[alto] Review on Cross-Domain Server Discovery

[wang xin <[e-mail]>]

Dear authors,


Here are my comments on your draft (https://tools.ietf.org/html/draft-kiesel-alto-xdom-disc-02).


Section 2.3 that specifies how to construct domain names from IP address parameter makes it concrete for the supporting of "ALTO Cross Domain Server Discovery" which refers to "third-party server discovery" in the previous draft (https://tools.ietf.org/html/draft-kiesel-alto-3pdisc-05). I think people can be clear about how to get the URI of particular ALTO server's IRD based on the input IP address and service name from the draft.


Section 3.2 that discusses how to support Endpoint Cost Service by the proposed solution might be not clear enough. Since one of the draft's background is multi-domain, it's easy to consider the source and destination of an ECS request reside in two different domains, each of which is allocated to different ALTO server. Then, in your example, X, Y, and Z may belong to three different ALTO servers, S_x, S_y, and S_z. The result (S_x) of parameter X doesn't have any information about Y and Z, and then it cannot complete the ECS request. One solution may be using aggregator (https://datatracker.ietf.org/doc/draft-bertz-alto-aggrimpl/). But, in this case, it should specify the mapping between URI, resource (or service) and domain name. Some resources (like Endpoint Property) may be in origin ALTO servers, others may be in the aggregator. But why don't point out that this draft doesn't consider this case for the simplicity? This draft really solves the third-party ALTO query of AR-33 (https://tools.ietf.org/html/rfc6708).


Thanks,

Xin