stryker@cca.ucsf.edu (Michael P. Stryker) (04/23/89)
Some ftp and SMTP transactions to some sites now intermittently time out under Ultrix 2.0 because this version of Ultrix has the IP_TIMETOLIVE parameter set to 15, which is too low a value for today's internet, whose configuration involves many more message hops than was previously necessary. I do not know whether this has been corrected in more recent releases of Ultrix. The symptoms are bounced mail and 'ftp: connect timed out' messages. 4.3 Unix has the /sys/netinet/tcp_timer.h TCP_TTL set to 30. In Ultrix 2.0, this parameter is 15. For binary-only Ultrix sites, the solution is to patch the kernel using adb. [Changing the #define TCP_TTL to 30 and rebuilding the kernel does not do the trick, since the relevant modules are not recompiled from source.] The local wizards have provided me with the following example of adb commands, which has worked well on our machines and solved our problems. After saving a copy of the existing /vmunix, use adb on /vmunix and change locations tcp_output+5d4 and tcp_respond+208 from the value ff6 to 1ef6. If you have not done this kind of thing before, here's what to do: # adb -w /vmunix tcp_output+5d4?x 80014ca0: ff6 ?w 1ef6 80014ca0: ff6 = 1ef6 tcp_respond+208?x 80015020: ff6 ?w 1ef6 80015020: ff6 = 1ef6 ^D # (Guess it's not clear what you type versus what adb responds with, but when you try it it should be obvious). After this you'll need to reboot so the changes can take affect. Michael Stryker (stryker@phyb.ucsf.edu or stryker@ucsfcca.bitnet) UCSF Physiology Department