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

Greg Shepherd <gjshep@gmail.com> Fri, 09 February 2018 17:40 UTC

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References: <20170721062741.GA3215@faui40p.informatik.uni-erlangen.de> <CA+wi2hOCZkLeuqnqr-waNMtaex+Pjq3rXzH-HVqJhLkWQUgj_Q@mail.gmail.com> <567fdbe4992c4207b54c77b1ec8cd0cd@XCH-ALN-001.cisco.com> <20170722133419.GA18218@faui40p.informatik.uni-erlangen.de> <37e324dc58454778b70c72255066536f@XCH-RCD-001.cisco.com> <20170725195211.GA7411@faui40p.informatik.uni-erlangen.de> <CABFReBpt088=SC3eBcfFbJ24e_+GkDmvKh05AaQtUmCoaKEG3w@mail.gmail.com> <cd2bcf2853684097a3d21fd20742d4ed@XCH-ALN-001.cisco.com> <CABFReBqEJu5nBMdJm0cmBuUYhatD+JRCpn7TppC-hgV4HGZ3sQ@mail.gmail.com> <CABFReBoBXn-Fc5B+Y9VdfEWC+sY=bLdmDUz3NqO6XXeDgbeW_g@mail.gmail.com> <CA+wi2hOtXBDgEnn6G9q+DeUUobZH7D3QNweAT+xOt1FY6i+HTA@mail.gmail.com>
From: Greg Shepherd <gjshep@gmail.com>
Date: Fri, 9 Feb 2018 09:40:02 -0800
Message-ID: <CABFReBqfoxkGZjzs8u_m7e_0nj+mjMqdaL3iPZjne+8JTvd3zg@mail.gmail.com>
To: Tony Przygienda <tonysietf@gmail.com>
Cc: "Les Ginsberg (ginsberg)" <ginsberg@cisco.com>, Toerless Eckert <tte@cs.fau.de>, "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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Sorry.. Crossed wires with Peter's comment on OSPF and I wanted to ensure
both IGP drafts are in sync. Peter corrected his comment. Please ignore me
at this time. :)

Greg

On Fri, Feb 9, 2018 at 9:20 AM, Tony Przygienda <tonysietf@gmail.com> wrote:

> Greg, where did you see that? The last standing working status was to have
> it as fixed field and just reserve 0 for IGP delivered SPF nexthops.
> thanks. tony
>
> On Fri, Feb 9, 2018 at 8:49 AM, Greg Shepherd <gjshep@gmail.com> wrote:
>
>> 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
>>>>
>>>>
>>>>
>>>
>>>
>>
>