Internet Engineering Task Force (IETF) L. Ginsberg
Request for Comments: 7883 Cisco Systems
Category: Standards Track N. Akiya
ISSN: 2070-1721 Big Switch Networks
M. Chen
Huawei
July 2016
Advertising Seamless Bidirectional Forwarding Detection (S-BFD)
Discriminators in IS-IS
Abstract
This document defines a means of advertising one or more Seamless
Bidirectional Forwarding Detection (S-BFD) Discriminators using the
IS-IS Router CAPABILITY TLV.
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
http://www.rfc-editor.org/info/rfc7883.
Ginsberg, et al. Standards Track [Page 1]RFC 7883 Advertising S-BFD Discriminators in IS-IS July 2016
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Table of Contents
1. Introduction ....................................................3
2. Encoding Format .................................................3
3. IANA Considerations .............................................4
4. Security Considerations .........................................4
5. Normative References ............................................4
Acknowledgements ...................................................5
Authors' Addresses .................................................5
Ginsberg, et al. Standards Track [Page 2]
RFC 7883 Advertising S-BFD Discriminators in IS-IS July 2016
1. Introduction
[RFC7880] defines a simplified mechanism for using Bidirectional
Forwarding Detection (BFD) [RFC5880]. This mechanism depends on
network nodes knowing the BFD Discriminators that each node in the
network has reserved for this purpose. The use of the Intermediate
System to Intermediate System (IS-IS) [IS-IS] protocol is one
possible means of advertising these discriminators.
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].
2. Encoding Format
The IS-IS Router CAPABILITY TLV as defined in [RFC4971] will be used
to advertise Seamless BFD (S-BFD) Discriminators. A new sub-TLV is
defined as described below. S-BFD Discriminators sub-TLVs are
formatted as specified in [RFC5305].
No. of octets
+-----------------------------+
| Type (20) | 1
+-----------------------------+
| Length (multiple of 4) | 1
+-----------------------------+
| Discriminator Value(s) | 4/Discriminator
: :
+-----------------------------+
The inclusion of an S-BFD Discriminators sub-TLV in a Router
CAPABILITY TLV is optional. Multiple S-BFD Discriminators sub-TLVs
MAY be advertised by an IS. How a given discriminator is mapped to a
specific use case when multiple S-BFD Discriminators are advertised
is out of scope for this document.
S-BFD Discriminator advertisements MAY be flooded within an area or
throughout the domain, using the procedures specified in [RFC4971].
The appropriate flooding scope depends on the intended use of S-BFD.
If S-BFD usage will be exclusively within a Level-1 area, then area
scope is appropriate. If S-BFD usage will span different Level-1
areas, then domain scope is appropriate.
Ginsberg, et al. Standards Track [Page 3]RFC 7883 Advertising S-BFD Discriminators in IS-IS July 2016
3. IANA Considerations
IANA has added a new sub-TLV in the "Sub-TLVs for TLV 242" registry.
The registration is as follows:
Value Description
----- --------------------
20 S-BFD Discriminators
4. Security Considerations
Security concerns for IS-IS are addressed in [IS-IS], [RFC5304], and
[RFC5310]. The new S-BFD Discriminators sub-TLV does not introduce
any new security risks for IS-IS.
Advertising the S-BFD Discriminators makes it possible for attackers
to initiate S-BFD sessions using the advertised information. The
vulnerabilities this poses and how to mitigate them are discussed in
[RFC7880].
5. Normative References
[IS-IS] International Organization for Standardization,
"Intermediate System to Intermediate System intra-domain
routeing information exchange protocol for use in
conjunction with the protocol for providing the
connectionless-mode network service (ISO 8473)",
ISO Standard 10589, 2002.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4971] Vasseur, JP., Ed., Shen, N., Ed., and R. Aggarwal, Ed.,
"Intermediate System to Intermediate System (IS-IS)
Extensions for Advertising Router Information", RFC 4971,
DOI 10.17487/RFC4971, July 2007,
<http://www.rfc-editor.org/info/rfc4971>.
[RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic
Authentication", RFC 5304, DOI 10.17487/RFC5304,
October 2008, <http://www.rfc-editor.org/info/rfc5304>.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, DOI 10.17487/RFC5305,
October 2008, <http://www.rfc-editor.org/info/rfc5305>.
Ginsberg, et al. Standards Track [Page 4]RFC 7883 Advertising S-BFD Discriminators in IS-IS July 2016
[RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
and M. Fanto, "IS-IS Generic Cryptographic
Authentication", RFC 5310, DOI 10.17487/RFC5310,
February 2009, <http://www.rfc-editor.org/info/rfc5310>.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
<http://www.rfc-editor.org/info/rfc5880>.
[RFC7880] Pignataro, C., Ward, D., Akiya, N., Bhatia, M., and S.
Pallagatti, "Seamless Bidirectional Forwarding Detection
(S-BFD)", RFC 7880, DOI 10.17487/RFC7880, July 2016,
<http://www.rfc-editor.org/info/rfc7880>.
Acknowledgements
The authors wish to thank Sam Aldrin, Manav Bhatia, and Carlos
Pignataro for input essential to defining the needed functionality.
Authors' Addresses
Les Ginsberg
Cisco Systems
510 McCarthy Blvd.
Milpitas, CA 95035
United States of America
Email: ginsberg@cisco.com
Nobo Akiya
Big Switch Networks
Email: nobo.akiya.dev@gmail.com
Mach(Guoyi) Chen
Huawei
Email: mach.chen@huawei.com
Ginsberg, et al. Standards Track [Page 5]
