Subject: Re: MPLS PID

From: "Thomas D. Nadeau" <[email-masked]>
Date: Wed, 26 Mar 2003 15:14:18 -0500

At 03:38 PM 3/25/2003 -0500, George Swallow wrote:
> > Regarding whether the MPLS WG has discussed this before, Eric Rosen 
> suggested at
> > the microphone in SF that it had, but at that time the decision 
> obviously was to
> > not include a PID within MPLS. The bottom line is that perhaps we are 
> seeing
> > that in hindsight this was an error, and if so this should be openly 
> resolved
> > within the MPLS WG.
>
>For a few of us is was foresight, but that didn't carry the day.  I
>would be most happy to have this discussed in MPLS.
>
>It would seem that there three identified uses for the PID.
>
>1.  Dealing with ECMP behavior
>2.  Inband OAM flows
>3.  Identifying flows for netmanagement applications.
>
>The first seems fairly straightforward.
>
>Define IPv4 and v6, reserve a few more values for possible future
>versions of IP.  Figure out whether there is any ST left in the
>world.
>
>For the second define a single PID for any OAM flow.  It would be
>imprudent to had out pair of PIDs to apps that want inband OAM.
>Something collecting flow information in the middle of the network
>won't be able to identify the inband OAM, but that may be a good thing
>as the result will be just counting the data.

         It is a good thing from a counting/flow perspective because
it means that the PW traffic takes the same switching path(s)
as the OAM for that PW that might be used to test the PW.
OTOH, this will not work for tracing; however, there are other
tools that can be used for tracing the PSN already, so this
is not a big issue IMHO.

>The third is a bit tickier.  Given the resolution of (1&2) we'll have a
>small number of PID values to play with to use for flow
>identification.  What that small set should be needs to be resolved.
>I look to operators of networks for input.

         For the last point, wouldn't an option be to just have a
single PID for OAM and then have sub-types follow inside the
packet to identify the apps?  This only requires us to allocate
a single PID for OAM.  This is incidentally, how we have
defined VCCV.

         --Tom

>...George
>
>==================================================================
>George Swallow       Cisco Systems                  (978) 497-8143
>                      250 Apollo Drive
>                      Chelmsford, Ma 01824
>_______________________________________________
>pwe3 mailing list
>[email-masked]
>https://www1.ietf.org/mailman/listinfo/pwe3