Re: Token Ring in the early '90s?
And to cap it all, 4Mb/s Token Ring! 16Mb/s was available in the '80s.
Token Ring had a traffic protocol whereby the packet would be sent by the sender, and received by the target, which would then set a flag and re-transmit the packet, still full. It would then flow around the ring until it arrived at the sending station, which would then 'empty' it and re-transmit the empty token to the next station on the ring. The sender of the original packet, which had just emptied it, was not allowed to fill it. In this way, it was made impossible for a small number of systems to monopolize the ring. All stations would get a crack at sending, as eventually the token would arrive 'empty' at every station.
Unfortunately, I believe that some of the non-IBM network drivers for Token Ring would not honor the rule about not immediately re-filling the token, and this allowed other stations on the ring to get 'locked out'.
Ethernet, both 10base5 and 10base2 would also seriously suffer under conditions of high congestion (because of CSMA/CD), and it was not until the advent of the 10baseT switches (as opposed to a hub, which acted much more like a cable than a slotted bus), that congestion problems began to go away.
It was always said, when I learned about networks, that Token Ring had higher overhead than Ethernet when the network was less busy, but coped better with high network loads.
I believe that the very last incarnation of Token Ring, using Madge intelligent CAUs and RJ45 Structured Cabling rather than MAUs, actually allowed more than one token to be passing around the network at any time (the number depended on the number of stations on the network), with some form of buffering to copy with stations with different speeds. This made it more like the 'token bus' that an earlier poster mentioned. But by that time, 100baseT and faster was becoming faster and cheaper.
I ran an IBM Call Center using Token Ring for a number of years, and I have a number of tales I could tell about how easy it was to break a Token Ring network!