Xref: utzoo comp.dcom.modems:2553 comp.mail.uucp:2022 Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!amdcad!weitek!pyramid!csg From: csg@pyramid.pyramid.com (Carl S. Gutekunst) Newsgroups: comp.dcom.modems,comp.mail.uucp Subject: Re: UUCP g stats (really: "f" with MNP?) Message-ID: <41298@pyramid.pyramid.com> Date: 30 Sep 88 03:43:39 GMT References: <944@oswego.Oswego.EDU> Organization: Pyramid Technology Corp., Mountain View, CA Lines: 32 In article <944@oswego.Oswego.EDU> ostroff@oswego.oswego.edu.UUCP (Boyd Ostroff) writes: >Since many of the new modems have MNP error checking/correction in >hardware/firmware, would it be possible to run UUCP without any packetizing >or error checking with MNP in "reliable" mode? > >I've read there are protocols (F, X ???) which do no error checking. Also 't' and 'e'. Of these, only 'f' is suitable over error-correcting modems, since the other three have no provisions for flow control, and no end-to-end error checking. That is, when talking over serial lines, you must have some way for the modem and the computer to occasionally tell each other "Slow down! You're sending too fast for me!" That's flow control, and on RS-232 lines it is usually done with XON-XOFF (CTRL-Q and CTRL-S). (The 'g' protocol uses a more sophisticated technique called a "sliding window.") In addition, you want some kind of protection against overruns and bits that scrambled between the modem and the computer. So you need a protocol that also does some error checking of its own. That said, 'f' works exceptionally well over MNP modems and TrailBlazers; in fact, before Telebit added 'g' protocol support, you could *only* use 'f' over a TrailBlazer. You you still have to use 'f' on the USR 9600HST and most other pseudo-standard high-speed modems. Unfortunately, 'f' has a very high overhead on binary files, much higher than 'g', because it is a 7-bit protocol that was intended for X.29 links. So it works well on plain text, but it gets bad on binary files, and positively stinky on compressed files! To use the alternative protocols like 'g', 'f', et al, they have to be built into the uucico's at both ends of the connection. Without uucp source, you cannot add any new protocols to your uucico. If your uucico does not have at least 'f', you should scream at your vendor.