[Http-crcsync] http-sync standard

[tridge at samba.org]

Hi Toby,

 > This is transmitted in two forms. One is an SHA1 hash of the complete chached
 > file, and the other is a set of block hashes.
...
 > Content-Hash:
 > This will be an sha1 hash of the entire cached body, and will allow the server
 > to transmit deltas based on its knowledge of past versions of the page.

How do you imagine that this hash would be used? I don't think it is
practical to think that servers would keep a record of all the dynamic
pages they have been served out, and for static pages I think the
normal cache tag mechanisms already work well.

I think a SHA1 or similar of the servers generated page is really
worthwhile, but a whole file hash of what the client has in cache
doesn't gain anything that I can see.

btw, I also wonder if you've seen this:

  http://www.ietf.org/rfc/rfc3229.txt

That is the result of earlier efforts to standardise delta encoding in
HTTP. I was a little bit involved in that effort, although it
concentrated on storing old copies on the server, which I wasn't
interested in.

Still, it should provide some very useful background to the current
effort.

Cheers, Tridge