I have been following the discussions on the list, and here comes my $0.02:
ASLA provides a generic mechanism of associating different applications and link attributes. The WG reached consensus of this architecture after long debate, so my understanding is new proposals should follow this path unless it’s impossible to use ASLA to define the new attributes. So far I’m not convinced by the discussions on the list that draft-ietf-lsr-flex-algo-bw-con can not use ASLA and has to specify an alternative, and the alternative is better. Thanks, Yingzhen > On Aug 18, 2021, at 1:20 PM, Les Ginsberg (ginsberg) > <[email protected]> wrote: > > Ron - > > Indeed – it is long past the time when we should be focusing on the “big > picture”. > I think Acee has stated it as succinctly as anyone – let me repeat for > emphasis: > > “The LSR WG developed ASLAs to cover usage of the link attributes (including > metrics) for different applications and mitigate all the vagaries of the > original TE link attribute specifications. ASLAs are implemented and > deployed. I believe it would be a mistake to bifurcate the IGP standards with > yet another way of encoding link attributes for different applications.” > > ASLA is an architecture – one designed to assure that we can explicitly > identify the set of applications using any link attribute . It is designed to > be extensible both to new applications and to new attributes. It was long > debated in the WG and underwent extensive review and is now standardized in > RFCs 8919, 8920. It has been implemented and deployed and forms the basis of > interoperable implementations. > > Now you (and others) decide to invent a new attribute. The attribute > certainly can be advertised using ASLA, but instead of acknowledging the > existence of the ASLA architecture and defining the new attribute to use > ASLA, you decide that maybe if we advertise this attribute in some new way > there might be some modest advantages. This ignores the consequences of > having to implement attribute specific encoding rules in order to map > attributes to applications. These consequences include greater code > complexity and higher probability of interoperability issues. > > And, based on your list of attributes below, what have we to look forward to? > More attribute specific encoding rules leading to even greater code > complexity and greater chance of interoperability problems it would seem. > > Look, you haven’t convinced me that your alternative proposals are “better”. > But even if they were, it would require a much greater benefit than you are > claiming to justify discarding the architecture that is designed to fully > address the association of link attributes and the applications which use > them. > > I don’t expect to convince you – and you have not convinced me – and we > probably never will agree. But since it is clear that ASLA does work for all > the cases that have been mentioned in this and related threads, I think this > discussion is a waste of WG time. > > It is time to close this discussion. > > Les > > > From: Lsr <[email protected] <mailto:[email protected]>> On Behalf Of > Ron Bonica > Sent: Tuesday, August 17, 2021 11:21 AM > To: Acee Lindem (acee) <[email protected] > <mailto:[email protected]>>; [email protected] <mailto:[email protected]> > Subject: Re: [Lsr] RFC 8919, RFC 8920, Flex Algo, and Flex Algo BW Constraints > > Acee, > > So, let us discuss whether there is a good reason for > draft-ietf-lsr-flex-algo-con to specify ASLA ! > > Link attributes are different from application configuration information. > Link attributes are properties of a link. They are independent of the > applications that use them. The following are examples: > > Total physical bandwidth > Number of LAG elements > Bandwidth of smallest lag member > Latency > > Link attributes do not benefit from ASLA encoding because they are not > application specific. > > Application configuration information constrains the behavior of an > application. It can apply to: > > The application and a link > The application only > > Bandwidth reservation applies to an application and a link. For example, a > link may advertise that it has: > > X Gbps available for RSVP-TE reservations > Y Gbps available for SR Policy reservations > Z Gbps available for TI-LFA reservations > > This class of configuration information clearly benefits from ASLA encoding, > because it is applicable to both the application and the link. > > Some applications (e.g., Flexalgo) can be configured to use a variety of link > attributes in SPF calculation. No matter how they acquire this configuration > information, it MUST be the same at each node. Otherwise, routing loops may > result. Configuration options are: > > Configure this information on each link and advertise link attributes with > ASLA > Configure this information on each node that runs the application > Configure this information in a few central places and advertise it to all > other nodes. The advertisement is not associated with a link. Flexalgo uses > the FAD in this manner. > > Neither Option 1 nor Option 2 is very appealing, because it requires > configuration on each node. Option 3 is better because: > > It requires configuration on only a few nodes > It maintains separation between link attributes and application configuration > information > It can support applications like Flexalgo, where each algorithm may use > different link attributes to calculate the shortest path > > > Ron > > > > > Juniper Business Use Only > From: Acee Lindem (acee) <[email protected] > <mailto:[email protected]>> > Sent: Friday, August 13, 2021 10:22 AM > To: Ron Bonica <[email protected] <mailto:[email protected]>>; > [email protected] <mailto:[email protected]> > Subject: Re: [Lsr] RFC 8919, RFC 8920, Flex Algo, and Flex Algo BW Constraints > > [External Email. Be cautious of content] > > Speaking as a WG member: > > Hi Ron, > My rationale is #1. The LSR WG developed ASLAs to cover usage of the link > attributes (including metrics) for different applications and mitigate all > the vagaries of the original TE link attribute specifications. ASLAs are > implemented and deployed. I believe it would be a mistake to bifurcate the > IGP standards with yet another way of encoding link attributes for different > applications. > Thanks, > Acee > > From: Lsr <[email protected] <mailto:[email protected]>> on behalf of > Ron Bonica <[email protected] > <mailto:[email protected]>> > Date: Thursday, August 12, 2021 at 3:46 PM > To: "Acee Lindem (acee)" <[email protected] > <mailto:[email protected]>>, "[email protected] > <mailto:[email protected]>" <[email protected] <mailto:[email protected]>> > Subject: Re: [Lsr] RFC 8919, RFC 8920, Flex Algo, and Flex Algo BW Constraints > > Acee, > > Please help me to parse your message. It is clear that you want > draft-ietf-lsr-flex-algo-bw-con to specify ASLA’s. However, your rationale is > not so clear. > > It is not because RFC 8919 mandates ASLA. In fact, we agree that it would be > strange for an RFC to include a mandate that precludes future proposals. > > Are any of the following your rationale: > > 1) Because there is a good technical reason for > draft-ietf-lsr-flex-algo-bw-con to specify ASLA > 2) Because it is possible, but not necessary, for > draft-ietf-lsr-flex-algo-bw-con to specify ASLA > 3) Because it was the unstated intention of RFC 8919 to include a mandate > that precludes future proposals (although we agree that this would be > strange). > > For the purposes of full disclosure, I think discussion regarding the first > rationale would be fruitful. However, I don’t think very much of the second > or third rationale. > > > Ron > > > > > Juniper Business Use Only > From: Lsr <[email protected] <mailto:[email protected]>> On Behalf Of > Acee Lindem (acee) > Sent: Tuesday, August 10, 2021 4:43 PM > To: [email protected] <mailto:[email protected]> > Subject: [Lsr] RFC 8919, RFC 8920, Flex Algo, and Flex Algo BW Constraints > > [External Email. Be cautious of content] > > Speaking as a WG Member: > > In reviewing RFC 8919 and RFC 8920, it is clear that the ASLA mechanism was > to be used for new link attributes and applications. While the documents do > not mandate that there never could be a new way to advertise link attributes, > this was clearly the intent. Indeed, it would be strange for an RFC to > include a mandate that precluded future proposals. The advertisement > enablement and deployment sections of these documents specifically cover > future attributes and applications. > > Given that we have ASLAs as building blocks, I don’t really see a reason to > introduce the generic metric. The proponents say it isn’t an alternative to > ASLAs but their examples cite different applications using different metric > types (i.e., application-specific metrics). Also, given that ASLA are used by > the base Flex Algo draft, it would be inconsistent to diverge for Flex Algo > BW constraints. > > Consequently, I would request that draft-ietf-lsr-flex-algo-bw-con-01 > revert to using ASLAs. Based on the LSR Email discussion prior to IETF 111, > this was definitely the consensus. > > Thanks, > Acee > > > _______________________________________________ > Lsr mailing list > [email protected] <mailto:[email protected]> > https://www.ietf.org/mailman/listinfo/lsr > <https://www.ietf.org/mailman/listinfo/lsr>
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