The MPLS WG Archive

[Abhijit M Gadgil <amg@sasken.com>]

Hi,
 after going thr' the topology and the scenario u described, I think,
the basic problem starts when C and D merge the FECs and send one label
upstream. The topoplogy u mentioned works because C/D is doing Pop and
then IP header is exposed. If there was some label given by E and/or F,
then its impossible for packets with label C1 to determine the
right FEC, and to attach correct label. Unless one does IP lookup after
the pop and then Push label depending upon the look up result. (which
defeats the purpose of using MPLS)

Any thoughts?

-abhijit

Abhijit Gadgil


On Mon, 14 May 2001, Chris Kuszmaul wrote:

>   Indeed, consider: (the following was sent as private email to a
> couple folks on the list, but I think it merits a broader audience)
>
>  In thinking about this, I ended up wondering what would happen when the
> next hop changes, in the following scenario:
>
> Suppose we have A connected to B, connected to C and D, with C and D each
> connected to E and F
>
>
>             ----C----E
> A---B<          X
>            -----D----F
>
> Suppose that we do unsolicited ordered advertisement, to create LSPs leading
> to E and F.
>
> C and D both aggregate their FECs, and B receives the following
> advertisements