The MPLS WG Archive

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

"Feng, Mark" wrote:
> 
> With what we discussed below, what would happen is that, if S1, S3
> only need 1M of bandwidth, and S2, S4 need 10M, on the path where
> S1, S3 take, even if they only need 1M, they will get a request of
> 10M and as a result, get a reservation of 10M. This seems to be
> wasteful on that particular path.
>
> ...
>                     ______
>                    |      |
>                +---|      |---+
>                |   |______|   |
>                |              |
>                |s1,s3         |s1,s3
>  s1,s2 ______  |              |  ______
>  -----|      |-+              +-|      | s1,s2,s3,s4
>  -----|      |-+              +-|      |------
>  s3,s4|______| |              | |______|
>                |s2,s4_____    |s2,s4
>                |   |      |   |
>                +---|      |---+
>                    |______|

It doesn't matter how much each one "requires".  If they are all in the
same session and the egress router chooses to use SE-style for the
reservation, then all will get the same bandwidth - 1M, 10M, or anything
else.  (But probably 10M, since that's the smallest size that will
satisfy everybody's request.)

If this is unacceptible, then the ingress router shouldn't put these
four LSPs all in the same session together.

-- David