Machine A: PC running Linux 6.1 in NY Machine B: Sun running Solaris 2.6 in NY Machine C: Sun running Solaris 2.6 in San Francisco Open a telnet session between A -> C, B -> C. The session between A -> C will get disconnected after aproximately 2 hours of inactivity with a "connection closed by remote host message". The connection between B -> C will remain active. I think there is T1 between the sites.
Sounds like system (C) has an idle timeout configured and system (B) doesn't. The obvious test is to see what happens if, after telnet to (B), you telnet from there to (C) and leave it idle - does that time out as well?
This problem could be attributed to any number of causes - network problems, idle timeouts, etc. I haven't ever seen this problem myself, so I think it's safe to call it a fluke.