Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!shaman!jiro From: jiro@shaman.com (Jiro Nakamura) Newsgroups: comp.dcom.modems Subject: Re: Slow T2500 transfer with long distance calls Keywords: Trailblazer, T2500, PEP Message-ID: <1991Mar12.025004.8094@shaman.com> Date: 12 Mar 91 02:50:04 GMT References: <356@alderan.uucp> Organization: Shaman Consulting Lines: 70 chris@alderan.uucp (Christoph Splittgerber) writes: > >However, when I do very long distance links (e.g. to the USA) in PEP >modus, my Trailblazer does behave very strange. I understand that I >should not expect 1400 char/sec but just imagine this: [ strange delays ] Sounds like your Trailblazers are having a hard time keeping the micro packets alive and are busy retransmitting them. I'd recommend e-mailing to modems@telebit.com and asking for their "ADVERSE COMMUNICATIONS LINKS" information. Most notably, you may have to tell the modem to stop using micro packets. Basically, their are three levels for bad lines: ---- Quoted from Adverse Communications Links ------- The three levels are in order of severity of line difficulties, from minor to major. Level 1. AT S120=12 J6 S36=1 Generally, Level 1 will have a very minor impact on performance, both in interactive use and file transfer. It is useful, however, for achieving a degree of reliability, even when the communication lines are very good. The J6 S36 register may be incremented up to 4 in order to better survive adverse line conditions. Level 2 AT S120=2 J6 S36=2 Level 2 will impact interactive performance severely while file transfers remain at close to normal performance. Level 3 AT S120=3 J6 S36=3 Level 3 is a last resort setting which will severly impact interactive performance and limit file transfer speeds to a maximum of 6000 bps. Data compression, S110=1, can make up some of the difference, but only if the data has not been previously compressed. The S121=1 register will enable compensation for echo cancellation on the circuit, and can be enabled at any of these levels. If a stand alone modem is in use, the special register commands should be sent to the modem and saved to Non-Volatile Memory, by sending the save command "AT&W". In situations where a mixture of local and long distance calls are being placed, it is recommended that these special settings be made in a modem initialization file or that the A/B selection switch be used. ==================================== For the meaning of the S120, S36, and J register settings, please get a hold ofthe whole document. I would be wasting net bandwidth to include the whole thing. - Jiro Nakamura jiro@shaman.com -- Jiro Nakamura jiro@shaman.com Shaman Consulting (607) 253-0687 VOICE "Bring your dead, dying shamans here!" (607) 253-7809 FAX/Modem