rules that deal with the
various forms of versioning provided for in the NFSv4 version various forms of versioning provided for in the NFSv4 version
management framework. management framework.
o The kinds of changes that may be made are addressed in the rules o The kinds of changes that may be made are addressed in the rules
in Sections 4.1.3, 4.2.3, 4.3.1, and 4.3.2. in Sections 4.1.3, 5.1.3, 5.2.1, and 5.2.2.
o Rules relating to the composition of changes into features are o Rules relating to the composition of changes into protocol
addressed in Section 6.1 features are addressed in Section 6.2
o Minor version construction, including rules applicable to features o Rules limiting the protocol features which may be effected as an
which cannot be used as extensions to existing minor versions are extension to an existing minor version appear in Section 8.
addressed in Section 9.1
o Minor version interaction rules are discussed in Sections 9.2.2 o Minor version construction, including rules applicable to protocol
and 9.2.1. features which cannot be used as extensions to existing minor
versions are addressed in Sections 10.1.1 and 10.1.2.
o Minor version interaction rules are discussed in Sections 10.3.2,
10.3.3, and 10.3.1.
This document supersedes minor versioning rules appearing in the This document supersedes minor versioning rules appearing in the
minor version specification RFC's, including those in [RFC5661]. As minor version specification RFC's, including those in [RFC5661]. As
a result, potential conflicts among these documents should be a result, potential conflicts among these documents should be
addressed as follows: addressed as follows:
o The specification of the actual protocols for minor versions o The specification of the actual protocols for minor versions
previously published as Proposed Standards take precedence over previously published as Proposed Standards take precedence over
minor versioning rules in either this document or in the minor minor versioning rules in either this document or in the minor
version specification RFC's. In other words, if the transition version specification RFC's. In other words, if the transition
from version A to version B violates a minor versioning rule, the from version A to version B violates a minor versioning rule, the
version B protocol stays as it is. In particular, many of the version B protocol stays as it is. In particular, many of the
changes made for NFSV4.1 would not be allowed in the version changes made for NFSV4.1 would not be allowed in the version
management framework defined here. See Section 4.2.3 for details. management framework defined here. See Section 5.1.3 for details.
o Since minor versioning rules #11 and #13 from [RFC5661] deal with o Since minor versioning rules #11 and #13 from [RFC5661] deal with
the interactions between multiple minor versions, the situation is the interactions between multiple minor versions, the situation is
more complicated. See Section 9.2 for a discussion of these more complicated. See Section 10.3 for a discussion of these
issues, including how potential conflicts between rules are to be issues, including how potential conflicts between rules are to be
resolved. resolved.
o Otherwise, any conflict between the version management rules in o Otherwise, any conflict between the version management rules in
this document and those in minor version specification RFC's are this document and those in minor version specification RFC's are
to be resolved based on the treatment in this document. In to be resolved based on the treatment in this document. In
particular, corrections may be made as specified in Section 10 for particular, corrections may be made as specified in Section 11 for
all previously specified minor versions and extensibility of all previously specified minor versions and the extensibility of
previously specified minor versions is to be handled in accord previously specified minor versions is to be handled in accord
with Section 8. with Section 9.
Future minor version specification documents should avoid specifying Future minor version specification documents should avoid specifying
minor versioning rules and reference this document in connection with minor versioning rules and reference this document in connection with
rules for NFSv4 version management. rules for NFSv4 version management.
4. NFSv4 Protocol Changes 4. XDR Considerations
Protocol changes that are to be managed within the NFSv4 versioning
framework may be of a number of types, which are discussed in the
sections below. Such changes include, but are not limited to,
changes in the underlying protocol XDR.
Each such change will be organized, documented and effected as part As an extensible XDR-based protocol, NFSv4 has to ensure interversion
of a given feature. The way this will be done depends on a number of compatibility, in situations in which the client and server use
factors, including the types of changes included in the feature. different XDR descriptions. The XDR extension paradigm, discussed in
This subject is discussed in Section 6.5. Section 4.1, assures that these descriptions are compatible, with
clients and servers able to determine and use those portions of the
protocol that they both share according to the methods described in
Sections 4.4.2 and 4.4.4.
4.1. XDR Extension 4.1. XDR Extension
When an NFSv4 version change requires a modification to the protocol When an NFSv4 version change requires a modification to the protocol
XDR, this is effected within a framework based on the idea of XDR XDR, this is effected within a framework based on the idea of XDR
extension. This is opposed to transitions between major NFS versions extension. This is opposed to transitions between major NFS versions
(including that between NFSv3 and NFSv4.0) in which the XDR for one (including that between NFSv3 and NFSv4.0) in which the XDR for one
version was replaced by a different XDR for a newer version. version was replaced by a different XDR for a newer version.
The use of XDR extension can facilitate compatibility between The use of XDR extension can facilitate compatibility between
different versions of the NFSv4 protocol. When XDR extension is used different versions of the NFSv4 protocol. When XDR extension is used
to implement non-required features, the greatest degree of inter- to implement OPTIONAL features, the greatest degree of inter-version
version compatibility is obtained. For specifics regarding rules for compatibility is obtained. For specifics regarding rules for
interversion compatibility, see Section 9.2.2. interversion compatibility, see Section 10.3.2. For a discussion of
compatibility issues that might arise between different version
groups, see Sections 10.1.2 and 10.3.3.
4.1.1. XDR Extension in General 4.1.1. XDR Extension in General
XDR extension allows an XDR description to be extended in a way which The XDR extension approach provides a way for an XDR description to
retains the structure of all previously valid messages. If a base be extended in a way which retains the structure of all previously
XDR description is extended to create a second XDR description, the valid messages. If a base XDR description is extended to create a
following will be true for the second description to be a valid second XDR description, the following will be true for the second
extension of the first: description to be a valid extension of the first:
o The set of valid messages described by the extended definition is o The set of valid messages described by the extended definition is
a superset of that described by the first. a superset of that described by the first.
o Each message within the set of valid messages described by the o Each message within the set of valid messages described by the
base definition is recognized as having exactly the same base definition is recognized as having exactly the same
structure/interpretation using the extended definition. structure/interpretation using the extended definition.
o Each message within the set of messages described as valid by the o Each message within the set of messages described as valid by the
extended definition but not the base definition must be extended definition but not the base definition must be
skipping to change at page 9, line 18 skipping to change at page 12, line 18
a valid XDR extension within NFSv4. a valid XDR extension within NFSv4.
o Because NFSv4 has chosen to structure itself around compound o Because NFSv4 has chosen to structure itself around compound
requests and callbacks, addition of previously unspecified RPC requests and callbacks, addition of previously unspecified RPC
operation codes is not allowed. operation codes is not allowed.
o Although they fit under the general category of enumerations, o Although they fit under the general category of enumerations,
operation codes (including those for callbacks) are so central to operation codes (including those for callbacks) are so central to
the structure of NFSv4, that they merit special treatment. the structure of NFSv4, that they merit special treatment.
o The fact that attribute sets are represented within nominally o The fact that attribute value sets are represented within NFSv4 by
opaque arrays calls for special handling. nominally opaque arrays calls for special handling.
4.1.3. Rules for XDR Extension within NFSv4 4.1.3. Rules for XDR Extension within NFSv4
In the context of NFSv4, an extension of a given XDR description In the context of NFSv4, an extension of a given XDR description
consists of one or more of the following: consists of one or more of the following:
o Addition of previously unspecified operation codes, within the o Addition of previously unspecified operation codes, within the
framework established by COMPOUND and CB_COMPOUND. framework established by COMPOUND and CB_COMPOUND.
o Addition of previously unspecified attributes. o Addition of previously unspecified attributes.
skipping to change at page 10, line 5 skipping to change at page 13, line 5
o Deletion of existing RPC operations, enum values, flag bit values o Deletion of existing RPC operations, enum values, flag bit values
and switch cases. Note that changes may be made to define use of and switch cases. Note that changes may be made to define use of
any of these as causing an error, as long as the XDR is any of these as causing an error, as long as the XDR is
unaffected. unaffected.
o Similarly, none of these items may be reused for a new purpose. o Similarly, none of these items may be reused for a new purpose.
o Any change to the structure of existing requests or replies other o Any change to the structure of existing requests or replies other
than those listed above. than those listed above.
4.2. Non-XDR Protocol Changes 4.2. Handling of Protocol Elements
Implementations handle protocol elements in one of three ways. Which
of the following ways are valid depends on the status of the protocol
element in the minor version being implemented:
o The protocol element is not a part of definition of the version in
question and so is "unknown". The responder, when it does not
report an RPC XDR decode error. reports an error indicative of
the element not being defined in the XDR such as
NFS4ERR_OP_ILLEGAL, NFS4ERR_BADXDR, or NFS4ERR_INVAL. See
Section 4.4.3 for details.
o The protocol element is a known part of the version but is not
supported by the particular implementation. The responder reports
an error indicative of the element being recognized as one which
is not supported such as NFS4ERR_NOTSUPP, NFS4ERR_UNION_NOTSUPP,
or NFS4ERR_ATTRNOTSUPP. See Section 6.5 for details.
o The protocol element is a known part of the version which is
supported by the particular implementation. The responder reports
success or an error other than the special ones discussed above.
Which of these are validly returned by the responder depends on the
status of the feature element in the minor version. The following
possibilities exist:
o The protocol element is not known in the minor version. In this
case all implementations of the minor version MUST indicate that
the protocol element is not known.
o The protocol element is specified mandatory to not implement in
the minor version. In this case as well, all implementations of
the minor version MUST indicate that the protocol element is not
known.
o The protocol element is defined as part of an extension in the
minor version. In this case, the requester can encounter
situations in which the protocol element is not known, is known
but not supported, or is supported.
o The protocol element is defined as an OPTIONAL part of the minor
version and not part of an extension to the minor version. In
this case, the requester can expect the protocol element to be
known but must deal with cases in which it is supported or not.
o The protocol element is defined as a REQUIRED part of the minor
version. In this case, the requester can expect the protocol
element to be both known and supported by the responder.
The listing of possibilities above does not mean that a requester
always needs to be prepared for all such possibilities. Often,
depending on the scope of the feature of which the protocol element
is a part, handling of a previous request using the same or related
protocol elements, will allow the requester to be sure that certain
of these possibilities cannot occur.
Requesters, typically clients, may test for knowledge of or support
for protocol elements as part of connection establishment. This may
allow the requester to be aware of responder lack of knowledge of or
support for problematic requests before they are actually issued.
4.3. Organization of Protocol Elements
To enable compatible operation within a version group, all of the
protocol elements within an NFSv4 minor version are organized as
follows:
o Each protocol element is defined as a member of exactly one
feature. One important reason for this organization (see
Section 6) for others is to regularize and simplify the
determination by the client/server as to what protocol elements
the other party supports.
o Each feature is defined as a member of a feature package, based on
how it was defined. Features established as part of a minor
version at the same time belong to the same feature package.
4.4. Inter-version Interoperability
Because of NFSv4's use of XDR extension, any communicating client and
server versions have XDR definitions that are each valid extensions
of a third version. Once that version is determined, it may be used
by both client and server to communicate. Each party can
successfully use a subset of protocol elements that are both known
and supported by both parties.
4.4.1. Requirements for Knowledge of Protocol Elements
With regard to requirements for knowledge of protocol elements, the
following rules apply. These rules are the result of the use of XDR
extension paradigm combined with the way in which extensions are
incorporated in existing minor versions (for details of which see
Section 9).
o Any protocol element initially defined as part of a particular
minor version is required to be known by that minor version. This
occurs whether the specification happens in the body of the minor
definition document or is in a feature definition document that is
made part of the minor version by being normatively referenced by
the minor version definition document.
o Any protocol element required to be known in a given minor version
is required to be known in subsequent minor version, unless and
until a minor version has made that protocol element as mandatory
to not implement.
o When a protocol element is defined as part of an extension to an
extensible minor version, it is not required to be known in that
minor version but is required to be known by the next minor
version. In the earlier minor version, it might not might not be
defined in the XDR, while in the later version it needs to be
defined in the XDR. In either case, if it is defined, it might or
might not be supported.
o When knowledge of protocol elements is optional in a given minor
version, the responder's knowledge of such optional elements must
obey the rule that if one such element is known, then all the
protocol elements defined in the same minor version definition
document must be known as well.
For many minor versions, all existing protocol elements, are required
to be known by both the client and the server, and so requesters do
not have to test for the presence or absence of knowledge regarding
protocol elements for which knowledge might be optional. This is the
case if there has been no extension for the minor version in
question. Extensions can be added to extensible minor versions as
described in Section 9 and can be used to correct protocol flaws as
described in Section 11.
Requesters can ascertain the knowledge of the responder in two ways:
o By issuing a request using the protocol element and looking at the
response. Note that, even if the protocol element used is not
supported by the responder can still determine if the element is
known by the responder.
o By receiving a request from the responder, acting in the role of
requester. For example, a client may issue a request enabling the
server to infer that it is aware of a corresponding callback.
In making this determination, the requester can rely on two basic
facts:
o If the responder is aware of a single protocol element within a
feature package, it must be aware of all protocol elements within
that feature package
o If a protocol element is one defined by the minor version
specified by a request (and not in an extension), or in a previous
minor version, the responder must be aware of it.
4.4.2. Establishing Interoperability
When a client and a server interact, they need to able to take
advantage of the compatibility provided by NFSv4's use of XDR
extension.
In this section, we will deal with situation in which the client and
server are of the same version group. Later, in Section 4.4.4, we
will discuss possible extensions to the inter-version-group case.
In this context, the client and server would be using a common minor
version which the client uses to send requests and the server
accepts. The server would use that minor version to send callbacks
which the client would then accept. This state of affairs could
arise in a number of ways:
o Client and server have been built using XDR versions that belong
to the same minor version
o The client's minor version is lower than that of the server. In
this case the server, in accord with Section 10.3.2, accepts the
client's minor version, and acts as if it has no knowledge of
extensions made in subsequent minor versions.
o The client's minor version is higher than that of the server. In
this case the client, in accord with Section 10.3.2, uses a lower
minor version that the server will accept. In this case, the
server has no knowledge of extensions made in subsequent minor
versions.
There are a number of cases to consider based on the characteristics
of the minor version chosen.
o The minor version consists of only a single version (no extension
or XDR corrections), so the client and the server are using the
same XDR description and have knowledge of the same protocol
elements.
o When the minor version consists of multiple versions (one or more
XDR extensions or XDR corrections), the client and the server are
using compatible XDR descriptions. The client is aware of some
set of extensions while he server may be aware of a different set.
The client can determine which of the extensions that he is aware
of, are also known to the server by using the approach described
in Section 4.4.3. Once this is done, the client and server will
both be using a common version. The versions that the client and
server were built with will both either be identical to this
version or a valid extension of it.
In either case, the client must determine which of the OPTIONAL
protocol elements within the common version are supported by the
server as described in Section 6.6.
4.4.3. Determining Knowledge of Protocol Elements
A requester may test the responder's knowledge of particular protocol
elements as defined below, based on the type of protocol element.
o When a GETATTR request is made specifying an attribute bit to be
tested and that attribute is not a set-only attribute, if the
GETATTR returns with the error NFS4ERR_INVAL, then it can be
concluded that the responder has no knowledge of the attribute in
question. Other responses, including NFS4ERR_ATTRNOTSUPP,
indicate that the responder is aware of the attribute in question.
o When a SETATTR request is made specifying the attribute bit to be
tested and that attribute is not a get-only attribute, if the
SETATTR returns with the error NFS4ERR_INVAL, then it can be
concluded that the responder has no knowledge of the attribute in
question. Other responses, including NFS4ERR_ATTRNOTSUPP,
indicate that the responder is aware of the attribute in question.
o When a request is made including an operation with a new flag bit,
if the operation returns with the error NFS4ERR_INVAL, then it can
be concluded that the responder has no knowledge of the flag bit
in question. Other responses indicate that the responder is aware
of the flag bit in question.
o When a request is made including the operation to be tested, if
the responder returns an RPC XDR decode error, or a response
indicating that the operation in question resulted in
NFS4ERR_OP_ILLEGAL or NFS4ERR_BADXDR, then it can be concluded
that the responder has no knowledge of the operation in question.
Other responses, including NFS4ERR_NOTSUPP, indicate that the
responder is aware of the operation in question.
o When a request is made including the switch arm to be tested, if
the responder returns an RPC XDR decode error, or a response
indicating that the operation in question resulted in
NFS4ERR_BADXDR, then it can be concluded that the responder has no
knowledge of the operation in question. Other responses,
including NFS4ERR_UNION_NOTSUPP, indicate that the responder is
aware of the protocol element in question.
A determination of the knowledge or lack of knowledge of a particular
protocol element is expected to remain valid as long as the clientid
associated with the request remains valid.
The above assumes, as should be the case, that the server will accept
the minor version used by the client. For more detail regarding this
issue, see Section 10.3.2.
4.4.4. Interoperability Between Version Groups
Within a minor version, we have complete compatibility in the sense
that:
o Servers are REQUIRED to implement a core set of feature which
cannot change within the minor version group, allowing clients to
depend on the continued existence of and support for these
features as long as one remains within the minor version group.
o The set of OPTIONAL features supported or known by servers may
change but clients, in using such OPTIONAL features need to be
prepared for the fact that they might not be implemented on all
servers implementing a minor version within the same version
group.
The same level of compatibility is not provided between different
minor version groups. Nevertheless, the same guarantees of inter-XDR
comprehensibility apply across minor version groups. For a
discussion of how this comprehensibility can be used between minor
version groups, see Section 10.3.3.
5. Other NFSv4 Protocol Changes
There are a number of types of protocol changes that are outside the
XDR extension framework discussed in Section 4. These changes are
also managed within the NFSv4 versioning framework and may be of a
number of types, which are discussed in the sections below
Each such change will be organized, documented and effected as part
of a given feature, just as changes discussed in Section 4 are. The
way such features will be incorporated in the NFSv4 protocol depends
on a number of factors, including the types of changes included in
the feature. This subject is discussed in Sections 7.4 and 8.
5.1. Non-XDR Protocol Changes
Despite the previous emphasis on XDR changes, additions and changes Despite the previous emphasis on XDR changes, additions and changes
to the NFSv4 protocols have not been limited to those that involve to the NFSv4 protocols have not been limited to those that involve
changes (in the form of extensions) to the protocol XDR. Examples of changes (in the form of extensions) to the protocol XDR. Examples of
other sorts of changes have been taken from NFSv4.1. other sorts of changes have been taken from NFSv4.1.
4.2.1. Field Interpretation and Use 5.1.1. Field Interpretation and Use
The XDR description of a protocol does not constitute a complete The XDR description of a protocol does not constitute a complete
description of the protocol. Therefore, versioning needs to consider description of the protocol. Therefore, versioning needs to consider
the role of changes in the use of fields, even when there is no the role of changes in the use of fields, even when there is no
change to the underlying XDR. change to the underlying XDR.
Although any XDR element is potentially subject to a change in its Although any XDR element is potentially subject to a change in its
interpretation and use the likelihood of such change will vary with interpretation and use, the likelihood of such change will vary with
the XDR type, as discussed below:. the XDR type, as discussed below:.
o When XDR elements are defined as strings, rules regarding the o When XDR elements are defined as strings, rules regarding the
appropriate string values are specified in protocol specification appropriate string values are specified in protocol specification
text with changes in such rules documented in minor version text with changes in such rules documented in minor version
definition documents. definition documents. Some types of strings within NFS4 are used
in server names (in location-related attributes), user and group
Some types of strings within NFS4 are used in server names (in names, and in the names of file objects within directories. Rules
location-related attributes), user and group names, and in the regarding what strings are acceptable appear in [RFC7530] and
names of file object within directories. Rules regarding what [RFC5661] with the role of the XDR limited to hints regarding
strings are acceptable appear in [RFC7530] and [RFC5661] with the UTF-8 and capitalization issues via XDR typedefs.
role of the XDR limited to hints regarding UTF-8 and
capitalization issues via XDR typedefs.
o Fields that are XDR-defined as opaque elements and which are truly o Fields that are XDR-defined as opaque elements and which are truly
opaque, do not raise versioning issues, except as regards inter- opaque, do not raise versioning issues, except as regards inter-
version use, which is effectively foreclosed by the rules in version use, which is effectively foreclosed by the rules in
Section 9.2. Section 10.3.1.
Note that sometimes a field will seem to be opaque but not Note that sometimes a field will seem to be opaque but not
actually be fully opaque when considered carefully. For example, actually be fully opaque when considered carefully. For example,
the "other" field of stateids is defined as an opaque array, while the "other" field of stateids is defined as an opaque array, while
the specification text specially defines appropriate treatment the specification text specially defines appropriate treatment
when the "other" field within it is either all zeros or all ones. when the "other" field within it is either all zeros or all ones.
Given this context, creation or deletion of reserved values for Given this context, creation or deletion of reserved values for
"special" stateids will be a protocol change which versioning "special" stateids will be a protocol change which versioning
rules need to deal with. rules need to deal with.
o Some nominally opaque elements have external XDR definitions that o Some nominally opaque elements have external XDR definitions that
overlay the nominally opaque arrays. This technique is useful overlay the nominally opaque arrays. This technique is useful
when the same element may be used in several ways when a switched when the same element may be used in several ways when a switched
union is not appropriate. union is not appropriate.
For example, each pNFS mapping type provides its own XDR For example, each pNFS mapping type provides its own XDR
definition for various pNFS-related fields defined in [RFC5661] as definition for various pNFS-related fields defined in [RFC5661] as
opaque arrays. For more information about the handling of pNFS opaque arrays. For more information about the handling of pNFS
within the NFSv4 versioning framework, see Section 4.3.1. within the NFSv4 versioning framework, see Section 5.2.1.
Another form of protocol change that changes how fields are Another form of protocol change that changes how fields are
presented, without affecting the XDR occurs when there is a change in presented, without affecting the XDR occurs when there is a change in
the data elements which may be presented as RDMA chunks. the data elements which may be presented as RDMA chunks.
4.2.2. Behavioral Changes 5.1.2. Behavioral Changes
Changes in the behavior of NFSv4 operations are possible, even if Changes in the behavior of NFSv4 operations are possible, even if
there is no change in the underlying XDR or change to field there is no change in the underlying XDR or change to field
interpretation and use. interpretation and use.
Many such behavioral changes have occurred in connection with the One class of behavioral change involves changes in the set of errors
addition of the session concept in NFSv4.1. to be returned in the event of various errors. When the set of valid
requests remain the same, and the behavior for each of them remains
the same, such changes can be implemented with only limited
disruption to existing clients.
Many more substantial behavioral changes have occurred in connection
with the addition of the session concept in NFSv4.1.
o Because exactly-once is semantics provided by sessions, the use of o Because exactly-once is semantics provided by sessions, the use of
owner-based sequence values in such operations as OPEN, LOCK, owner-based sequence values in such operations as OPEN, LOCK,
LOCKU are now longer needed and the server is to ignore them. LOCKU are now longer needed and the server is to ignore them.
o Because of the requirement to begin almost all COMPOUNDs with a o Because of the requirement to begin almost all COMPOUNDs with a
SEQUENCE operation, the semantics of previously defined operations SEQUENCE operation, the semantics of previously defined operations
was changed and all formerly valid COMPOUNDs were defined as was changed and all formerly valid COMPOUNDs were defined as
resulting in errors. resulting in errors.
o Because the clientid is inferable from a previous SEQUENCE o Because the clientid is inferable from a previous SEQUENCE
operation, the clientid is not needed in operations such as OPEN operation, the clientid is not needed in operations such as OPEN
and LOCK, and the client is required to pass a value of zero. and LOCK, and the client is required to pass a value of zero.
Also changes were made regarding the required server behavior as to Also, changes were made regarding the required server behavior as to
the interaction of the MODE and ACL attributes. the interaction of the MODE and ACL attributes.
4.2.3. Rules for non-XDR changes 5.1.3. Rules for non-XDR changes
In the past (e.g. in [RFC5661]) there was often uncertainty about In the past (e.g. in [RFC5661]) there was often uncertainty about
whether any particular difference from NFSv4.0 was: whether any particular difference from NFSv4.0 was:
o A purely editorial change, which may be relevant to other minor o A purely editorial change, which may be relevant to other minor
versions. versions.
o The correction of a protocol mistake, best handled as described in o The correction of a protocol mistake, best handled as described in
Section 10. Section 11.
o A protocol improvement relevant to a new minor version or feature, o A protocol improvement relevant to a new minor version or feature,
to be documented as described in Section 6.4. to be documented as described in Section 7.3.
In order to avoid such situations, all such changes will be In order to avoid such situations, all such changes will be
documented as part of a feature, specifying the specific changes documented as part of a feature, specifying the specific changes
relative to protocol versions that do not incorporate that new relative to protocol versions that do not incorporate that new
feature. Also, to provide greater clarity about such changes, the feature. Also, to provide greater clarity about such changes, the
following rules apply: following sets of rules apply.
o Any such change must be part of a feature in which there is also The following rules apply to "substantive behavior changes", i.e.
an XDR extension present, to enable testing for presence of the all changes in which there is a substantive change to non-error
feature. behavior. In other words, the change is not one which only changes
the set of valid error codes or prescribes that different error codes
are to be returned in particular situations.
o No feature including such a change can be made required at initial o Any substantive behavior change must be part of a feature in which
introduction. there is also an XDR extension present, to enable testing for
presence of the feature.
o No feature including a substantive behavior change can be made
REQUIRED at initial introduction.
The following rules apply to all behavioral changes.
o No feature including such a change can be introduced as an o No feature including such a change can be introduced as an
extension. While the feature may be documented in a separate extension. While the feature may be documented in a separate
feature definition document in such cases, that document should be feature definition document in such cases, that document should be
referenced normatively by the minor version specification. referenced normatively by the minor version specification.
o While it is allowed to include multiple such changes in the same o While it is allowed to include multiple such changes in the same
feature this should only be done if there is a good reason for all feature this should only be done if there is a good reason for all
of these to be included or not included together. Such changes of these to be included or not included together. Such changes
should not be included in the same feature simply because all such should not be included in the same feature simply because all such
changes were introduced in the same minor version. changes were introduced in the same minor version.
4.3. Specification of Associated Protocols 5.2. Specification of Associated Protocols
The definition of ancillary protocols is a form of protocol extension The definition of ancillary protocols is a form of protocol extension
that is provided as part of pNFS and might be made available for that is provided as part of pNFS and might be made available for
other uses in the future. other uses in the future.
As in the case of pNFS, the NFSv4 protocol proper would provide the As in the case of pNFS, the NFSv4 protocol proper would provide the
basic framework for performing some protocol-related task, while basic framework for performing some protocol-related task, while
allowing multiple independent means of performing that task to be allowing multiple independent means of performing that task to be
defined. The version management considerations appropriate to defined. The version management considerations appropriate to
creating such additional forms of protocol extension are discussed in creating such additional forms of protocol extension are discussed in
Section 4.3.2 Section 5.2.2
4.3.1. Associated Protocols via pNFS Mapping Types 5.2.1. Associated Protocols via pNFS Mapping Types
pNFS is structured around the ability to define alternate mapping pNFS is structured around the ability to define alternative mapping
types in addition to the one defined in [RFC5661], (e.g. [RFC5663], types in addition to the one defined in [RFC5661], (e.g. [RFC5663],
[RFC5664]). Each mapping type specifies the data-transfer protocol [RFC5664]). Each mapping type specifies the data-transfer protocol
to be used to access data represented by layouts as well as mapping- to be used to access data represented by layouts as well as mapping-
type-specific XDR definitions of layout-related data structures. type-specific XDR definitions of layout-related data structures.
Specifying a new mapping type is an additional form of protocol Specifying a new mapping type is an additional form of protocol
change within the NFSv4 version management framework. A feature change within the NFSv4 version management framework. A feature
consisting of the new mapping type is not tied to a specific minor consisting of the new mapping type is not tied to a specific minor
version. As explained in Section 7, it is available in multiple version. As explained in Section 8, if a feature consists only of
minor versions upon publication. that single change, it is available in multiple minor versions upon
publication.
4.3.2. Additional Forms of Associated Protocols Such a feature has a file system scope and the attribute
fs_layout_type can used to determine whether support is present.
5.2.2. Additional Forms of Associated Protocols
The same sort of approach used for pNFS might be used in other The same sort of approach used for pNFS might be used in other
circumstances where there is a clear need to standardize a set of circumstances where there is a clear need to standardize a set of
protocol-related requirements and where it is desirable, for various protocol-related requirements and where it is desirable, for various
reasons, to leave open the choice of mechanism by which those reasons, to leave open the choice of mechanism by which those
requirements might be met. requirements might be met.
Such cases might arise where the function to be performed is likely Such cases might arise where the function to be performed is likely
to be too enmeshed with the structure of the file system to be too enmeshed with the structure of the file system
implementation to allow a single protocol mechanism to be specified. implementation to allow a single protocol mechanism to be specified.
skipping to change at page 13, line 32 skipping to change at page 22, line 50
o The establishment of a registry of identifiers for the o The establishment of a registry of identifiers for the
standardized mechanisms to satisfy the established requirements. standardized mechanisms to satisfy the established requirements.
o Definition of data structures related to the function to be o Definition of data structures related to the function to be
performed to include both a mechanism identifier, and a nominally performed to include both a mechanism identifier, and a nominally
opaque portion, the real format of which is to have a mechanism- opaque portion, the real format of which is to have a mechanism-
specific definition. specific definition.
o The ability to specify multiple protocols to perform the same o The ability to specify multiple protocols to perform the same
function, which may include a minor version of NFSv4, a particular function, which may include a minor version of NFSv4, a particular
use an established protocol, or a new protocol designed for the use of an established protocol, or a new protocol designed for the
purpose. purpose.
New instances of such a two-level approach might be established in New instances of such a two-level approach might be established in
the future, subject to the following restrictions: the future, subject to the following restrictions:
o That there is a feature establishing the requirements that the o That there is a template feature establishing the requirements
associated protocols are to meet. that the associated protocols are to meet.
o That that feature is defined as an integral feature of a o That the template feature is defined as an integral part of a
particular minor version and not as an extension. This does not particular minor version and not as an extension. This does not
exclude the feature being defined in a separate document to which exclude this feature being defined in a separate document to which
the minor version specification has a normative reference. the minor version specification has a normative reference.
o The template feature defines the scope that the individual feature
instances will have.
o The template feature defines a means by which support for
particular feature instances might be determined by a client.
o That there be at least one instance of a specific protocol o That there be at least one instance of a specific protocol
mechanism meeting the established requirements. To limit mechanism meeting the established requirements. To limit
confusion, the requirements and the initial mechanism should be confusion, the requirements and the initial mechanism (an instance
defined in separate documents. of the template feature) should be defined in separate documents.
The above are a minimal set of restrictions for establishing such an The above are a minimal set of restrictions for establishing such an
additional extension mechanism. The working group may, as part of additional extension mechanism. The working group may, as part of
defining the core feature establishing the extension mechanism may defining the core feature establishing the extension mechanism
specify further restrictions governing when minor versions may specify further restrictions governing as to when minor versions are
incorporate particular instances of that extension mechanism. allowed to incorporate particular instances of that extension
mechanism. In the absence of such restrictions, particular
extensions will be incorporated, as is the case with pNFS mapping
types, in all minor versions upon publication of the instance as a
Proposed Standard.
5. Documentation Approach 6. NFSv4 Protocol Features
Documentation of future changes to the NFSv4 protocol will use Individual changes, whether they are XDR extensions or other sorts of
feature specification documents as described in Section 6.4. There changes, are organized in term of protocol features. This is in
are a number of ways in which such documents may be used, as order to
discussed in Section 6.5
5.1. Indexing material o allow the protocol documentation to more clearly specify what XDR
extensions and other changes must be supported together.
The following items, referred to collectively as "Indexing material" o help the client determine which particular changes are present and
will be useful in many contexts. The reason for frequently implemented by the server.
publishing such material is to prevent a situation in which large
numbers of documents must be scanned to find the most current
description of a particular protocol element.
o A table mapping operations and callbacks to the most recent o support the independent development and specification of changes
document containing a description of that operation. to the protocol, without artificially tying features together in a
paradigm solely based on minor versions.
o A table mapping attributes to the most recent document containing o provide support for a feature-based documentation structure, as
a description of that attribute. described in Section 7.3.
o A table giving, for each operation in the protocol, the errors In contrast with some previous uses of the feature concept, every
that may validly be returned for that operation. If possible, it protocol element is defined as a member of exactly one protocol
would be desirable to give, as does [RFC5661], the operations feature.
which may validly return each particular error.
o A table giving for each operation, callback, and attribute and for Because support for particular protocol features may depend on
each feature element in a published extension giving its status facilities provided by the underlying file systems, or may vary based
(required or not, or mandatory-to-not implement), and its on characteristics of the session within which communication is
relationship to the feature which allows its inclusion (i.e., occurring, each protocol feature will be defined as having a
required for every implementation of the feature, or optional in particular scope, which may be any of the following:
the presence of the feature). This would be similar to the
material in Section 14 of [NFSv42], expanded in scope to include
all feature elements.
6. NFSv4 Features o Client scope in which case support for a given feature is assumed
to be uniform between given client and server as long as neither
reboots.
Individual changes, whether they are XDR extensions or other sorts of o Session scope in which case different sessions associated with the
changes, are organized in term of features. This is in order to same client may have difference as to feature support but
otherwise support is uniform.
o allow the protocol documentation to more clearly specify what XDR o file system scope in which case different file systems may have
extensions and other changes must be supported together. differences as to feature support but otherwise support is
uniform.
o help the client determine which particular changes are present and 6.1. Previous Uses of the Feature Concept
implemented by the server.
o to support the independent development and specification of The word "feature" has been used inconsistently in previous documents
changes to the protocol, without artificially tying features bearing on issues related NFSv4 versioning, making it necessary to
together in a paradigm based on minor versions. offer some clarification here.
o provide support for a feature-based documentation structure, as o In some cases, the term "feature" is used colloquially
described in Section 6.4.
6.1. Rules for Feature Construction o In some cases, the word "feature" is used to refer to protocol
extensions which are incorporated in the protocol are referred to
as "protocol elements." The term "feature elements" is similar
but it differs in that it includes changes in field interpretation
and use (Section 5.1.1) and protocol behavior (See Section 5.1.2).
A feature consists of one or more valid NFSv4 changes, which work o In some cases the word is used to refer to groups of feature
together as a functional whole. The change elements may be of any of elements, as defined by tables in [RFC5661] and [NFSv42]. This is
the types described in Section 4 although the specific types of similar to, but not exactly the same as the way we use the word
changes will affect how the feature can be integrated in the NFSv4 "feature" is used in this document.
Often, as in previous minor versioning rules it is not always clear
which sense of the word "feature" is meant.
6.2. Rules for Protocol Feature Construction
A protocol feature consists of one or more valid NFSv4 changes, which
work together as a functional whole. The change elements may be of
any of the types described in Section 5 although the specific types
of changes will affect how the feature can be integrated in the NFSv4
protocol. protocol.
6.2. Feature Statuses A critical distinction in this regard is the one between features
which can added to the protocol without a new minor version and those
which require a new minor version. In this document:
o Features which do not require a new minor version are discussed in
Section 8, while the process of incorporation depends on the type
of features and is discussed in Sections 9, 11, 5.2.1, and 5.2.2,
o For handling of the remaining features which do require a new
minor version, see Section 10.
6.3. Statuses of Features
Each feature has one of three statuses with regard to each minor Each feature has one of three statuses with regard to each minor
version of which it might be a part. version of which it might be a part.
o The feature is a required part of the minor version. o The feature is a REQUIRED part of the minor version.
o The feature is not a required part of the minor version, but may o The feature is not a REQUIRED part of the minor version, but may
be implemented as part of that version.. be implemented as part of that version, i.e. it is OPTIONAL
o The feature is not a valid part of the minor version. o The feature is not a valid part of the minor version.
For features which have been previously defined as valid, this is For features which have been previously defined as valid, this is
represented as being "mandatory to not implement" as opposed to represented as being "mandatory to not implement" as opposed to
simply being undefined. simply being undefined.
These statuses define whether a client implementing the minor version These statuses define whether a client implementing the minor version
has to be prepared for the existence of the feature and/or its non- has to be prepared for the protocol feature's non-support by a server
support by the server. implementation, even if the feature in question is known by the
server.
The working group is still free to make recommendations regarding the The working group is still free to make recommendations regarding the
desirability of server and client support for particular features in desirability of server and client support for particular features in
particular minor versions in the minor version definition document, particular minor versions in the minor version definition document,
or in other, presumably informational, documents. or in other, presumably informational, documents.
Particular protocol elements have similar statuses, which are derived
from a combination of the status of feature of which the protocol
element, the status of that protocol element within its feature, and,
in some cases, within other supported features. See Section 6.4 for
details.
In addition to feature status, there may be other constraints that In addition to feature status, there may be other constraints that
define when an implementation must or may support a feature. In define when an implementation must or may support a feature. In
particular, support for one feature may require support for another, particular, support for one feature may require support for another,
or the presence of one feature may require that another feature not or the presence of one feature may require that another feature not
be supported. be supported.
6.3. Feature Discovery 6.4. Statuses of Protocol Elements Within Features
The status of a protocol element within its containing feature
reflects two pieces of information that are used in determining
support for feature and associated protocol elements.
o A status value that allows support for the feature to be inferred
based on support for the protocol element. This is referred to as
the protocol element's E-to-F status.
o A status value that allows support for the feature element to be
inferred based on support for the feature. This is referred to as
the protocol element's F-to-E status with regard to the feature.
The purpose of defining these status values is to allow the support
or non-support for one protocol elements to be determined based on
responses for others, avoiding the complexity that a client would
have to deal with if each such support decision were independent.
The simpler model of simply assigning protocol elements to feature-
based equivalence was not adopted since it is not compatible with
many current and expected feature patterns:
o Many existing protocol features contain protocol elements that are
optional in the context of the feature.
o Some existing protocol elements are used by more than one feature.
o Boolean attributes that indicate the presence of support for a
given feature are tied to that feature, even though the attribute
can be supported when he feature is not, in which case the
attribute is supported and has the value FALSE.
The following are possible E-to-F statuses.
o Support or non-support for the feature is always the same as that
for the protocol element. This is represented as an "IFF" value.
o Support for the feature can be inferred from support for the
protocol element but not necessarily the reverse. This is
represented as an "SINF" value.
o Lack of support for the feature can be inferred from lack of
support for the protocol element but not necessarily the reverse.
This is represented as an "NSINF" value.
o Lack of support for the feature can be inferred from lack of
support for the protocol element but the reverse can be determined
by using the protocol element to determine whether support for the
feature is present. An example would be a Boolean attribute
indicating whether support for the feature is present. This is
represented as an "SVAL" value.
Generally, it will be clear how a client may determine whether any
particular OPTIONAL feature is supported. Typically there will be
one or more protocol elements belonging to the feature whose E-F
status is "IFF" or "SVAL". In these cases, support for the protocol
elements in question can be determined as described in Section 6.4
In more complicated cases, the feature specification should clearly
specify how to determine whether support is present.
The following are possible F-to-E statuses.
o Support for the protocol element is REQUIRED when support for the
feature is present.
o Support for the protocol element is OPTIONAL when support for the
feature is present.
o Support for the protocol element unaffected by the presence of
support for the feature.
The overall status of a feature element within a minor version is
generally determined as follows:
o If there are one or more REQUIRED features which give the protocol
element an F-to-E status of REQUIRED, then the overall status of
the protocol element within the minor version is REQUIRED.
o Otherwise, if there are one or more REQUIRED or OPTIONAL features
which give the protocol element an F-to-E status of REQUIRED or
OPTIONAL, then the overall status of the protocol element within
the minor version is OPTIONAL.
o If neither of the above is true, the protocol element is treated
as not a part of the minor version. That is, it is treated as
mandatory to not implement.
In some cases the overall status may be different from that specified
above. For example, it could be that there were two features, each
of which is OPTIONAL, and it is specified that exactly one of these
must always me supported. In such a case, if both features assign a
protocol element an F-to-E status of REQUIRED, then the overall
status of the protocol element is REQUIRED.
6.5. Determining Protocol Element Support
If it has already been determined that a particular protocol element
is known to the server, the client can determine whether it is
supported based on its type, as follows:
o If the protocol element is an attribute, the supported_attr
attribute can be interrogated to determine if support is present.
o If the protocol element is an operation, the operation can be
attempted, with an error of NFS4ERR_NOTSUPP indicating the
operation is known but not supported.
o If the protocol element is a switch case, use of that case can be
attempted, with an error of NFS4ERR_UNION_NOTSUPP indicating t the
operation is known but not supported.
o If the protocol element is an operation flag bit and the operation
is REQUIRED, use if that flag bit can be attempted with an error
of NFS4ERR_UNION_NOTSUPP indicating the operation is known but not
supported.
o If the protocol element is an operation flag bit and the operation
defines an error to return in the case of unsupported flag bits,
use if that flag bit can be attempted with the specified error
indicating the operation is known but not supported.
Once this is done, all of the protocol elements the client is aware
of can be divided into three sets:
o Those that the server is unaware of and thus cannot support.
o Those that the server knows about but does not support.
o Those that the server supports.
Information obtained in the process of determining knowledge of
protocol elements (see Section 4.4.3) may be saved and used in
connection with the interrogations above. For example, in testing
for knowledge of a given operation, the specific error code returned
will indicate support or non-support as well as indicating support or
non-support, as well as knowledge of the corresponding operation.
Note that in doing so care needs to be taken regarding protocol
elements associated with features whose scope is more limited than
that of an entire client, since support may be different for
different sessions or different file systems.
6.6. Feature Discovery
In many cases, a client will need to determine whether particular
features are supported before using protocol elements that are part
of those features. While some clients may choose to defer this
determination until the features in question are actually needed,
others may make the determination as part of first connecting with a
server, using a session or accessing a file system, depending on the
scope of the feature in question.
Once such a determination of feature support or non-support are made,
the client may assume that it remains valid and will not change so
long as the object defining the feature scope remains valid.
o For features of client scope as long as the clientid remains
valid.
o For features of session scope as long as the sessionid remains
valid.
o For features of file system scope as long as the clientid and fsid
both remain valid.
In making this determination, the client is entitled to rely on, and
the server is REQUIRED to obey any inter-feature constraints that are
specified as applying to the minor version being used.
The presence or absence of particular features may be determined in a The presence or absence of particular features may be determined in a
number of ways: number of ways:
o For features which are required within a given minor version, a o For features which are REQUIRED within a given minor version, the
client can determine whether the feature is supported by seeing if client can treat the fact that the server accepted a request with
the minor version is supported. that minor version (and did not return
NFS4ERR_MINOR_VERSION_MISMATCH) as indicating that support is
present.
o For non-required features that contain an XDR-extending protocol o For features which consist only of the addition of a pNFS layout
element, a client can try to use techniques described in type, the fs_layout_type attribute for the fs in question can be
Section 8.2.1 to determine what features the server supports. interrogated and scanned for the layout type.
o For non-required features that do not contain an XDR-extending o For features which consist only of the addition of an instance of
protocol element, appropriate feature discovery facilities can be a feature template as defined in Section 5.2.2, the template
constructed on an ad hoc basis by defining a non-required per- feature definition will describe the means by which the presence
server or per-fs boolean attribute to serve as an indication of of support for particular feature instances is to be determined.
support. To address compatibility issues with earlier servers, an
appropriate default value to assume when the attribute is not
supported should be specified.
6.4. Feature Specification Documents For the remaining features, which are all OPTIONAL and contain an
XDR-extending protocol element, the E-to-F statuses of the
constituent protocol elements (see Section 6.4) can be used to
determine if support is present within the scope defined by the
feature in question. In most cases, support for the protocol element
is tested as described in Section 6.5.
o If there are one or more protocol elements whose status is "IFF",
support for any of these may be tested, with the result
determining support for the feature
o If there are one or more protocol elements whose status is "SVAL",
support for it can be tested, and if present the value returned
can be tested as described by the feature specification, resulting
in a determination of support for the feature.
o If there are protocol elements with statuses of "SINF" and
"NSINF", testing of these protocol elements can be used, although,
it is not always certain that testing all such will always resolve
the question.
o If none of these approaches are determinative, the feature
specification should define a method of resolving the question.
Once the set of supported features is determined:
o For protocol elements which have an F-to-E status of REQUIRED for
at least one supported feature, it can be assumed that support is
present.
o For other protocol elements which have an F-to-E status of
OPTIONAL for at least one supported feature, support needs to be
tested for as described in Section 6.5.
o For the remaining protocol elements, it can be assumed that
support is not present.
7. Documentation of Protocol Changes
As mentioned previously, NFSv4 is evolving towards a finer-grained
documentation model. The use of extensions within minor versions
will continue this trend.
7.1. Documentation Approach
Documentation of future changes to the NFSv4 protocol will use
feature specification documents as described in Section 7.3. There
are a number of ways in which such documents may be used, as
discussed in Section 7.4
The documentation approach is intended to avoid the unnecessary
production of large documents in which many unrelated features are
tied together because either:
o The entire protocol is described in a single document, as happened
with NFSv4.0 (in [RFC7530]) and NFSv4.1 (in [RFC5661]).
o Many unrelated features are described in a single document as
occurred with NFSv4.2 (in [NFSv42]).
The production of a larger number of smaller documents will
streamline document production and review. A potential problem is
that a profusion of smaller documents might cause difficulty for
those learning about and implementing the protocol.
The production of indexing material described in Section 7.2 is
intended to limit such difficulties. The result will be that, for
operations and attributes, we will have essentially a single table of
contents, referencing material from multiple minor version definition
documents and feature specification documents.
7.2. Indexing material
The following items, referred to collectively as "Indexing material"
will be useful in many contexts. The reason for frequently
publishing such material is to prevent a situation in which large
numbers of documents must be scanned to find the most current
description of a particular protocol element.
o A table mapping operations and callbacks to the most recent
protocol definition document containing a description of that
operation.
o A table mapping attributes to the most recent protocol definition
document containing a description of that attribute.
o A table giving, for each operation in the protocol, the errors
that may validly be returned for that operation. If possible, it
would be desirable to give, as does [RFC5661], the operations
which may validly return each particular error.
o A table giving for each operation, callback, and attribute and for
each feature element in a published extension giving its status
(REQUIRED, OPTIONAL, or mandatory-to-not implement), the name of
the feature of which it is a part, its associated E-to-F and
F-to-E status values and information about other features for
which it has a non-empty F-to-E status value. This would be
similar to the material in Section 14 of [NFSv42], expanded to
include all feature elements.
7.3. Feature Specification Documents
Features will be documented in the form of a working-group standards- Features will be documented in the form of a working-group standards-
track document which define one or more features. Generally, only track document which define one or more features. Generally, only
closely related features should be defined in the same document. closely related features should be defined in the same document.
The definition of each of the new features may include one or more The definition of each of the new features may include one or more
"feature elements" which change the protocol in any of the ways "feature elements" which change the protocol in any of the ways
discussed in Section 4. Feature elements include new operations, discussed in Section 5. Feature elements include new operations,
callbacks, attributes, and enumeration values. The functionality of attributes, and enumeration values. Note that in this context,
some existing operations may be extended by the addition of new flags "Operations" include both forward and callback operations. The
bits in existing flag words, by new cases in existing switched functionality of some existing operations may be extended by the
unions, and by valid semantic changes to existing operations. addition of new flags bits in existing flag words, by new cases in
existing switched unions, and by valid semantic changes to existing
operations.
Such feature definition documents would contain a number of items, Such feature definition documents would contain a number of items,
following the pattern of the NFSv4.2 specification. The only following the pattern of the NFSv4.2 specification. The only
difference would be that while the NFSv4.2 specification defines a difference would be that while the NFSv4.2 specification defines a
number of features to be incorporated into NFSv4.2, the feature number of features to be incorporated into NFSv4.2, the feature
definition documents would each define a single feature, or a small definition documents would each define a single feature, or a small
set of closely related features. set of closely related features.
In addition to a general explanation of the feature in question, the In addition to a general explanation of the feature(s) in question,
items to be included in such feature definition documents would be: the items to be included in such feature definition documents would
be as listed below. In some cases these items, in addition to
descriptive text, would contain fragments of XDR code, to aid in
preparation of XDR files that include the additions defined by the
feature added to the base protocol that is being extended. For
information regarding preparation of such XDR files, see Section 7.5.
o Description of new operations (corresponding to Sections 16 and 17 o Description of new operations (corresponding to Sections 15 and 16
of [NFSv42]). of [NFSv42]). Such descriptions will contain XDR code defining
the structure the arguments and results of the new operation along
with preparatory XDR definitions used only by that operation.
o Description of any modified operations (corresponding to o Description of any modified operations (corresponding to
Section 15 of [NFSv42]). Section 15 of [NFSv42]). Such description may contain XDR code
defining the new flag bits, enum values, and cases to be added to
existing switched unions. Note that addition of new attributes is
not considered an extension of GETATTR, SETATTR, VERIFY, or
NVERIFY.
o Description of new attributes (corresponding to Section 13 of o Description of new attributes (corresponding to Section 13 of
[NFSv42]). [NFSv42]). XDR code defining the types of the attributes would be
part of this description.
o Description of any added error codes (corresponding to o Description of any added error codes (corresponding to
Section 12.1 of [NFSv42]). Section 12.1 of [NFSv42]).
o All operation descriptions, whether for new or modified o All operation descriptions, whether for new or modified
operations, should indicate when operations or the corresponding operations, should indicate when operations or the corresponding
results may be presented as RDMA chunks. results may be presented as RDMA chunks.
o A summary description of all changes made by this feature to the o A set of XDR code fragments giving the numeric values of added
XDR definition of the protocol, including operation codes, operation codes, attribute numbers, and error codes.
attribute numbers, added flag bits and enumeration values, and
request and response structures for new operations together with o Descriptions of all other extensions made to existing flag words,
the other XDR extensions needed to support them. enums and switched unions used by existing operations. Such
descriptions will contain XDR code defining the new flag bits,
enum values, and cases to be added to existing switched unions.
o Descriptions of all added of new structures, enums, flag words,
and switched unions that are used by more than one new operation,
or which are available for future use by multiple operations.
Such descriptions will contain XDR code defining the new
structures/union and assigning the new numeric values for enum and
flag bits.
o A listing giving the valid errors for each new operation and o A listing giving the valid errors for each new operation and
callback (corresponds to Sections 12.2 and 12.3 of [NFSv42]). callback (corresponds to Sections 12.2 and 12.3 of [NFSv42]).
o A table giving for each new feature element its status (required o For each feature, a table giving for each feature element that is
or not) and its relationship to the feature(s) being described part of the feature, its overall status within the minor version
(i.e., required for every implementation of the feature, or and its E-to-F and F-to-E status values. This would be similar to
optional in the presence of the feature). This would be similar the material in Section 14 of [NFSv42] but restricted to the
to the material in Section 14 of [NFSv42] but restricted to the feature(s) defined in the document and expanded to include all
feature(s) defined in the document and expanded in scope to feature elements.
include all feature elements.
o A table presenting support requirement for each protocol element
which is either a part of a feature defined in the document or has
an F-to-E status with relation with a feature defined in the
document. This could present the F-to-E status value for each
relevant combination of feature element and feature. An
alternative presentation would give, for each protocol element, a
boolean expression in term of supported feature, that allow and
guarantee support for the specified element.
o All of the additional Sections required for RFC publication, such o All of the additional Sections required for RFC publication, such
as "Security Considerations", "IANA considerations", etc. as "Security Considerations", "IANA considerations", etc.
6.5. Feature Incorporation Note that the listing above is not intended to define, in detail, the
structure of the specification. Rather, the intention is to define
the things it needs to contain. If there would be no content for a
particular element, there is no need for an empty section
corresponding to that list element. If it makes more sense to
describe a new structure together with an extended one, then the need
for a readily understandable document is primary.
7.4. Feature Incorporation
All protocol changes will be organized, documented and effected as All protocol changes will be organized, documented and effected as
part of a given feature. This includes XDR extension and the various part of a given feature. This includes XDR extension and the various
sorts of non-XDR-based changes allowed. sorts of non-XDR-based changes allowed.
Such features may be made part of the protocol in a number of ways: Such features may be made part of the protocol in a number of ways:
o In new minor versions, as discussed in Section 9. o In new minor versions, as discussed in Section 10.
o In separately documented new features. When new features are non- o In separately documented new features. When new features are
required and do not include any non-XDR-based changes, they may be OPTIONAL and do not include any non-XDR-based changes, they may be
incorporated in an extensible minor version under construction. incorporated in an extensible minor version under construction.
See Section 8 for details. See Section 9 for details.
o When appropriate compatibility arrangement are in effect, they may o When appropriate compatibility arrangement are in effect, they may
be used to correct protocol problems in already approved minor be used to correct protocol problems in already approved minor
versions and features. See Section 10 for details. versions and features. See Section 11 for details.
7. Extensions within Minor Versions 7.5. XDR File Considerations
As mentioned previously, feature specification documents will
contain, in addition to description of XDR extensions, XDR code
fragments that embody those extensions. There will be various
occasions on which people will have occasion to produce XDR files
that combine one or more extensions together with the XDR for an
existing minor version.
o When a minor version is specified by a number of feature
specification documents, there will be a need to produce, in as
simple fashion as possible, the corresponding XDR specification
document for the new minor version.
o Within an extensible minor version, there will be a need for those
developing and testing the feature to have an XDR file that
incorporates XDR definitions from early drafts of the feature
specification document.
o Also, for an extensible minor version, there will be a need to
periodically produce Consolidated XDR documents that reflect all
features approved as Proposed Standards and thus incorporated in
the current minor version.
o Developers may need to be able to produce XDR files that reflect
particular combination of approved features, features under
development or experimental features not yet ready for working
group consideration.
We are assuming here that the primary task is producing XDR files and
that corresponding XDR documents can be produced relatively easily if
there is a well understood process to produce the underlying XDR
files.
The Feature specification document should contain all of the
necessary lines of XDR codes to be added to a base XDR file to effect
the extension. The only remaining issue is where to place each
addition to arrive at the correct consolidated file.
o One could rely on those preparing updated XDR file to place the
additional XDR code lines in the appropriate place, based on
inference from the document text.
o One could rely on the Feature Specification Document to indicate,
in the descriptive text, where each XDR extension is to be placed.
o One could formalize a set of conventions whereby the appropriate
placements are indicated by specific instructions embedded within
comments within the XDR code fragments to be placed.
8. Extensions within Minor Versions
The NFSv4 version management framework allows, with certain The NFSv4 version management framework allows, with certain
restrictions, features to be added to existing minor versions restrictions, features to be added to existing minor versions
o In the case of features which consist only of a pNFS mapping type, o In the case of features which consist only of a pNFS mapping type,
the protocol may be extended by publishing the new mapping type the protocol may be extended by publishing the new mapping type
definition as a Proposed Standard. This effects an extension to definition as a Proposed Standard. This effects an extension to
all minor versions in which pNFS is a valid feature. all minor versions in which pNFS is a valid feature.
Similar extension facilities could be made available if additional Similar extension facilities could be made available if additional
pNFS-like extension frameworks were created (See Section 4.3.2). pNFS-like extension frameworks were created (See Section 5.2.2).
o Minor versions designated as extensible (see Section 8) may be o Minor versions designated as extensible (see Section 9) may be
extended by the publication of a standards-track document defining extended by the publication of a standards-track document defining
the additional feature. Details are set out in Section 8. The the additional feature. Details are set out in Section 9. The
features to be added are considered non-required in the extensible features to be added are considered OPTIONAL in the extensible
minor version and must consist only of valid XDR-based extensions minor version and must consist only of valid XDR-based extensions
8. Adding Features to Extensible Minor Versions 9. Adding Features to Extensible Minor Versions
Addition of features to an extensible minor version will take Addition of features to an extensible minor version will take
advantage of the existing NFSv4 infrastructure that allows optional advantage of the existing NFSv4 infrastructure that allows optional
features to be added to new minor versions, but without in this case features to be added to new minor versions, but without in this case
requiring any change in the minor version number. Adding features in requiring any change in the minor version number. Adding features in
this way will enable compatibility with existing clients and servers, this way will enable compatibility with existing clients and servers,
who may be unaware of the new feature. who may be unaware of the new feature.
8.1. Use of Feature Specification Documents 9.1. Use of Feature Specification Documents
Each such extension will be in the form of a working-group standards- Each such extension will be in the form of a working-group standards-
track document which defines one or more new non-required features. track document which defines one or more new OPTIONAL features. The
The definition of each of the new feature may include one or more definition of each of the new feature may include one or more
"protocol elements" which extend the existing XDR as already "protocol elements" which extend the existing XDR as already
discussed (in Section 4.1). Other sorts of XDR modification are not discussed (in Section 4.1). Other sorts of XDR modification are not
allowed. Protocol elements include new operations, callbacks, allowed. Protocol elements include new operations, callbacks,
attributes, and enumeration values. The functionality of some attributes, and enumeration values. The functionality of some
existing operations may be extended by the addition of new flags bits existing operations may be extended by the addition of new flags bits
in existing flag words and new cases in existing switched unions. in existing flag words and new cases in existing switched unions.
New error codes may be added but the set of valid error codes to be New error codes may be added but the set of valid error codes to be
returned by an operation is fixed, except that existing operations returned by an operation is fixed, except that existing operations
may return new errors to respond to situations that only arise when may return new errors to respond to situations that only arise when
previously unused flag bits are set or when extensions to a switched previously unused flag bits are set or when extensions to a switched
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to existing operations) associated with the new feature are to existing operations) associated with the new feature are
complete and do not conflict with those in the existing protocol complete and do not conflict with those in the existing protocol
or those currently under development. or those currently under development.
o At the time the working group document is complete, the working o At the time the working group document is complete, the working
group, in addition to normal document review, can and should look group, in addition to normal document review, can and should look
at what prototype implementations of the feature have been done at what prototype implementations of the feature have been done
and use that information to determine the work-ability and and use that information to determine the work-ability and
maturity of the feature. maturity of the feature.
8.2. Compatibility Issues 9.2. Compatibility Issues
Because the receiver of a message may be unaware of the existence of Because the receiver of a message may be unaware of the existence of
a specific extension, certain compatibility rules need to be a specific extension, certain compatibility rules need to be
observed. In some cases (e.g., addition of new operations or observed. In some cases (e.g., addition of new operations or
callbacks or addition of new arms to an existing switched union) callbacks or addition of new arms to an existing switched union)
older clients or servers may be unable to do XDR parsing on an older clients or servers may be unable to do XDR parsing on an
extension of whose existence they are unaware. In other cases (e.g., extension of whose existence they are unaware. In other cases (e.g.,
error returns) there are no XDR parsing issues but existing clients error returns) there are no XDR parsing issues but existing clients
and servers may have expectations as to what may validly be returned. and servers may have expectations as to what may validly be returned.
Detailed discussion of these compatibility issues appears below: Detailed discussion of these compatibility issues appears below:
o Issues related to messages sent to the server are discussed in o Issues related to messages sent to the server are discussed in
Section 8.2.1. Section 9.2.1.
o Issues related to messages sent to the client are discussed in o Issues related to messages sent to the client are discussed in
Section 8.2.2. Section 9.2.2.
8.2.1. Compatibility Issues for Messages Sent to Servers 9.2.1. Compatibility Issues for Messages Sent to Servers
This section deals with compatibility issues that relate to messages This section deals with compatibility issues that relate to messages
sent to the server, i.e., requests and replies to callbacks. In the sent to the server, i.e., requests and replies to callbacks. In the
case of requests, it is the responsibility of the client to determine case of requests, it is the responsibility of the client to determine
whether the server supports the extension in question before sending whether the server supports the extension in question before sending
a request containing it for any purpose other than determining a request containing it for any purpose other than determining
whether the server is aware of the extension. In the case of whether the server is aware of the extension. In the case of
callback replies, the server demonstrates its awareness of proper callback replies, the server demonstrates its awareness of proper
parsing for callback replies by sending the associated callback. parsing for callback replies by sending the associated callback.
Regarding the handling of requests: Regarding the handling of requests:
o Existing server implementations will return NFS4ERR_NOTSUPP or o Existing server implementations will return NFS4ERR_NOTSUPP or
NFS4ERR_OP_ILLEGAL in response to any use of a new operation, NFS4ERR_OP_ILLEGAL in response to any use of a new operation,
allowing the client to determine that the requested operation (and allowing the client to determine that the requested operation (and
potentially the feature in question) is not supported by the potentially the feature in question) is not known or known but not
server. supported by the server.
o Clients can determine whether particular new attributes are o Clients can determine whether particular new attributes are
supported by a given server by examining the value returned when supported by a given server by examining the value returned when
the supported_attr attribute is interrogated. Clients need to do the supported_attr attribute is interrogated. Clients need to do
this before attempting to use attributes defined in an extension this before attempting to use attributes defined in an extension
since they cannot depend on the server returning since they cannot depend on the server returning
NFS4ERRATTRNOTSUPP for requests which include a mask bit NFS4ERR_ATTRNOTSUPP for requests which include a mask bit
corresponding to a previously unspecified attribute number (as corresponding to a previously unspecified attribute number (as
opposed to one which is defined but unsupported). opposed to one which is defined but unsupported).
o Existing server implementations that do not recognize new flag o Existing server implementations that do not recognize new flag
bits will return NFS4ERR_INVAL, enabling the client to determine bits will return NFS4ERR_INVAL, enabling the client to determine
that the new flag value is not supported by the server. that the new flag value is not supported by the server.
o Existing server implementations that do not recognize the new arm o Existing server implementations that do not recognize the new arm
of a switched union in a request will return NFS4ERR_INVAL or of a switched union in a request will return NFS4ERR_INVAL or
NFS4ERR_UNION_NOTSUPP, enabling the client to determine that the NFS4ERR_UNION_NOTSUPP, enabling the client to determine that the
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o Error values returned to the server for all callbacks that do not o Error values returned to the server for all callbacks that do not
use new features will only be those previously allowed. Only when use new features will only be those previously allowed. Only when
the server uses a new extension feature can a previously invalid the server uses a new extension feature can a previously invalid
error value be returned. error value be returned.
o Callback replies may only include a new arm of an existing o Callback replies may only include a new arm of an existing
switched union when the server, typically in the callback being switched union when the server, typically in the callback being
responded to, has used a feature element associated with the responded to, has used a feature element associated with the
feature that defined the new switched union arm. feature that defined the new switched union arm.
8.2.2. Compatibility Issues for Messages Sent to Clients 9.2.2. Compatibility Issues for Messages Sent to Clients
This sections deals with compatibility issues that relate to messages This sections deals with compatibility issues that relate to messages
sent to clients, i.e., request replies and callbacks. In both cases, sent to clients, i.e., request replies and callbacks. In both cases,
extensions are only sent to clients that have demonstrated awareness extensions are only sent to clients that have demonstrated awareness
of the extensions in question by using an extension associated with of the extensions in question by using an extension associated with
the same feature. the same feature.
Regarding the handling of request replies: Regarding the handling of request replies:
o Error values returned to the client for all requests that do not o Error values returned to the client for all requests that do not
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callbacks that are part of the extension. For example, a flag bit callbacks that are part of the extension. For example, a flag bit
in the EXCHANGE_ID request may serve this purpose. in the EXCHANGE_ID request may serve this purpose.
o In both of the above cases, the ability to accept and parse the o In both of the above cases, the ability to accept and parse the
specified callback is considered separate from support for the specified callback is considered separate from support for the
callback. The feature specification will indicate whether support callback. The feature specification will indicate whether support
for the callback is required whenever the feature is used by the for the callback is required whenever the feature is used by the
client. In cases in which support is not required, the client is client. In cases in which support is not required, the client is
free to return NFS4ERR_NOTSUPP upon receiving the callback. free to return NFS4ERR_NOTSUPP upon receiving the callback.
8.3. Additional Documents to be Produced 9.3. Additional Documents to be Produced
Additional documents will be required from time to time. These Additional documents will be required from time to time. These
documents will eventually become RFC's (informational or standards documents will eventually become RFC's (informational or standards
track as described below), but the work of the working group and of track as described below), but the work of the working group and of
implementers developing features will be facilitated by a progression implementers developing features will be facilitated by a progression
of document drafts that incorporate information about new features of document drafts that incorporate information about new features
that are being developed or have been approved as Proposed Standards. that are being developed or have been approved as Proposed Standards.
8.3.1. Minor Version Indexing Document 9.3.1. Minor Version Indexing Document
One document will organize existing material for a minor version One document will organize existing material for a minor version
undergoing extension so that implementers will not have to scan a undergoing extension so that implementers will not have to scan a
large set of feature definition documents or minor version large set of feature definition documents or minor version
specifications to find information being sought. Successive drafts specifications to find information being sought. Successive drafts
of this document will serve as an index to the current state of the of this document will serve as an index to the current state of the
extensible minor version. Some desirable elements of this indexing extensible minor version. Some desirable elements of this indexing
document would include: document would include:
o A list of all feature definition documents that have been approved o A list of all feature definition documents that have been approved
as working group documents but have not yet been approved as as working group documents but have not yet been approved as
Proposed Standards. Proposed Standards.
o All of the items of indexing material (see Section 5.1) o All of the items of indexing material (see Section 7.2)
appropriately adjusted to reflect the contents of all extensions appropriately adjusted to reflect the contents of all extensions
accepted as Proposed Standards. accepted as Proposed Standards.
The frequency of updates for this document will be affected by The frequency of updates for this document will be affected by
implementer needs and the ability to easily generate document drafts, implementer needs and the ability to easily generate document drafts,
preferably by automated means. The most desirable situation is one preferably by automated means. The most desirable situation is one
in which a new draft is available soon after each feature reaches the in which a new draft is available soon after each feature reaches the
status of a Proposed Standard. status of a Proposed Standard.
8.3.2. Consolidated XDR Document 9.3.2. Consolidated XDR Document
This document will consist of an updated XDR for the protocol as a This document will consist of an updated XDR for the protocol as a
whole including feature elements from all features and minor versions whole including feature elements from all features and minor versions
accepted as Proposed Standards. accepted as Proposed Standards.
A new draft should be prepared whenever a new feature within an A new draft should be prepared whenever a new feature within an
extensible minor version is accepted as a Proposed Standard. In most extensible minor version is accepted as a Proposed Standard. In most
cases, feature developers will be using a suitable XDR which can then cases, feature developers will be using a suitable XDR which can then
be reviewed and published. In cases in which multiple features reach be reviewed and published. In cases in which multiple features reach
Proposed Standard status at approximately the same time, a merge of Proposed Standard status at approximately the same time, a merge of
the XDR changes made by each feature may be necessary. the XDR changes made by each feature may be necessary.
8.3.3. XDR Assignment Document 9.3.3. XDR Assignment Document
This document will contain consolidated lists of XDR value This document will contain consolidated lists of XDR value
assignments that are relevant to the protocol extension process. It assignments that are relevant to the protocol extension process. It
should contain lists of assignments for: should contain lists of assignments for:
o operation codes (separate lists for forward operations and for o operation codes (separate lists for forward operations and for
callbacks) callbacks)
o attribute numbers o attribute numbers
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For each set of assignments, the individual assignments may be of For each set of assignments, the individual assignments may be of
three types: three types:
1. permanent assignments associated with a minor version or a 1. permanent assignments associated with a minor version or a
feature extension that has achieved Proposed Standard status. feature extension that has achieved Proposed Standard status.
These assignments are permanent in that the assigned value will These assignments are permanent in that the assigned value will
never be re-used. However, a subsequent minor version may define never be re-used. However, a subsequent minor version may define
some or all feature elements associated with a feature to be some or all feature elements associated with a feature to be
Mandatory to NOT support. mandatory to not implement.
2. provisional assignments associated with a feature under 2. provisional assignments associated with a feature under
development (i.e., one which has been approved as a working group development (i.e., one which has been approved as a working group
document but has not been approved as a Proposed Standard). document but has not been approved as a Proposed Standard).
Provisional assignments are not are not permanent and the values Provisional assignments are not are not permanent and the values
assigned can be re-used in certain circumstances. In particular, assigned can be re-used in certain circumstances. In particular,
when a feature with provisional assignments is not progressing when a feature with provisional assignments is not progressing
toward the goal of eventual Proposed Standard status, the working toward the goal of eventual Proposed Standard status, the working
group can judge the feature effort to have been abandoned, group can judge the feature effort to have been abandoned,
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Standard. Standard.
o A new feature is accepted for development and a draft of the o A new feature is accepted for development and a draft of the
corresponding working-group standards-track document is produced corresponding working-group standards-track document is produced
o A feature previously accepted for development is abandoned. o A feature previously accepted for development is abandoned.
o The working group decides to make some change in assignments for o The working group decides to make some change in assignments for
experimental use. experimental use.
8.3.4. Transition of Documents to RFC's 9.3.4. Transition of Documents to RFC's
Each of these documents should be published as an RFC soon after the Each of these documents should be published as an RFC soon after the
minor version in question ceases to be considered extensible. minor version in question ceases to be considered extensible.
Typically this will happen when the working group makes the Typically this will happen when the working group makes the
specification for the subsequent minor version into a working group specification for the subsequent minor version into a working group
document. Some specifics about the individual documents are listed document. Some specifics about the individual documents are listed
below: below:
o The most current draft of the indexing document for the minor o The most current draft of the indexing document for the minor
version would be published as an informational RFC. version would be published as an informational RFC.
o The most current draft of the consolidated XDR document should be o The most current draft of the consolidated XDR document should be
published as a standards-track RFC. It would update the initial published as a standards-track RFC. It would update the initial
specification of the minor version specification of the minor version
o The most recent draft of the XDR assignment document should be o The most recent draft of the XDR assignment document should be
published as an informational RFC. published as an informational RFC.
Handling of these documents in the event of a post-approval XDR Handling of these documents in the event of a post-approval XDR
correction is discussed in Section 10.1 correction is discussed in Section 11.2
8.4. Relationship Between Minor Versioning and Extensions within a 9.4. Relationship Between Minor Versioning and Extensions within a
Minor Version Minor Version
Extensibility of minor versions are governed by the following rules: Extensibility of minor versions are governed by the following rules:
o Minor versions zero and one are not extensible. Each has a fixed o Minor versions zero and one are not extensible. Each has a fixed
set of non-required features as described in [RFC7530] and set of OPTIONAL features as described in [RFC7530] and [RFC5661].
[RFC5661].
o Minor versions beyond one are presumed extensible as discussed o Minor versions beyond one are presumed extensible as discussed
herein. However, any statement within the minor version herein. However, any statement within the minor version
specification disallowing extension will cause that minor version specification disallowing extension will cause that minor version
to be considered non-extensible. to be considered non-extensible.
o No new feature may be added to a minor version may be made once o No new feature may be added to a minor version once the
the specification document for a subsequent minor version becomes specification document for a subsequent minor version becomes a
a working group standards-track document. working group standards-track document.
Even when a minor version is non-extensible, or when a previous minor Even when a minor version is non-extensible, or when a previous minor
version is closed to further extension, the features that it contains version is closed to further extension, the features that it contains
are still subject to updates to effect protocol corrections. In many are still subject to updates to effect protocol corrections. In many
cases, making an XDR change, in the form of an extension will be the cases, making an XDR change, in the form of an extension will be the
best way of correcting an issue. See Section 10 for details. best way of correcting an issue. See Section 11 for details.
While making minor versions extensible will decrease the frequency of While making minor versions extensible will decrease the frequency of
new minor versions, it will not eliminate the need for them. In new minor versions, it will not eliminate the need for them.
particular: Protocol features that cannot be used as extensions (see
Section 10.1.1 require a new minor version.
o A new minor version will be required for any change in the status In addition, change which involve modifications to the set of
of a feature element (i.e., an operation, callback, attribute, protocol elements which are REQUIRED or mandatory to not implement
added flag or switch case). For example, changes which make require a new minor version which starts a new minor version group.
feature elements Recommended, Required or Mandatory to Not Changes to the organization of protocol features are treated
Implement will require a minor version. similarly, since they have a similar potential to cause interversion
incompatibility. See Section 10.1.2 for details.
o Any incompatible semantic change in the required or allowed 10. Minor Versions
processing of an existing operation or attribute will require a
minor version.
o Any change that extends the set of errors returned that an 10.1. Reasons for New Minor Versions
existing operation, with the exception noted above. New errors
may be added when the conditions that give rise to these new
errors cannot arise as long as new flag bits or switched union
arms are not used. In these cases, it is clear that existing
clients cannot receive these errors.
o Any change in the mapping of feature elements to features will It is important to note that this section, in describing situations
require a minor version. For example, if a feature is to be split that would require new minor versions or minor version groups to be
into two separate features clients would no longer be able to created, does not thereby imply that situations will exist in the
infer support for one operation from support for the other, in the future. Judgments regarding desirability of future changes will be
same way that had been done previously, invalidating logic in made by the working group or its successors and any guidance that can
existing clients be offered at this point is necessarily quite limited.
9. Minor Versions Creation of a new minor version or minor version group is an option
that the working group retains. The listing of situations below that
would prompt such actions is not meant to be exhaustive.
9.1. Minor Version Construction 10.1.1. New Minor Versions within an Existing Group
In addition to the sorts of non-required features that may be made in The following sorts of features are not allowed as extensions and
the context of extensible minor version, a number of other sorts of would require creation of a new minor version:
changes may be made in a new minor version. Because such changes
have the potential to disrupt inter-version such changes should only
be made after careful consideration of the effects on interversion
interoperability.
o Addition of new features that incorporate any of the non-XDR-based o Features that incorporate any of the non-XDR-based changes
changes discussed in Sections 4.2.1 and 4.2.2. Such features must discussed in Sections 5.1.1 and 5.1.2.
always be introduced as non-required.
o Addition of required new features. o Any feature which includes a new mapping type (as described in
Section 5.2.1) and includes any other change.
o Changes to the status of existing features or to inter-feature To prevent new mapping types from evading this restriction by
constraints. splitting the mapping type and other changes into two separate
changes, if new mapping type makes a reference to protocol changes
in an extension, it may not be incorporated in minor versions in
which that extension is defined but only in later minor versions.
o Changes to feature organization. Such changes may have the effect o Any feature that creates a new expansion mechanism as described in
of making support for some change element obligatory in in Section 5.2.2.
circumstances when it had not been previously.
9.2. Minor Version Interaction 10.1.2. New Minor Version Groups
The following sorts of changes can only occur in the context of a new
minor version group:
o Addition of REQUIRED new features.
o Changes to the status of existing features including converting
features to be mandatory to not implement.
o Changes to the status of existing feature elements within
features, causing those feature elements to be required or
optional when they previously had not been.
o Changes to the scope of existing features.
o Changes to feature organization or to inter-feature constraints.
Such changes may have the effect of making support for some change
element required or optional in circumstances in which it
previously had not been
Changes to the status or organization of features will, in most case,
result in changes to the status of individual protocol elements,
changing them between REQUIRED and OPTIONAL, or making them mandatory
to not implement.
Conversion of protocol elements to be mandatory to not implement,
will not, as had previously been the practice, result in their
deletion from the protocol XDR. However, the server will be REQUIRED
to treat such protocol elements as not known when responding to
requests within minor versions in which they are not to be
implemented. See Sections 4.4.3 and 10.3.2 for details.
Such changes give rise to potential compatibility issues. In most
cases in which such changes will actually be made, careful
consideration of compatibility issues can limit the scope of
potential compatibility issues or ensure that actual compatibility
issues are quite limited.
This is opposed to the first new minor version group, that associated
with minor version one, which resulted in a situation in which
clients for minor version zero could not interoperate with servers
for minor version one and vice versa. Issues related to the question
of what to do about such situations are discussed in Section 10.1.3
The addition of REQUIRED features may serve to illustrate the issues.
Such additions pose no compatibility issue for existing clients. On
the other hand, all servers will need to be updated to support the
new features. The effort required and any potential for disruption
depend on the scope of the feature being added.
A number of features introduced as REQUIRED in NFSv4.1 can serve to
illustrate the issues.
o suppattr_exclattr was added as a REQUIRED attribute. This was
very simple for servers to implement.
o RECLAIM_COMPLETE was added as a REQUIRED operation.
o TEST_STATEID and FREE_STATEID were added as REQUIRED operations.
Some examples of potential feature status changes may be helpful in
illustrating compatibility issues
o Converting a REQUIRED feature to be mandatory to not implement
poses the greatest level of difficulty from an interoperability
point of view. Clients need to change to use an alternative means
of providing the functionality provided by the feature. Existing
servers need to be updated, even if there is a replacement feature
available.
Such a transition is only possible if the feature in question has
already fallen into disuse.
o Converting an OPTIONAL feature to be mandatory to not implement
poses similar difficulties. If clients have ceased to use the
feature, after they have become aware, formally or informally,
that it is moribund, the difficulties can be quite limited.
o Converting a REQUIRED feature to be OPTIONAL poses no difficulty
for existing server implementations. It may pose difficulties for
clients who have not made preparations for server non-support of
the feature.
The degree of such difficulties and the readiness of clients to
make such changes should be key considerations in making such a
state transition.
o Converting an OPTIONAL feature to be REQUIRED poses no difficulty
for existing client implementations. The difficulties for
existing server implementations depend on the scope of the feature
involved and the set of implementations without support for the
feature in question.
The degree of such difficulties and the readiness of servers to
make such changes should be key considerations in making such a
state transition. Nevertheless, it should not be the only
consideration. If all existing servers support the feature, it
does not thereby follow that the transition should be made. The
possible effect of making server development more complicated
should also be considered.
A number of other changes allowed only in a new minor version group,
raise analogous issues.
o In the case of inter-feature constraints or similar
reorganizations, the basic issue is whether the client has to deal
with the absence of a protocol element when it previously had not
had to deal with that or the server has to provide support for a
protocol element in situations in which it previously had not had
to. When a set of changes cause both sorts of issues, the
greatest interoperability difficulties arise, making such a set of
changes hard to implement.
o If a feature scope is changed to be more fine-grained, the client
has to deal with combinations of support and non-support it
previously had not had to deal with, while the reverse forces the
server to maintain a unity of support it had previously not had
to. The unlikely case of conversion between session and file
system scope causes difficulties for both parties.
The tradeoff between interoperability issues and desirable changes to
the protocol is one for the working group to make. If the decision
is made to create a new minor version group, the working group has
decided that absolutely compatibility is not required. Nevertheless,
it should strive to make necessary changes as non-disruptive as
possible.
10.1.3. Limits on Minor Version Groups
The guidance that needs to be offered with regard to appropriate
limits on changes that form new version groups does not appear
reducible to specific rules.
Instead it is appropriate to return to the basic goal of allowing the
NFSv4 protocol to adapt to future circumstances as they develop.
Although this was not explicitly stated, it seems to be intended that
this would not involve generation of essentially a new protocol, even
if that were, in some sense, a better one.
So the best way we can address the question of limits on new version
groups is to state that the purpose of the rules in this document,
including the creation of new minor version groups is not the
creation of a successor protocol to NFSv4.
If this or a future working group does find itself defining a new
file access protocol, it would be helpful if proper care were taken
to retain what is valuable in the intellectual heritage of NFSv4.
Nevertheless, in doing so, it is important not to assume that
adherence to the rules in this document, is, in and of itself, a
guarantee that the new protocol is thereby a version of NFSv4.
In dealing with such a future changed situation, the better option
would be to face the issue of necessary change forthrightly and
acknowledge that such a large change creates a fundamentally new
situation. Appropriate responses might include replacing the XDR in
whole or in part, using a successor to XDR, or other means.
10.2. Role of Minor Versions
Clearly, the ability to provide protocol extensions without creation
of a new minor version, has lessened the role of minor versions in
extending the NFSv4 protocol to meet future needs.
We have gone from a situation in which there was a single mechanism,
creation of a new minor version, to extend the protocol, to a three-
level approach:
o OPTIONAL features which extend but do not change protocol
semantics may be added without creating a new minor version.
o Other OPTIONAL features may be added by creating a new minor
version within an existing version group, as long as the sets of
protocol elements which are REQUIRED and mandatory to not
implement.
o Changes which do as the sets of protocol elements which are
REQUIRED and mandatory to not implement are only allowed in a new
minor version group.
This document does explore the situations that, if they arise, would
require the creation of new minor versions or version groups. This
does not imply that such situations will exist or that the working
will choose to address things in that way. Such choices are left for
future decision by the working group and the IESG.
The discussion in Section 10.1.3 raises similar issues. It is
possible that situations might arise that would cause NFSv4
development to be done outside the framework established here.
Nevertheless, this does not imply that such situations will arise.
10.3. Minor Version Interaction Rules
This section addresses issues related to rules #11 and #13 in the This section addresses issues related to rules #11 and #13 in the
minor versioning rules in [RFC5661]. With regard to the supersession minor versioning rules in [RFC5661]. With regard to the supersession
of minor versioning rules, the treatment here overrides that in of minor versioning rules, the treatment here overrides that in
[RFC5661] when either of the potentially interacting minor versions [RFC5661] when either of the potentially interacting minor versions
has not yet been published as a Proposed Standard. has not yet been published as a Proposed Standard.
Note that these rules are the only ones directed to minor version Note that these rules are the only ones directed to minor version
implementers, rather than to those specifying new minor versions. implementers, rather than to those specifying new minor versions.
9.2.1. Minor Version Identifier Transfer Issues 10.3.1. Minor Version Identifier Transfer Issues
Each relationship between a client instance and a server instance, as Each relationship between a client instance and a server instance, as
represented by a clientid, is to be devoted to a single minor represented by a clientid, is to be devoted to a single minor
version. If a server detects that a COMPOUND with an inappropriate version. If a server detects that a COMPOUND with an inappropriate
minor version is being used, it MUST reject the request. In doing minor version is being used, it MUST reject the request. In doing
so, it may return either NFS4ERR_BAD_CLIENTID or so, it may return either NFS4ERR_BAD_CLIENTID or
NFS4RR_MINOR_VERS_MISMATCH. NFS4RR_MINOR_VERS_MISMATCH.
As a result of the above, the client has the assurance that the set As a result of the above, the client has the assurance that the set
of required and allowed features will not change within the context of REQUIRED and OPTONAL features will not change within the context
of a single clientid. Server implementations MUST ensure that the of a single clientid. Server implementations MUST ensure that the
set of supported features does not change within such a context. set of supported features and protocol elements does not change
within such a context.
9.2.2. Minor Version Compatibility Issues 10.3.2. Minor Version Intra-Group Compatibility
Within a set of minor versions that belong to the same minor version
group, it is relatively easy for clients and servers to provides the
needed compatibility by following the following rules.
o Servers supporting a given minor version MUST support any earlier
minor version in the same minor version group and return
appropriate errors for use of protocol elements that were not a
valid part of that earlier minor version. For details see below.
o Servers supporting a given minor version MUST, in returning errors
for operation which were a valid part of the minor version, return
the errors allowed for the current operation in the minor version
actually being used.
o Clients MUST deal with an NFS4ERR_MINOR_VERS_MISMATCH error by a
searching for a lower minor version number in the same minor
version group that the server will accept.
With regard to protocol elements not known in a given minor version,
the appropriate error codes are given below. Essentially, the
server, although it has a more extensive XDR reflective of a newer
minor version, must act as a server with a more limited XDR would.
o When an operation is used which is not known in the specified
minor version, NFS4ERR_OP_ILLEGAL (as opposed to NFS4ERR_NOTSUPP)
should be returned.
o When an attribute is used which is not known in the specified
minor version, NFS4ERR_INVAL (as opposed to NFS4ERR_ATTRNOTSUPP)
should be returned.
o When a switch case is used which is not known in the specified
minor version, NFS4ERR_BADXDR (as opposed to
NFS4ERR_UNION_NOTSUPP) should be returned. Even though the
message may be XDR-decodable by the server's current XDR, it is
not so according to the minor version being used.
o When a flag bit is used which is not known in the specified minor
version, NFS4ERR_INVAL (as opposed to NFS4ERR_NOTSUPP Or any other
error defined as indicated non-support a flag bit) should be
returned.
10.3.3. Minor Version Inter-Group Compatibility
It is desirable for client and server implementations to support a It is desirable for client and server implementations to support a
wide range of minor versions. The difficulty of doing so can be wide range of minor versions. The difficulty of doing so can be
affected by choices made by the working group in defining those minor affected by choices made by the working group in defining those minor
versions. versions, and the particulars of the changes made which establish new
version groups.
Within a set of minor versions that have exactly the same set of Options for compatibility are affected by the scale and frequency of
required features, it is relatively easy for clients and servers to the changes which require a new minor version group and the working
provide appropriate compatibility and they are well-advised to do so. group needs to take needs for inter-group compatibility into account
when making such changes. In all cases, the following rules apply:
Servers SHOULD accept any minor version number within the range and o Servers supporting a given minor version SHOULD support minor
return NFS4ERR_OPNOTSUPP or NFS4ERR_OP_ILLEGAL for non-supported versions in earlier minor version groups. When doing so, it MUST
operations based on the version number. behave appropriately given the definition of the minor version
used. For details see below.
Clients SHOULD deal with an NFS4ERR_MINOR_VERS_MISMATCH error by o Clients SHOULD deal with an NFS4ERR_MINOR_VERS_MISMATCH error by a
searching the appropriate minor version range for one the server will searching for a lower minor version number within the appropriate
accept. minor version range until it finds one that the server will
accept.
Servers and clients MAY deal with changes in the set of required In some cases, the server needs to behave as a more restricted one
features by supporting at least the union of the set of required for an earlier minor version might, despite it having extensions for
features for all minor versions within the range to be supported. protocol elements added in later minor versions. In these cases, the
This may involve logic to specifically withhold support for features errors described in Section 10.3.2 should be returned in this case as
when not allowed for a particular minor version. well.
9.3. Minor Version Documentation In the case in which the earlier version contains protocol elements
subsequently made mandatory to not implement, the server needs to
know of those protocol elements and not return the errors that would
appropriate if the most up-to-date minor version were used. In cases
in which support for these protocol elements is REQUIRED, support
will have to be provided by the server and if it cannot do that, it
MUST return NFS4ERR_MINOR_VERS_MISMATCH for any requests using that
minor version.
In addition to using an appropriate subset of the protocol XDR
definition, the server needs to respect the non-XDR elements of the
earlier minor version group as well. In particular, the serve needs
to:
o Support REQUIRED features as specified by the earlier minor
version group.
o Support (or not) features according to E-to-F statuses specified
by the earlier minor version group.
o Respect the inter-feature constraints specified by the earlier
minor version group.
o Respect the feature scopes specified by the earlier minor version
group.
o Support (or not) protocol elements according to the F-to-E
statuses specified in the earlier minor version group.
10.4. Minor Version Documentation
Minor versions should be documented by specifying and explaining the Minor versions should be documented by specifying and explaining the
changes made relative to the previous minor version. changes made relative to the previous minor version.
Features added to the minor version should be documented in their own Features added to the minor version should be documented in their own
feature specification documents and normatively referenced. feature specification documents and normatively referenced.
Changes to the status or organization of existing features should be Changes to the status or organization of existing features should be
documented by presenting a summary of the status of all existing documented by presenting a summary of the status of all existing
protocol elements, their relationship to non-required features, and protocol elements, their relationship to OPTIONAL features, and any
any relevant feature dependencies. relevant feature dependencies.
In addition, to avoid situation where a large number of minor In addition, to avoid situation where a large number of minor
versions must be scanned to find the most recent valid treatment of a versions must be scanned to find the most recent valid treatment of a
specific protocol element, minor version definition documents will specific protocol element, minor version definition documents will
contain the indexing material described in Section 5.1. contain the indexing material described in Section 7.2.
10. Correction of Existing Minor Versions and Features 11. Correction of Existing Minor Versions and Features
The possibility always exists that there will be a need to correct an The possibility always exists that there will be a need to correct an
existing feature in some way, after the acceptance of that feature or existing feature in some way, after the acceptance of that feature or
a minor version containing it, as a Proposed Standard. While the a minor version containing it, as a Proposed Standard. While the
working group can reduce the probability of such situations arising working group can reduce the probability of such situations arising
by waiting for running code before considering a feature as done, it by waiting for running code before considering a feature as done, it
cannot reduce the probability to zero. As features are used more cannot reduce the probability to zero. As features are used more
extensively and interact with other features, previously unseen flaws extensively and interact with other features, previously unseen flaws
may be discovered and will need to be corrected. may be discovered and will need to be corrected.
Such corrections are best done in a bis document updating the RFC Such corrections are best done in a document obsoleting or updating
defining the relevant feature definition document or minor version the RFC defining the relevant feature definition document or minor
specification. In making such a correction, the working will have to version specification. In making such corrections, the working will
carefully consider how to assure interoperability with older clients have to carefully consider how to assure interoperability with older
and servers. clients and servers.
Often, corrections can be done without changing the protocol XDR. Often, corrections can be done without changing the protocol XDR. In
However, incompatible changes in server or client behavior should not many cases, a change in client and server behavior can be implemented
be mandated in order to avoid XDR changes. When XDR changes are without taking special provision with regard to interoperability with
necessary as part of correcting a flaw, these should be done in a earlier implementations. In those case, and in cases in which a
manner similar to that used when implementing new minor versions or revision merely clarifies an earlier protocol definition document, a
features within them. In particular, new document can be published which simply updates the earlier
protocol definition document. Subsequently, the indexing material
would be updated to reflect the existence of the newer document.
In other cases, it is best if client or server behavior needs to
change in a way which raises interoperability concerns. In such
cases, incompatible changes in server or client behavior should not
be mandated in order to avoid XDR changes.
11.1. XDR Changes to Implement Protocol Corrections
When XDR changes are necessary as part of correcting a flaw, these
should be done in a manner similar to that used when implementing new
minor versions or features within them. In particular,
o Existing XDR structures may not be modified or deleted. o Existing XDR structures may not be modified or deleted.
o XDR extensions may be used to correct existing protocol facilities o XDR extensions may be used to correct existing protocol facilities
in a manner similar to those used to add additional optional in a manner similar to those used to add additional optional
features. Such corrections may be done in an otherwise non- features. Such corrections may be done in an otherwise non-
extensible minor version, if the working group judges it extensible minor version, if the working group judges it
appropriate. appropriate.
o When a correction is made to a non-required feature, the result is o When a correction is made to an OPTIONAL feature, the result is
similar to a situation in which there are two independent non- similar to a situation in which there are two independent OPTIONAL
required features. A server may choose to implement either or features. A server may choose to implement either or both.
both.
o When a correction is made to a required feature, the situation o When a correction is made to a required feature, the situation
becomes one in which neither the old nor the new version of the becomes one in which neither the old nor the new version of the
feature is required. Instead, it is required that a server feature is required. Instead, it is required that a server
support at least one of the two, while each is individually non- support at least one of the two, while each is individually
required. Although use of the corrected version is ultimately OPTIONAL. Although use of the corrected version is ultimately
better, and may be recommended, it should not be described as better, and may be recommended, it should not be described as
"RECOMMENDED", since the choice of which version to support if "RECOMMENDED", since the choice of which version to support if
only one is supported will depend on the needs of clients, which only one is supported will depend on the needs of clients, which
may be slow to adopt the updated version. may be slow to adopt the updated version.
o In all of the cases above, it is appropriate that the old version o In all of the cases above, it is appropriate that the old version
of the feature, be considered obsolescent, with the expectation of the feature, be considered obsolescent, with the expectation
that the working group might, in a later minor version, decide that the working group might, in a later minor version, decide
that the older version is to become mandatory to not implement. that the older version is to become mandatory to not implement.
Issues related to the effect of XDR corrections on existing Issues related to the effect of XDR corrections on existing
documents, including co-ordination with other minor versions, are documents, including co-ordination with other minor versions, are
discussed in Section 10.1. discussed in Section 11.2.
By doing things this way, the protocol with the XDR modification can By doing things this way, the protocol with the XDR modification can
accommodate clients and servers that support either the corrected or accommodate clients and servers that support either the corrected or
the uncorrected version of the protocol and also clients and servers the uncorrected version of the protocol and also clients and servers
aware of and capable of supporting both alternatives. aware of and capable of supporting both alternatives.
o A client that supports only the earlier version of the feature o A client that supports only the earlier version of the feature
(i.e., an older unfixed client) can determine whether the server (i.e., an older unfixed client) can determine whether the server
it is connecting to supports the older version of feature. It is it is connecting to supports the older version of feature. It is
capable of interoperating with older servers that support only the capable of interoperating with older servers that support only the
skipping to change at page 29, line 26 skipping to change at page 52, line 44
o A server that supports only the earlier version of the feature o A server that supports only the earlier version of the feature
(i.e., an older unfixed server) can only successfully interoperate (i.e., an older unfixed server) can only successfully interoperate
with older clients. However newer clients can easily determine with older clients. However newer clients can easily determine
that the feature cannot be used on that server. that the feature cannot be used on that server.
o A server that supports only the newer version of the feature o A server that supports only the newer version of the feature
(i.e., a new or updated server) can only successfully interoperate (i.e., a new or updated server) can only successfully interoperate
with newer clients. However, older clients can easily determine with newer clients. However, older clients can easily determine
that the feature cannot be used on that server. In the case of that the feature cannot be used on that server. In the case of
non-required features, clients can be expected to deal with non- OPTIONAL features, clients can be expected to deal with non-
support of that particular feature. support of that particular feature.
o A server that supports both the older and newer versions of the o A server that supports both the older and newer versions of the
feature can interoperate with all client variants. feature can interoperate with all client variants.
By using extensions in this manner, the protocol creates a clear path By using extensions in this manner, the protocol creates a clear path
which preserves the functioning of existing clients and servers and which preserves the functioning of existing clients and servers and
allowing client and server implementers to adopt the new version of allowing client and server implementers to adopt the new version of
the feature at a reasonable pace. the feature at a reasonable pace.
10.1. Documentation of XDR Changes 11.2. Documentation of XDR Changes
In the event of an XDR correction, as discussed above, some document In the event of an XDR correction, as discussed above, some document
updates will be required. For the purposes of this discussion we updates will be required. For the purposes of this discussion we
call the minor version for which XDR correction is required minor call the minor version for which XDR correction is required minor
version X and the minor version on which development is occurring version X and the minor version on which development is occurring
minor version Y. minor version Y.
The following discusses the specific updated documents which could be The following discusses the specific updated documents which could be
required: required:
skipping to change at page 30, line 35 skipping to change at page 54, line 5
based on the most recent such document associated with minor based on the most recent such document associated with minor
version Y and will serve as the basis for later XDR assignment version Y and will serve as the basis for later XDR assignment
drafts for minor version Y. drafts for minor version Y.
The informational RFC's associated with minor version Y (version The informational RFC's associated with minor version Y (version
indexing document and XDR assignment document) will contain the indexing document and XDR assignment document) will contain the
effects of the correction when published. Similarly, the minor effects of the correction when published. Similarly, the minor
version specification RFC will contain the XDR changes associated version specification RFC will contain the XDR changes associated
with the correction. with the correction.
11. Security Considerations 12. Security Considerations
Since no substantive protocol changes are proposed here, no security Since no substantive protocol changes are proposed here, no security
considerations apply. considerations apply.
As features and minor versions are designed and specified in As features and minor versions are designed and specified in
standards-track documents, their security issues will be addressed standards-track documents, their security issues will be addressed
and each RFC candidate will receive the appropriate security review and each RFC candidate will receive the appropriate security review
from the NFSv4 working group and IESG. from the NFSv4 working group and IESG.
12. IANA Considerations 13. IANA Considerations
The current document does not require any actions by IANA. The current document does not require any actions by IANA.
Depending on decisions that the working group makes about how to Depending on decisions that the working group makes about how to
address the issues raised in this document, future documents may address the issues raised in this document, future documents may
require actions by IANA. require actions by IANA.
13. References 14. References
13.1. Normative References 14.1. Normative References
[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, March 1997. Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
13.2. Informative References 14.2. Informative References
[NFSv42] Haynes, T., Ed., "NFS Version 4 Minor Version 2", April [NFSv42] Haynes, T., Ed., "NFS Version 4 Minor Version 2",
2015, <http://www.ietf.org/id/ September 2015, <http://www.ietf.org/id/
draft-ietf-nfsv4-minorversion2-38.txt>. draft-ietf-nfsv4-minorversion2-39.txt>.
Work in progress. Work in progress.
[NFSv42-dot-x] [NFSv42-dot-x]
Haynes, T., Ed., "NFS Version 4 Minor Version 2 Protocol Haynes, T., Ed., "NFS Version 4 Minor Version 2 Protocol
External Data Representation Standard (XDR) Description", External Data Representation Standard (XDR) Description",
April 2015, <http://www.ietf.org/id/ September 2015, <http://www.ietf.org/id/
draft-ietf-nfsv4-minorversion2-dot-x-38.txt>. draft-ietf-nfsv4-minorversion2-dot-x-39.txt>.
Work in progress. Work in progress.
[RFC3530] Shepler, S., Callaghan, B., Robinson, D., Thurlow, R., [RFC3530] Shepler, S., Callaghan, B., Robinson, D., Thurlow, R.,
Beame, C., Eisler, M., and D. Noveck, "Network File System Beame, C., Eisler, M., and D. Noveck, "Network File System
(NFS) version 4 Protocol", RFC 3530, April 2003. (NFS) version 4 Protocol", RFC 3530, DOI 10.17487/RFC3530,
April 2003, <http://www.rfc-editor.org/info/rfc3530>.
[RFC5661] Shepler, S., Eisler, M., and D. Noveck, "Network File [RFC5661] Shepler, S., Ed., Eisler, M., Ed., and D. Noveck, Ed.,
System (NFS) Version 4 Minor Version 1 Protocol", RFC "Network File System (NFS) Version 4 Minor Version 1
5661, January 2010. Protocol", RFC 5661, DOI 10.17487/RFC5661, January 2010,
<http://www.rfc-editor.org/info/rfc5661>.
[RFC5662] Shepler, S., Eisler, M., and D. Noveck, "Network File [RFC5662] Shepler, S., Ed., Eisler, M., Ed., and D. Noveck, Ed.,
System (NFS) Version 4 Minor Version 1 External Data "Network File System (NFS) Version 4 Minor Version 1
Representation Standard (XDR) Description", RFC 5662, External Data Representation Standard (XDR) Description",
January 2010. RFC 5662, DOI 10.17487/RFC5662, January 2010,
<http://www.rfc-editor.org/info/rfc5662>.
[RFC5663] Black, D., Fridella, S., and J. Glasgow, "Parallel NFS [RFC5663] Black, D., Fridella, S., and J. Glasgow, "Parallel NFS
(pNFS) Block/Volume Layout", RFC 5663, January 2010. (pNFS) Block/Volume Layout", RFC 5663,
DOI 10.17487/RFC5663, January 2010,
<http://www.rfc-editor.org/info/rfc5663>.
[RFC5664] Halevy, B., Welch, B., and J. Zelenka, "Object-Based [RFC5664] Halevy, B., Welch, B., and J. Zelenka, "Object-Based
Parallel NFS (pNFS) Operations", RFC 5664, January 2010. Parallel NFS (pNFS) Operations", RFC 5664,
DOI 10.17487/RFC5664, January 2010,
<http://www.rfc-editor.org/info/rfc5664>.
[RFC7530] Haynes, T. and D. Noveck, "Network File System (NFS) [RFC7530] Haynes, T., Ed. and D. Noveck, Ed., "Network File System
Version 4 Protocol", RFC 7530, March 2015. (NFS) Version 4 Protocol", RFC 7530, DOI 10.17487/RFC7530,
March 2015, <http://www.rfc-editor.org/info/rfc7530>.
[RFC7531] Haynes, T. and D. Noveck, "Network File System (NFS) [RFC7531] Haynes, T., Ed. and D. Noveck, Ed., "Network File System
Version 4 External Data Representation Standard (XDR) (NFS) Version 4 External Data Representation Standard
Description", RFC 7531, March 2015. (XDR) Description", RFC 7531, DOI 10.17487/RFC7531, March
2015, <http://www.rfc-editor.org/info/rfc7531>.
Author's Address Appendix A. Acknowledgements
The author wishes to thank Tom Haynes of Primary Data for his role in
getting this effort started and his work in co-authoring the first
version of this document.
The author also wishes to thank Chuck Lever of Oracle for his
thorough document review and many helpful suggestions.
Author's Address
David Noveck David Noveck
Hewlett-Packard Hewlett-Packard
165 Dascomb Road 165 Dascomb Road
Andover, MA 01810 Andover, MA 01810
US US
Phone: +1 978 474 2011 Phone: +1 978 474 2011
Email: davenoveck@gmail.com Email: davenoveck@gmail.com
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