> this is a good idea. 16k might be even better if it worked reliably > (the usual default is 32 to 64k).
Your information might be somewhat obsolete... Have a look at my machine (a pretty ordinary recent Linux) connecting to tor.eff.org: lanthane.45747 > 209.237.230.67.www: SWE 4264190125:4264190125(0) win 5840 <mss 1460,sackOK,timestamp 315382960 0,nop,wscale 6> 209.237.230.67.www > lanthane.45747: S 3004159902:3004159902(0) ack 4264190126 win 65535 <mss 1460,nop,wscale 1,nop,nop,timestamp 1445924711 315382960,sackOK,eol> Lanthane (my machine) opened a connection to tor.eff.org. Since it doesn't have any information about the connection's RTT yet, it declares a very small TCP window (5.8 kB). Tor.eff.org has a somewhat more traditional implementation of TCP, so it starts with a window size of 64 kB. (Note that both sides negociated the wscale option, so from now on we need to multiply lanthane's values by 64, and tor.eff.org's by 2). A little while later, the situation has evolved as so: 209.237.230.67.www > lanthane.pps.jussieu.fr.45747: P 4112:4445(333) ack 4629 win 33304 <nop,nop,timestamp 1445925772 315383225> lanthane.pps.jussieu.fr.45747 > 209.237.230.67.www: . ack 4445 win 408 <nop,nop,timestamp 315383277 1445925772> As you may see, tor.eff.org has grown its receive window to 67 kB, while Lanthane has gone up to 26 kB. Juliusz