Internet DRAFT - draft-haynes-nfsv4-minorversioning
draft-haynes-nfsv4-minorversioning
NFSv4 T. Haynes
Internet-Draft NetApp
Intended status: Standards Track November 08, 2013
Expires: May 12, 2014
Minor versioning Rules for NFSv4
draft-haynes-nfsv4-minorversioning-00
Abstract
This document specifies the minor versioning rules for NFSv4. It
also specifices how those minor versioning rules may be modified.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 12, 2014.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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publication of this document. Please review these documents
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include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Modifying the minor version rules . . . . . . . . . . . . . . 2
4. The minor versioning rules . . . . . . . . . . . . . . . . . 3
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.1. Normative References . . . . . . . . . . . . . . . . . . 6
7.2. Informative References . . . . . . . . . . . . . . . . . 6
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 6
Appendix B. RFC Editor Notes . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
To address the requirement of an NFS protocol that can evolve as the
need arises, the Network File System (NFS) version 4 (NFSv4) protocol
contains the rules and framework to allow for future minor changes or
versioning.
The base assumption with respect to minor versioning is that any
future accepted minor version will be documented in one or more
Standards Track RFCs. Minor version 0 of the NFSv4 protocol is
represented by [RFC3530], minor version 1 by [RFC5661], and minor
version 2 by [NFSv42]. The COMPOUND (see Section 14.2 of [RFC3530])
and CB_COMPOUND (see Section 15.2 of [RFC3530]) procedures support
the encoding of the minor version being requested by the client.
2. Terminology
A basic familarity with the NFSv4 terminology is assumed in this
document, the reader is pointed to [RFC3530].
3. Modifying the minor version rules
The minor versioning rules had been being maintained inside the
various Standards Track RFCs, which had the impact of the minor
versioning rules being modified as needed per release of the minor
versions. The rules for minor versions SHOULD stand outside the
minor versions and be tracked by their own Standard Track RFCs. As
such, all modifications to the minor versioning rules MUST be
documented not in the minor version documents, but in Standard Track
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RFCs which are focused entirely on the minor versioning rules
themselves.
4. The minor versioning rules
The following items represent the basic rules for the development of
minor versions.
1. Procedures are not added or deleted.
To maintain the general Remote Procedure Call (RPC) model, NFSv4
minor versions will not add to or delete procedures from the NFS
program.
2. Minor versions may add operations to the COMPOUND and
CB_COMPOUND procedures.
The addition of operations to the COMPOUND and CB_COMPOUND
procedures does not affect the RPC model.
* Minor versions may append attributes to the bitmap4 that
represents sets of attributes and to the fattr4 that
represents sets of attribute values.
This allows for the expansion of the attribute model to allow
for future growth or adaptation.
* Minor version X must append any new attributes after the last
documented attribute.
Since attribute results are specified as an opaque array of
per-attribute, XDR-encoded results, the complexity of adding
new attributes in the midst of the current definitions would
be too burdensome.
3. Minor versions must not modify the structure of an existing
operation's arguments or results.
Again, the complexity of handling multiple structure definitions
for a single operation is too burdensome. New operations should
be added instead of modifying existing structures for a minor
version.
This rule does not preclude the following adaptations in a minor
version:
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* adding bits to flag fields, such as new attributes to
GETATTR's bitmap4 data type, and providing corresponding
variants of opaque arrays, such as a notify4 used together
with such bitmaps
* adding bits to existing attributes like Access Control Lists
(ACL) that have flag words
* extending enumerated types (including NFS4ERR_*) with new
values
* adding cases to a switched union
4. Note that when adding new cases to a switched union, a minor
version must not make new cases be REQUIRED. While the
encapsulating operation may be REQUIRED, the new cases (the
specific arm of the discriminated union) is not. The error code
NFS4ERR_UNION_NOTSUPP is used to notify the client when the
server does not support such a case.
5. Minor versions must not modify the structure of existing
attributes.
6. Minor versions must not delete operations.
This prevents the potential reuse of a particular operation
"slot" in a future minor version.
7. Minor versions must not delete attributes.
8. Minor versions must not delete flag bits or enumeration values.
9. Minor versions may declare an operation MUST NOT be implemented.
Specifying that an operation MUST NOT be implemented is
equivalent to obsoleting an operation. For the client, it means
that the operation MUST NOT be sent to the server. For the
server, an NFS error can be returned as opposed to "dropping"
the request as an XDR decode error. This approach allows for
the obsolescence of an operation while maintaining its structure
so that a future minor version can reintroduce the operation.
1. Minor versions may declare that an attribute MUST NOT be
implemented.
2. Minor versions may declare that a flag bit or enumeration
value MUST NOT be implemented.
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10. Minor versions may declare an operation to be OBSOLESCENT, which
indicates an intention to remove the operation (i.e., make it
MANDATORY TO NOT implement) in a subsequent minor version. Such
labeling is separate from the question of whether the operation
is REQUIRED or RECOMMENDED or OPTIONAL in the current minor
version. An operation may be both REQUIRED for the given minor
version and marked OBSOLESCENT, with the expectation that it
will be MANDATORY TO NOT implement in the next (or other
subsequent) minor version.
11. Note that the early notification of operation obsolescence is
put in place to mitigate the effects of design and
implementation mistakes, and to allow protocol development to
adapt to unexpected changes in the pace of implementation. Even
if an operation is marked OBSOLESCENT in a given minor version,
it may end up not being marked MANDATORY TO NOT implement in the
next minor version. In unusual circumstances, it might not be
marked OBSOLESCENT in a subsequent minor version, and never
become MANDATORY TO NOT implement.
12. Minor versions may downgrade features from REQUIRED to
RECOMMENDED, from RECOMMENDED to OPTIONAL, or from OPTIONAL to
MANDATORY TO NOT implement. Also, if a feature was marked as
OBSOLESCENT in the prior minor version, it may be downgraded
from REQUIRED to OPTIONAL from RECOMMENDED to MANDATORY TO NOT
implement, or from REQUIRED to MANDATORY TO NOT implement.
13. Minor versions may upgrade features from OPTIONAL to
RECOMMENDED, or RECOMMENDED to REQUIRED. Also, if a feature was
marked as OBSOLESCENT in the prior minor version, it may be
upgraded to not be OBSOLESCENT.
14. A client and server that support minor version X SHOULD support
minor versions 0 through X-1 as well.
15. Except for infrastructural changes, a minor version must not
introduce REQUIRED new features.
This rule allows for the introduction of new functionality and
forces the use of implementation experience before designating a
feature as REQUIRED. On the other hand, some classes of
features are infrastructural and have broad effects. Allowing
infrastructural features to be RECOMMENDED or OPTIONAL
complicates implementation of the minor version.
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16. A client MUST NOT attempt to use a stateid, filehandle, or
similar returned object from the COMPOUND procedure with minor
version X for another COMPOUND procedure with minor version Y,
where X != Y.
5. Security Considerations
There are no security considerations in this document.
6. IANA Considerations
There are no IANA considerations in this document.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", March 1997.
[RFC3530] Shepler, S., Callaghan, B., Robinson, D., Thurlow, R.,
Beame, C., Eisler, M., and D. Noveck, "Network File System
(NFS) version 4 Protocol", RFC 3530, April 2003.
[RFC5661] Shepler, S., Eisler, M., and D. Noveck, "Network File
System (NFS) Version 4 Minor Version 1 Protocol", RFC
5661, January 2010.
7.2. Informative References
[NFSv42] Haynes, T., "NFS Version 4 Minor Version 2", draft-ietf-
nfsv4-minorversion2-20 (Work In Progress), August 2013.
Appendix A. Acknowledgments
Appendix B. RFC Editor Notes
[RFC Editor: please remove this section prior to publishing this
document as an RFC]
[RFC Editor: prior to publishing this document as an RFC, please
replace all occurrences of RFCTBD10 with RFCxxxx where xxxx is the
RFC number of this document]
Author's Address
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Thomas Haynes
NetApp
495 E Java Dr
Sunnyvale, CA 95054
USA
Phone: +1 408 419 3018
Email: thomas@netapp.com
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