Subject: Re: glp draft based on BGP

From: Matt Squire <[email-masked]>
Date: Thu, 04 Mar 1999 21:30:08 -0500

>> 3. One drawback that I find in this approach is that the policy for
forwarding
>>     route information is present at every TBGP speaker (section 7.3) and
hence
>>     when the information arrives at a particular speaker, it is already
subjected
>>     to a cascade of policies, which it doesn't even know. Support for
exchange
>>     of full database (as in SCSP based draft) seems to be useful, if the
policy
>>     leading to decision, should be applied independently in each domain. Of
>>     course, changes are exchanged incrementally so the network wouldn't
be flooded.
>
>If an administrative domain happens to lie on a specific call route, the
>TBGP speakers representing that domain definitely have the right to
>enforce their own policies on that route before advertising it further.
>If an administrative domain doesn't have any policies to enforce, that's
>fine.
>
>Even the SCSP-based proposal permits intermediate LSes to enforce their
>own policies (Matt, please correct me if I am wrong?). In the
>inter-domain case, intermediate LSes may modify attributes and may
>perform aggregation. They're not just synchronizing their databases.
>

Right.  The SCSP/BGP question addresses probably the simplest part of the
GLP problem, how to keep peer LSs synchronized.  It may turn out to be a
controversial issue, but at least the problem is simple, and could be
solved by a number of other protocols as well.  There are some subtle
underlying issues to the debate, but the basic problem is just a two-party
database synchronization.  

IMHO, the tougher questions deal with the information being synchronized,
what is it, how does it get represented, how does it get aggregated, etc.
These are issues that both approaches must eventually address better than
they currently do.  

- Matt

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From: "David R. Oran" <[email-masked]>
Date: Fri, 5 Mar 1999 16:08:59 -0500

> database synchronization.
I guess routing has finally made the big time, when people consider the
routing convergence, scalability, policy satisfiability, and robustness
problems "simple". :-)

Oh, and yes, what makes you think this is a two-party problem? If you
can convince me that it is, I'll retract what I said above and stop
worrying about all the usual things I worry about when designing a
routing scheme.

> These are issues that both approaches must eventually address
While I agree in principle, there are certain mathematical/physical
constraints which will so constrain the solution space that we'd better
face that up front. For example, the general multi-metric optimization
problem has exponential time complexity. Information that gets
aggregated needs to have at least a globally-defined partial order. Etc.
Etc.

> - Matt
This is going to be fun!

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