Re: [alto] Comments on draft-kiesel-alto-xdom-disc-02

[Sebastian Kiesel <[e-mail]>]

Hi Wendy,

On Tue, Jul 19, 2016 at 03:18:24PM -0400, Wendy Roome wrote:
> draft-kiesel-alto-xdom-disc-02 has this (Sect 3.2, Endpoint Cost Service):
> 
> If an ALTO client wants to query the Endpoint Cost Service (see Section
> 11.5 of RFC 7285 [RFC7285]) for the costs from source address X to
> destination address(es) Y (and Z), it has to invoke the crossdomain ALTO
> server discovery procedure with parameter X. The result will be the IRD
> URI of the ALTO server to query for the costs from X to Y (and Z).
> 
> My first comment was why do cross-domain ALTO server discover on X, rather
> than Y or Z?
> 
> Then I realized there is a good reason. I believe most ECS queries will be
> either 1->N or N->1. That is, costs from many sources to one destination
> (client selecting server from which to download a file) or one source to
> many dests (client selecting server for upload).
> 
> So if the query is 1->N or N->1, do cross-domain discovery on the one
> address. That is probably the address of the real client - the one which
> needs ALTO guidance. So use the ALTO server which has the best data for
> that address.

exactly!

This does not only save on the number of transactions with different
ALTO servers, it helps also to deal with our (deliberately)
not-so-well-defined "routingcost" default metric.

Thanks
Sebastian