Re: I-D ACTION:draft-tewari-webi-wcdp-00.txt,.ps

Ted,

       Here are some of the answers, AFAIK, to the excellent questions you
       raised.



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       Odd that heartbeats travel from server to client, not the more
       traditional direction, from client to server.  Is there a
       justification
       for this?


The justification you gave was exactly right.


       Does scalability goal include the ability for WCDP clients to
       communicate with very many WCDP servers?



Yes.


       It doesn't seem like the refresh directive avoids any extra messages
       compared to simple invalidation.  Is it only intended to reduce
       latency?


This is true for web caches, where invalidations and updates are
       functionally equivalent.

But for web servers, we actually need to perform file creates and deletes
       with each

refresh directive.



       The force option in the invalidate request seems dubious.  What
       happens
       if a client declines to perform the invalidation in response
       response to
       a force, or an update perhaps due to a network outage.  What does it
       "mean" for the server to specify force?  How does force impact the
       semantics of the consistency guarantees?


The thought back then was that invalidations are more cache-specific,
       whereas

invalidate-force is equivalent to a "delete file" at all web servers and

just a plain invalidate at all caches. So the former would be a no-op as

far as web servers were concerned.


       The wave description of propagating invalidations in section 4.6 is
       confusing.  How does the invalidation wave carry with it the list of
       notified clients and how does this influence the pulling of data?

Since deletions are local operations, this information seemed unnecessary.



-srikanth