PCE Working Group C. Li
Internet-Draft H. Zheng
Intended status: Standards Track Huawei Technologies
Expires: 1 March 2025 S. Sivabalan
Ciena
S. Sidor
Z. Ali
Cisco Systems, Inc.
28 August 2024
Conveying Vendor-Specific Information in the Path Computation Element
(PCE) Communication Protocol (PCEP) extensions for Stateful PCE.
draft-ietf-pce-stateful-pce-vendor-07
Abstract
A Stateful Path Computation Element (PCE) maintains information on
the current network state, including computed Label Switched Path
(LSPs), reserved resources within the network, and the pending path
computation requests. This information may then be considered when
computing new traffic-engineered LSPs, and for any associated and
dependent LSPs, received from a Path Computation Client (PCC).
RFC 7470 defines a facility to carry vendor-specific information in
stateless PCE Communication Protocol (PCEP) messages.
This document extends this capability for the Stateful PCEP messages.
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
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 1 March 2025.
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Copyright Notice
Copyright (c) 2024 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 (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
1.2. Use of RBNF . . . . . . . . . . . . . . . . . . . . . . . 3
2. Procedures for the Vendor Information Object . . . . . . . . 4
3. Procedures for the Vendor Information TLV . . . . . . . . . . 6
4. Manageability Considerations . . . . . . . . . . . . . . . . 6
4.1. Control of Function and Policy . . . . . . . . . . . . . 7
4.2. Information and Data Models . . . . . . . . . . . . . . . 7
4.3. Liveness Detection and Monitoring . . . . . . . . . . . . 7
4.4. Verifying Correct Operations . . . . . . . . . . . . . . 7
4.5. Requirements On Other Protocols . . . . . . . . . . . . . 7
4.6. Impact On Network Operations . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
6. Implementation Status . . . . . . . . . . . . . . . . . . . . 8
6.1. Cisco Systems . . . . . . . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . 10
Appendix A. Contributor Addresses . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
The Path Computation Element Communication Protocol (PCEP) [RFC5440]
provides mechanisms for a Path Computation Element (PCE) to perform
path computation in response to a Path Computation Client (PCC)
request.
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A Stateful PCE is capable of considering, for the purposes of the
path computation, not only the network state in terms of links and
nodes (referred to as the Traffic Engineering Database or TED) but
also the status of active services (previously computed paths, and
currently reserved resources, stored in the Label Switched Paths
Database (LSP-DB)). [RFC8051] describes general considerations for a
Stateful PCE deployment and examines its applicability and benefits,
as well as its challenges and limitations through a number of use
cases.
[RFC8231] describes a set of extensions to PCEP to provide stateful
control. A Stateful PCE has access to not only the information
carried by the network's Interior Gateway Protocol (IGP), but also
the set of active paths and their reserved resources for its
computations. The additional state allows the PCE to compute
constrained paths while considering individual LSPs and their
interactions. [RFC8281] describes the setup, maintenance, and
teardown of PCE-initiated LSPs under the Stateful PCE model. These
extensions add new messages in PCEP for Stateful PCE.
[RFC7470] defines the Vendor Information object that can be used to
carry arbitrary, proprietary information such as vendor-specific
constraints in stateless PCEP. It also defines the VENDOR-
INFORMATION-TLV that can be used to carry arbitrary information
within any existing or future PCEP object that supports TLVs.
The Vendor Information Object and the VENDOR-INFORMATION-TLV are also
valuable in the Stateful PCE model. The VENDOR-INFORMATION-TLV can
be included within any of the new objects introduced in PCEP for
Stateful PCE as defined in [RFC7470]. This document extends stateful
PCEP messages to incorporate the Vendor Information Object.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
1.2. Use of RBNF
The message formats in this document are illustrated using Routing
Backus-Naur Form (RBNF) encoding, as specified in [RFC5511]. The use
of RBNF is illustrative only and may elide certain important details;
the normative specification of messages is found in the prose
description. If there is any divergence between the RBNF and the
prose, the prose is considered authoritative.
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2. Procedures for the Vendor Information Object
A Path Computation LSP State Report message (also referred to as
PCRpt message) [RFC8231] is a PCEP message sent by a PCC to a PCE to
report the current state of an LSP. A PCC that wants to convey
proprietary or vendor-specific information or metrics to a PCE does
so by including a Vendor Information object in the PCRpt message.
The contents and format of the object, including the VENDOR-
INFORMATION object and the VENDOR-INFORMATION-TLV, are described in
Section 4 of [RFC7470]. The PCE determines how to interpret the
information in the Vendor Information object by examining the
Enterprise Number it contains.
The Vendor Information object is OPTIONAL in a PCRpt message.
Multiple instances of the object MAY be contained in a single PCRpt
message. Different instances of the object MAY have different
Enterprise Numbers.
The message formats in this document are specified using Routing
Backus-Naur Format (RBNF) encoding as specified in [RFC5511].
The format of the PCRpt message (with [RFC8231] as the base) is
updated as follows:
<PCRpt Message> ::= <Common Header>
<state-report-list>
Where:
<state-report-list> ::= <state-report>[<state-report-list>]
<state-report> ::= [<SRP>]
<LSP>
<path>
[<vendor-info-list>]
Where:
<vendor-info-list> ::= <VENDOR-INFORMATION>
[<vendor-info-list>]
<path> is defined in [RFC8231].
A Path Computation LSP Update Request message (also referred to as
PCUpd message) [RFC8231] is a PCEP message sent by a PCE to a PCC to
update the attributes of an LSP. The Vendor Information object can
be included in a PCUpd message to convey proprietary or vendor-
specific information.
The format of the PCUpd message (with [RFC8231] as the base) is
updated as follows:
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<PCUpd Message> ::= <Common Header>
<update-request-list>
Where:
<update-request-list> ::= <update-request>
[<update-request-list>]
<update-request> ::= <SRP>
<LSP>
<path>
[<vendor-info-list>]
Where:
<vendor-info-list> ::= <VENDOR-INFORMATION>
[<vendor-info-list>]
<path> is defined in [RFC8231].
A Path Computation LSP Initiate Message (also referred to as
PCInitiate message) [RFC8281] is a PCEP message sent by a PCE to a
PCC to trigger an LSP instantiation or deletion. The Vendor
Information object can be included in a PCInitiate message to convey
proprietary or vendor-specific information.
The format of the PCInitiate message (with [RFC8281] as the base) is
updated as follows:
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<PCInitiate Message> ::= <Common Header>
<PCE-initiated-lsp-list>
Where:
<PCE-initiated-lsp-list> ::= <PCE-initiated-lsp-request>
[<PCE-initiated-lsp-list>]
<PCE-initiated-lsp-request> ::=
(<PCE-initiated-lsp-instantiation>|
<PCE-initiated-lsp-deletion>)
<PCE-initiated-lsp-instantiation> ::= <SRP>
<LSP>
[<END-POINTS>]
<ERO>
[<attribute-list>]
[<vendor-info-list>]
Where:
<vendor-info-list> ::= <VENDOR-INFORMATION>
[<vendor-info-list>]
<PCE-initiated-lsp-deletion> and <attribute-list> is as per
[RFC8281].
A legacy implementation that does not recognize the Vendor
Information object will act according to the procedures set out in
[RFC8231] and [RFC8281]. An implementation that supports the Vendor
Information object, but receives one carrying an Enterprise Number
that it does not support, MUST ignore the object in the same way as
described in [RFC7470].
3. Procedures for the Vendor Information TLV
The Vendor Information TLV can be used to carry vendor-specific
information that applies to a specific PCEP object by including the
TLV in the object. This includes objects used in Stateful PCE
extensions such as Stateful PCE Request Parameter (SRP) and LSP
objects. All the procedures are as per section 3 of [RFC7470].
4. Manageability Considerations
All manageability requirements and considerations listed in
[RFC5440], [RFC7470], [RFC8231], and [RFC8281] apply to PCEP protocol
extensions defined in this document. In addition, the requirements
and considerations listed in this section apply.
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4.1. Control of Function and Policy
The requirements for control of function and policy for vendor-
specific information as set out in [RFC7470] continue to apply to
Stateful PCEP extensions specified in this document.
4.2. Information and Data Models
The PCEP YANG module is specified in [I-D.ietf-pce-pcep-yang]. Any
standard YANG module will not include details of vendor-specific
information.
4.3. Liveness Detection and Monitoring
Mechanisms defined in this document do not imply any new liveness
detection and monitoring requirements in addition to those already
listed in [RFC5440].
4.4. Verifying Correct Operations
Mechanisms defined in this document do not imply any new operation
verification requirements in addition to those already listed in
[RFC5440] and [RFC8231].
4.5. Requirements On Other Protocols
Mechanisms defined in this document do not imply any new requirements
on other protocols.
4.6. Impact On Network Operations
Mechanisms defined in [RFC5440] and [RFC8231] also apply to PCEP
extensions defined in this document.
Section 6.6 of [RFC7470] highlights how the presence of additional
vendor-specific information in PCEP messages may congest the
operations and how to detect and handle it. A similar approach
SHOULD be considered for Stateful PCEP messages and for a PCE.
Encoding optimization for the Vendor Information Object, for example,
in case of the object with the same content encoded for multiple
LSPs, is considered out of the scope of this document and may be
proposed in the future as a separate document applicable to other
PCEP objects.
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5. IANA Considerations
There are no IANA actions in this document, only a clarification.
[RFC7470] defines the Enterprise Numbers allocated by IANA and
managed through an IANA registry [RFC2578]. This document clarifies
the Private Enterprise Numbers (PEN) as described in the IANA
registry. The registration procedures and the registry location are
described by [RFC9371].
6. Implementation Status
[NOTE TO RFC EDITOR : This whole section and the reference to RFC
7942 is to be removed before publication as an RFC]
This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in [RFC7942].
The description of implementations in this section is intended to
assist the IETF in its decision processes in progressing drafts to
RFCs. Please note that the listing of any individual implementation
here does not imply endorsement by the IETF. Furthermore, no effort
has been spent to verify the information presented here that was
supplied by IETF contributors. This is not intended as, and must not
be construed to be, a catalog of available implementations or their
features. Readers are advised to note that other implementations may
exist.
According to [RFC7942], "this will allow reviewers and working groups
to assign due consideration to documents that have the benefit of
running code, which may serve as evidence of valuable experimentation
and feedback that have made the implemented protocols more mature.
It is up to the individual working groups to use this information as
they see fit".
6.1. Cisco Systems
* Organization: Cisco Systems, Inc.
* Implementation: Cisco IOS-XR PCE and PCC
* Description: Vendor Information Object used in PCRpt, PCUpd and
PCInitiate messages.
* Maturity Level: Production
* Coverage: Full
* Contact: ssidor@cisco.com
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7. Security Considerations
The protocol extensions defined in this document do not change the
nature of PCEP. Therefore, the security considerations set out in
[RFC5440], [RFC7470], [RFC8231] and [RFC8281] apply unchanged.
As per [RFC8231] it is RECOMMENDED that these PCEP extensions only be
activated on authenticated and encrypted sessions across PCEs and
PCCs using Transport Layer Security (TLS) [RFC8253], as per the
recommendations and best current practices in RFC 9325 [BCP195]
(unless explicitly set aside in [RFC8253]).
The use of vendor-specific information as defined in [RFC7470] and in
this document may provide a covert channel that could be misused by
PCEP speaker implementations or by malign software at PCEP speakers.
There is little protection against this, however, an operator that
monitors the PCEP sessions can determine that vendor-specific
information is being used and ask their suppliers (the PCE and PCC
implementers) to provide a mechanism to decode the vendor-specific
information.
8. Acknowledgments
Thanks to Adrian Farrel, Avantika, Mahendra Singh Negi, Udayasree
Palle, and Swapna K for their suggestions.
9. References
9.1. Normative References
[BCP195] Best Current Practice 195,
<https://www.rfc-editor.org/info/bcp195>.
At the time of writing, this BCP comprises the following:
Moriarty, K. and S. Farrell, "Deprecating TLS 1.0 and TLS
1.1", BCP 195, RFC 8996, DOI 10.17487/RFC8996, March 2021,
<https://www.rfc-editor.org/info/rfc8996>.
Sheffer, Y., Saint-Andre, P., and T. Fossati,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 9325, DOI 10.17487/RFC9325, November
2022, <https://www.rfc-editor.org/info/rfc9325>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
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[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009,
<https://www.rfc-editor.org/info/rfc5440>.
[RFC5511] Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax
Used to Form Encoding Rules in Various Routing Protocol
Specifications", RFC 5511, DOI 10.17487/RFC5511, April
2009, <https://www.rfc-editor.org/info/rfc5511>.
[RFC7470] Zhang, F. and A. Farrel, "Conveying Vendor-Specific
Constraints in the Path Computation Element Communication
Protocol", RFC 7470, DOI 10.17487/RFC7470, March 2015,
<https://www.rfc-editor.org/info/rfc7470>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
Computation Element Communication Protocol (PCEP)
Extensions for Stateful PCE", RFC 8231,
DOI 10.17487/RFC8231, September 2017,
<https://www.rfc-editor.org/info/rfc8231>.
[RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path
Computation Element Communication Protocol (PCEP)
Extensions for PCE-Initiated LSP Setup in a Stateful PCE
Model", RFC 8281, DOI 10.17487/RFC8281, December 2017,
<https://www.rfc-editor.org/info/rfc8281>.
9.2. Informative References
[I-D.ietf-pce-pcep-yang]
Dhody, D., Beeram, V. P., Hardwick, J., and J. Tantsura,
"A YANG Data Model for Path Computation Element
Communications Protocol (PCEP)", Work in Progress,
Internet-Draft, draft-ietf-pce-pcep-yang-25, 21 May 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-pce-
pcep-yang-25>.
[RFC2578] McCloghrie, K., Ed., Perkins, D., Ed., and J.
Schoenwaelder, Ed., "Structure of Management Information
Version 2 (SMIv2)", STD 58, RFC 2578,
DOI 10.17487/RFC2578, April 1999,
<https://www.rfc-editor.org/info/rfc2578>.
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[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016,
<https://www.rfc-editor.org/info/rfc7942>.
[RFC8051] Zhang, X., Ed. and I. Minei, Ed., "Applicability of a
Stateful Path Computation Element (PCE)", RFC 8051,
DOI 10.17487/RFC8051, January 2017,
<https://www.rfc-editor.org/info/rfc8051>.
[RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody,
"PCEPS: Usage of TLS to Provide a Secure Transport for the
Path Computation Element Communication Protocol (PCEP)",
RFC 8253, DOI 10.17487/RFC8253, October 2017,
<https://www.rfc-editor.org/info/rfc8253>.
[RFC9371] Baber, A. and P. Hoffman, "Registration Procedures for
Private Enterprise Numbers (PENs)", RFC 9371,
DOI 10.17487/RFC9371, March 2023,
<https://www.rfc-editor.org/info/rfc9371>.
Appendix A. Contributor Addresses
Dhruv Dhody
Huawei
India
EMail: dhruv.ietf@gmail.com
Mike Koldychev
Ciena
EMail: mkoldych@proton.me
Authors' Addresses
Cheng Li
Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd.
Beijing
100095
China
Email: c.l@huawei.com
Haomian Zheng
Huawei Technologies
H1, Huawei Xiliu Beipo Village, Songshan Lake
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Dongguan
Guangdong, 523808
China
Email: zhenghaomian@huawei.com
Siva Sivabalan
Ciena
385 Terry Fox Drive
Kanata Ontario K2K 0L1
Canada
Email: msiva282@gmail.com
Samuel Sidor
Cisco Systems, Inc.
Email: ssidor@cisco.com
Zafar Ali
Cisco Systems, Inc.
Email: zali@cisco.com
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