Re: Possible addition to Squid? + more

From: Kolics Bertold, University of Veszprem <>
Date: Tue, 10 Dec 1996 08:14:12 +0100 (MET)

Dear All,

> One of my colleagues asked a few days ago if Squid compressed inter-cache
> object transfers. As far as I know it does not, but this sounds like it
> would be a worthwhile feature to have. Maybe lempel-ziv compression and
> packed transfers (and entire page's worth (or all objects requested/held in
> the cache) of objects in one transfer, instead of one transfer per object)
> for inter-cache transfers?

Similarly to HTTP/1.1, a kind of Transfer-Encoding header (which can be
used for indicating gzip or unix compress type compression) should be
implemented in ICP as well. However, if it will be implemented in Squid, I
think compression should be optional and Squid must be able to fall back
to uncompressed mode whenever a sibling or a parent can not handle or do
not want to handle compression for transfer.
I can't estimate how much load compression will add to the system's load.

From my experience the average stored object size is about 12 Kbytes, but
objects that are fetched but not stored (in my case objects > 4 MB) are
not calculated in this result.
But objects larger than 4 MBytes are in most cases ftp objects. And I
think ftp files larger than 4 MBytes are often compressed.
So, I think a kind of investigation is needed before implementing.

But this compression idea can be used in the origin server - proxy cache
communication as well, because HTTP/1.1 includes Transfer-Encoding and
there will be HTTP servers that implement HTTP/1.1. (Apache/1.2b1
implements HTTP/1.1, but I am not sure whether it uses Transfer-Encoding
as well, and as far as I know Jigsaw for W3C works with HTTP/1.1).

Another crucial issue would be 'persistent connections'. The latest Apache
supports that since this is the default mode for HTTP/1.1 servers.
What about that?


 Kolics, Bertold E-Mail:
 University of Veszprem, Hungary W3:
 Information Engineering Course
Received on Mon Dec 09 1996 - 23:24:10 MST

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