Re: [Lsr] I-D Action: draft-ietf-isis-segment-routing-msd-11.txt

"Les Ginsberg (ginsberg)" <ginsberg@cisco.com> Tue, 15 May 2018 14:38 UTC

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From: "Les Ginsberg (ginsberg)" <ginsberg@cisco.com>
To: Christian Hopps <chopps@chopps.org>
CC: "lsr@ietf.org" <lsr@ietf.org>
Thread-Topic: [Lsr] I-D Action: draft-ietf-isis-segment-routing-msd-11.txt
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Date: Tue, 15 May 2018 14:38:53 +0000
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Subject: Re: [Lsr] I-D Action: draft-ietf-isis-segment-routing-msd-11.txt
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Chris -



> -----Original Message-----

> From: Christian Hopps <chopps@chopps.org>

> Sent: Tuesday, May 15, 2018 1:54 AM

> To: Les Ginsberg (ginsberg) <ginsberg@cisco.com>

> Cc: lsr@ietf.org

> Subject: Re: [Lsr] I-D Action: draft-ietf-isis-segment-routing-msd-11.txt

>

>

> Hi Les,

>

> I was going over the 2 SR-MSD documents (IS-IS and OSPF) just wondering

> how viable it would be and if we should combine them.

>

[Les:] (I knew somebody would ask this question. :-) )

The two documents were fairly mature before the official merging of the two IGP WGs and certainly before we actively started pursuing combined documents in cases where it makes sense.



Whatever benefit might accrue from combining the documents (and you can see from the responses on the list that there are different opinions about this) it is overwhelmed by the delay that is likely to be introduced by taking two documents that have already passed last call and revising them into one document.



We have mature documents, we have implementations, we need to proceed to publication without introducing unnecessary delays.



> In any case doing the diff highlighted a couple issues in the IS-IS version.

>

> Issue: Under both the Node and Link sub-tlv's the MSD type (1?) is not

> actually mentioned, only the "MSD value", if one was pedantic it would mean

> that regardless of the type the value was always the same, certainly not what

> is intended. :)



[Les:] In both sections the draft says (emphasis added):



"Value: field consists of one or more pairs of a 1 octet MSD-Type

   (IANA Registry) and 1 octet Value.



Why do you see this as unclear?



>

> Issue: The OSPF version adds text about what to do in the presence of

> multiple instances of the same TLV. This highlighted the fact that the IS-IS

> draft doesn't do this, but also doesn't talk about there only being 1 allowed.

>



[Les:] MSD inherits the procedures defined in https://tools.ietf.org/html/rfc7981#section-3 .

There is therefore no need for further specification.



The meaning of "one allowed" is not the same in IS-IS. Clearly multiple MSD sub-TLVs are allowed since there are 255 possible MSD types and they would not all fit into a single sub-TLV.



> Maybe Issue: We've got 2 drafts creating the same sub-[-sub]-tlv MSD type

> registry. I fully agree that we should only have one registry, but it's

> interesting that we'll have 2 publications that create and reference it. Also,

> where does this registry go in IANA? There are distinct IS-IS, OSPFv2 and

> OSPFv3 pages that contain the IANA registries for each protocol. Should we

> create a new shared LSR or IGP page? Anyway this might be a reason to

> combine the 2 documents.

>

[Les:] Peter has already responded as to "where the registry goes" - which is clearly stated in the drafts:



"This document requests creation of an IANA managed registry under a

   new category of "Interior Gateway Protocol (IGP) Parameters" IANA

   registries..."



I agree only one document should define the registry and the other should reference it. That was the agreement between the authors - but it seems we did execute well. We will discuss and decide which draft to change.



    Les

> While somewhat inelegant we could probably avoid any need to re-Last Call if

> the combination was basically a cut and paste operation.

>

> Thanks,

> Chris.

>

> Les Ginsberg (ginsberg) <ginsberg@cisco.com<mailto:ginsberg@cisco.com>> writes:

>

> > This is a minor editorial revision to make the draft consistent w draft-ietf-

> ospf-segment-routing-msd-12.

> >

> >    Les

> >

> >> -----Original Message-----

> >> From: Lsr <lsr-bounces@ietf.org<mailto:lsr-bounces@ietf.org>> On Behalf Of

> >> internet-drafts@ietf.org<mailto:internet-drafts@ietf.org>

> >> Sent: Thursday, May 10, 2018 5:49 PM

> >> To: i-d-announce@ietf.org<mailto:i-d-announce@ietf.org>

> >> Cc: lsr@ietf.org<mailto:lsr@ietf.org>

> >> Subject: [Lsr] I-D Action: draft-ietf-isis-segment-routing-msd-11.txt

> >>

> >>

> >> A New Internet-Draft is available from the on-line Internet-Drafts

> directories.

> >> This draft is a work item of the Link State Routing WG of the IETF.

> >>

> >>         Title           : Signaling MSD (Maximum SID Depth) using IS-IS

> >>         Authors         : Jeff Tantsura

> >>                           Uma Chunduri

> >>                           Sam Aldrin

> >>                           Les Ginsberg

> >>       Filename        : draft-ietf-isis-segment-routing-msd-11.txt

> >>       Pages           : 9

> >>       Date            : 2018-05-10

> >>

> >> Abstract:

> >>    This document defines a way for an IS-IS Router to advertise multiple

> >>    types of supported Maximum SID Depths (MSDs) at node and/or link

> >>    granularity.  Such advertisements allow entities (e.g., centralized

> >>    controllers) to determine whether a particular SID stack can be

> >>    supported in a given network.  This document only defines one type of

> >>    MSD maximum label imposition, but defines an encoding that can

> >>    support other MSD types.

> >>

> >>

> >> The IETF datatracker status page for this draft is:

> >> https://datatracker.ietf.org/doc/draft-ietf-isis-segment-routing-msd/

> >>

> >> There are also htmlized versions available at:

> >> https://tools.ietf.org/html/draft-ietf-isis-segment-routing-msd-11

> >> https://datatracker.ietf.org/doc/html/draft-ietf-isis-segment-routing

> >> -msd-

> >> 11

> >>

> >> A diff from the previous version is available at:

> >> https://www.ietf.org/rfcdiff?url2=draft-ietf-isis-segment-routing-msd

> >> -11

> >>

> >>

> >> Please note that it may take a couple of minutes from the time of

> >> submission until the htmlized version and diff are available at

> tools.ietf.org.

> >>

> >> Internet-Drafts are also available by anonymous FTP at:

> >> ftp://ftp.ietf.org/internet-drafts/

> >>

> >> _______________________________________________

> >> Lsr mailing list

> >> Lsr@ietf.org<mailto:Lsr@ietf.org>

> >> https://www.ietf.org/mailman/listinfo/lsr

> >

> > _______________________________________________

> > Lsr mailing list

> > Lsr@ietf.org<mailto:Lsr@ietf.org>

> > https://www.ietf.org/mailman/listinfo/lsr