Internet Engineering Task Force (IETF) J. Tantsura
Request for Comments: 9104 Microsoft
Category: Standards Track Z. Wang
ISSN: 2070-1721 Q. Wu
Huawei
K. Talaulikar
Cisco Systems
August 2021
Distribution of Traffic Engineering Extended Administrative Groups
Using the Border Gateway Protocol - Link State (BGP-LS)
Abstract
Administrative groups are link attributes used for traffic
engineering. This document defines an extension to the Border
Gateway Protocol - Link State (BGP-LS) for advertisement of extended
administrative groups (EAGs).
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9104.
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Table of Contents
1. Introduction
1.1. Requirements Language
2. Advertising Extended Administrative Groups in BGP-LS
3. IANA Considerations
4. Manageability Considerations
5. Security Considerations
6. References
6.1. Normative References
6.2. Informative References
Acknowledgments
Authors' Addresses
1. Introduction
Administrative groups (commonly referred to as "colors" or "link
colors") are link attributes that are advertised by link-state
protocols like IS-IS [RFC1195], OSPFv2 [RFC2328], and OSPFv3
[RFC5340]. The Border Gateway Protocol - Link State (BGP-LS)
advertisement of the originally defined (non-extended) administrative
groups is encoded using the Administrative Group (color) TLV 1088 as
defined in [RFC7752].
These administrative groups are defined as a fixed-length 32-bit
bitmask. As networks grew and more use cases were introduced, the
32-bit length was found to be constraining, and hence extended
administrative groups (EAGs) were introduced in [RFC7308].
The EAG TLV (Section 2) is not a replacement for the Administrative
Group (color) TLV; as explained in [RFC7308], both values can
coexist. It is out of scope for this document to specify the
behavior of the BGP-LS consumer [RFC7752].
This document specifies an extension to BGP-LS for advertisement of
the extended administrative groups.
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.
2. Advertising Extended Administrative Groups in BGP-LS
This document defines an extension that enables BGP-LS speakers to
signal the EAG of links in a network to a BGP-LS consumer of network
topology such as a centralized controller. The centralized
controller can leverage this information in traffic engineering
computations and other use cases. When a BGP-LS speaker is
originating the topology learned via link-state routing protocols
like OSPF or IS-IS, the EAG information of the links is sourced from
the underlying extensions as defined in [RFC7308].
The EAG of a link is encoded in a new Link Attribute TLV [RFC7752]
using the following format:
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 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended Administrative Group (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Extended Administrative Group TLV Format
Where:
Type: 1173
Length: variable length that represents the total length of the
value field in octets. The length value MUST be a multiple of 4.
If the length is not a multiple of 4, the TLV MUST be considered
malformed.
Value: one or more sets of 32-bit bitmasks that indicate the
administrative groups (colors) that are enabled on the link when
those specific bits are set.
3. IANA Considerations
IANA has assigned a code point from the "BGP-LS Node Descriptor, Link
Descriptor, Prefix Descriptor, and Attribute TLVs" registry as
described in the following table.
+============+===============================+===================+
| Code Point | Description | IS-IS TLV/Sub-TLV |
+============+===============================+===================+
| 1173 | Extended Administrative Group | 22/14 |
+------------+-------------------------------+-------------------+
Table 1
4. Manageability Considerations
The new protocol extensions introduced in this document augment the
existing IGP topology information that is distributed via [RFC7752].
Procedures and protocol extensions defined in this document do not
affect the BGP protocol operations and management other than as
discussed in Section 6 ("Manageability Considerations") of [RFC7752].
Specifically, the tests for malformed attributes, to perform
syntactic checks as described in Section 6.2.2 ("Fault Management")
of [RFC7752], now encompass the new BGP-LS Attribute TLV defined in
this document. The semantic or content checking for the TLV
specified in this document and its association with the BGP-LS
Network Layer Reachability Information (NLRI) types or its BGP-LS
Attribute are left to the consumer of the BGP-LS information (e.g.,
an application or a controller) and not to BGP itself.
A consumer of the BGP-LS information retrieves this information over
a BGP-LS session (refer to Sections 1 and 2 of [RFC7752]).
5. Security Considerations
The procedures and protocol extensions defined in this document do
not affect the BGP security model. See the "Security Considerations"
section of [RFC4271] for a discussion of BGP security. This document
only introduces a new Attribute TLV, and any syntactic error in it
would result in the BGP-LS Attribute being discarded [RFC7752].
Also, refer to [RFC4272] and [RFC6952] for analyses of security
issues for BGP. Security considerations for acquiring and
distributing BGP-LS information are discussed in [RFC7752]. The TLV
introduced in this document is used to propagate the EAG extensions
defined in [RFC7308]. It is assumed that the IGP instances
originating this TLV will support any required security mechanisms
for OSPF and IS-IS, in order to prevent any security issues when
propagating the Sub-TLVs into BGP-LS.
Security concerns for OSPF are addressed in [RFC7474], [RFC4552], and
[RFC7166]. Further security analysis for the OSPF protocol is done
in [RFC6863].
Security considerations for IS-IS are specified by [RFC5304].
The advertisement of the link attribute information defined in this
document presents no significant additional risk beyond that
associated with the existing link attribute information already
supported in [RFC7752].
6. References
6.1. 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>.
[RFC7308] Osborne, E., "Extended Administrative Groups in MPLS
Traffic Engineering (MPLS-TE)", RFC 7308,
DOI 10.17487/RFC7308, July 2014,
<https://www.rfc-editor.org/info/rfc7308>.
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016,
<https://www.rfc-editor.org/info/rfc7752>.
[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>.
6.2. Informative References
[RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
dual environments", RFC 1195, DOI 10.17487/RFC1195,
December 1990, <https://www.rfc-editor.org/info/rfc1195>.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998,
<https://www.rfc-editor.org/info/rfc2328>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>.
[RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis",
RFC 4272, DOI 10.17487/RFC4272, January 2006,
<https://www.rfc-editor.org/info/rfc4272>.
[RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality
for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006,
<https://www.rfc-editor.org/info/rfc4552>.
[RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic
Authentication", RFC 5304, DOI 10.17487/RFC5304, October
2008, <https://www.rfc-editor.org/info/rfc5304>.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
<https://www.rfc-editor.org/info/rfc5340>.
[RFC6863] Hartman, S. and D. Zhang, "Analysis of OSPF Security
According to the Keying and Authentication for Routing
Protocols (KARP) Design Guide", RFC 6863,
DOI 10.17487/RFC6863, March 2013,
<https://www.rfc-editor.org/info/rfc6863>.
[RFC6952] Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
BGP, LDP, PCEP, and MSDP Issues According to the Keying
and Authentication for Routing Protocols (KARP) Design
Guide", RFC 6952, DOI 10.17487/RFC6952, May 2013,
<https://www.rfc-editor.org/info/rfc6952>.
[RFC7166] Bhatia, M., Manral, V., and A. Lindem, "Supporting
Authentication Trailer for OSPFv3", RFC 7166,
DOI 10.17487/RFC7166, March 2014,
<https://www.rfc-editor.org/info/rfc7166>.
[RFC7474] Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed.,
"Security Extension for OSPFv2 When Using Manual Key
Management", RFC 7474, DOI 10.17487/RFC7474, April 2015,
<https://www.rfc-editor.org/info/rfc7474>.
Acknowledgments
The authors would like to thank Eric Osborne, Les Ginsberg, Tim
Chown, Ben Niven-Jenkins, and Alvaro Retana for their reviews and
valuable comments.
Authors' Addresses
Jeff Tantsura
Microsoft
Email: jefftant.ietf@gmail.com
Zitao Wang
Huawei
Yuhua District
101 Software Avenue
Nanjing
Jiangsu, 210012
China
Email: wangzitao@huawei.com
Qin Wu
Huawei
Yuhua District
101 Software Avenue
Nanjing
Jiangsu, 210012
China
Email: bill.wu@huawei.com
Ketan Talaulikar
Cisco Systems
Email: ketant@cisco.com