brad@looking.UUCP (Brad Templeton) (04/26/88)
Now that I've got a telebit, I'm actually noticing more waste in my telecommunications. With the speed and error correcting nature of these and other modems, such as 9600 baud MNP modems, using the various protocols we've got with short packets and lots of backtalk, along with slow handshaking. If I watch a uucp mail transfer at 19200 with my telebit, at least half the time, if not more, is spent doing nothing while the UUCPs figure out what file to send next and handshake about it. Data flows the other half of the time if you're lucky. The other wastage is machines that can't take input data at 19200, and even those who can't send it. I get the full 1400 or 1500 bytes/second when the vax I talk to is unloaded, but it drops a lot during the day. What we need is a protocol that: a) Bunches up all the files before initiating the call, so it's just a constant data stream b) Uses big fat packets, 10K or 20K in size. (or uses a packet time in seconds rather than bytes, ie "5 seconds" means 150 bytes at 300 baud and ~5K at 9600 baud.) c) Does minimal error checking, ie. one CRC per 10K packet. d) Can use a restricted character set so that more efficient 'line at a time' tty driver modes can be used, and also so that LANS and packet switch nets don't interfere. e) Possibly uses shorter packets but doesn't actually wait for the ACK before sending the next packet, but rather sits and examines any NAKs that come or ACKS that don't, and resends those packets. Anybody doing anything like this? In theory it should be a lot simpler than the protocols that had to handle high-error lines. This would also be useful over dedicated serial links, for example. -- Brad Templeton, Looking Glass Software Ltd. - Waterloo, Ontario 519/884-7473
sl@van-bc.UUCP (pri=-10 Stuart Lynne) (04/27/88)
In article <1576@looking.UUCP> brad@looking.UUCP (Brad Templeton) writes: >Now that I've got a telebit, I'm actually noticing more waste in my >With the speed and error correcting nature of these and other modems, such >as 9600 baud MNP modems, using the various protocols we've got with short >packets and lots of backtalk, along with slow handshaking. >What we need is a protocol that: > a) Bunches up all the files before initiating the call, so it's > just a constant data stream > b) Uses big fat packets, 10K or 20K in size. > (or uses a packet time in seconds rather than bytes, ie > "5 seconds" means 150 bytes at 300 baud and ~5K at 9600 baud.) > c) Does minimal error checking, ie. one CRC per 10K packet. > d) Can use a restricted character set so that more efficient > 'line at a time' tty driver modes can be used, and also so > that LANS and packet switch nets don't interfere. > e) Possibly uses shorter packets but doesn't actually wait for the > ACK before sending the next packet, but rather sits and examines > any NAKs that come or ACKS that don't, and resends those packets. You are confusing two issues here. We need two protocols. A file transfer protocol which can "batch" small things together for transfer, and a more effective transport protocol which can be more efficently implemented on micros and mini's. In the first instance, there has been some discussion about using BSMTP to allow multiple mail messages to be transferred in one file. For the second problem what you described sounds a lot like ZMODEM. It was designed with a lot of these issue's in mind and attempts to be efficent both from the use of the available bandwidth and CPU cycles for implementing. -- {ihnp4!alberta!ubc-vision,uunet}!van-bc!Stuart.Lynne Vancouver,BC,604-937-7532
moretz@topaz.rutgers.edu (Lawrence R. Moretz) (04/27/88)
Hi folks! I'm looking for a little help that I thought modem people could help with. I've got an old model VenTel 2400 baud external modem that I have no doc. for and need to figure how to use it. It has two interfaces on the back, one RS232 marked Business Machine, (which I know what to do with) and one 6-pin interface marked TTY. Question 1: How do I wire this to my telephone? Or is this modem designed to be used only over private lines? I can see wiring it into a junction box and then turning the modem on afetr a carrier tone is heared over the ttelephone, but I'm not sure. Next, the modem has two push buttons on the front and several led lights, the lights indicate things like data send, data recieve, etc... but does anyone have a clue as to what the buttons do? Any help would be appreciated. Thanks, Larry Moretz