Re: Parents, Child, and Siblings?? Can't we all just get along...

From: Stewart Forster <>
Date: Fri, 14 Aug 1998 09:15:35 +1000

> Questions. I have one child squid (A) with two parents ( B and C ) and
> parent B has sibling (D).
> D ---- B C
> \ /
> \ /
> A
> When squid A asks for a page from the parents, does squid B check with
> sibling before giving answer or only if it has to actually fetch the page?
> And if it does ask sibling D first and D has it, does this count as a hit on
> Parent B from A?

        In your diagram A sends ICP requests to C & D. C & D will reply
via ICP (without contacting ANYONE else) whether or not they have the object
in question.

        If B returns ICP_HIT, A sends the HTTP request to B, and B will
satisfy it. Same again for C.

        If B & C have both returned ICP_MISS, then A will choose whichever
responded first to send the HTTP request to. If C got there first, it will
retrieve the object from the remote site (assumption) and pass it back to A.

        If B responded first, the HTTP request comes to B from A. B now has
a request for an object it doesn't have, so it asks its peers via ICP, ie
B does an ICP request to D. After that, you know the rest.... If D hits,
HTTP request from B to D, if D misses, B satisfies via direct source.

        In answer to your question, ICP requests are not passed implicitly
around a hierarchy, they are strictly point-to-point.

Received on Thu Aug 13 1998 - 16:17:13 MDT

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