Section 13.2.3
Ben Laurie (ben@algroup.co.uk)
Mon, 03 Jun 1996 20:29:32 +0100
13.2.3
All HTTP implementations, but especially origin servers and caches,
should use NTP[28] or some similar protocol to synchronize their clocks
to a globally accurate time standard
This is unrealistic and besides is a requirement on the users of the
implementation rather than the implementation itself, unless we are
seriously suggesting that every HTTP implementation should run NTP
internally. Unrealistic, BTW, because of firewalls, Intranets, and dumb
operating systems, particularly at the client end (and, dont forget,
there are more client caches than any other type).
If this point is accepted then much of the age calculation becomes
wrong. I would suggest a simple fix. The responder includes in the
header the local time at which the response is generated. The time slip
between the responder and the client can be estimated by the following:
time_slip=server_now-(request_time+response_time)/2. This can then be
used to correct as appropriate.
Cheers,
Ben.
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Ben Laurie Phone: +44 (181) 994 6435
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