Re: [Tsv-art] [Last-Call] Tsvart last call review of draft-ietf-mpls-rmr-12

Colin Perkins <> Sun, 04 October 2020 08:45 UTC

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From: Colin Perkins <>
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Date: Sun, 4 Oct 2020 09:44:50 +0100
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To: Kireeti Kompella <>
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Subject: Re: [Tsv-art] [Last-Call] Tsvart last call review of draft-ietf-mpls-rmr-12
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Hi Kireeti,

Apologies for not following-up on this earlier myself. These changes look to address my concerns. 


> On 16 Sep 2020, at 15:52, Kireeti Kompella <> wrote:
> Hi Colin,
> Sorry for the very belated response!
> Thank you for your review.  All of your comments have been addressed in the -13 update; section 1.2 has a summary of the changes, marked with [TAR] for the Transport Area Review.  Section 4.2 has updated text on timers; unfortunately, there are two typos here: one, this change was made in response to TAR, not SAD; two, the actual change was duplicated.  Section 5 defers the value of the OAM timer to the OAM protocol being used.
> The nits in section 1 & 1.1 have also been fixed.
> Hopefully, all your concerns have been addressed.
> Cheers,
> Kireeti.
> On Tue, Nov 5, 2019 at 3:30 PM Colin Perkins via Datatracker < <>> wrote:
> Reviewer: Colin Perkins
> Review result: Almost Ready
> This document has been reviewed as part of the transport area review team's
> ongoing effort to review key IETF documents. These comments were written
> primarily for the transport area directors, but are copied to the document's
> authors and WG to allow them to address any issues raised and also to the IETF
> discussion list for information.
> When done at the time of IETF Last Call, the authors should consider this
> review as part of the last-call comments they receive. Please always CC
> <> if you reply to or forward this review.
> The draft describes how MPLS can be used to configure ring topologies,
> as is frequently used to provide resilience. This seems like a reasonable
> thing to do - indeed I'm surprised such a specification doesn't already
> exist. From a transport perspective, this looks reasonable, but I do have
> some comments:
> - The draft discusses resilience mechanisms, by which the ring can be
> used to protect from link failures. There is, however, no discussion of
> how to recover from loss of the various messages used to announce and
> manage the ring network. It may be that the protocol used to convey
> these messages provides appropriate reliability mechanisms and the
> draft just needs to reference and clarify that. However, if not, it would
> seem worth considering robustness to loss of the ring advertisement
> and maintenance messages.
> - Auto-discovery in Section 4 uses timers T1 and T2. It's not clear what
> is the timeout value for these timers, and whether their value needs to
> be statically chosen or somehow tuned based on the size of the network. 
> - Similarly, Section 5 on Ring OAM specifies two timers. These have fixed
> values of 3.3ms and 1s. It's not clear why these values were chosen or why
> they are correct.
> Nits:
> - The Introduction talks about "transport networks". It's not clear what
> is meant by this, and there might be an alternative term that's clearer.
> - The last paragraph before Section 1.1 states: “The intent is not to
>  construct rings in a mesh network,  and use those for protection”. I
> can’t parse the grammar here – can you clarify?
> -- 
> Kireeti
> -- 
> last-call mailing list