jgb@medivax.UUCP (J. Grant Bristow) (03/18/87)
I hope this is the right place to post this!
Our department is currently communicating with 5 remote sites
via 10 leased lines and 20 2400 baud modems. We are running Ultrix 1.2
on an VAX 11/750. Obviously, one leased line to each site is
mandatory, but surely not 4. All lines are normal serial tty ports.
Questions:
Are you using multiplexors over leased lines? What brand?
What speed? What modems? How much did the multiplexor cost?
Any advice?pozar@hoptoad.uucp (Tim Pozar) (03/18/87)
In article <116@medivax.UUCP> jgb@medivax.UUCP (J. Grant Bristow) writes: >Our department is currently communicating with 5 remote sites >via 10 leased lines and 20 2400 baud modems. We are running Ultrix 1.2 >on an VAX 11/750. Obviously, one leased line to each site is >mandatory, but surely not 4. All lines are normal serial tty ports. > >Questions: > > Are you using multiplexors over leased lines? What brand? > What speed? What modems? How much did the multiplexor cost? > > Any advice? I am also interested in any information concering multiplexors. Our radio station is tied with our sister station in San Jose through a T1 carrier. I have one extra channel that I wish to plug a multiplexor into. The unit is built by Rockwell (you know, the shuttle Chalenger people). Its compatible with units built by Coastcom. I'm interested in multiplexing 6 9600b/s paths (6*9600=56000). Any suggestions out there? Has any one had any problems I should look for? Thanks Tim -- Tim Pozar UUCP pozar@hoptoad.UUCP Fido 125/406 USNail KLOK-FM 77 Maiden Lane San Francisco CA 94108 terrorist cryptography DES drugs cipher secret decode NSA CIA NRO IRS coke crack pot LSD russian missile atom nuclear assassinate libyan RSA
howard@cos.COM (Howard Berkowitz) (03/19/87)
In article <116@medivax.UUCP>, jgb@medivax.UUCP (J. Grant Bristow) writes: > Our department is currently communicating with 5 remote sites > via 10 leased lines and 20 2400 baud modems. We are running Ultrix 1.2 > on an VAX 11/750. Obviously, one leased line to each site is > mandatory, but surely not 4. All lines are normal serial tty ports. > > Questions: > Are you using multiplexors over leased lines? What brand? > What speed? What modems? How much did the multiplexor cost? > Any advice? I've run multiplexers (GDC, Codex, Vidar, Micom, Timeplex, Bridge, DEC, etc.) and related technologies on lines from 2400 BPS to 10 megabits. There is no general answer to what multiplexer is best. Just think of the various types that are available for wide area (i.e., using long-haul telephone-based transmission, rather than campus or LAN wiring): statistical, fixed bit-interleaved, fixed character-interleaved, etc. X.25 PAD's also can be very effective multiplexers. To give you more help, I need more information: How far are the remote sites from the host? There may be some viable alternatives between LAN and telephone multiplex technologies, such as limited distance modems. What speeds and protocols are used by the terminals? What sort of applications (e.g., do they receive lots of reports back which have lots of blanks which could be suppressed by an intelligent multiplexer)? Do the terminals ever need connectivity to other than the VAX? If they do, you variously may need dial-out ports on the VAX or X.25 may be a better solution than standard multiplexing. Howard C. Berkowitz (703) 848-2100 (office) (703) 998-5017 (home)
howard@cos.COM (Howard Berkowitz) (03/19/87)
> > I am also interested in any information concering multiplexors. Our > radio station is tied with our sister station in San Jose through a T1 carrier. > I have one extra channel that I wish to plug a multiplexor into. The unit is > built by Rockwell (you know, the shuttle Chalenger people). Its compatible > with units built by Coastcom. I'm interested in multiplexing 6 9600b/s paths > (6*9600=56000). Any suggestions out there? Has any one had any problems I > should look for? I'm unclear if your extra channel is another T1 or a "56" KBPS channel. (The 1.544 MBPS rate, technically, is a DS1 signal, while its subrate 64 KBPS channels, often bit-stuffed to 56KBPS transparency, are DS0. "T1", technically, is the Bell System (or nonsystem) code for DS1 signals over repeatered twisted pair, as opposed to other transmission media such as microwave or fiber). If your channel is DS0, you're going in the right direction; it's much cheaper to use 2-stage multiplexing to get a relatively slow speed (in DS1 terms) such as 9600 BPS. You rarely want an intelligent (statistical) multiplexer on DS1; your approach to engineering the system should assume transmission speed is essentially free. A fixed-slot bit-interleaved multiplexer usually is best (see GDC, Timeplex, etc.). If you are not running synchronous protocols on the 9600, my recommendations are likely to change. Let me know what you are running and I'll try to help. When buying the mux, be sure your mux vendor works with you and the T1 mux people to understand where all the clocks are coming from, and how they stay locked to each other. This can be nontrivial. Howard Berkowitz (703) 848-2100.
dricej@drilex.UUCP (Craig Jackson) (03/19/87)
We have a fairly large multiplexor-based network at DRI. We use Infotron
muxes. We also use Infotron equipment for PADs and switching. I'm not a
datacom guy, so I couldn't tell you details on their operation. However,
the only real problems we've had with them (at least at the application
level) is some lack of remote configurability (by the application).
Codex also makes a whole line of muxes, I believe.
--
Craig Jackson
UUCP: {harvard!axiom,linus!axiom,ll-xn}!drilex!dricej
BIX: cjackson