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

Greg Shepherd <gjshep@gmail.com> Fri, 09 February 2018 16:49 UTC

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From: Greg Shepherd <gjshep@gmail.com>
Date: Fri, 9 Feb 2018 08:49:27 -0800
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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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Les,
draft-ietf-bier-isis-extensions still mentions BAR. Is this intentional?
Then consensus on the thread was to remove BAR.

Greg

On Tue, Feb 6, 2018 at 3:45 PM, Greg Shepherd <gjshep@gmail.com> wrote:

> 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 This thread is outdated.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>gt;; 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/dr
>> aft-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
>>
>>
>>
>
>