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:[email protected]] > Sent: Saturday, July 22, 2017 6:34 AM > To: Les Ginsberg (ginsberg) > Cc: Tony Przygienda; Hannes Gredler ([email protected]); Greg Shepherd; > [email protected]; [email protected] 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:[email protected]] On Behalf Of Tony Przygienda > > Sent: Friday, July 21, 2017 5:17 AM > > To: Toerless Eckert > > Cc: Hannes Gredler ([email protected]); Greg Shepherd; [email protected]; > > [email protected] 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 > <[email protected]<mailto:[email protected]>> 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 > > [email protected]<mailto:[email protected]> > > 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 > > -- > --- > [email protected] _______________________________________________ Isis-wg mailing list [email protected] https://www.ietf.org/mailman/listinfo/isis-wg
