Re: [mpls] working group last call on draft-ietf-mpls-tp-p2mp-framework

Lou Berger <> Mon, 04 November 2013 06:22 UTC

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Date: Sun, 03 Nov 2013 20:17:17 -0800
From: Lou Berger <>
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To: Zhenlong Cui <>,
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Subject: Re: [mpls] working group last call on draft-ietf-mpls-tp-p2mp-framework
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	Thank you for the comments. Please see below for responses in-line.

On 10/22/2013 2:18 AM, Zhenlong Cui wrote:
> Dear authors,
> I have a comment/question on this draft.
> As described in section 1.3, in the ring topology, we have to consider the drop-and-continue node case. 
> In this case, the drop-and-continue node will become an intermediate point. 

Agreed.  This node will be both a transit node and an egress/leaf.  This
case is covered in RFC4875.

> So, can we configure a MEP on an intermediate node(= drop-and-continue node)?

I think this is a matter of semantics.  By definition a MEP is only on
egress (leaf) nodes and a MIP only on transit nodes.  Assuming you are
asking about the case stated in the previous point, that a node is both
egress and transit, then I think it could have both MEP and MIP
functionality separately instantiated.  Section 3.7 already covers P2MP
MIPs and MEPs.

> As described in section 3.3 of RFC 6371, a MEP terminates all the OAM packets it receives from the MEG, 
> may discards silently if addressing information in the OAM payload is different with termination node. 
> It means that the intermediate node must NOT be configured as a MEP when per-node OAM configuration is used, 
> because downstream nodes can't receive the OAM packets from root node.

Why do you say this?  If a node is both transit and egress, it will
replicate OAM packets (just like the data) when performing its transit
role before then terminating the data/OAM packets as part of its egress

> On the other hand, if the intermediate node can't be configured as a MEP, the path protection may 
> not be able to work at this point. I think this is a serious problem.

Perhaps I'm missing something, but I simply don't see an issue here that
isn't already addressed in RFC6371 (and 4875.) I guess 6371 could have
shown this case as an example, or provided a related detailed walk
through, but either way I don't see any "serious problem" here.

Perhaps the best way to proceed on this is to propose text to the
already referenced "additional detail" draft
draft-hmk-mpls-tp-p2mp-oam-framework.  Does this work for you?


> Best regards,
> zhenlong
>> -----Original Message-----
>> From: [] On Behalf Of Loa Andersson
>> Sent: Friday, October 18, 2013 1:29 PM
>> To:
>> Cc:;
>> Subject: [mpls] working group last call on draft-ietf-mpls-tp-p2mp-framework
>> Working Group,
>> this is to start a two week working group last call on draft-ietf-mpls-tp-p2mp-framework-04.
>> Please send your comment to working group mailing lists (
>> We did an IPR poll on this document prior to starting the wglc.
>> The each authors responded to the IPR poll that they not aware of any IPR's relating to this document.
>> There are no IPRs disclosed against this document.
>> The working group last call will end Friday November 1, 2913.
>> /Loa
>> mpls wg co-chair
>> --
>> Loa Andersson                        email:
>> Senior MPLS Expert                
>> Huawei Technologies (consultant)     phone: +46 739 81 21 64
>> _______________________________________________
>> mpls mailing list