Subject: Re: rfc 2370 doubt

From: "Naidu, Venkata" <[email-masked]>
Date: Fri, 13 Sep 2002 11:12:05 -0400

Rohit,

-> Hi,
-> RFC 2370 in its abstract says that "This memo defines
-> enhancements to the OSPF protocol to support a new ..
-> application-specific information.  The information
-> field may be used directly by OSPF or by other
-> applications"
->
-> My doubt is that how can OSPF use Opaque LSAs for its
-> own purposes as it doesnt run SPF over these LSAs?

  It is a very naive idea that `all the information exchanged
  by OSPF LSAs must be used in SPF. If not, then the
  information is not for OSPF use`. OSPF floods/uses lot of
  flooded information for *optimization*, *reliability*,
  *accuracy* etc reasons (other than just SPF purpose).

-> I can understand their use for TE/MPLS/GMPLS but their
-> use with OSPF is not clear.

  For example, OSPF uses Opaque LSAs for its own purpose:
    - Hitless Restart
    - Flooding Optimizations
    - Dynamic Hostname
    - Dynamic Mesh Groups
    - If CSPF is implemented in OSPF then TE LSAs are also
      considered as part of OSPF (not part of application).
      There are some implementations that did this too.
      In the history, there are implementations where,
      new LSA types are used, instead of Opaque LSAs.
      (for example, draft-zhang-qos-ospf-01 and SriSuresh
      TE LSAs etc)

  For that matter, what is the difference between an *application*
  and *self* ? Where is the clear demarcation ? If you look at
  protocols so closely, you can *differentiate* each sub-module
  as a separate application (using some services provided by
  other sub-modules). If you look at protocols at 1000 ft view,
  you can see *integrated* view, such that the whole protocol
  itself is an application on top of some lower layer protocols.

--
Venkata.