Nathan Sharp wrote: <snip>
> I think note should be taken that IRC uses such a ping-pong solution. > I'd be willing to bet that AOL, Yahoo, and MSN all include such a > feature as the TCP timeout logic is severely limited (there was a > discussion of this point a month ago or so on this list). I know that Yahoo and MSN do not; I suspect that AOL does not either. ICQ used to use heartbeats, but that was because they were a UDP-based protocol. It took on average between 3-5 minutes for a disconnected user to register as disconnected, and later I believe the official clients started actually ignoring offline notifications because UDP traffic was too lossy. IRC's use of ping/pong has been used many times in the past in peer DoS attacks - however that is neither here nor there. As a counterpoint, however - a single-byte application-level ping/pong is still going to take a minimum of 82 bytes of network traffic. It is likely that for five million online users, the ~7MB/s traffic a once-a-minute ping/pong would generate might not considered worth it. Some of the portal services above may have implicit pings via a tcp keepalive message; I wouldn't consider it beyond them to alter the underlying tcp stack to send faster keepalives and even to perform fewer retransmissions. -David Waite _______________________________________________ jdev mailing list [EMAIL PROTECTED] http://mailman.jabber.org/listinfo/jdev
