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IETF RFC 5543
BGP Traffic Engineering Attribute
Last modified on Tuesday, May 5th, 2009
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Network Working Group H. Ould-Brahim
Request for Comments: 5543 Nortel Networks
Category: Standards Track D. Fedyk
Alcatel-Lucent
Y. Rekhter
Juniper Networks
May 2009
BGP Traffic Engineering Attribute
 Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (c) 2009 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 in effect on the date of
publication of this document (http://trustee.ietf.org/license-info).
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document.
Abstract
This document defines a new BGP attribute, the Traffic Engineering
attribute, that enables BGP to carry Traffic Engineering information.
The scope and applicability of this attribute currently excludes its
use for non-VPN reachability information.
Ould-Brahim, et al. Standards Track PAGE 1 
RFC 5543 BGP TE Attribute May 2009
1. Introduction
In certain cases (e.g., Layer-1 VPNs (L1VPNs) [RFC 5195]), it may be
useful to augment the VPN reachability information carried in BGP
with Traffic Engineering information.
This document defines a new BGP attribute, the Traffic Engineering
attribute, that enables BGP [RFC 4271] to carry Traffic Engineering
information.
Section 4 of [RFC 5195] describes one possible usage of this
attribute.
The scope and applicability of this attribute currently excludes its
use for non-VPN reachability information.
Procedures for modifying the Traffic Engineering attribute, when
re-advertising a route that carries such an attribute, are outside
the scope of this document.
2. Specification of Requirements
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 [RFC 2119].
3. Traffic Engineering Attribute
The Traffic Engineering attribute is an optional, non-transitive BGP
attribute.
The information carried in this attribute is identical to what is
carried in the Interface Switching Capability Descriptor, as
specified in [RFC 4203] and [RFC 5307].
The attribute contains one or more of the following:
Ould-Brahim, et al. Standards Track PAGE 2
RFC 5543 BGP TE Attribute May 2009
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 [RFC 3471].
The Encoding field contains one of the values specified in Section
3.1.1 of [RFC 3471].
The Reserved field SHOULD be set to 0 on transmit and MUST be ignored
on receive.
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.
The content of the Switching Capability specific information field
depends on the value of the Switching Capability field.
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.
Ould-Brahim, et al. Standards Track PAGE 3
RFC 5543 BGP TE Attribute May 2009
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.
When the Switching Capability field is Layer-2 Switch Capable (L2SC),
there is no Switching Capability specific information field present.
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.
When the Switching Capability field is Lambda Switch Capable (LSC),
there is no Switching Capability specific information field present.
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.
Ould-Brahim, et al. Standards Track PAGE 4
RFC 5543 BGP TE Attribute May 2009
Constructing the Traffic Engineering attribute when aggregating
routes with identical Traffic Engineering attributes follows the
procedure of [RFC 4201].
5. Implication on Scalability
The use of the Traffic Engineering attribute does not increase the
number of routes, but may increase the number of BGP Update messages
required to distribute the routes, depending on whether or not these
routes share the same BGP Traffic Engineering attribute (see below).
When the routes differ other than in the Traffic Engineering
attribute (e.g., 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.
6. IANA Considerations
This document defines a new BGP attribute, Traffic Engineering. This
attribute is optional and non-transitive.
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.
8. Acknowledgements
The authors would like to thank John Scudder and Jeffrey Haas for
their review and comments.
9. References
9.1. Normative References
[IEEE] IEEE, "IEEE Standard for Binary Floating-Point Arithmetic",
Standard 754-1985, 1985 (ISBN 1-5593-7653-8).
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
Ould-Brahim, et al. Standards Track PAGE 5
RFC 5543 BGP TE Attribute May 2009
[RFC 3471] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description", RFC
3471, January 2003.
[RFC 4201] Kompella, K., Rekhter, Y., and L. Berger, "Link Bundling in
MPLS Traffic Engineering (TE)", RFC 4201, October 2005.
[RFC 4271] 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
[RFC 4203] Kompella, K., Ed., and Y. Rekhter, Ed., "OSPF Extensions in
Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4203, October 2005.
[RFC 5195] Ould-Brahim, H., Fedyk, D., and Y. Rekhter, "BGP-Based
Auto-Discovery for Layer-1 VPNs", RFC 5195, June 2008.
[RFC 5307] 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
Ould-Brahim, et al. Standards Track PAGE 6
BGP Traffic Engineering Attribute
RFC TOTAL SIZE: 11883 bytes
PUBLICATION DATE: Tuesday, May 5th, 2009
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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