The MPLS WG Archive

[David Charlap <david.charlap@marconi.com>]

Fabris Sergio wrote:
> 
> Traffic Engineering:
> 
> ..........A standard IP packet arrives at Interface 1 of LSR 1. After
> performing a longest-match
> lookup in its IP routing table, LSR 1 discovers that the best match is with
> Prefix X and that
> all traffic matching Prefix X should to be forwarded on Interface 2 with a
> Label = 10.............
> 
> How LSR1 discover that the best match is whit that Prefix X??
> Does It made same classification based on source address??

The same way a non-MPLS router would determine the next-hop router.

Through any means it is configured for.  Maybe by destination address
alone.  Maybe also counting source address.  Or perhaps L4 protocol,
port number, stateful packet inspection, load-balancing formulae, or
anything else you can think of.

Traffic engineering is just a fancy name for routing based on
information other than the destination address.  There is no fundamental
difference between a traditional router choosing a next-hop and an LER
choosing an LSP.

-- David