Re: FW: Alvaro Retana's Discuss on draft-ietf-isis-sbfd-discriminator-02: (with DISCUSS)

On Wed, Nov 18, 2015 at 05:16:05PM +0000, Alvaro Retana (aretana) wrote:
> Jeff/Reshad:
> 
> Hi!  How are you?

I *was* almost caught up with my BFD work post-IETF, thanks. :-)

> I need you to please drive the discussion below.  The outcome should be
> consensus on how the mapping between multiple discriminators and
> applications/use cases on a node should be handled.  I can guess at 3
> potential outcomes:
> 
> 1. The "applications (e.g., OSPF/IS-IS)" should handle it.
> 2. The S-BFD Base specification will detail how to do it (not requiring
> additional work from the applications).
> 3. We'll deal with this issue somewhere else (not requiring additional
> work from the applications).
> 
> [Maybe there are more options.]
> 
> Please keep isis/ospf/l2tpext in the loop.
> 
> Even in the best case, we're probably going to need some clarification in
> draft-ietf-bfd-seamless-base.
> 
> BTW, if you decide to follow this thread..  I fat fingered the address of
> the l2tpext WG. :-(

We'll give the authors a chance to reply, but basically:
- discriminators must already be domain-wide unique.
- The uniqueness property tends to imply provisioning.
- Thus the foreknowledge for the mapping is probably implied.

See section 5, second to last paragraph for reinforcement that it's a local
matter.

The better questions are "why would you give a given node more than one
discriminator?"  The typical case is likely to be for scaling the number of 
BFD sessions on that node.

I leave comments about more clever things to do with this for the authors.

-- Jeff