Internet Engineering Task Force (IETF) C. Hopps
Request for Comments: 6213 L. Ginsberg
Category: Standards Track Cisco Systems
ISSN: 2070-1721 April 2011
IS-IS BFD-Enabled TLV
Abstract
This document describes a type-length-value (TLV) for use in the IS-
IS routing protocol that allows for the proper use of the
Bidirectional Forwarding Detection (BFD) protocol. There exist
certain scenarios in which IS-IS will not react appropriately to a
BFD-detected forwarding plane failure without use of either this TLV
or some other method.
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 5741.
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/rfc6213.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Hopps & Ginsberg Standards Track [Page 1]
RFC 6213 IS-IS BFD-Enabled TLV April 2011
Table of Contents
1. Introduction ....................................................2
1.1. Requirements Language ......................................2
2. The Problem .....................................................2
3. The Solution ....................................................3
3.1. State Definitions ..........................................3
3.2. Adjacency Establishment and Maintenance ....................4
3.3. Advertisement of Topology-Specific IS Neighbors ............4
4. Transition ......................................................4
5. Graceful Restart ................................................5
6. The BFD-Enabled TLV .............................................5
7. Security Considerations .........................................6
8. IANA Considerations .............................................6
9. Acknowledgements ................................................6
10. Normative References ...........................................7
1. Introduction
The Bidirectional Forwarding Detection (BFD) protocol [RFC5880] is a
protocol that allows for detection of a forwarding plane failure
between two routers. A router can use [RFC5880] to validate that a
peer router's forwarding ability is functioning.
One specific application of BFD as described in [RFC5882] is to
verify the forwarding ability of an IS-IS [RFC1195] router's
adjacencies; however, the method described in [RFC5882] does not
allow for certain failure scenarios. We will define a TLV that will
allow for proper response to the detection of all forwarding failures
where the use of BFD is employed with IS-IS.
1.1. 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].
2. The Problem
We observe that, in order to allow for mixed use (i.e., some routers
running BFD and some not), [RFC5882] does not require a BFD session
be established prior to the establishment of an IS-IS adjacency.
Thus, if a router A has neighbors B and C, and B does not support
BFD, A would still form adjacencies with B and C, and it would only
establish a BFD session with C.
Hopps & Ginsberg Standards Track [Page 2]
RFC 6213 IS-IS BFD-Enabled TLV April 2011
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