Subject: LLC/SNAP encapsulation

From: " Francois.Paillet" <[email-masked]>
Date: Wed, 19 Jan 2000 15:05:03 +0100

Hi,

Excuse-me if a lot of e-mails have been written about this issue,
but I've some doubts about the chapter 7 ("Use of VPI/VCIs") in the
draft-ietf-mpls-atm-02.txt (Is it the last version ? Its
expiration date is October 1999).
These doubts concern the encapsulation of non-labelled packets
between ATM-LC interfaces, here are my questions:

- Does LDP have to be carried on a VPI/VCI connection with LLC/SNAP
encapsulation ? Does the draft forbid to use a NULL-encapsulation
connection to bear LDP ?

- If yes, what's the reason ? If a LSR only supports IP protocol at
layer 3 (no other protocol such as IPX, ...), it seems to be useless
to add the LLC/SNAP encapsulation, doesn't it ?

Thank in advance for your responses.
Best regards,

Francois Paillet.

--
Francois PAILLET                                Ericsson (MET)
Tel : 33 1 64 47 66 10                          19, avenue Carnot
Fax : 33 1 64 47 50 33                          91348 Massy Cedex
mailto:[email-masked]         FRANCE

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From: Eric Rosen <[email-masked]>
Date: Wed, 19 Jan 2000 10:48:30 -0500

Francois> Does LDP have to be  carried on a VPI/VCI connection with LLC/SNAP
Francois> encapsulation?

Yes. 

Francois> Does the  draft forbid to  use a NULL-encapsulation  connection to
Francois> bear LDP?  

Yes.

Francois> What's the reason ? If a  LSR only supports IP protocol at layer 3
Francois> (no other  protocol such as IPX,  ...), it seems to  be useless to
Francois> add the LLC/SNAP encapsulation, doesn't it? 

Supporting the LLC/SNAP encapsulation on the control VPI/VCI is no big deal,
and it just makes everything simpler  if there is only one encapsulation and
everybody uses  it.  (If both  are allowed, then for  interoperability, both
must be  required.  Then there has  to be a way,  possibly configuration, to
determine  which is being  used.  In  this particular  case, it  just seemed
simplest to  require the  LLC/SNAP encapsulation, and  it's hard to  see any
downside to it.)