Re: IDR WG Last Call

[Jeffrey Haas <[e-mail]>]

Dave,

On Tue, Jan 15, 2002 at 11:13:42AM -0800, Dave Thaler wrote:
> SAFI 3 was put in at operator's requests (Dorian, for one, I forget who
> else now).  They considered it a MUST to avoid doubling the routing
> table size and amount of BGP traffic when one's unicast and multicast
> topology are the same.
> 
> Before taking it out, you might want to check with Dorian.

While I agree that its nice in theory, you have the added difficulty
of having to maintain additional state for things such as WRD
and potentially awkward queue mechanisms for outgoing routes.
As such, you actually implement at least as much, if not more, 
infrastructure to deal with the additional overhead of having
a SAFI that covers the unicast+multicast case.

Additionally, policy is now a real pain - and very ambiguous in
the current spec.  If you say "accept unicast and multicast routes",
does that mean accept only SAFI 3 or SAFI's 1, 2 and 3?

As Sue has mentioned, treating them as bits works fine for these
three SAFI's.  But I'd rather not have to.

I'm not going to argue very hard for removing SAFI 3 - we already
implement it.  But there are complications that don't seem to be
accounted for with regards to its supposed information overhead reduction.

> -Dave

-- 
Jeff Haas 
NextHop Technologies