[dns-operations] charter, sitefinder, opendns (slashdot today)

Duane Wessels wessels at packet-pushers.com
Fri Feb 16 00:09:06 UTC 2007

On Thu, 15 Feb 2007, Paul Vixie said:

> now i'll grant you, HTCP use hasn't exactly blossomed.  but i believe that
> any web caching agent who indexes its content only by URI is *broken*, since
> many web pages will have the same URI but content that differs according to
> things like "what human language did the browser prefer to receive?"

Yes, Vary exists for this purpose.  As a writer of Squid code it
has been (and continues to be) a thorn in my side.[*]

But your proposed syntax puts the meat into the message body, not
a header.  You can't Vary on the body content.

I don't have a very high opinion of POST either.  Its the kind of
thing that developers spend 50% of their time on when its only about
5% of the traffic.  HTTP message bodies complicate persistent
connections.  Google for "http request smuggling".

If you want DNS-over-HTTP to play nice with HTTP proxy caches you'll have
to use GET and put the query name in the URL.

[*] I have a client using Squid in some CDN-like configuration.
They wanted to support "Vary: User-agent". When they turned it on,
their hit ratio dropped and the number of objects in cache increased
significantly.  In one case we saw more than 50,000 variants of the
same URL.  Turns out there is at least one spyware out there that
inserts an MD5-like identifier into the User-agent string.

Are we offtopic yet?


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