RFC 4920 on Crankback Signaling Extensions for MPLS and GMPLS RSVP-TE

A new Request for Comments is now available in online RFC
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        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:    adrianolddog.co.uk, 
                    asatyanacisco.com, 
                    a-iwataah.jp.nec.com, 
n-fujitabk.jp.nec.com, 
                    gash5107yahoo.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information used to compute a path may be out of date.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
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