Les, On Mon, Feb 19, 2018 at 9:32 PM, Les Ginsberg (ginsberg) <ginsb...@cisco.com > wrote:
> I am very sympathetic to doing “as little as possible” given we are > talking about documents which are going through final reviews. > > At the same time, I think defining the authoritative source for algorithm > values is important. > > > > I therefore agree w Ice – let’s keep the current 8 bit algorithm value – > but make it clear that the identifiers come from the IGP Registry. > I do not hear from you or Ice a clear technical reason nor willingness to address the concerns that I raised about the impact on the use of BIER. I see no technical reasons being used to recommend combining the BIER BAR registry and the IGP Algorithms registry. Andrew – I do not think there is agreement on what the function of a “BAR > sub-type” is. Therefore I am not comfortable in adding it to the drafts. > > Certainly this may prove to be useful, but let’s add it when we know how > it will be used and how to assign values to it. That requires more > discussion than can reasonably be had in the current context. > > > > Tony / Alia – the argument that 256 algorithm values is not enough for all > use cases (BIER specific and IGP specific and Babel specific…) – or even > that 128 is not enough (if we allow the Flex-Algo proposal to reserve half > of the space) – simply does not ring true to me. > > If I waited for you to buy me a beer when we reached 10 algorithms I > likely will go thirsty for a very long time. > It is fascinating to see that you believe me too busy to keep up on the side discussions happening - or perhaps merely too distracted to recall the emails discussing acquiring half of the IGP Algorithm space for flex-algo. I do talk to my WG Chairs. Please engage substantively with technical arguments. If you have them, you are more than capable of representing them accurately. So Option E seems best to me. > That was not part of my listed options. Regards, Alia > > Les > > > > *From:* BIER [mailto:bier-boun...@ietf.org] *On Behalf Of *Tony Przygienda > *Sent:* Monday, February 19, 2018 6:20 PM > *To:* Dolganow, Andrew (Nokia - SG/Singapore) <andrew.dolga...@nokia.com> > *Cc:* BIER WG <b...@ietf.org>; IJsbrand Wijnands <i...@cisco.com>; > isis-wg@ietf.org list <isis-wg@ietf.org> > *Subject:* Re: [Bier] [Isis-wg] BAR field length in > draft-ietf-bier-isis-extensions > and draft-ietf-bier-ospf-extensions > > > > My reaction to AD's options: > > IF you prefer or can accept the current status, but think there should be > an IANA registry > as is usual for managing code-points, please say so. No more > justification is needed. > > > > > +1 to this option, i.e. current status with IANA BIER BAR registry. > > I think we have a clear and current case which is anchored already in the > architecture RFC as section 6.9 > > The draft https://tools.ietf.org/html/draft-zzhang-bier-algorithm-00 goes > into more detail in this respect and I hope the draft being adopted and at > least a single BAR value being assigned to deal with brownfield deployments > today where not all routers support BIER. This clearly necessitates a BIER > BAR registry. > > > IF you prefer Option B, C, and/or D, please say so with your explanation. > More technical depth than "'we might need it" would be helpful; the > availability of sub-TLVs already > provides future proofing. > > > +2 for Option B). Albeit we can meet future use cases with BAR subtype > being a sub-TLV a bar type/bar subtype 16 bits field (subtype with or > without registry and of course we can name those things differently) all > sub-TLVs in IGPs are traditionally “optional”, i.e. adding sub-TLVs later > _may_ cause backwards compatibility problems. Defining the subtype today > will allow us to specify that only type/subtype 0/0 is well defined & any > unknown type/subtype combination must be avoided. The subtype will allow > for BAR 0 or future BAR types to understand that subtype is in a sense a > “mandatory sub-TLV” and the routers sending out such subtype must be > avoided, even if the type itself is known. Several possibilities come to > mind immediately such as using Unicast IGP Algorithm Registry as subtype > for certain BAR values or accommodate interesting, future work like Flex > Algo into BIER right after IGP RFCs are available which IMO would present a > very beneficial future direction for BIER technology cleanly governed by a > BIER BAR registry. > > PS: I think we should control the urges of workgroup participants to > explore the number of letters in the roman alphabet that we can use to > introduce their preferred solutions if we want to get to some kind of > consensus on this thread. > > PPS: Option E has been discussed in the last 16-bit thread to the point of > logical conclusion of a "all routing protocols under the sun algorithm > registry" and found to be a rathole I thought ... > > > > > > > On Mon, Feb 19, 2018 at 6:09 PM, Dolganow, Andrew (Nokia - SG/Singapore) < > andrew.dolga...@nokia.com> wrote: > > All, > > > > As we discussed here (as a WG) and in this topic: > > - We need to have ability to define way for independent BIER > computation algorithms (for BIER specific computations or other use cases, > some of which Alia highlighted in her email below) > - We want to have extensibility to use other non-BIER specific > algorithms (as others brought up) > > > > The original draft can be argued not to provide both of those > capabilities, and thus Option A below (marked as Current status) really > just defers the issue. I find Option E that Ice added also > counterproductive as it eliminates the top use case above. Thus we really > left with options B, C, D as a compromise. From those, Option B seems to me > the best: > > - It meets the requirements above > - It allows a clean implementation (as opposed to Option C which is a > bit more kludgy). Thanks to a sub-TLV defining what BAR field carries – a > BIER-specific algorithm defined in BIER specific registry (a registry that > should be BIER specific, regardless of IGP used), or something else to meet > needs expressed by others, we meet the requirements from those who wanted > to change the Current status > > > > Option C/D are acceptable alternatives; however, Option B seems > technically cleanest, most flexible, and meeting all requirements. > > > > Andrew > > > > > > *From: *Isis-wg <isis-wg-boun...@ietf.org> on behalf of Alia Atlas < > akat...@gmail.com> > *Date: *Tuesday, February 20, 2018 at 12:05 PM > *To: *"(Ice) IJsbrand Wijnands" <i...@cisco.com> > *Cc: *BIER WG <b...@ietf.org>, "isis-wg@ietf.org list" <isis-wg@ietf.org> > *Subject: *Re: [Isis-wg] [Bier] BAR field length in > draft-ietf-bier-isis-extensions > and draft-ietf-bier-ospf-extensions > > > > Ice, > > > > On Mon, Feb 19, 2018 at 7:57 PM, IJsbrand Wijnands <i...@cisco.com> wrote: > > Alia, > > > > I appreciate that you have finally decided to discuss this on the BIER > mailing list. > > > I know that there are individual drafts draft-ppsenak-ospf-sr-flex-algo-00 > and draft-hegdeppsenak-isis-sr-flex-algo-02. > I see a bit of discussion on the is-is mailing list and at IETF 100, but, > of course, no WG adoption. > > I see BIER as a fundamental technology that can be used in different > situations. For instance, there is not merely > discussion of how Babel and BIER could interact - but actual code (thanks > Sandy!); of course, that is not a WG-adopted > draft yet either, so this is merely a thought experiment example. How do > the different algorithms > work for an IGP that isn't link-state? What about the ideas around using > BIER with caches? Are there issues there? > What about algorithms that make sense for BIER or multicast - but not for > unicast? > > IANA registries are not price prohibitive. Why would we tie BIER to the > link-state IGP registry? > > > > We are talking about what needs to be advertised in OSPF and ISIS in order > to select the BIER underlay. We are not discussing Babel or any other > candidate underlay technologies for BIER. Moreover, we are not limiting any > new innovation with BIER regarding the underlay. This discussion is > strictly related to the drafts in the title. > > > > I do not hear you making a technical argument. > > > > This is an architectural argument! > > > > An architectural argument can't also limit itself to the drafts in the > title. > > > > If it sounded like the IANA registry was suggested as separate for BIER > OSPF and BIER ISIS, then your attempt to reframe the conversation might be > reasonable. Let me clarify - I see no current reason for an OSPF BAR > registry and an ISIS BAR registry; it would just be a BAR registry. Perhaps > > that clarification is a good reason to get the IANA registry included in > the next update? > > > > The routing layer is separate from the BIER layer. The BAR is for the > BIER layer. > > > > Regards, > > Alia > > > > > > Hope this clarifies, > > > > Thx, > > > > Ice. > > > > > Regards, > Alia > > > On Mon, Feb 19, 2018 at 7:03 PM, IJsbrand Wijnands <i...@cisco.com> wrote: > Hi Alia, > > There is one more option that I think is not fully covered from the choice > of options related to getting a registry. > > The topic of the discussion is what information we need to pass in the IGP > in order for BIER to select the correct underlay. What identifies the > underlay is really what ever information is needed to select the Table > (MT-ID) and Algorithm. An example of Algorithm work that is going on is > Flex-Algo. My preferred option is to align with what ever the IGPs are > using to identify the Algorithm. > > Option E: Change BAR into “IGP Algorithm” registry as documented in > https://www.iana.org/assignments/igp-parameters/igp-parameters.xhtml#igp- > algorithm-types > > Thx, > > Ice. > > On 19 Feb 2018, at 13:51, Alia Atlas <akat...@gmail.com> wrote: > > As the Sponsoring AD for draft-ietf-bier-isis-extensions-07 and > draft-ietf-bier-ospf-extensions-12, I have been following the discussion > on the mailing list with interest. > > I have not seen clear consensus for any change. > > Let me be clear on what I see the options are from the discussion. Then > I'll elaborate > a bit on how you can express your perspective most usefully. > > 1) Current Status: Bier Algorithm (BAR) field is 8 bits. Currently, only > value 0 is specified. The drafts do not have an IANA registry - with the > expectation that one will be created when the first additional use is > clear. It is possible that there will be objections from the IESG to > progressing without an IANA registry. Given the lack of clarity for future > use-cases and after discussion, I decided not to force one after my AD > review - but I will not push back against having a BIER IANA registry if > raised by others. > > 2) Option B: Add a BAR sub-type of 8 bits. This would modify the current > TLVs. > Define an IANA registry for the BAR type. The meaning of the BAR > sub-type derives > from the BAR type. We can debate over the registration policy for the > BAR type. > > 3) Option C: Change the BAR field to be 16 bits and define an IANA > registry. Part of the range can be FCFS with Expert Review, part can be > Specification Required, and part can be IETF Consensus. > > 4) Option D: At some point in the future, if there is an actual understood > and documented need, a BAR sub-type could be added a sub-TLV. The length > of the BAR sub-type could be determined when the sub-TLV is defined. > > Given > > a) option D exists > b) there is currently only one defined value for BAR > c) I do not see strong consensus for change to one particular other > option > > I see no current reason for a change and I certainly see absolutely no > reason for > a delay in progressing the documents. > > I do want to be clear about what the WG wants to do on this issue. > Therefore, here is > my following request. > > Please send your feedback to the mailing list as follows: > > IF you prefer or can accept the current status, please say so. No more > justification > or reasoning is required. I just don't want the bulk of folks who are > content to be > overlooked by those suggesting change. > > IF you prefer or can accept the current status, but think there should be > an IANA registry > as is usual for managing code-points, please say so. No more > justification is needed. > > IF you prefer Option B, C, and/or D, please say so with your explanation. > More technical depth than "'we might need it" would be helpful; the > availability of sub-TLVs already > provides future proofing. > > IF you have a clear technical objection to why the Current Status is not > acceptable, > please express that - with clear details. > > IF you feel that additional code-points should be allocated in a BAR IANA > Registry or > have thoughts on the appropriate policy, please say so with your > explanation for what > those should be. > > Unless I see clear and strong consensus for something other than the > Current Status, > that will remain. > > IF there is clear and strong consensus for Option B, C, or D, or adding an > IANA registry with particular values, then it will be possible to have a > change up through this Weds night - with a 1 week WGLC on that particular > technical change. > > My priority is to have the base BIER specifications published as Proposed > Standards so that more BIER implementations and deployment can be done. I > would like the WG to wrap up the core work (as expressed in the proposed > recharter) so that you all can look > at how to use it. > > Given this topic was raised last Weds and given that there are no > technical objections raised to the documents as are, there isn't much time > - so please just respond to this email ASAP. My deadline for a decision is > 6pm EST on Weds. > > Regards, > Alia > > _______________________________________________ > BIER mailing list > b...@ietf.org > https://www.ietf.org/mailman/listinfo/bier > > > > <PastedGraphic-6.png> > > > > [image: cid:6D5DA0C0-E3D6-4998-A2B2-FBE7253DB66D@cisco.com] > > > > > > > _______________________________________________ > BIER mailing list > b...@ietf.org > https://www.ietf.org/mailman/listinfo/bier > > > > _______________________________________________ > Isis-wg mailing list > Isis-wg@ietf.org > https://www.ietf.org/mailman/listinfo/isis-wg > >
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