[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [PWE3] Fat PW - a couple of points I was asked about.

Yang Yang wrote:
Hello Stewart,
Please see the comments inline.
Best Regards!
Yang

On Dec 6, 2007 5:10 AM, Stewart Bryant <stbryant at cisco.com <mailto:stbryant at cisco.com>> wrote:

    Yang Yang wrote:
    > Hello Stewart,
    >     I'm wondering how to use the LB label inside PSN. If LB label is
    > only used by the ingress T-PE for load-balancing, maybe it's no
    > necessary to carry the LB label across the PSN.
    >
    >     Best Regards!
    >         Yang

    It is carried across the PSN.

    Any P router that includes the bottom label in its ECMP
    calculation takes
    advantage of it.

So, the ingess T-PE adds load-balancing label, and the Ps use the LB label for ECMP calculation. How does the P notice the existing of the LB label? And is it PW load-balancing? I'm a little confused. It's like that the P couldn't get the right information for ECMP calculation and then the T-PE should add some information.
The P router hashes the label stack.

However you need to make sure that different flows have different
hash outputs to spread the flows over the ECMP set.

Since the egress PE label and the PW label for this high
bandwidth PW are the same for every packet all flows
within the PW go the same way (we designed
the PW to make that happen). However since acesss
speed is now high compared to core speed this can
be a problem with some PWs.

So you need to add some flow info into the labels stack and
you can either do this by using a number of signalled PW
labels and mapping some flows to each, or you can add
an additional label (that you hope the P routers will
include in their hash) and put some form of flow identifier
in  that additional label.

- Stewart








    Stewart




_______________________________________________
pwe3 mailing list
pwe3 at ietf.org
https://www1.ietf.org/mailman/listinfo/pwe3