Subject: RE: Ethernet over MPLS

From: "Andrew Smith" <[email-masked]>
Date: Fri, 28 Mar 2003 09:04:23 -0800

Eric,

If you ask me (which you didn't), the example that you describe sounds
like a rather kludged architecture for a switch - to couple the MPLS
functionality to only specific interface types (e.g. non-Ethernet) may
be an implementation shortcut but it's a bad way to build a general
purpose PE - I would have thought that most customers would not want to
buy into such a restricted product (what? I can't run MPLS/PWE3 over my
core Ethernet links?). Leaving aside the "legacy switch" issue for a
moment, of course it's up to the WG to decide whether it thinks the
standard ought to support such "optimisations" for future
implementations (right now I'm seeing no clear consensus one way or the
other).

Andrew Smith

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Eric
Rosen
Sent: Friday, March 28, 2003 6:34 AM
To: Muneyoshi Suzuki
Cc: [email-masked]
Subject: Re: [PWE3] Ethernet over MPLS 

> Could you clarify the reason why the hw cannot support raw mode if a
> frame has a "provider tag"? 

In my example,  the tag manipulation is part of the  processing path
that is
invoked when  an ethernet frame is  about to be transmitted  out an
ethernet
interface.   However, in  an ingress  PE,  the ethernet  frame never
passes
through this processing path.  Hence the provider tag cannot be removed.

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From: "Andrew G. Malis" <[email-masked]>
Date: Mon, 31 Mar 2003 11:33:17 -0500

I'm personally of two minds regarding tagged mode ...

On one hand, my HW can push and pop tags just fine on both ingress and 
egress, so from a purely proprietary standpoint raw mode meets my needs.

On the other hand, the great majority of currently deployed routers with 
Ethernet interfaces don't have this capability in their HW.  So if we want 
something standardized that is going to succeed in the marketplace, it's 
probably a non-starter to require service providers to replace their 
deployed router Ethernet interfaces in order to be able to run Ethernet 
over a pseudo-wire.

So even though it's not necessary from an architectural standpoint, it 
looks like we can't do away with tagged mode from a practical standpoint.

What started this whole thread was the clear inadequacy of the current raw 
and tagged mode descriptions in the Ethernet draft.  Perhaps if we can 
distill the thread into better descriptions that include, as Eric put it, 
suitable text as to tagged mode's purpose and applicability, then we can 
call it a day and move on.

Andy

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