- From: Julian Reschke <julian.reschke@gmx.de>
- Date: Mon, 08 Mar 2010 20:21:27 +0100
- To: Mark Nottingham <mnot@mnot.net>
- CC: HTTP Working Group <ietf-http-wg@w3.org>, Alex Rousskov <rousskov@measurement-factory.com>, Roy Fielding <fielding@gbiv.com>
On 04.03.2010 05:39, Mark Nottingham wrote: > We haven't heard back from Alex, and the other issue I mentioned didn't seem to get enough support to move on. So, I suggest we do the conservative thing: > > Current text: >> age_value - Age header field-value received with the response >> date_value - Date header field-value received with the response >> request_time - local time when the cache made the request >> resulting in the stored response >> response_time - local time when the cache received the response >> now - current local time >> >> apparent_age = max(0, response_time - date_value); >> corrected_received_age = max(apparent_age, age_value); >> response_delay = response_time - request_time; >> corrected_initial_age = corrected_received_age + response_delay; >> resident_time = now - response_time; >> current_age = corrected_initial_age + resident_time; > > Replacement text: >> age_value - Age header field-value received with the response; >> 0 if not available. >> date_value - Date header field-value received with the response; >> see [ref] for requirements regarding responses >> without a date_value. >> request_time - local time when the cache made the request >> resulting in the stored response >> response_time - local time when the cache received the response >> now - current local time >> >> apparent_age = max(0, response_time - date_value); >> response_delay = response_time - request_time; >> corrected_initial_age = max(apparent_age, age_value + response_delay) >> resident_time = now - response_time; >> current_age = corrected_initial_age + resident_time; > > Comments? Looks good to me. I tried both the old and the new formula with a set of input values, and came up with: Request_time Age_value Date_value Response_time RFC2616_corrected_initial_age proposed_corrected_initial_age 1000 2 0995 1020 45 25 1000 2 1000 1020 40 22 1000 2 1005 1020 35 22 1000 2 1010 1020 30 22 1000 2 1015 1020 25 22 1000 2 1020 1020 22 22 1000 2 1025 1020 22 22 1000 0 1001 1002 3 2 1000 1 1001 1002 3 3 1000 2 1001 1002 4 4 1000 3 1001 1002 5 5 1000 4 1001 1002 6 6 1000 5 1001 1002 7 7 ...so the new formula (last column) indeed is less conservative. I agree with Adrien's comment that we should also avoid the term "local time". Best regards, Julian
Received on Monday, 8 March 2010 19:23:12 UTC