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From: Pyda Srisuresh (srisuresh_at_YAHOO.COM)
Date: Wed Sep 18 2002 - 10:55:25 CDT
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.
--- Rohit Gupta <rohitgupta416YAHOO.COM> wrote:
> 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
> --- Internet-DraftsIETF.ORG wrote:
> > 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.
> > A URL for this Internet-Draft is:
> > To remove yourself from the IETF Announcement list,
> > send a message to
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> > Login with the username
> > "anonymous" and a password of your e-mail address.
> > After logging in,
> > type "cd internet-drafts" and then
> > "get draft-srisuresh-ospf-te-03.txt".
> > A list of Internet-Drafts directories can be found
> > in
> > http://www.ietf.org/shadow.html
> > or ftp://ftp.ietf.org/ietf/1shadow-sites.txt
> > Internet-Drafts can also be obtained by e-mail.
> > Send a message to:
> > mailservietf.org.
> > In the body type:
> > "FILE
> > /internet-drafts/draft-srisuresh-ospf-te-03.txt".
> > NOTE: The mail server at ietf.org can return the
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