Subject: I-D ACTION:draft-srisuresh-ospf-te-03.txt

From: [email-masked]
Date: Tue, 17 Sep 2002 08:00:04 -0400

A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the Internet Traffic Engineering Working Group of the IETF.

        Title           : TE LSAs to extend OSPF for Traffic Engineering
        Author(s)       : P. Srisuresh, P. Joseph
        Filename        : draft-srisuresh-ospf-te-03.txt
        Pages           : 42
        Date            : 2002-9-16

OSPF is a link state routing protocol used for IP-network
topology discovery and collection and dissemination of link
access metrics. The resulting Link State Database (LSDB) is
used to compute IP address forwarding table based on
shortest-path criteria. Traffic Engineering extensions(OSPF-TE)
outlined in this document are built on the native OSPF
foundation, utilizing new LSAs, designed specifically for TE.
OSPF-TE sets out to discover TE network topology and perform
collection and dissemination of TE metrics within the TE network.
This results in the generation of an independent TE-LSDB, that
would permit computation of TE circuit paths. Unlike the native
OSPF link metrics, TE metrics can be rapidly changing and
varied across different elements of the network. TE circuit
paths are computed using varied TE criteria, often different
from the shortest-path, to route traffic around congestion
paths. Principal motivations to designing the OSPF-TE over
[OPQLSA-TE] and transition path for vendors currently using
[OPQLSA-TE] to adapt the OSPF-TE are outlined in separate
sections within the document. OSPF-TE provides a single unified
mechanism for traffic engineering across packet and non-packet
networks, and may be adapted for a peer networking model.

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From: Rohit Gupta <[email-masked]>
Date: Tue, 17 Sep 2002 05:17:49 -0700

Hi,
What exactly is the difference between this draft and
the one proposed by Yeoung and Katz on TE extensions
to OSPF?

Both appear to do the same.

-- Rohit
>         "FILE
> /internet-drafts/draft-srisuresh-ospf-te-03.txt".
>

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---

From: Pyda Srisuresh <[email-masked]>
Date: Wed, 18 Sep 2002 08:55:25 -0700

Hi Rohit,

The draft-srisuresh-ospf-te-xx uses OSPF-TE LSAs, unlike the draft-katz-yeung
draft, which uses Opaque LSAs. As such the draft-srisuresh-ospf-te-xx
is scalable to networks with multiple areas, usable in TE/non-TE mixed networks
and extensable to packet/non-packet mixed networks. Section 4.0 in the draft
explains the motivations for designing the OSPF-TE LSAs as opposed to using
Opaque LSAs. Section 6 is devoted to describing a transition strategy for
implementations using Opaque LSAs.

The draft also complements the draft-katz-yeung draft in that it uses the
Link-TE TLAs used by the draft-katz-yeung draft.

The following TE-LSAs give a flavor of what to expect from the draft.

     - TE-Router LSA (0x81) describes TE capabilities of the Router and
       all its TE-links using router-TE TLVs and Link-TE TLVs.

       The LSDB built by draft-katz-yeung has no knowledge of the
       TE capabilities of the routers.

     - TE-incremental-link-Update LSA (0x8d) is used to disseminate
       incremental updates (i.e., Delta TLVs) for the TE-links.

       Opaque LSAs are not suited to advertising incremental TLV
       changes. A change in any TLV of a TE-link will mandate the
       entire Opaque-LSA (with all the TLVs included) to be transmitted.

     - TE-Circuit-paths LSA(0x8C) is used to announce availability of
       pre-established circuit paths in the network meetign a certain
       criteria. The LSA advertisement can include the duration of the
       static path, including the setup and teardown times.

       Opaque LSAs are not suited to advertising static circuit paths.

Hope this helps.

regards,
suresh

> > implementation to automatically retrieve the ASCII

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