tcp-ip@ucbvax.ARPA (07/25/85)
From: Charles Hedrick <HEDRICK@RUTGERS.ARPA> We use a pair of ECU's between a DEC-20 and an IMP. Both connections are local host. The ECU's are connected by a 9600 baud line from ATT, using ATT modems. The only strange things I have seen are failures, almost always of the line. We have had one ECU failure in several years. -------
tcp-ip@ucbvax.ARPA (07/31/85)
From: Mike Muuss <mike@BRL.ARPA> We have about 8 ECU links here, and no trouble that can't be cleared by the RESET switch, at worst. We run anywhere from 9600 baud to 480,000 baud, with most links at 50,000 64,000 and 100,000 baud, and one each at 9600 and 480,000. All operate as Distant Hosts. Most connect to an ACC LH/DH-11, the remainder connect to BBNCC C/70 computers. My only observation so far is that when the 9600 baud link becomes marginal, things work worse that I would have expected. There may be some timeouts in the ECUs which need tuned for link speed. Another factor which is important: For our hosts operating at the end of ECU links, especially ones which go marginal, we turn off RFNM counting in the software. Even though TCP can handle dropped packets, the IMP/HOST protocol (ISO layer 2) can NOT stand dropped RFNM packets, and if this is happening to your host, it will "gum up" and give "out of buffer space" messages. On 4.2 BSD systems, a "netstat -h" with values of 8 in the RFNM column indicate that you have this problem. I can supply C code patches for this if you need it. -Mike