Re: htdig: virtual hosts revisited

Geoff Hutchison (
Tue, 15 Dec 1998 09:13:38 -0500

At 2:56 AM -0500 12/15/98, Walter Hafner wrote:
>And a second thought on document checksums: Quite often I see root
>documents more than 100 kb in size. Why not just computing a checksum of
>the header. A HTTP 1.1 'HEAD' command would be sufficient and imho this
>would save a lot of bandwidth and computing time.

First, any mention of HTTP 1.1 commands require switching to HTTP 1.1
support. :-) But there's actually something better than HEAD. Many servers
(esp. Apache) return "Etag:" headers with the checksums already computed.
So if we get such a tag, we have no need to compute the checksum at all.

As far as using the HEAD for the checksum, my point is that most documents
we already GET, so we don't save any bandwidth. I'm also not completely
sure that there's enough to ensure the checksums are unique. (This is why
I'd want to test the feature very thoroughly.)

-Geoff Hutchison
Williams Students Online

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