RFC 9357
Label Switched Path (LSP) Object Flag Extension for Stateful PCE
Label Switched Path (LSP) Object Flag Extension for Stateful PCE 🎀
Okay bestie, this is RFC 9357, and it's basically a glow-up for the LSP object 💅✨ The title block tea: it's by Q. Xiong from ZTE Corporation, it's a Standards Track doc (so it's the real deal, not a draft experiment), and it's dated February 2023. The ISSN is 2070-1721. The header doesn't list anything it obsoletes or updates, so no drama there 🫶
Abstract
So here's the setup 🧚 RFC 8231 gives PCEP (the Path Computation Element Communication Protocol) stateful powers to control MPLS-TE and GMPLS LSPs. One of its main pieces is the LSP object, which has a Flag field that's 12 bits long. The problem is that every single bit in that field is already taken 💀 This doc fixes that by defining a new LSP-EXTENDED-FLAG TLV, which gives the LSP object an extended Flag field 🦋
Status of This Memo
This is an Internet Standards Track document 👑 It's a product of the IETF and represents the consensus of the IETF community. It got public review and was approved for publication by the IESG. For more on Internet Standards, see Section 2 of RFC 7841. For the current status, any errata, and how to send feedback, check https://www.rfc-editor.org/info/rfc9357.
Copyright Notice
Copyright (c) 2023 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, since they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.
Table of Contents 📑
1. Introduction
2. Conventions Used in this Document
2.1. Terminology
2.2. Requirements Language
3. PCEP Extension
3.1. The LSP-EXTENDED-FLAG TLV
3.2. Processing
4. Advice for Specification of New Flags
5. Backward Compatibility
6. IANA Considerations
6.1. LSP Object
6.1.1. PCEP TLV Type Indicators
6.1.2. LSP Extended Flags Field
7. Management Considerations
8. Security Considerations
9. References
9.1. Normative References
9.2. Informative References
Appendix A. Working Group Discussion
Acknowledgements
Contributors
Author's Address1. Introduction ✨
[RFC5440] describes PCEP, which is used between a PCE and a Path Computation Client (PCC) (or other PCE) to compute Multi-protocol Label Switching for Traffic Engineering (MPLS-TE) Label Switched Paths (LSPs). It's the matchmaking service for paths 💖
PCEP Extensions for the Stateful PCE Model [RFC8231] adds a set of extensions to PCEP so you can actively control MPLS-TE and Generalized MPLS (GMPLS) tunnels. One of those extensions is the LSP object, which has a Flag field. The bits in that field are used to signal things like delegation, synchronization, removal, and so on 🔥
As defined in [RFC8231], the Flag field is 12 bits long, and every one of those bits is already defined, as Table 1 shows. So this document extends the Flag field for future use by defining a new LSP-EXTENDED-FLAG TLV, which gives the LSP object an extended Flag field. Details are in Section 3.1 🦋
+=====+======================+==================+
| Bit | Description | Reference |
+=====+======================+==================+
| 0 | PCE-allocation | [BIND-LABEL-SID] |
+-----+----------------------+------------------+
| 1 | ERO-compression | [RFC8623] |
+-----+----------------------+------------------+
| 2 | Fragmentation | [RFC8623] |
+-----+----------------------+------------------+
| 3 | P2MP | [RFC8623] |
+-----+----------------------+------------------+
| 4 | Create | [RFC8281] |
+-----+----------------------+------------------+
| 5-7 | Operational (3 bits) | [RFC8281] |
+-----+----------------------+------------------+
| 8 | Administrative | [RFC8281] |
+-----+----------------------+------------------+
| 9 | Remove | [RFC8281] |
+-----+----------------------+------------------+
| 10 | SYNC | [RFC8281] |
+-----+----------------------+------------------+
| 11 | Delegate | [RFC8281] |
+-----+----------------------+------------------+
Table 1: LSP Object Flag Field2. Conventions Used in this Document ✨
2.1. Terminology 📖
The terminology comes from [RFC5440] and [RFC8231].
2.2. Requirements Language 🫶
The BCP 14 key words are "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL". In this document they're interpreted as described in BCP 14 [RFC2119] [RFC8174], and only when they appear in all capitals, as shown here. Lowercase versions are just regular words, so no sneaky requirements there 😌
3. PCEP Extension 💜
The LSP object is defined in Section 7.3 of [RFC8231]. This document defines a new LSP-EXTENDED-FLAG TLV for an extended Flag field in the LSP object 🎀
3.1. The LSP-EXTENDED-FLAG TLV 🌸
The format of the LSP-EXTENDED-FLAG TLV, shown in Figure 1, follows the format of all PCEP TLVs, as defined in [RFC5440].
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=64 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// LSP Extended Flags //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: LSP-EXTENDED-FLAG TLV FormatHere's what each field does:
Type (16 bits):64Length (16 bits): This is the length of the value portion, in bytes. It MUST be in multiples of 4 and greater than 0. 📏LSP Extended Flags: This is an array of 32-bit flag units, numbered from the most significant bit as bit zero. Each bit represents one LSP flag, for operation, feature, or state. TheLSP Extended Flagsfield SHOULD use the minimal amount of space needed to encode the flag bits. Right now, no bits are assigned. Unassigned bits MUST be set to zero on transmission and MUST be ignored on receipt 🧚
As an example of how the LSP-EXTENDED-FLAG TLV gets used, the E-flag is requested for entropy label configuration, as proposed in [PCEP-ENTROPY-LABEL] 🍓
3.2. Processing 🧠
The LSP Extended Flags field is an array of 32-flag units, allocated starting from the most significant bit. Future documents will assign the bits of the LSP Extended Flags field. This document doesn't define any flags. Flags that an implementation doesn't support MUST be set to zero on transmission. Implementations that don't understand a particular flag MUST ignore that flag.
Heads up: PCEP peers MUST handle varying lengths of the LSP-EXTENDED-FLAG TLV. This is the part people skip, and it matters 🙈
If a PCEP speaker receives an LSP-EXTENDED-FLAG TLV longer than it currently supports or understands, it MUST ignore the bits beyond that length.
If a PCEP speaker receives an LSP-EXTENDED-FLAG TLV shorter than the length its implementation supports, it MUST act as if the bits beyond that length were not set. 💖
8. Security Considerations 🔒
Okay bestie, this part is SERIOUS 🥺🔒. [RFC8231] already covers the security considerations for PCEP when you're talking to a stateful PCE, and this document does not change any of that 💅. For LSP object processing, go read [RFC8231] ✨.
The flags for the LSP object and their security considerations are spread across [RFC8231], [RFC8281], [RFC8623], and [BIND-LABEL-SID] 🌸.
This document makes room for new flags in the LSP object down the road 🦋. Any future document that specifies new flags must also discuss any associated security implications. No skipping that part, periodt 🙅♀️. No additional security issues are raised in this document beyond the ones that already exist in the referenced documents 🫶.
Heads up: any future flag spec must discuss its security implications. That one's non-negotiable 💀.
Also, [RFC8231] recommends that the stateful PCEP extension be authenticated and encrypted using Transport Layer Security (TLS) [RFC8253] [PCEPS-TLS1.3], following the recommendations and best current practices in [RFC9325] 🔐. If that recommendation is followed, then the flags will be protected by TLS 💖✨.
9. References 📚
9.1. Normative References
[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>.
[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>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[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>.9.2. Informative References
[BIND-LABEL-SID]
Sivabalan, S., Filsfils, C., Tantsura, J., Previdi, S.,
and C. Li, Ed., "Carrying Binding Label/Segment Identifier
(SID) in PCE-based Networks.", Work in Progress, Internet-
Draft, draft-ietf-pce-binding-label-sid-15, 20 March 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-pce-
binding-label-sid-15>.
[PCEP-ENTROPY-LABEL]
Xiong, Q., Peng, S., and F. Qin, "PCEP Extension for SR-
MPLS Entropy Label Position", Work in Progress, Internet-
Draft, draft-peng-pce-entropy-label-position-08, 29 August
2022, <https://datatracker.ietf.org/doc/html/draft-peng-
pce-entropy-label-position-08>.
[PCEPS-TLS1.3]
Dhody, D., Turner, S., and R. Housley, "PCEPS with TLS
1.3", Work in Progress, Internet-Draft, draft-dhody-pce-
pceps-tls13-01, 20 October 2022,
<https://datatracker.ietf.org/doc/html/draft-dhody-pce-
pceps-tls13-01>.
[RFC5088] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
Zhang, "OSPF Protocol Extensions for Path Computation
Element (PCE) Discovery", RFC 5088, DOI 10.17487/RFC5088,
January 2008, <https://www.rfc-editor.org/info/rfc5088>.
[RFC5089] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
Zhang, "IS-IS Protocol Extensions for Path Computation
Element (PCE) Discovery", RFC 5089, DOI 10.17487/RFC5089,
January 2008, <https://www.rfc-editor.org/info/rfc5089>.
[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>.
[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>.
[RFC8623] Palle, U., Dhody, D., Tanaka, Y., and V. Beeram, "Stateful
Path Computation Element (PCE) Protocol Extensions for
Usage with Point-to-Multipoint TE Label Switched Paths
(LSPs)", RFC 8623, DOI 10.17487/RFC8623, June 2019,
<https://www.rfc-editor.org/info/rfc8623>.
[RFC8786] Farrel, A., "Updated Rules for Processing Stateful PCE
Request Parameters Flags", RFC 8786, DOI 10.17487/RFC8786,
May 2020, <https://www.rfc-editor.org/info/rfc8786>.
[RFC9325] 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>.Appendix A. Working Group Discussion 💬
The working group discussed the idea of a fixed length (with 32 bits)
for the LSP-EXTENDED-FLAG TLV. Though 32 bits would be sufficient
for quite a while, the use of variable length with a multiple of 32
bits allows for future extensibility where we would never run out of
flags and there would not be a need to define yet another TLV in the
future. Further, note that [RFC5088] and [RFC5089] use the same
approach for the PCE-CAP-FLAGS sub-TLV and are found to be useful.Acknowledgements 🫶
The authors want to thank Loa Andersson, Adrian Farrel, Aijun Wang, and Gyan Mishra for their reviews, suggestions, and comments on this document 🌷.
Contributors 🎀
The following people have substantially contributed to this document:
Dhruv Dhody
Huawei Technologies
Email: dhruv.ietf@gmail.com
Greg Mirsky
Ericsson
Email: gregimirsky@gmail.comAuthor's Address 🧚
Quan Xiong
ZTE Corporation
No.6 Huashi Park Rd
Wuhan
Hubei, 430223
China
Email: xiong.quan@zte.com.cn📦 where this page comes from
- ietf: rfc9357 2023-02
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