< draft-farrel-pce-stateful-flags-00.txt   draft-farrel-pce-stateful-flags-01.txt >
PCE Working Group A. Farrel PCE Working Group A. Farrel
Internet-Draft Old Dog Consulting Internet-Draft Old Dog Consulting
Updates: 8231 (if approved) June 24, 2019 Updates: 8231 (if approved) August 16, 2019
Intended status: Standards Track Intended status: Standards Track
Expires: December 26, 2019 Expires: February 17, 2020
Updated Rules for Processing Stateful PCE Request Parameters Flags Updated Rules for Processing Stateful PCE Request Parameters Flags
draft-farrel-pce-stateful-flags-00 draft-farrel-pce-stateful-flags-01
Abstract Abstract
Extensions to the Path Computation Element communications Protocol Extensions to the Path Computation Element communications Protocol
(PCEP) to support stateful Path Computation Elements (PCEs) are (PCEP) to support stateful Path Computation Elements (PCEs) are
defined in RFC 8231. One of the extensions is the Stateful PCE defined in RFC 8231. One of the extensions is the Stateful PCE
Request Parameters (SRP) object. That object includes a Flags field Request Parameters (SRP) object. That object includes a Flags field
that is a set of 32 bit flags, and RFC 8281 defines an IANA registry that is a set of 32 bit flags, and RFC 8281 defines an IANA registry
for tracking assigned flags. However, RFC 8231 does not explain how for tracking assigned flags. However, RFC 8231 does not explain how
an implementation should set unassigned flags in transmitted an implementation should set unassigned flags in transmitted
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
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This Internet-Draft will expire on December 26, 2019. This Internet-Draft will expire on February 17, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Updated Procedures . . . . . . . . . . . . . . . . . . . . . 3 3. Updated Procedures . . . . . . . . . . . . . . . . . . . . . 3
4. Compatibliity Considerations . . . . . . . . . . . . . . . . 3 4. Compatibility Considerations . . . . . . . . . . . . . . . . 3
5. Management Considerations . . . . . . . . . . . . . . . . . . 4 5. Implementation Status . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4 6. Management Considerations . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 7. Security Considerations . . . . . . . . . . . . . . . . . . . 4
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
9.1. Normative References . . . . . . . . . . . . . . . . . . 4 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
9.2. Informative References . . . . . . . . . . . . . . . . . 5 10.1. Normative References . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5 10.2. Informative References . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction 1. Introduction
[RFC5440] describes the Path Computation Element Communication [RFC5440] describes the Path Computation Element Communication
Protocol (PCEP). PCEP defines the communication between a Path Protocol (PCEP). PCEP defines the communication between a Path
Computation Client (PCC) and a Path Computation Element (PCE), or Computation Client (PCC) and a Path Computation Element (PCE), or
between PCEs, enabling computation of Multiprotocol Label Switching between PCEs, enabling computation of Multiprotocol Label Switching
(MPLS) for Traffic Engineering Label Switched Path (TE LSP) (MPLS) for Traffic Engineering Label Switched Path (TE LSP)
characteristics. characteristics.
skipping to change at page 3, line 27 skipping to change at page 3, line 29
Flags (32 bits): None defined yet. Flags (32 bits): None defined yet.
This document updates that text as follows: This document updates that text as follows:
Flags (32 bits): This document does not define any flags. Flags (32 bits): This document does not define any flags.
Unassigned flags MUST be set to zero on transmission and MUST be Unassigned flags MUST be set to zero on transmission and MUST be
ignored on receipt. Implementations that do not understand any ignored on receipt. Implementations that do not understand any
particular flag MUST ignore the flag. particular flag MUST ignore the flag.
4. Compatibliity Considerations 4. Compatibility Considerations
While one of the main objectives of the changes made by this document While one of the main objectives of the changes made by this document
is to enable backward compatibility, there remains an issue of is to enable backward compatibility, there remains an issue of
compatiblity between existing implementations of RFC 8231 and compatibility between existing implementations of RFC 8231 and
implementations that are consistent with this document. implementations that are consistent with this document.
It should be noted that common behavior for flags fields is as
described by the updated text presented in Section 3 so many
implementations, lacking guidance from RFC 8231, will still have
implemented a consistent and future-proof approach. However, for
completeness it is worth noting how behaviors might interact between
implementations.
SRP objects generated by an implementation of this document will set SRP objects generated by an implementation of this document will set
all unknown flag bits to zero and will therefore cause no issues to all unknown flag bits to zero and will therefore cause no issues to
an older implementation even if it inspects those bits. Similarly, an older implementation even if it inspects those bits. Similarly,
an implementation of this document will not inspect any unknow flag an implementation of this document will not inspect any unknown flag
bits and so will be unaffected by older implementations no matter how bits and so will be unaffected by older implementations no matter how
they set the flags. they set the flags.
There will remain an issue with compatibility between implementations There will remain an issue with compatibility between implementations
of RFC 8231 that might set any of the unassigned flags, and current of RFC 8231 that might set any of the unassigned flags, and current
(such as [RFC8281]) and future (such as (such as [RFC8281]) and future (such as
[I-D.ietf-pce-lsp-control-request]) specifications. That problem [I-D.ietf-pce-lsp-control-request]) specifications. That problem
cannot be fixed in old implementations by any amount of cannot be fixed in old implementations by any amount of
documentation, and can only be handled for future specifications by documentation, and can only be handled for future specifications by
obsoleting the Flags field and using a new technique. Fortunatley, obsoleting the Flags field and using a new technique. Fortunately,
however, most implementations will have been constructed to set however, most implementations will have been constructed to set
unused flags to zero which is consistent with the behavior described unused flags to zero which is consistent with the behavior described
in this document. in this document.
5. Management Considerations 5. Implementation Status
[NOTE TO RFC EDITOR: Please remove this section before publication as
an RFC.]
While this document describes changes to [RFC8231] that are important
for implementation, and while the document gives advice to
implementations, there is nothing specific in this document to
implement.
A private and unscientific poll of implementers of RFC 8231 conducted
by the author suggests that existing implementations already abide by
the modification set out in this document.
6. Management Considerations
Implementations receiving set SRP flags that they do not recognize Implementations receiving set SRP flags that they do not recognize
MAY log the fact. That could be helpful for diagnosing backward MAY log the fact. That could be helpful for diagnosing backward
compatiblity issues with future features that utilise those flags. compatibility issues with future features that utilize those flags.
6. Security Considerations 7. Security Considerations
[RFC8231] sets out security considerations for PCEP when used for [RFC8231] sets out security considerations for PCEP when used for
communication with a stateful PCE. This document does not change communication with a stateful PCE. This document does not change
those considerations. those considerations.
However, by defining the expected behavior of implementations, this However, by defining the expected behavior of implementations, this
document may improve the stability of networks and so reduce the document may improve the stability of networks and so reduce the
attack surface. attack surface.
7. IANA Considerations 8. IANA Considerations
This document makes no requests for IANA action. This document makes no requests for IANA action.
8. Acknowledgements 9. Acknowledgements
Thanks to the authors of [I-D.ietf-pce-lsp-control-request] for Thanks to the authors of [I-D.ietf-pce-lsp-control-request] for
exposing the need for this work. Thanks to Dhruv Dhody and Julien exposing the need for this work. Thanks to Dhruv Dhody and Julien
Meuric for discussing the solution. Meuric for discussing the solution.
9. References 10. References
9.1. Normative References 10.1. 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, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
skipping to change at page 5, line 11 skipping to change at page 5, line 30
Extensions for Stateful PCE", RFC 8231, Extensions for Stateful PCE", RFC 8231,
DOI 10.17487/RFC8231, September 2017, DOI 10.17487/RFC8231, September 2017,
<https://www.rfc-editor.org/info/rfc8231>. <https://www.rfc-editor.org/info/rfc8231>.
[RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path [RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path
Computation Element Communication Protocol (PCEP) Computation Element Communication Protocol (PCEP)
Extensions for PCE-Initiated LSP Setup in a Stateful PCE Extensions for PCE-Initiated LSP Setup in a Stateful PCE
Model", RFC 8281, DOI 10.17487/RFC8281, December 2017, Model", RFC 8281, DOI 10.17487/RFC8281, December 2017,
<https://www.rfc-editor.org/info/rfc8281>. <https://www.rfc-editor.org/info/rfc8281>.
9.2. Informative References 10.2. Informative References
[I-D.ietf-pce-lsp-control-request] [I-D.ietf-pce-lsp-control-request]
Raghuram, A., Goddard, A., Karthik, J., Sivabalan, S., and Raghuram, A., Goddard, A., Karthik, J., Sivabalan, S., and
M. Negi, "Ability for a stateful Path Computation Element M. Negi, "Ability for a Stateful Path Computation Element
(PCE) to request and obtain control of a Label Switched (PCE) to request and obtain control of a Label Switched
Path (LSP)", draft-ietf-pce-lsp-control-request-05 (work Path (LSP)", draft-ietf-pce-lsp-control-request-07 (work
in progress), June 2019. in progress), August 2019.
[RFC4657] Ash, J., Ed. and J. Le Roux, Ed., "Path Computation [RFC4657] Ash, J., Ed. and J. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol Generic Element (PCE) Communication Protocol Generic
Requirements", RFC 4657, DOI 10.17487/RFC4657, September Requirements", RFC 4657, DOI 10.17487/RFC4657, September
2006, <https://www.rfc-editor.org/info/rfc4657>. 2006, <https://www.rfc-editor.org/info/rfc4657>.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440, Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009, DOI 10.17487/RFC5440, March 2009,
<https://www.rfc-editor.org/info/rfc5440>. <https://www.rfc-editor.org/info/rfc5440>.
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