Hi all,

 With an aim towards starting a discussion on the mailing list, it may be 
useful to discuss requirements for the query response feature of the ALTO 
service. My take on this is that it could have the following goals (this 
follows on from some of what I presented and the discussions with others at 
Minn)

1. The query should allow the client to express interest in one or more metrics 
that the ALTO service being queried supports
2. The ALTO service should be able to respond with a peer selection 
corresponding to the query annotated with metric values for peers
3. The query/response format should be general enough to accommodate the 
interests of many different kind of ALTO service providers from an ISP-friendly 
peer selection to a latency optimizing peer selection to a path disjointness 
optimizing peer selection.

Supporting (1) could require that we have a way for a client to contact an ALTO 
service and retrieve a set of metrics that are supported (these metrics could 
be pDistance, RTT, bw or something else that is ALTO service-specific) prior to 
the actual ALTO query.

In addition, we have to think about whether and how a client is allowed to 
express some function of the metrics in the query to the ALTO service such as: 
a peer selection in which a client asks the ALTO service to provide a peer 
selection that satifies all peers >128Kbps and ordered by latency. Or a peer 
selection in which a client asks for a peer selection/ranking that minimizes 
ISP costs annotated with average turnaround time. 

The current P4P interface first requires the client to place itself in the 
context of the ALTO service provider by the getPID interface. We should also 
think about something more general that allows the ALTO service to provide or 
obtain context about the client prior to servicing ALTO client queries. The 
context could be different for different types of ALTO service providers.

Thoughts?

-Saumitra

www.saumitra.info 


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