Subject: RE: MPLS PID

From: "Andrew G. Malis" <[email-masked]>
Date: Tue, 25 Mar 2003 18:52:02 -0500

Shahram and Alia both make excellent points:

At 3/25/2003 02:18 PM -0800, Shahram Davari wrote:
> >1.  Dealing with ECMP behavior
> >2.  Inband OAM flows
> >3.  Identifying flows for netmanagement applications.
>
>I don't think any of them justifies adding PID.
>
>1) ECMP could use only label hashing and not hash IP header.
>2) OAM flows could use IPv4/V6 null or MPLS Alert label
>3) Netmanagment could identify the flow at the ingress.

At 3/25/2003 06:15 PM -0500, Alia Atlas wrote:
>How does requiring a PID in the PWE3 L2 control word solve or handle the 
>case where a control word is not mandatory?
>
>There are pseudo-wires, such as ethernet, where a control word is not 
>mandatory.  This would imply that the first nibble (which would be 
>identified as the suggested PID) would be that from the ethernet frame.

We're going to have to change the PWE3 drafts to require the control word, 
and change both the SONET/SDH and some of the ATM encapsulations, to 
support a hack.  If you REALLY want multi-protocol identification, then 
have the MPLS WG put a REAL multiprotocol identifier, a la RFC 2427 or 
2684, between the labels and the payload.  See, for example, 
draft-moreels-multiproto-mpls-00.txt for a much more general (and useful) 
method than just a four-bit hack.  And sorry for the cross-post, but this 
really does affect both WGs.

Cheers,
Andy