> From: Saku Ytti <[email protected]> > Sent: Monday, June 15, 2020 10:31 AM > > On Mon, 15 Jun 2020 at 12:24, <[email protected]> wrote: > > > > Yes this is where each node needs to have a label uniquely identifying > > every LSP passing through it. > > Saku, > > With IP header you don't need this, > > Consider this: > > PE1 to PE2 via 3 P-core nodes > > With ECMP in IP, then PE1 just needs single FEC the DST-IP of PE2, > > which will be load-shared across all 3 paths. > > Using MPLS If you need to uniquely identify each path you need 3 FECs > > (3 LSPs one via each P core node), now imagine you have 100K possible > > paths across the fabric -that's a lot of FECs on PE1 or any node in > > the fabric where each has to have a unique label for every possible > > unique path via the core that the particular node is part of. > > Are we talking about specific implementations of fundamentals? It sounds > like we are talking about a specific case where IP next-hop is unilist of N > next- > hops, and MPLS next-hop is a single item without indirection? This is not a > fundamental difference, this is implementation detail. > There is no particular reason MPLS next-hop couldn't be unilist of N > destinations. > Yes it can indeed, and that's moving towards the centre between the extreme cases that David laid out. It's about how granular one wants to be in identifying an end-to-end path between a pair of edge nodes. I agree with you that MPLS is still better than IP, and I tried to illustrate that even enumerating every possible paths using deep label stack is not a problem (and even that can be alleviated using hierarchy of LSPs). adam
_______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
