[tor-talk] exit node cache

[Andreas Krey]

On Thu, 18 Oct 2012 23:42:41 +0000, jiang song wrote:
...
> 1) if the Tor exit node is continueing acknowledging the webserver on
> receipt of tcp segments,
> then the Tor exit node will have to cache a lot data, is it right?
> or
> 2) actually the TCP ack is from the Tor client? if the Tor exit node
> doesn't receive the TCP ack from the Tor client,
> it will never acknowledge the receipt of tcp segments from the webserver?
> 
> which understanding is right?

The second one is much closer to reality. :-) The exit nodes stops
reading from the connection to the web server when it can't forward
the data to the client fast enough.

But the web server isn't slowed down/stopped by not sending ACKs but
rather by reducing the window size to zero. ACKs are still sent as
data is received (moduly shortly delaying acks for other reasons).
This is all done within the TCP stack which does all this ACK and
window size stuff; the tor process just reads from the socket.

Andreas

-- 
"Totally trivial. Famous last words."
From: Linus Torvalds <torvalds@*.org>
Date: Fri, 22 Jan 2010 07:29:21 -0800