Subject: Re: AS scope Opaque LSA

From: Don Goodspeed <[email-masked]>
Date: Thu, 17 Jul 2003 17:34:15 -0400

Minto,

Since most everyone is probably in Vienna, I'll take a go at responding...

1. Technically, yes, since the opaque LSA RFC does not explicitly
state this.  While it is tempting to think of an AS-wide opaque
LSA as being flooded like an AS External LSA (only by an ASBR,
not flooded into stub areas), the same does not apply to an AS-wide
opaque LSA as it does not (necessarily) have anything to do with
"external route" information that an ASBR is responsible for
advertising.

2. I'll let Padma or Acee respond to this one.

3. Not that I am aware of in general OSPF implementations, but there
may be something from the newer drafts like Path Computation Server
that might use AS-wide opaque LSAs.

-don

======================================================
Hi ,
i have few Question regarding AS scope Opaque LSA.

1. Is it possible to originate an AS scope LSA by a non ASBR router.

2. if Opaque LSA supports DNA , Then howcome we remove the Stale DNA
Opaque LSA.
(This will Happen only, non ASBR router may originate AS scope
Opaque LSA)

3. And , is there any As scope Opaque LSA currently used ?

Cheers
Minto Mascarenhas

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From: Acee Lindem <[email-masked]>
Date: Fri, 18 Jul 2003 00:28:06 -0400

Hi Don, Minto,

> "external route" information that an ASBR is responsible for

Don - Agreed. RFC 2370 doesn't require a router originating an
AS scoped opaque LSA to be an ASBR.

> 2. I'll let Padma or Acee respond to this one.

Minto - I think you've uncovered a problem here. A router in
an area other than the originating router will not have route
to the originating router and will purge the stale DoNotAge LSA.
 From RFC 1793:

  2.3.  Removing stale DoNotAge LSAs

       Because LSAs with the DoNotAge bit set are never aged, they can
       stay in the link state database even when the originator of the
       LSA no longer exists. To ensure that these LSAs are eventually
       flushed from the routing domain, and that the size of the link
       state database doesn't grow without bound, routers are required to
       flush a DoNotAge LSA if BOTH of the following conditions are met:

         (1) The LSA has been in the router's database for at least
             MaxAge seconds.

         (2) The originator of the LSA has been unreachable (according to
             the routing calculations specified by Section 16 of [1]) for
             at least MaxAge seconds.

One solution would be for any router announcing any AS scoped LSA to
advertise itself as an ASBR (as per its router bit in the router LSA).
Other solutions are welcome :^)

> that might use AS-wide opaque LSAs.

The OSPF capabilities draft may utilize an AS scoped opaque LSA.

--
Acee