Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!uunet!lll-winken!arisia!mdixon From: mdixon@thelonius.PARC.xerox.com (Mike Dixon) Newsgroups: comp.sys.next Subject: buggy tcp interactions Message-ID: Date: 23 Aug 89 01:21:34 GMT Sender: news@arisia.Xerox.COM Distribution: comp Organization: Xerox PARC, Palo Alto, CA Lines: 49 i spend a fair amount of time rlogin'd from my next to a nearby sun, and occasionally get into problems where the connection seems to go "out of sync" -- the last packet worth of output isn't displayed until i type another character or a couple of seconds goes by (making it feel as if the sun has suddenly become rather slow). this afternoon when it happend i tcpdumped from another machine, and looking at the trace it's clear that the next is getting into some mode where it simply doesn't ack packets. when this happens, there doesn't seem to be any reasonable way to fix it (e.g. logging out of the sun and back in again doesn't help; presumably rebooting the next would). on the other hand, it usually fixes itself after five or ten minutes. anyone have any idea what's going on here? ------------------------------------------------------------ watcher# tcpdump between sun next # i type 'ls' followed by cr 17:55:41.81 next.1023 > sun.login: P -1653878447:-1653878446(1) ack 675399367 win 4096 17:55:41.83 sun.login > next.1023: P 1:2(1) ack 1 win 4096 17:55:41.89 next.1023 > sun.login: P 1:2(1) ack 2 win 4096 17:55:41.89 sun.login > next.1023: P 2:3(1) ack 2 win 4096 17:55:42.01 next.1023 > sun.login: P 2:3(1) ack 3 win 4096 # it echoes the cr, then sends the output. the next displays the # cr/lf immediately but not the ls output, and acks neither 17:55:42.01 sun.login > next.1023: P 3:5(2) ack 3 win 4096 17:55:42.71 sun.login > next.1023: P 3:597(594) ack 3 win 4096 # the sun times out & resends, this time the next acks 17:55:44.71 sun.login > next.1023: P 3:597(594) ack 3 win 4096 17:55:44.73 next.1023 > sun.login: . ack 597 win 4096 # i just type a cr 17:55:48.61 next.1023 > sun.login: P 3:4(1) ack 597 win 4096 # this packet is displayed immediately, but not acked 17:55:48.61 sun.login > next.1023: P 597:599(2) ack 4 win 4096 # eventually the sun gives up and sends it again, aloong with the # the prompt 17:55:52.21 sun.login > next.1023: P 597:606(9) ack 4 win 4096 # and the next *still* doesn't echo until i type another cr... 17:55:56.83 next.1023 > sun.login: P 4:5(1) ack 606 win 4096 # more of same 17:55:56.85 sun.login > next.1023: P 606:608(2) ack 5 win 4096 17:56:00.71 sun.login > next.1023: P 606:615(9) ack 5 win 4096 17:56:03.99 next.1023 > sun.login: P 5:6(1) ack 615 win 4096 17:56:04.01 sun.login > next.1023: P 615:617(2) ack 6 win 4096 17:56:08.71 sun.login > next.1023: P 615:624(9) ack 6 win 4096 -- Mike Dixon Xerox PARC mdixon@arisia.xerox.com