The MPLS WG Archive

[richard.spencer@bt.com]

If an operator already has L2TP deployed, why not just continue to use L2TP VPNs? Why go to the trouble of upgrading the edge to support MPLS and leave L2TP in the core? Surely the real advantages of using MPLS are for CAC, FRR, and TE across the core. This isn't analogous to the IP/GRE case as these don't have their own muxing capabilities and therefore MPLS is used for this purpose. So in the MPLS over L2TP case, what advantages does swapping one muxing field at the edge for another have? 

If its a greenfield network, again why would an operator choose to deploy a mesh of PE-PE L2TP tunnels in the core with MPLS just at the edge? The operator would have all the downsides of using MPLS (i.e. an extra protocol to manage/troubleshoot) with none of the benefits.

The only scenarios I can think of where L2TP would make sense are:

i)   Migration: If an operator is migrating from L2TP over to MPLS (short term solution)
ii)  Support for multiple PSN types: If an operator had deployed (or acquired) IP/L2TP and MPLS PSNs (probably short term solution if the operator is looking for convergence)
iii) Inter-provider: a) Where an operator with an L2TP network wants to offer peer-to-peer inter-provider VPNs with another operator that uses MPLS (avoids PW demux/signalling interworking), or b) where an operator with an L2TP network wants to offer MPLS transit services, or c) where two MPLS VPN providers want to use IP ASBR-ASBR instead of MPLS and want use the L2TP cookie for increased security over IP/GRE. 

Are these the types of scenarios that those supporting the draft need it for? If so perhaps it would be worth adding them to the applicability statement.

Regards,
Richard

> -----Original Message-----
> From: mpls-bounces@lists.ietf.org 
> [mailto:mpls-bounces@lists.ietf.org]On
> Behalf Of Loa Andersson
> Sent: 04 February 2005 09:43
> To: W. Mark Townsley
> Cc: mpls@ietf.org
> Subject: Re: [mpls] MPLS over L2TPv3 as WG item
> 
> 
> Working Group,
> 
> the reception of the draft was a wee bit ambigious (some no, some no
> need and some yes), with some service providers strongly in favor.
> We would like to poll the working group on whether we want to make
> draft-townsley-mpls-over-l2tpv3-00.txt a wg doc.
> 
> To make it possible to publish a working group document, given a rough
> consensus in the wg, we need to have comments Feb 11.
> 
> Send comments to the mailing list or wg chairs. We are looking for
> both positive and negative comments.
> 
> /Loa and George
> 
> W. Mark Townsley wrote:
> 
> > 
> > As requested by Loa at the last MPLS WG meeting, I have 
> renamed the MPLS 
> > over L2TPv3 draft as follows:
> > 
> > draft-townsley-mpls-over-l2tpv3-00.txt
> > 
> > With consensus confirmation from this list, I would like to 
> resubmit 
> > this version as a WG item (preferably before the upcoming 
> deadline for 
> > the next meeting).
> > 
> > Thanks,
> > 
> > - Mark
> > 
> > 
> > _______________________________________________
> > mpls mailing list
> > mpls@lists.ietf.org
> > https://www1.ietf.org/mailman/listinfo/mpls
> > 
> 
> -- 
> Loa Andersson
> 
> Principal Networking Architect
> Acreo AB                           phone:  +46 8 632 77 14
> Isafjordsgatan 22                  mobile: +46 739 81 21 64
> Kista, Sweden                      email:  loa.andersson@acreo.se
>                                             loa@pi.se
> 
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