Network Working Group                                    C.Y Lee
Internet Draft                                           A. Farrel
Expiration Date: September 2002


                                                         March, 2002



Exclude Routes - Extension to RSVP-TE
<draft-lee-rsvp-te-exclude-route-00.txt>

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

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Abstract

The current RSVP-TE specification [RSVP-TE] and GMPLS extensions
[GMPLS-RSVP-TE] allow abstract nodes and resources to be explicitly
included in a path setup, but not to be explicitly excluded.

In many systems this is fine because exclusions can be specified
through a management system and passed to an offline computation
engine which can generate a route that is sufficiently explicit
to ensure that the exclusions are avoided.

Other systems, however, rely on the use of loose routes or partially
specified abstract nodes.  These routes are resolved within the
network as the hops of the explicit route are evaluated.  In these
cases exclusions cannot currently be communicated to the nodes that
will evaluate the routes.

This draft specifies ways to communicate route exclusions during path
setup using RSVP-TE.


. Overview

We identified two main types of exclusions to apply:

i)  Do not include any of the abstract nodes in a given set.  This is
    referred to as XRO (exclude route object)

ii) Do not include certain abstract nodes or resources between a
    specific pair of abstract nodes within an ERO.  This is referred
    to as NOT(ERO subobject).

A new RSVP-TE object shall be specified for the first type of
exclude route.

The second type of exclude route require modification of the existing
ERO or a new C_Type for the existing ERO to be specified. This type
of
exclude route will be added to this draft in a future version.


. Exclude Route

The exclude route identifies a list of abstract nodes that must NOT
be
traversed along the path.

2.1 Exclude Route Object

   Abstract nodes to be excluded are specified via the EXCLUDE_ROUTE
   object (XRO).  The Exclude Route Class value is TBD.
   Currently one C_Type is defined, Type 1 Exclude Route.  The
   EXCLUDE_ROUTE object has the following format:


   Class = TBD, C_Type = 1

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                        (Subobjects)                          //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Subobjects

   The contents of an EXCLUDE_ROUTE object are a series of variable-
   length data items called subobjects.  The subobjects are identical
   to those defined in [RSVP-TE] and [GMPLS-RSVP-TE] for use in EROs.

   The following subobject types are supported.

                   1   IPv4 prefix
                   2   IPv6 prefix
                  32   Autonomous system number
         The defined values for Type above are specified in [RSVP-TE]

   The L bit that denotes a loose hop when the subobject is used in
   the ERO has no meaning in the XRO and should be ignored.

2.2. Semantics of the Exclude Route Object

    The exclude route is encoded as a series of subobjects contained in
    an EXCLUDE_ROUTE object.  Each subobject identifies a group of nodes
    in the exclude route.  An exclude route is thus a specification of
    groups of nodes NOT to be traversed.

    In [RSVP-TE], a node may be an abstract node, which is made up of a
    group of nodes (as in an Autonomous System).Hence an exclude route that
    consists solely of Autonomous System number subobjects specifies the
    Autonomous Systems not to be traversed.

. Security

The new exclude route object poses no security exposures over and
above
[RSVP-TE].

. Acknowledgment

This draft reuse text from [RSVP-TE] for the description of
EXCLUDE_ROUTE.


. Authors' Information

Cheng-Yin Lee, Cheng-Yin.Lee@alcatel.com

Adrian Farrel, afarrel@movaz.com


References

[RSVP-TE]  ftp://ftp.isi.edu/in-notes/rfc3209.txt

[GMPLS-RSVP-TE]  Generalized MPLS Signaling - RSVP-TE Extensions,
                 Internet Draft <draft-ietf-mpls-generalized-rsvp-te-
                 06.txt>, November, 2001