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Re: MPLS packet encapsulation?

  • From: James Carlson <carlson@ironbridgenetworks.com>
  • Date: 11 May 1999 07:27:48 -0400
  • Organization: UltraNet Communications , an RCN Company http://www.ultranet.com/
  • X-Complaints-To: abuse@ultra.net
  • X-Ultra-Time: 11 May 1999 11:27:51 GMT


Alex <Alejandro.E.Icaza@rose-hulman.edu> writes:
> Could anyone tell me how IP packets are encapsulated for transport over an MPLS
> ATM core?  Sure the label is applied to the VPI/VCI field in the ATM cell
> header, but how are IP packets packaged within these cells?  They are put into
> cells aren't they?  Is this packaging similar to what's specified in RFC 1483?

Yes, it's null-encapsulated AAL-5.  (In other words, it's just raw IP
in the AAL-5 frame.)  See:

http://search.ietf.org/internet-drafts/draft-ietf-mpls-atm-02.txt

> If so, could one say that IP packets are transported over ATM VCs in the same
> fashion as the overlay model solutions such as LANE and IP over ATM?

Yes and no.  The big difference is how signaling and VPI/VCI numbering
spaces are managed.

-- 
James Carlson, Software Architect                   <carlson@ibnets.com>
IronBridge Networks / 55 Hayden Avenue   71.246W   Vox:  +1 781 372 8132
Lexington MA  02421-7996 / USA           42.423N   Fax:  +1 781 372 8090
"PPP Design and Debugging" --- http://people.ne.mediaone.net/carlson/ppp