Deterministic Networks used at all? Token Ring?

[AgaBoogaBoo]

In CCNA1 they're talking about deterministic networks like the token ring and FDDI. Do these have any real use? I'd imagine they were developed with certain reasoning but I'm just not seeing that right now, sounds inefficent and proprietary to me...

 

[spidey07]

Its not inefficient and it isn't proprietary. And in many ways much better than ethernet. (deterministic behavior, greater throughput)

What really killed these technologies was gigabit ethernet. The high performing networks of the past were built on token ring with a FDDI backbone. FDDI made an ideal backbone technology as it was a self healing ring.

But once gigabit ethernet came out coupled with cheap layer3 switching and the price of 10/100 meg ethernet ports were so drastically low a case to use token ring/fddi could not be made. at that point ethernet offered way too much bang for the buck.

FDDI and Token Ring were the kings in the late 80s, early to mid 90s. If you wanted a high performance network, you avoided ethernet at all costs. It was simply too slow.

 

[AgaBoogaBoo]

Hmm... what am I missing then, what makes them so great? If only one computer can transmit data at a time, isn't that a bit slow?

Sorry if I sound ignorant!

 

[spidey07]

Not when you compare it to CSMACD which is more of a "shout until I'm told to shut up" approach or "if nobody is talking I'll talk". Token ring/fddi everybody gets their turn. In CSMACD you can have a single or few staions literally hogging the wire and other stations can barely send a frame.

Plus 10 Base-T just about maxed out at 30-40% utilization. At that point collisions were very heavy depending on the number of nodes on the network. So you're talking 3-4 meg vs

16 megabit, almost 100% utilization for Token Ring
100 Megabit, almost 100% utilization for FDDI

These technologies were FAR faster than ethernet. Plus they had large frame support. to this day FDDI is still faster than 100 Base-T.

But with the advent of switching and full duplex we have eliminated collisions from a modern network - every link is a switched link and there are no half-duplex connections. So you can achieve 95-98% utilization on a full-duplex link depending on frame size, both ways (TX and RX)

-edit- but to be fair, 10/100 ethernet and 1000 Base gig ethernet literally own the LAN arena. You'd be lucky to even find token ring/fddi that you can purchase - it is considered dead technology. Although I think it is important for people to learn them, because once you leave the LAN, deterministic ring technologies dominate (SONET)

 

[us3rnotfound]

Thank the good Lord for Alohanet, the beginning of Ethernet

 

[AgaBoogaBoo]

Originally posted by: us3rnotfound
Thank the good Lord for Alohanet, the beginning of Ethernet

Oh I remember that, the thing by Robert Mcaff or something in Hawaii?

 

[cmetz]

AgaBoogaBoo, I don't know what they're defining "deterministic networks", but SONET is a ring like TR and FDDI, and Extreme's EAPS and IEEE's in-progress ROR allow you to build rings out of Ethernet links.

Rings are a way to build self-healing networks that heal very quickly, because every node knows exactly what to do in case of a failure. With a shortest-path or spanning-tree topology network, you need topology change information to propogate everywhere before every node knows what to do about the failure, which inherently takes longer. In many environments, links/raw bandwidth is cheap, but reliability problems are very costly, so a "wasteful" network topology is fine.