dd@ariel.unm.edu (dd) (12/08/89)
I am trying to front-end an IBM 7171 with a CISCO ASM. I have gotten it to work, but there are some performance problems. Has anyone out there done this thing, and could I please ask you some questions? Thanks in advance. -- Don Doerner dd@ariel.unm.edu University of New Mexico CIRT 2701 Campus Blvd, NE Albuquerque, NM, 87131 (505) 277-8036
robert@trwind.UUCP (Robert W. Snyder) (12/15/89)
Robert Snyder > >I am trying to front-end an IBM 7171 with a CISCO ASM. I have >gotten it to work, but there are some performance problems. Has >anyone out there done this thing, and could I please ask you some >questions? > I have not seen any responses on this that helped you with the 7171 problems so I thought I would try to help by sharing the problems I recalled. I developed a terminal server for TRW and I eventually had a field engineer interface one to a 7171 in a milking machine fashion. There were a few problems I had to contend with. 1. At the time the 7171 did not do xon/xoff flowcontrol properly Symptom: The network conection would appear to lock up or have character loss. Analysis: After looking at a lot of serial data analyzer output, I discovered that when the terminal server flow controlled the 7171, the 7171 not only discontinued the transmission of normal data traffic but also discontinued sending xons/xoffs, which caused it to enter a "catch 22" state where both sides where flow-controlled and neither could release flow-control until some action was taken by the other or it would drop characters on the floor because the 7171 refused to inform the terminal server that it could not receive anymore characters. Resolution: IBM fixed their code by offering an option to either allow flowcontrolling of flowcontrol characters or a mode that I needed to succeed that allowed flowcontrol characters to be transmitted. 2. The 7171 that I was interfacing to required that certain hardware lines be asserted to transmit characters to the unit. Once those lines were asserted the 7171 began transmiting characters almost instantly. Symptom: The user would see a message the looked like this "gin:" instead of "Login:" (I dont remember the actual message but it was some sort of logon message) Analysis: When the hardware line were asserted the network link was not quite up. It was a couple character times off Resolution: I fixed my code. I mention the second problem just because the 7171 was the only device I ran into that exhibited this operation. Disclaimer: My experiences with the 7171 are specific to interfacing problems I experienced about 3 to 4 years ago. I am not an expert on the 7171, just good with terminal servers and serial devices. -- Robert Snyder Disclaimer -- nobody claims dis, but me TRW Information Networks Division 23800 Hawthorne Blvd, Torrance CA 90505 USENET: trwind!robert INTERNET: robert@trwind.TRW.COM Phone 213-373-9161