Internet DRAFT - draft-gp-l2tpext-sbfd-discriminator
draft-gp-l2tpext-sbfd-discriminator
Networking Working Group V. Govindan
Internet-Draft C. Pignataro
Intended status: Standards Track Cisco Systems
Expires: September 06, 2015 March 05, 2015
Advertising S-BFD Discriminators in L2TPv3
draft-gp-l2tpext-sbfd-discriminator-00.txt
Abstract
This document defines a new AVP for advertising one or more S-BFD
Discriminators using the L2TPv3 Control Protocol AVP.
Requirements Language
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].
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. S-BFD Target Discriminator ID AVP . . . . . . . . . . . . . . 3
2.1. Encoding Format . . . . . . . . . . . . . . . . . . . . 3
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
6. Contributing Authors . . . . . . . . . . . . . . . . . . . . 4
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
7.1. Normative References . . . . . . . . . . . . . . . . . . 4
7.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
[I-D.ietf-bfd-seamless-base] defines a simplified mechanism to use
Bidirectional Forwarding Detection (BFD)[RFC5880]. This mechanism
depends on network nodes knowing the BFD discriminators which each
node in the network has reserved for this purpose. Use of the Layer2
Tunneling protocol Version 3 (L2TPv3) [RFC3931] is one possible means
of advertising these discriminators. S-BFD requires the usage of
unique discriminators within an administrative domain.
This document specifies the encoding to be used when S-BFD
discriminators are advertised using L2TPv3.
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2. S-BFD Target Discriminator ID AVP
This AVP is exchanged during session negotiation (ICRQ, ICRP, OCRQ,
OCRP).
2.1. Encoding Format
The S-BFD Target Discriminator ID AVP, Attribute Type TBD, is an
identifier used to advertise the S-BFD target discriminators
supported by an LCCE for S-BFD Reflector operation. This AVP
indicates that the advertiser implements a S-BFD reflector supporting
the specified target discriminators and is ready for S-BFD Reflector
operation. The receiving LCCE MAY use this AVP if it wants to
monitor connectivity to the advertising LCCE using S-BFD or BFD.
The Attribute Value field for this AVP has the following format:
S-BFD Discriminator Advertisement (ICRQ, ICRP, ICCN, OCRQ, OCRP,
OCCN):
No. of octets
+-----------------------------+
| Discriminator Value(s) | 4/Discriminator
: :
+-----------------------------+
An LCCE MAY include the S-BFD Discriminator Advertisement AVP in a
L2TP Control Protocol message (ICRQ, ICRP, OCRQ, OCRP) [RFC3931].
Multiple S-BFD Discriminators AVPs MAY be advertised by a LCCE. If
the other LCCE does not wish to monitor connectivity using S-BFD, it
MAY safely discard this AVP without affecting the rest of session
negotiation. While current use-cases
[I-D.ietf-bfd-seamless-use-case] of S-BFD require advertisement of
only one discriminator, the AVP encoding allows specification an
arbitrary number of discrminators for extensibility. When multiple
S-BFD discriminators are advertised, the mechanism to choose a subset
of specific discriminator(s) is out of scope for this document.
The M bit of the L2TP Control Protocol Message (ICRQ, ICRP, OCRQ,
OCRP) [RFC3931] MUST NOT be set inside the S-BFD Target Discriminator
ID AVP advertisement.
3. IANA Considerations
This number space is managed by IANA as per [RFC3438].
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A summary of the new AVPs requested for Attribute Type 0 follows:
Control Message Attribute Value Pairs
Attribute
Type Description
--------- ------------------
TBD S-BFD Discriminators
4. Security Considerations
Security concerns for L2TP are addressed in [RFC3931]. Introduction
of the S-BFD Discriminator Advertisement AVP introduces no new
security risks for L2TP.
Advertisement of the S-BFD discriminators does make 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 the Security Considerations section of
[I-D.ietf-bfd-seamless-base].
5. Acknowledgements
Authors would like to thank Nobo Akiya, Stewart Bryant and Pawel
Sowinski for providing core inputs for the document and for
performing thorough reviews and providing number of comments.
Authors would like to thank Nagendra Kumar for his reviews.
6. Contributing Authors
Mallik Mudigonda
Cisco Systems
Email: mmudigon@cisco.com
7. References
7.1. Normative References
[I-D.ietf-bfd-seamless-base]
Akiya, N., Pignataro, C., Ward, D., Bhatia, M., and J.
Networks, "Seamless Bidirectional Forwarding Detection
(S-BFD)", draft-ietf-bfd-seamless-base-04 (work in
progress), January 2015.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC3438] Townsley, W., "Layer Two Tunneling Protocol (L2TP)
Internet Assigned Numbers Authority (IANA) Considerations
Update", BCP 68, RFC 3438, December 2002.
[RFC3931] Lau, J., Townsley, M., and I. Goyret, "Layer Two Tunneling
Protocol - Version 3 (L2TPv3)", RFC 3931, March 2005.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, June 2010.
7.2. Informative References
[I-D.ietf-bfd-seamless-use-case]
Aldrin, S., Bhatia, M., Mirsky, G., Kumar, N., and S.
Matsushima, "Seamless Bidirectional Forwarding Detection
(BFD) Use Case", draft-ietf-bfd-seamless-use-case-01 (work
in progress), December 2014.
Authors' Addresses
Vengada Prasad Govindan
Cisco Systems
Email: venggovi@cisco.com
Carlos Pignataro
Cisco Systems
Email: cpignata@cisco.com
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