Exactly.  The Network Map service on custom.alto.example.com should return
the same vtag as the cost services in that IRD.  Eventually the Network Map
services on custom.alto.example.com and alto.example.com should return the
same map, with the same vtag, but it might lag for a few days, because it
requires human intervention to reconcile them.

- Wendy Roome

From:  "Y. Richard Yang" <[email protected]>
Date:  Thu, July 11, 2013 13:39
To:  Wendy Roome <[email protected]>
Cc:  IETF ALTO <[email protected]>
Subject:  Re: [alto] Clarifying Cost Map Dependencies on a Network Map

Let me better understand your second setting. Assume that the time is t.

If a client fetches a network map from alto.example.com
<http://alto.example.com> , the client can get a
network map with vtag n+1.

If the client fetches the cost map from custom.alto.example.com
<http://custom.alto.example.com> , the client gets
a cost map, whose network map vtag can be n (the version that the second
group
still uses). The client cannot fetch the network map from alto.example.com
<http://alto.example.com> , unless
we support a version system, but the client can fetch from the network map
at
custom.alto.example.com <http://custom.alto.example.com> .

I believe that the preceding is what you have in mind.

This insight of using network-map snapshot, by the second group, in your
example,
for consistency is a very nice idea. I know one major software company
depends 
on snapshots of packages for better consistency efficiency.

Hence, ALTO should support this feature as well.

Whether we should make the decision that each ALTO Server can define only
one
network map is still not clear. A single net map is indeed simpler. A
question is 
whether we may may encounter use cases with a large number of topologies
(network maps). Do you have any data points or thinking here?


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