dpm@k.gp.cs.cmu.edu (David Maynard) (01/24/89)
I am trying to set up a SLIP connection between two machines. I had to slightly modify the protocol (just quoting more characters) because the line passes through a terminal concentrator that traps some characters. I am also unable to use hardware flow control because of the concentrator. I have things working to the point that 'ping' seems to work in both directions. Telnet from host-a to host-b works fairly reliably (hangs very occasionally). However, other programs (and telnet in the opposite direction) hang sometime after the connection is established. When I look at netstat on host-a, the hung connections have characters waiting in the Send-Q. On host-b, the queues are empty; however, "netstat -s" reports that the number of ip packets with "data size < data length" has increased. Even after these connections hang, I can still ping host-b and establish new telnet connections from a to b (or continue to use existing telnet connections). I am assuming that some kind of flow control problem is preventing certain types of packets from being received properly on host-b. However, I don't know enough about tcp-ip to know what types of packets to suspect. I would suspect long ones, but some of the connections hang with only 2 characters in the Send-Q. I also tried reducing the SLMTU for the line to 128 with no noticeable improvement. I would appreciate any hints as to where the problem might be. I would also appreciate possible workarounds if I can't find a real solution. Host-a is a Sun-2/120 running SunOS3.5. Host-b is a Sun-3/75 also running 3.5. Both hosts are running Van Jacobson's tcp software. Thanks, David --- David P. Maynard (dpm@cs.cmu.edu) Dept. of Electrical and Computer Engineering Carnegie Mellon University Pittsburgh, PA 15213 --- Any opinions expressed are mine only. I haven't asked the ECE department or CMU what they think. --- --
ron@ron.rutgers.edu (Ron Natalie) (01/26/89)
We saw some funky asymetrical slip behaviour, and the same short packet observation when we forgot to turn of XON/XOFF on the modem we were using. -Ron