Re: [Isis-wg] [Bier] WGLC: draft-ietf-bier-isis-extensions-04

Greg Shepherd <gjshep@gmail.com> Tue, 06 February 2018 23:45 UTC

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From: Greg Shepherd <gjshep@gmail.com>
Date: Tue, 6 Feb 2018 15:45:02 -0800
Message-ID: <CABFReBqEJu5nBMdJm0cmBuUYhatD+JRCpn7TppC-hgV4HGZ3sQ@mail.gmail.com>
To: "Les Ginsberg (ginsberg)" <ginsberg@cisco.com>
Cc: Toerless Eckert <tte@cs.fau.de>, Tony Przygienda <tonysietf@gmail.com>, "Hannes Gredler (hannes@gredler.at)" <hannes@gredler.at>, "bier@ietf.org" <bier@ietf.org>, "isis-wg@ietf.org list" <isis-wg@ietf.org>, Christian Hopps <chopps@chopps.org>
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Subject: Re: [Isis-wg] [Bier] WGLC: draft-ietf-bier-isis-extensions-04
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Thanks Les.

Any other feedback? Looks like the concerns have been addressed. Speak now.

Cheers,
Greg

On Thu, Feb 1, 2018 at 7:26 AM, Les Ginsberg (ginsberg) <ginsberg@cisco.com>
wrote:

> Greg –
>
>
>
> This thread is outdated.
>
> In V6 of the draft we removed the restriction to limit IS-IS BIER support
> to area boundaries – so Toerless’s comment (and my proposed text) are no
> longer relevant.
>
>
>
> Specifically:
>
>
>
> Section 4.1:
>
>
>
> “At present, IS-IS support for a given BIER domain/sub-domain
> is
>
>                    limited to a single area - or to the IS-IS L2
> sub-domain.”
>
>
>
> The above text was removed.
>
>
>
> Section 4.2
>
>
>
> o  BIER sub-TLVs MUST NOT be included when a prefix reachability
>
>       advertisement is leaked between levels.
>
>
>
> Was changed to
>
>
>
> o  BIER sub-TLVs MUST be included when a prefix reachability
>
>       advertisement is leaked between levels.
>
>
>
> This aligns IS-IS and OSPF drafts in this regard.
>
>
>
>     Les
>
>
>
> *From:* Greg Shepherd [mailto:gjshep@gmail.com]
> *Sent:* Thursday, February 01, 2018 2:23 AM
> *To:* Toerless Eckert <tte@cs.fau.de>
> *Cc:* Les Ginsberg (ginsberg) <ginsberg@cisco.com>om>; Tony Przygienda <
> tonysietf@gmail.com>gt;; Hannes Gredler (hannes@gredler.at) <
> hannes@gredler.at>gt;; bier@ietf.org; isis-wg@ietf.org list <isis-wg@ietf.org>rg>;
> Christian Hopps <chopps@chopps.org>
>
> *Subject:* Re: [Bier] WGLC: draft-ietf-bier-isis-extensions-04
>
>
>
> Have these changes been reflected in the draft? We're in WGLC but this
> discussion needs to come to a conclusion so we can progress.
>
>
>
> Greg
>
>
>
> On Tue, Jul 25, 2017 at 12:52 PM, Toerless Eckert <tte@cs.fau.de> wrote:
>
> Thanks, Less, that would be lovely!
>
> I didn't check the OSPF draft, if its similar state, explanatory text wold
> equally be appreciated.
>
>
> On Sun, Jul 23, 2017 at 11:28:08PM +0000, Les Ginsberg (ginsberg) wrote:
> > Toerless -
> >
> > I am thinking to add a statement in Section 4.1 - something like:
> >
> > "At present, IS-IS support for a given BIER domain/sub-domain is limited
> to a single area - or to the IS-IS L2 sub-domain."
> >
> > If you believe this would be helpful I will spin a new version (subject
> to review/agreement from my co-authors).
> >
> >    Les
> >
> >
> > > -----Original Message-----
> > > From: Toerless Eckert [mailto:tte@cs.fau.de]
> > > Sent: Saturday, July 22, 2017 6:34 AM
> > > To: Les Ginsberg (ginsberg)
> > > Cc: Tony Przygienda; Hannes Gredler (hannes@gredler.at); Greg
> Shepherd;
> > > bier@ietf.org; isis-wg@ietf.org list; Christian Hopps
> > > Subject: Re: [Bier] WGLC: draft-ietf-bier-isis-extensions-04
> > >
> > > Thanks Les
> > >
> > > When searching various terms in the doc to figure out what happens i
> am not
> > > sure why i missed this one.
> > >
> > > But: IMHO, RFCs can not only be the minimum number of words to get a
> > > running implementation. It also needs to specify what this
> implementation
> > > intends to achieve. Otherwise its not possible to do a useful review:
> > > The reviewer can to verify whether the spec will achieve what it
> claims to
> > > achieve is there no definitionn of what it claims to achieve.
> > >
> > > If i understand ISIS correctly, my reverse engineering of the intent
> is:
> > >
> > > - BIER TLVs stay within single ISIS areas. BFIR and BFER must
> therefore be
> > >   in the same ISIS area: There is no inter-area BIER traffic possible
> > >   with this specification. This is also true for ISIS area 0.
> > >
> > > - The same BIER sub-domain identifiers can be re-used
> > >   across different ISIS areas without any current impact. If these
> BFR-IDs
> > >   are non-overlapping, then this would allow in the future to create a
> single
> > >   cross ISIS area BIER sub-domain by leaking TLVs for such a BIER
> sub-domain
> > >   across ISIS levels. Leakage is outside the scope of this
> specificication.
> > >
> > > I actually even would like to do the following:
> > >
> > > - If BIER sub-domains are made to span multiple ISIS areas and BFR-ids
> > > assignemtns
> > >   are made such that all BFR-ids with the same SI are in the same ISIS
> ara,
> > >   then it should be in the future reasonably easy to create inter-area
> BIER
> > >   not by leaking of the BIER TLV but by having BFIR MPLS unicastBIER
> packets
> > >   for different SIs to an appropriate L2L1 BFIR that is part of the
> destination
> > > area/SI.
> > >   (if you would use SI number that are the same as ISIS area numbers
> then
> > >    you could probably do this without any new signaling. Not quite
> sure if
> > >    you can today easily find L1L2 border router for another area via
> existing
> > >    TLVs).
> > >
> > >   Alas, this idea will probably be killed because of the BIER
> architecture
> > >   intent not to engineer SI assignments in geographical fashions to
> > >   minimize traffic duplication in the presence of multiple SIs.
> > >
> > > Cheers
> > >     Toerless
> > >
> > > On Sat, Jul 22, 2017 at 06:03:53AM +0000, Les Ginsberg (ginsberg)
> wrote:
> > > > Tony/Toerless ???
> > > >
> > > > There is an explicit statement as to scope:
> > > >
> > > > <snip>
> > > > Section 4.2
> > > > ???
> > > >    o  BIER sub-TLVs MUST NOT be included when a prefix reachability
> > > >       advertisement is leaked between levels.
> > > > <end snip>
> > > >
> > > > Tony seems to have forgotten that we had a discussion about how BIER
> > > might be supported across areas and the conclusion was we did not know
> > > how to do that yet.
> > > > (Sorry Tony)
> > > >
> > > > Note this is ???consistent??? with https://www.ietf.org/id/draft-
> ietf-bier-
> > > ospf-bier-extensions-07.txt Section 2.5<https://www.ietf.org/id/
> draft-ietf-
> > > bier-ospf-bier-extensions-07.txt%20Section%202.5> - which limits the
> > > flooding scope of BIER information to a single area unless it can be
> validated
> > > that the best path to the prefix with BIER info can be validated to be
> to a
> > > router which itself advertised the BIER info. This is not something
> IS-IS can do
> > > since a single IS-IS instance only supports one area and therefore
> does not
> > > have the Level-1 advertisements of the originating router when that
> router is
> > > in another area.
> > > >
> > > > A few more responses inline.
> > > >
> > > > From: BIER [mailto:bier-bounces@ietf.org] On Behalf Of Tony
> Przygienda
> > > > Sent: Friday, July 21, 2017 5:17 AM
> > > > To: Toerless Eckert
> > > > Cc: Hannes Gredler (hannes@gredler.at); Greg Shepherd; bier@ietf.org
> ;
> > > > isis-wg@ietf.org list; Christian Hopps
> > > > Subject: Re: [Bier] WGLC: draft-ietf-bier-isis-extensions-04
> > > >
> > > > Terminology is a bit nits  IMO since the doc is reading clear enough
> for
> > > someone who read BIER & ISIS. I can reread it or Les can comment
> whether
> > > we should tighten glossary ...
> > > >
> > > > With the scope I agree, that got lost and the doc should be possibly
> rev'ed
> > > before closing LC. Yes, we flood AD wide was the agreement but
> something
> > > mentioning that this could change in the future is good so we are
> forced to
> > > give it some thought how that would transition ...
> > > >
> > > > Thinking further though, in ISIS we have a clean document really.
> The  BIER
> > > sub-TLVs go into well defined TLVs in terms of flooding scope. Normal
> L1-L2
> > > redistribution can be used to get the info to all needed places AFAIS.
> So
> > > maybe nothing needs to be written. I wait for Les to chime in.
> > > >
> > > > OSPF I would have to look @ scopes again & think whether we need to
> > > write something or maybe Peter can comment ...
> > > >
> > > > --- tony
> > > >
> > > >
> > > >
> > > > On Fri, Jul 21, 2017 at 8:27 AM, Toerless Eckert
> > > <tte@cs.fau.de<mailto:tte@cs.fau.de>> wrote:
> > > > Sorry, past the two weeks, but hopefully  benign textual comments:
> > > >
> > > > We tried to find an explicit statement about the scope of BIER TLVs
> - eg:
> > > > are they meant to stay within an area, have some redistribution
> across
> > > > areas/levels or not.
> > > >
> > > > Tony said WG agreement was to have these TLV be flooded across the
> > > > whole ISIS domain for now (this draft). So an explicit statement to
> that
> > > effect would
> > > > be great (All BIER sub-domains TLVs are flooded across all ISIS
> areas/levels,
> > > so they span the whole ISIS domain).
> > > >
> > > > Also, if future work may/should could improve on that maybe some
> > > > sentence about that (i guess one could just have ISIS intra-area
> BIER sub-
> > > domains ?).
> > > >
> > > > Also: Do a check about possible ambiguity of any generic terms like
> > > sub-domain, level, area, topology so that reader that don't know the
> > > terminology ofall protocols (ISIS, BIER) by heart can easily know which
> > > protocol is referred to.
> > > >
> > > > [Les:] There is no mention of ???level??? in the document.
> > > > The use of ???sub-domain??? is clearly always associated with
> ???BIER???.
> > > > ???topology??? is always used as an RFC 5120 topology ??? therefore
> > > clearly an IS-IS topology.
> > > > There is only one use of the term ???area??? (in Section 5.1). That
> text
> > > might deserve a bit of clarification given this might be either a
> Level 1 area or
> > > the Level2 sub-domain. I???ll take a pass at it.
> > > > (BTW ??? I am talking about IS-IS area/L2sub-domain Toerless. ???)
> > > >
> > > > I don???t see that any other clarification is needed ??? but
> Toerless ??? if
> > > you can point to any specific sentences/paragraphs which you find
> confusing
> > > - I???ll take a second look.
> > > >
> > > >    Les
> > > >
> > > >
> > > > I guess there are no BIER level, area or topologies, but still makes
> > > > reading easier if the doc would say "ISIS level", "ISIS area", or at
> > > > least have them in the Terminology section. And probably in
> > > > terminology say "domain -> in the context of this document the BIER
> > > domain which is also the same as the ISIS domain"
> > > > (which i hope is the correct statement, see above).
> > > >
> > > > Cheers
> > > >     Toerless
> > > >
> > > > _______________________________________________
> > > > BIER mailing list
> > > > BIER@ietf.org<mailto:BIER@ietf.org>
> > > > https://www.ietf.org/mailman/listinfo/bier
> > > >
> > > >
> > > >
> > > > --
> > > > We???ve heard that a million monkeys at a million keyboards could
> > > produce the complete works of Shakespeare; now, thanks to the Internet,
> > > we know that is not true.
> > > > ???Robert Wilensky
> > >
> > > --
> > > ---
> > > tte@cs.fau.de
>
>
>