The MPLS WG Archive

[Yakov Rekhter <yakov@juniper.net>]

Bora,

> 1. You need to specify both ingress and egress identifiers for two reasons:
> 	a) On broadcast media (think GigE, 10 GigE) when a router has 
> multiple interfaces attached to the same switch, you want the RSVP 
> packet and MPLS LSPs to use the correct adjacency. And the only way 
> to get that is to specify a pair. This scenario is commonly used in 
> POP architectures where there are two GigE switches in the middle and 
> each router has one link to each GigE switch and the GigE switches 
> are interconnected.

Could you tell us how the head-end LSR would be able to figure out
the "correct adjacency" in the scenario you described above.

> 	b) Specifying both ingress and egress is more explicit and 
> leaves no guesswork.
> 
> 2. I just asked a simple question with respect to fast reroute: How 
> do you do it when you have unnumbered interfaces. At first thought, I 
> thought it would be very hard to do, after thinking about it for a 
> few minutes I think if you make certain assumptions and make 
> extensive use of the IGP-TE database, you can possibly get by. But 
> why? Why are we arguing over 4 more bytes in the signaling message. 
> We don't have 56K leased line links any more. OC192c has become the 
> standard and 768c is right around the corner. I don't see any point 
> it haggling on four bytes. Hence we defined the EERO.

We aren't arguing over 4 more bytes - the issue is whether
it is truly necessary. And so far you've yet to construct a
case that shows that it is necessary.

Yakov.