Squid and TCP congestion avoidance

Hello,

It comes to my mind, when thinking about DiffServ application
(http://www.ietf.org/html.charters/diffserv-charter.html)
a way to reduce bandwidth used by a particular squid
connection.

If we would like to inform dynamically to squid to reduce
the bandwidth used by a socket, we could mark such packet
(at a border router for example) with a specified ToS
(or DS nowadays..) value, and squid could
reduce the window size of this particular socket.

This is an alternative of simply dropping a packet, which, even
with exponential backoff of TCP, is a waste of bandwidth.

There's just two 'little' problems:

Does TCP allow to negogiate the receiving window of an
open socket? (I don't think so)? If yes, is there an API
for doing that?

Does the BSD socket API support any form of
TOS monitoring for the upper application layer?
(TOS at IP (layer 3) -> Squid (layer 7)) so squid
could be notified when packet with a defined TOS value
come in, it will reduce it's receiving window? I doubt
such a thing exist either, but people more
experienced with network programming could
(in)validate?

Thanks!

-- 
Philippe Strauss, ingenieur reseau/systemes, Urbanet SA
philippe.strauss@urbanet.ch
tel +41 21 623 30 20
--