Re: [Lsr] Working Group Last Call for draft-ietf-lsr-ip-flexalgo-04 - "IGP Flexible Algorithms (Flex-Algorithm) In IP Networks"

[Robert Raszuk <[e-mail]>]

Hi Ketan,

> KT2> I see the primary use case for IP FlexAlgo (or another data plane)
> > to be that the data plane is used by itself. In the (rare?) case where
> > multiple data planes are required to coexist, it is simpler both from
> > implementation and deployment POV to use different algos. It would be
> > good to have operator inputs here. The only cost that I see for this is
> > that the same FAD may get advertised twice only in the case where it is
> > identical for multiple data planes. So I am still not seeing the benefit
> > of enabling multiple (i.e. per data plane) computations for a single
> > algo rather than just keeping it a single computation per algo where a
> > single data plane is associated with a specific algo.
>
> ##PP3
> I really do not see the problem. As you stated above repeating the same
> FAD for multiple algos would be inefficient. The beauty of FAD is that
> it is app independent and can be used by many of them.
>


As I had very same doubts as you I think the advantage here is that even
for the same FAD you can have different links attribute/metric values
advertised on a per "app" basis. Hence you may effectively get different
topologies on a per "application" basis while still using same algorithm.

Again as I and others said it few times the name "app" is badly chosen to
describe forwarding behaviour in data plane but I guess no one is going to
listen and change that name now :)

Practically if folks will use different algorithms to construct different
topologies or use the same algorithm with different metrics all depends on
what real user _applications_ the network is to carry modulo what
flexibility network elements used to construct such network provide.

Thx,
R.