- From: Mike Meyer <mwm@contessa.phone.net>
- Date: Thu, 17 Aug 95 02:19:14 PST
- To: http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
> the IMS last modified date is already a value that must be stored > out of band in the cache. I think I pointed that out; it's important to note, though. > > A new header from servers: Version: Version-string > > A new header from clients: If-Not-Version: Version-string > This would work pretty well but has the disadvantage of not being > reproducable on the client end. The IMS LM date has the same problem - the client can't reproduce it. I like the more generic "If-different" header. We can even tweak it to save 15 of the 20 bytes you complained about: If-Different: 1#( field-name value ; ) The server then verifies that for each field-name/value pair, it is going to send a header with that name whose value (after trimming leading and trailing whitespace) is the same as the client sent on the if-different field. If one of them is different it sends the document. Otherwise, it sends a 3xx reply "Not different". You can therefore get the behavior you want from if-modified-since: last-modified ; size=length with if-different: last-modified ; content-length length and leave if-modified-since with the current definition for those who have a use for that. Optional bandwidth reducer: allow the server to not send any headers that are named on the if-different header that haven't changed. <mike
Received on Thursday, 17 August 1995 02:28:13 UTC