Hi all, First, I agree with Kai : " >> I think whether to use the source/destination or to split up queries >> depends on the application. If it is selecting a destination for a >> given source, it certainly can choose XDOM-DISC(SRC). If the selection >> is about sources, probably XDOM-DISC(DST) is more reasonable. " Then, Xin's idea is reasonable for me. Suppose XDOM-DISC(X) just can get cost(X,*), an ALTO Client want to ask a reasonable cost(X,*) with a given X, it can achieve through XDOM-DISC(X), but when it want to ask a reasonable cost(*,Y) with a give Y, it should sent to all servers(except Y) to get the info, so I agree with Xin's here. XDOM-DISC(X) should register cost( X, *), cost(*,X), so it will save the query processor.
Besides that, I think we can reduce some extra cost information of XDOM-DISC(X) by training in a specific situation(It depends on different applications and scene). When some cost information has not been called for a long time, we can consider to remove them to simplify cost data store. Then, a typo in 2.3, paragraph 2, line 3: and it is rooted in the in the special domain "IN-ADDR.ARPA." At 2016-07-15 23:14:44, "Sebastian Kiesel" <[email protected]> wrote: >Hi Kai and all, > >On Fri, Jul 15, 2016 at 10:27:14AM +0800, Gao Kai wrote: >> On 13/07/16 05:09, Sebastian Kiesel wrote: >> > On Tue, Jul 12, 2016 at 02:55:52PM -0400, Wendy Roome wrote: >> >> My comments on draft-kiesel-alto-xdom-disc-02: >> >> Section 3.2: >> >> >> >> If a client wants the cost from X => Y, why just do cross-domain discovery >> >> on address X? Why not do it for Y instead? Or do it for both X & Y? >> > This is again to cope with the not so well-defined "routingcost" metric. >> > >> > Our assumtion is that XDOM-DISC(X) will discover one ALTO server, >> > which will be able to express costs (X,Y) and costs (X,Z) using a >> > (locally) consistent routingcost metric, i.e., with the meaning that >> > a lower value indicates a higher preference. >> > >> > If we used XDOM-DISC(Y) and XDOM-DISC(Z) we would probably discover >> > two servers, which could use completely incompatible definitions. >> > >> > >> > In other words, the example query given in sec. 11.5.1.7. of RFC 7285 >> > should be sent to the server yielded from XDOM-DISC(192.0.2.2). >> > >> > If the "srcs" list contained more than one IP address, the query >> > should be split up in several queries, each containing only one >> > IP address in "srcs" (but keep all in "dsts"), and each of these >> > "sub-queries" would need its own call to XDOM-DISC. >> >> I had the same question as Wendy because for me, sources and >> destinations are somewhat symmetric > >if src/dst and the costs between are really symmetric, it doesn't >make a difference. > >> so it is tempting to think there >> should be something like XDOM-DISC(X, Y), which might be overcomplicated >> though. > >That would be too complicated indeed. > > >> I think whether to use the source/destination or to split up queries >> depends on the application. If it is selecting a destination for a >> given source, it certainly can choose XDOM-DISC(SRC). If the selection >> is about sources, probably XDOM-DISC(DST) is more reasonable. > >I agree. So the idea is, that we call XDOM-DISC(X), in oder to find an >ALTO server that can answer both ECS queries, whether > >routingcost(src=X, dst=Y) > routingcost(src=X, dst=Z). > >and whether > >routingcost(src=Y, dst=X) > routingcost(src=Z, dst=X). > > >In other words, we use the common address X that appears in all the >tuples we want to compare as parameter for the XDOM-DISC. > >For the Endpoint Cost Service ECS, queries may have to be split in >a way that either the "srcs" or the "dsts" list in the query contains >only one IP address - and this address is used for XDOM-DISC. >What that means for the other ALTO services we still need to define. > >> If the >> application wants to pick the best source-destination pair, maybe the >> queries should never be split up. > >Not splitting the queries would be the best thing to do from an >optimization perspective. It would be great if there were >a bunch of ALTO servers all with the same knowledge, so we could >just discvover any one of them (e.g. using RFC7286) and ask it >arbitrary questions or download a comprehensive NxN cost map. >But for various reasons I believe that this is not going to happen >on an Internet scale (and after all, we are the Internet Engineering >Task Force ;) ). So we need to find a solution that works if knowledge >is partitioned. > >Thanks >Sebastian > >_______________________________________________ >alto mailing list >[email protected] >https://www.ietf.org/mailman/listinfo/alto
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