Re: Section 8.2
Ben Laurie (ben@gonzo.ben.algroup.co.uk)
Fri, 31 May 1996 20:58:27 +0100 (BST)
Jeffrey Mogul wrote:
>
> 'HTTP/1.1 servers SHOULD maintain persistent connections and use TCPs
> flow control mechanisms to resolve temporary overloads, rather than
> terminating connections with the expectation that clients will retry.
> The latter technique can exacerbate network congestion.'
>
> On a practical note; how do I distinguish between an idle client, a dead
> client, and one that is avoiding network congestion? Should the standard
> give some guidelines?
>
> Actually, the real question is "how do I distinguish between an idle
> client, a dead client, and one that can no longer be reached over
> the network?" (Network congestion tends to result in slow but not
> totally failed communication.)
A host that detectably can't be reached over the network will produce a "host
unreachable" response. An undetectable one is indistiguishable from a dead
host or one that is avoiding network congestion (I think).
> The answer to the real question is "you can't, so don't bother to try."
> Treat them all the same: when you get tired of waiting, give up. Many
> servers seem to use a timeout of about 20 minutes for this.
20 minutes seems like a very long time to tie up valuable resources.
> I mean, you could use the TCP keepalive mechanism to disinguish between
> idle clients and the other cases, but it's pretty pointless, and it's
> not a good way to reduce network congestion.
Agreed.
Cheers,
Ben.
>
> -Jeff
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