old modems & a packet switcher

From: Ethan Dicks <erd_at_infinet.com>
Date: Mon Aug 3 00:48:30 1998

William Donzelli (william_at_ans.net) writes:
> > I'm not sure anything beyond ethernet would strictly be considered
> > 'classic',
>
> There are lots of old networking standards from the years prior to 1988
> (or even 1978), for both LANs and WANs. You have 56K, T1 (fractional or
> whole), V.35, ARCnet, token thing, FDDI...

As I've mentioned elsewhere on this list, I used to make bisync and sdlc
interface cards for PDP-11's and VAXen. They replaced the "HASPBOX" in
1982 (the HASPBOX was a PDP-11/04 or PDP-11/03 with 100% DEC boards that
plugged into a unibus machine via DR11C and ran a custom communications
package). It used a 68000 and between 32K and 2M of RAM (depending on
the model) with a parallel port (Dataproducts, not Centronics) and a sync
serial port (COM5025 UART or Z8530 SCC). It ran beteen 2400 baud to 64Kb
(in Europe, 56Kb in the US). At that company, we didn't have Ethernet to
link our machines. We used COMBOARD(R) to link VAXen for file transfers,
and DMF-32/DMR11 and sync modem eliminators to link them for DECnet remote
logins and such. The COMBOARDs were much lighter on the CPU, but were not
useful for transparent kinds of I/O. You had to run (external) commands
like SEND and RJEOPR to manipulate the files. Just for kicks (since I
legally retain the copyrights of my former employer), I did an Altavista
search for "RJEOPR" and the like and dug up a web page from a university
that had put their VMS help files on the Web. Part of our installation
procedure was to optionally mangle your help files to insert pages for
our custom commands (back in the VMS3/4 days, before the advent of combination
logicals to point to several directories simultaneously a-la SYS$MANAGER).
The complete text of our help messages are up on the Web. While technically
a copyright violation, I'm not concerned about protecting 15-year-old help
files, if DEC/Compaq isn't concerned about same. Posting *source* is right
out!

But anyway, Yes, Virginia, there were networks before Ethernet. Not as
fast, but viable over inter-state distances.
 
> > but I have a set of DS5000/200s connected via FDDI.
>
> FDDI, the _real_ networking standard!
>
> I will run a few FDDI lines between the house and garage some day, but I
> will have to bury a conduit first to encase them. With approriate
> routing cards, I may be able to get 3 lines between the RS/6000s on either
> end, but that might be stretching it. Two is quite possible. Anyway, that
> would be one helluva pipe!

At McMurdo Station, Antarctica, we have a station-wide FDDI ring linking the
larger work centers. It's well over 1Km long, and is a very stable way of
routing multiple Ethernets through dozens of buildings. It's been so stable
that more than once, it escaped the attention of the network engineer that
the ring was broken and wrapping, until he happened to make a visual inspection
of a router that happened to be in my office, and noticed a particular light
was on, indication this dangerous condition. (For the FDDI-impaired, FDDI
is a token-style network with an A ring and a B ring, that can withstand one
break, and "wrap" from end to end, like turning a circle into a horseshoe.
This impairs efficiency, but not basic functionality, until a second break
occurs, dividing your network into two independent segments. This Is Bad.
It's important to nip that in the bud and restore the ring nature of the
network before traffic or additional failures cause headaches).

-ethan
Received on Mon Aug 03 1998 - 00:48:30 BST