> > The easiest way to demonstrate is turn on ECN yourself on a linux-2.4 > > or linux-2.6 host. > > Just "echo 1 > /proc/sys/net/ipv4/tcp_ecn" as root.... > > Then you will find list.org doesn't work, until you... > > "echo 0 > /proc/sys/net/ipv4/tcp_ecn" as root.... > I don't know what the tcp_ecn stuff does, but I can repro that easily. > Just followed your steps and then telnet www.list.org 25. No go. At the > same time I could still reach other servers. Well, indeed....
This is because "list.org" server has a broken firewall of some form. Major firewall manafacturers had code that exhibited this problem and have fixed it basically. But, this problem is "all-but" gone away. I.e. much better than it used to be, but some places are still broken! [like "list.org"]. What ECN [Explicit Congestion Notification] does, is allow intermediate internet routers to 'notify' a TCP connection of congestion BEFORE a state of high-latency/packet_loss occurs. This is generally a good-thing-for-everyone etc. In order for this to work, the TCP-client needs to USE TCP_ECN (by setting the relevant flags in TCP header initially), and the TCP-server needs to 'support' ECN, and the congested router needs to support marking TCP packets when busy.... > Kai --"enyc" <[EMAIL PROTECTED]> ------------------------------------------------------ Mailman-Users mailing list Mailman-Users@python.org http://mail.python.org/mailman/listinfo/mailman-users Mailman FAQ: http://www.python.org/cgi-bin/faqw-mm.py Searchable Archives: http://www.mail-archive.com/mailman-users%40python.org/ Unsubscribe: http://mail.python.org/mailman/options/mailman-users/archive%40jab.org
