[rfc-dist] RFC 4920 on Crankback Signaling Extensions for MPLS and GMPLS RSVP-TE

rfc-editor@rfc-editor.org rfc-editor at rfc-editor.org
Sat Jul 14 13:26:15 PDT 2007

A new Request for Comments is now available in online RFC libraries.

        RFC 4920

        Title:      Crankback Signaling Extensions for MPLS 
                    and GMPLS RSVP-TE 
        Author:     A. Farrel, Ed.,
                    A. Satyanarayana, A. Iwata,
                    N. Fujita, G. Ash
        Status:     Standards Track
        Date:       July 2007
        Mailbox:    adrian at olddog.co.uk, 
                    asatyana at cisco.com, 
                    a-iwata at ah.jp.nec.com,  n-fujita at bk.jp.nec.com, 
                    gash5107 at yahoo.com
        Pages:      38
        Characters: 88679
        Updates/Obsoletes/SeeAlso:   None

        I-D Tag:    draft-ietf-ccamp-crankback-06.txt

        URL:        http://www.rfc-editor.org/rfc/rfc4920.txt

In a distributed, constraint-based routing environment, the
information used to compute a path may be out of date.  This means
that Multiprotocol Label Switching (MPLS) and Generalized MPLS
(GMPLS) Traffic Engineered (TE) Label Switched Path (LSP) setup
requests may be blocked by links or nodes without sufficient
resources.  Crankback is a scheme whereby setup failure information is
returned from the point of failure to allow new setup attempts to be
made avoiding the blocked resources.  Crankback can also be applied to
LSP recovery to indicate the location of the failed link or node.

This document specifies crankback signaling extensions for use in MPLS
signaling using RSVP-TE as defined in "RSVP-TE: Extensions to RSVP for
LSP Tunnels", RFC 3209, and GMPLS signaling as defined in "Generalized
Multi-Protocol Label Switching (GMPLS) Signaling Functional
Description", RFC 3473.  These extensions mean that the LSP setup
request can be retried on an alternate path that detours around
blocked links or nodes.  This offers significant improvements
in the successful setup and recovery ratios for LSPs, especially in
situations where a large number of setup requests are triggered at the
same time.  [STANDARDS TRACK]

This document is a product of the Common Control and Measurement Plane
Working Group of the IETF.

This is now a Proposed Standard Protocol.

STANDARDS TRACK: 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.

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