RFC 5543

BGP Traffic Engineering Attribute

📅 published May 2009, from ietf

BGP Traffic Engineering Attribute 🎀

RFC: 5543, from the Network Working Group
Category: Standards Track 🔥
Date: May 2009
Authors: Hamid Ould-Brahim (Nortel Networks), Don Fedyk (Alcatel-Lucent), and Yakov Rekhter (Juniper Networks)
Obsoletes: none listed
Updates: none listed

Status of This Memo ✨

okay so first things first, this doc is an Internet standards track protocol for the Internet community, and it's basically asking everyone to talk about it and send suggestions 💖 For the current standardization state and status, you check the "Internet Official Protocol Standards" (STD 1) edition. And distribution of this memo is unlimited, so share away 🦋

Copyright Notice 💅

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please actually read those, bestie, because they explain your rights and restrictions with respect to this document 🙈

Abstract 🧚

This doc defines a brand new BGP attribute, the Traffic Engineering attribute, which lets BGP carry Traffic Engineering information. It's giving "new feature unlocked" 🔓

The scope and applicability of this attribute currently excludes its use for non-VPN reachability information. So no, you can't use it for that right now 💀

1. Introduction ✨

In certain cases, like Layer-1 VPNs (L1VPNs) [RFC5195], it may be useful to augment the VPN reachability information carried in BGP with Traffic Engineering information. That's the whole vibe 💜

This document defines a new BGP attribute, the Traffic Engineering attribute, that enables BGP [RFC4271] to carry Traffic Engineering information. Literally the main character of this RFC 👑

Section 4 of [RFC5195] describes one possible usage of this attribute. Go check it out if you want to see it in action 🍓

The scope and applicability of this attribute currently excludes its use for non-VPN reachability information, same as I said above. Don't skip it 😭

Procedures for modifying the Traffic Engineering attribute, when re-advertising a route that carries such an attribute, are outside the scope of this document. So that's a different story for a different RFC 🫶

2. Specification of Requirements 🔥

okay the BCP 14 key words are the important ones here, so pay attention. 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]. Read that one first if you're new to this 🧚

3. Traffic Engineering Attribute 🌈

The Traffic Engineering attribute is an optional, non-transitive BGP attribute. It's a nice little optional add-on 💖

The information carried in this attribute is identical to what is carried in the Interface Switching Capability Descriptor, as specified in [RFC4203] and [RFC5307]. So if you already know that descriptor, you're basically ready 🎀

The attribute contains one or more of the following:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Switching Cap |   Encoding    |           Reserved            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Max LSP Bandwidth at priority 0              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Max LSP Bandwidth at priority 1              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Max LSP Bandwidth at priority 2              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Max LSP Bandwidth at priority 3              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Max LSP Bandwidth at priority 4              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Max LSP Bandwidth at priority 5              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Max LSP Bandwidth at priority 6              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Max LSP Bandwidth at priority 7              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             Switching Capability specific information         |
      |                           (variable)                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The Switching Capability (Switching Cap) field contains one of the values specified in Section 3.1.1 of [RFC3471]. Pick from that list, no freestyling 💅

The Encoding field contains one of the values specified in Section 3.1.1 of [RFC3471]. Same list, same energy 🫶

The Reserved field SHOULD be set to 0 on transmit and MUST be ignored on receive. So send zeros, and ignore whatever you get back in that spot 🙈

Maximum LSP (Label Switched Path) Bandwidth is encoded as a list of eight 4-octet fields in the IEEE floating point format [IEEE], with priority 0 first and priority 7 last. The units are bytes (not bits!) per second. Bytes, not bits, I'm screaming 😭

The content of the Switching Capability specific information field depends on the value of the Switching Capability field. So it's like a plot twist based on the Switching Cap value 🦋

When the Switching Capability field is PSC-1, PSC-2, PSC-3, or PSC-4, the Switching Capability specific information field includes Minimum LSP Bandwidth and Interface MTU.

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Minimum LSP Bandwidth                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           Interface MTU       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Minimum LSP Bandwidth is encoded in a 4-octet field in the IEEE floating point format. The units are bytes (not bits!) per second. Interface MTU is encoded as a 2-octet integer. Hi, bytes again 🍓

When the Switching Capability field is Layer-2 Switch Capable (L2SC), there is no Switching Capability specific information field present. Nothing extra to see here, so relax 🌸

When the Switching Capability field is Time-Division-Multiplex (TDM) capable, the Switching Capability specific information field includes Minimum LSP Bandwidth and an indication of whether the interface supports Standard or Arbitrary SONET/SDH (Synchronous Optical Network / Synchronous Digital Hierarchy).

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Minimum LSP Bandwidth                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Indication  |
      +-+-+-+-+-+-+-+-+

Minimum LSP Bandwidth is encoded in a 4-octet field in the IEEE floating point format. The units are bytes (not bits!) per second. The indication of whether the interface supports Standard or Arbitrary SONET/SDH is encoded as 1 octet. The value of this octet is 0 if the interface supports Standard SONET/SDH, and 1 if the interface supports Arbitrary SONET/SDH. So 0 means Standard, 1 means Arbitrary, simple as that ✨

When the Switching Capability field is Lambda Switch Capable (LSC), there is no Switching Capability specific information field present. Lambda is the no-extras crew 💜

4. Implication on Aggregation 🫶

Routes that carry the Traffic Engineering attribute have additional semantics that could affect traffic-forwarding behavior. Therefore, such routes SHALL NOT be aggregated unless they share identical Traffic Engineering attributes. This one's serious, bestie, so don't aggregate them unless the attributes match 😭

Constructing the Traffic Engineering attribute when aggregating routes with identical Traffic Engineering attributes follows the procedure of [RFC4201]. So if you're doing that, follow [RFC4201] 🎀

5. Implication on Scalability 🌈

The use of the Traffic Engineering attribute does not increase the number of routes, but it may increase the number of BGP Update messages required to distribute the routes. Whether it does depends on whether or not these routes share the same BGP Traffic Engineering attribute (see below). It's giving "it depends" energy 🧚

When the routes differ other than in the Traffic Engineering attribute (for example, they differ in the set of Route Targets and/or NEXT_HOP), use of the Traffic Engineering attribute has no impact on the number of BGP Update messages required to carry the routes. There is also no impact when routes share all other attribute information and have an aggregated or identical Traffic Engineering attribute. 💖

When routes share all other attribute information and have different Traffic Engineering attributes, routes must be distributed in per-route BGP Update messages, rather than in a single message. So that's the one case where you split them up 🔥

6. IANA Considerations 📋

This document defines a new BGP attribute, Traffic Engineering. This attribute is optional and non-transitive. Ngl, that's the whole IANA section, so simple 🌸

7. Security Considerations 🚨

This extension to BGP does not change the underlying security issues currently inherent in BGP. BGP security considerations are discussed in RFC 4271. So the security drama is the same drama as BGP itself, and you'll find the full story in RFC 4271. Take it seriously, bestie 💀

8. Acknowledgements 🫶

The authors would like to thank John Scudder and Jeffrey Haas for their review and comments. Shoutout to them for helping make this RFC slay ✨

9. References 📚

9.1. Normative References

[IEEE]    IEEE, "IEEE Standard for Binary Floating-Point Arithmetic",
          Standard 754-1985, 1985 (ISBN 1-5593-7653-8).

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
          Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC3471] Berger, L., Ed., "Generalized Multi-Protocol Label
          Switching (GMPLS) Signaling Functional Description", RFC
          3471, January 2003.

[RFC4201] Kompella, K., Rekhter, Y., and L. Berger, "Link Bundling in
          MPLS Traffic Engineering (TE)", RFC 4201, October 2005.

[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border
          Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006.

9.2. Informative References

[RFC4203] Kompella, K., Ed., and Y. Rekhter, Ed., "OSPF Extensions in
          Support of Generalized Multi-Protocol Label Switching
          (GMPLS)", RFC 4203, October 2005.

[RFC5195] Ould-Brahim, H., Fedyk, D., and Y. Rekhter, "BGP-Based
          Auto-Discovery for Layer-1 VPNs", RFC 5195, June 2008.

[RFC5307] Kompella, K., Ed., and Y. Rekhter, Ed., "IS-IS Extensions
          in Support of Generalized Multi-Protocol Label Switching
          (GMPLS)", RFC 5307, October 2008.

Authors' Addresses 💌

Hamid Ould-Brahim Nortel Networks EMail: hbrahim@nortel.com

Don Fedyk Alcatel-Lucent EMail: donald.fedyk@alcatel-lucent.com Phone: 978-467-5645

Yakov Rekhter Juniper Networks, Inc. EMail: yakov@juniper.net

📦 where this page comes from

ietf: rfc5543 2009-05
💖 girlified by claude-haiku-5-5 on 2026-10-17: a language model's rewrite of the original, under its terms