Thanks again KJ. 

Dino

> On Aug 11, 2021, at 6:14 PM, 선경재 <[email protected]> wrote:
> 
> 
> Dino,
> 
> Thank you for discussing this topic. It was very helpful for making clear to 
> our proposal.
> 
> I will update draft depending on these discussions.
> 
> Additional comments and discussion by LISP folks are always welcome.
> 
> Sincerely
> 
> KJ.
> ᐧ
> 
> 2021년 8월 12일 (목) 오전 5:29, Dino Farinacci <[email protected]>님이 작성:
>> > First of all, thank you very much to give detailed comments on our draft. 
>> > Please check answers for your comments inline.
>> 
>> KJ, thanks for the quick response. I have cut out the text where I 
>> agree/accept with your responses. See inline for additional commentary and 
>> answers to your questions.
>> 
>> Once you update the spec, I'll give another thorough review. Thanks!
>> 
>> > 
>> >> Which indicates that ETR only wants packets sent to C and D when A and B 
>> >> are not reachable from the ITR (by using multiple mechanisms but the most 
>> >> robust is RLOC-probing).
>> >> 
>> >> Note the use of an RLOC-set comes in multiple forms:
>> >> 
>> >> (1) A list like above (default)
>> >> (2) An ELP, where the RLOC-record indicates a encap-path from ITR to ETR.
>> >> (3) An RLE, where the RLOC-record indicates that all RLOCs listed are 
>> >> used (multicast replication).
>> >> 
>> >> You could use 1 or all combinations of these with filtering/policy 
>> >> support on the map-server.
>> > 
>> > KJ: The priority you mentioned just represents the network-related 
>> > capability in the dynamic anycast viewpoint. However, if parameters to be 
>> > required for selecting routing path are not only network-related metrics 
>> > but also service-related metrics (i.e., computing loads, number of flows, 
>> > etc.), we need other indirection for that.
>> 
>> If you want to control where packets go on the underay, you can also 
>> consider draft-ietf-lisp-te. That is where ELPs are introduced and designed 
>> into the LISP architecture.
>> 
>> >> 
>> >>> <PastedGraphic-39.png>
>> >> 
>> >> It is important to note that if you use equal priorities in an RLOC-set, 
>> >> that the ITR can load-split traffic across RLOCs and that will break 
>> >> connnection oriented applications (or applications that require remote 
>> >> state for a session).
>> >> 
>> >> So an ITR that is configured that a particular EID in its map-cache is an 
>> >> anycast-EID, it can use an RLOC-set above with each RLOC priority=1 and 
>> >> then choose based on the implementation's idea of what is a better RLOC 
>> >> to use.
>> >> 
>> >> IMO opinion, the better way to design/implement this is using an 
>> >> anycast-EID-to-anycast-RLOC mapping. Which means you only need a register 
>> >> from one place (an SDN controller) or each ETR registering the same RLOC 
>> >> (without merge semantics). So the serivce is chosen by destination 
>> >> address in a packet (the anycast-EID) which maps to an anycast-RLOC where 
>> >> the underlay takes you to the "closest" LISP site. But closest is just 
>> >> one way of getting to a service. You may have other ways and hence why 
>> >> you introduced a metric.
>> > 
>> > KJ:  In my understanding, in your suggestion, anycast RLOC is allocated to 
>> > the ETRs which can deliver packet destined to anycast-EID by internal 
>> > routing and routing between those ETRs are chosen in the underlay. Is it 
>> > right? 
>> 
>> Yes. You assign the same RLOC address to multiple ETRs and have underlay 
>> routing take a source to the closest LISP site.
>> 
>> >> 
>> >> Yes, it is better to gather the metrics data outside of LISP. But yes, 
>> >> the control-plane could store it. I would suggest just mapping your 
>> >> collection metrics to priorities so no protocol messages would need to be 
>> >> modified. I believe LISP already has designed in everything you need. Do 
>> >> you agree?
>> > 
>> > KJ: yes. I agree with your point that LISP already has the solution to 
>> > mapping metrics to priorities. That is the one of reasons that I think 
>> > that it is possible to provide dynamic anycast routing using LISP without 
>> > huge modifications.
>> 
>> Yes agree. Then the ITR came make an RLOC selection based on existing 
>> documented approaches. But if the metrics change too much then the contents 
>> of the RLOC-set changes which requires more frequent map-cache updates. So 
>> we have to analyze this tradeoff more in depth.
>> 
>> > So, I think that we should not give fixed solutions on how to collect and 
>> > store metrics but we can mention possible solutions for that. Because it 
>> > is more implemental issue. Is it right approach?
>> 
>> Yes, I agree.
>> 
>> > <PastedGraphic-45.png>
>> >> 
>> >> Yes, it can, see draft-rodrigueznatal-lisp-multi-tuple-eids.
>> > 
>> > KJ:  Thank you for giving that information. I will check and update    
>> 
>> Thanks again,
>> Dino
>> 
> 
> 
> -- 
> ====================================================================
> 
> 선경재 / Kyoungjae Sun (KJ Sun)
> 
> 연구원 / 클라우드 및 네트워크 연구실
> 
> Researcher / Distributed Cloud and Network lab
> 
> Office : +82-2-814-0151    Phone : +82-10-3643-5627
> 
> Email : [email protected]
> 
> ====================================================================
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