Ben raises an interesting point: do we expect clients will actually
contact multiple ALTO servers and compare the costs they return? That
never occurred to me. It does seem like a lot of effort for little gain.
I'm reminded of the old observation that "A man with one watch knows the
time of day. A man with two watches is never sure."
Also, comparing the costs from multiple ALTO servers only makes sense if
those servers use the same PID map. That implies those servers are tied
together administratively. And that in turn implies the servers are
probably getting their costs from the same underlying source, and
differences are most likely due to delays in propagating the cost
information to the servers.
That, in turn, implies that it might be useful if the ALTO server returned
an optional time-stamp for the cost data. The time stamp should be for the
overall cost map, not on individual pid-pair costs. Time stamps would be
arbitrary numbers, and would only be comparable for cost maps with the
same map-vtag. Higher value means "more recent."
- Bill Roome
On 08/30/2011 09:55, "Ben Niven-Jenkins" <[email protected]> wrote:
>It would seem to only apply to cases where clients are speaking with
>multiple ALTO servers returning different costs for the same PIDs pairs
>so the client can normalise or otherwise distinguish which ALTO server's
>response is the one to 'trust' for a given PID/path because if a client
>only speaks to one ALTO server then inferred cost data is presumably
>preferable to no cost data (as the client can always ignore the data from
>the ALTO server anyway), no?
>
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