Re: [Mpls-interop] MPLS over MPLS-TP

Andy,

OK I see your point. If the network is screwed up all bets are off.

Ben

On 11/12/2008 20:11, "Malis, Andrew G. (Andy)" <andrew.g.malis@verizon.com>
wrote:

> How is it any better for a PW? You still have a label at the top of the
> stack. There are two scenarios:
> 
> 1. A label is popped at the MPLS-TP layer that shouldn't have been
> 
> That's either going to expose another label at that layer that won't be
> have the proper context, or the start of an IP packet that'll be
> misinterpreted as a label (since MPLS-TP switches presumably won't know
> how to forward IP, at least in the fast path). In either case, if
> there's a matching label allocation to the 20 bits in the header, then
> it'll be forwarded out a random interface, or dropped if there's no
> match.
> 
> 2. An MPLS-TP label wasn't popped that should have been
> 
> That'll expose (probably) the bottom-most MPLS-TP label to the IP/MPLS
> client router. Again, what happens next depends on how that label is
> interpreted by the router.
> 
> Either way, how are things any better if you use a PW label?
> 
> Cheers,
> Andy
> 
> -----Original Message-----
> From: Ben Niven-Jenkins [mailto:benjamin.niven-jenkins@bt.com]
> Sent: Thursday, December 11, 2008 3:03 PM
> To: Malis, Andrew G. (Andy); Adrian Farrel; Drake, John E;
> mpls-interop@ietf.org
> Subject: Re: [Mpls-interop] MPLS over MPLS-TP
> 
> Andy,
> 
> 
> On 11/12/2008 15:31, "Malis, Andrew G. (Andy)"
> <andrew.g.malis@verizon.com>
> wrote:
>> AM> The intention would be that the MPLS-TP EOS bit would only be
>> encountered at boundary the MPLS-TP network, and the payload would
>> delivered to the client to do with as it desires (and expects),
> whether
>> it's IP to forward, MPLS to switch using router-allocated labels, PW
>> contents, or something else entirely. To the client, there should be
> no
>> difference (at some layer of abstraction above the interface details)
>> between using MPLS-TP for transport and POS or GFP encapsulation for
>> transport.
> 
> Yes, but my concern is that IP & MPLS may well be 'recognised' in the
> network core and if something happened (e.g. Erroneous label pop) to
> expose
> them they could be forwarded natively in error.  Other traffic types are
> unlikely to have this happen as the network core is unlikely to support
> natively forwarding them.
> 
> Ben
> 

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