tjc@ecs.soton.ac.uk (Tim Chown) (01/17/91)
In <1991Jan16.175003.2978@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes: >If your users know what they're doing and can be trusted to treat your >cable with respect, or are unsophisticated enough that they treat all >hardware with respect, thin should be fine. Otherwise, consider thick >or twisted-pair (which runs separate cable from each user's box to a >central hub where faults can be isolated). We use thin within our machine >room, but plan to go with twisted pair if/when we start doing Ethernet to >users' offices. What exactly is "twisted pair" and what are its performance characteristics when compared against conventional (thin) ethernet? You mention that you run the twisted pair back to a central hub. Does this mean a separate connection to each office from the hub? Thanks for any comments (I'll post a summary if I get any e-mail), Cheers, Tim
lstowell@pyrnova.pyramid.com (Lon Stowell) (01/19/91)
In article <6314@ecs.soton.ac.uk> tjc@ecs.soton.ac.uk (Tim Chown) writes: > >What exactly is "twisted pair" and what are its performance >characteristics when compared against conventional (thin) ethernet? > >You mention that you run the twisted pair back to a central hub. Does >this mean a separate connection to each office from the hub? > You'll likely get a lot of answers, but here is the quick one. Twisted Pair is aka "unshielded twisted pair"....used in high quality telephone wiring--thus its advantage. For Ethernet, it is called 10BaseT or 802.3i. It is star-wired to a central smart hub. Although the DTE's think they are on a bus topology, these smart hubs can do a LOT for network reliability and fault isolation. No More BeeperNet! With the advent of twisted pair Ethernet and the fault isolation advantages of the accompanying smart hubs, IMHO Ethernet will do a lot to stem the rising incidence of Token Ring in all but true blue IBM shops....OR in situations where the deterministic thru-put of T/R is an absolute requirement.. PLEASE NOTE that that last is a personal opinion....ONLY.
sellers@bert.ER.Bell.CA (Dave Sellers) (01/19/91)
In article <6314@ecs.soton.ac.uk> tjc@ecs.soton.ac.uk (Tim Chown) writes: >In <1991Jan16.175003.2978@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes: > >>central hub where faults can be isolated). We use thin within our machine >>room, but plan to go with twisted pair if/when we start doing Ethernet to >>users' offices. > >What exactly is "twisted pair" and what are its performance >characteristics when compared against conventional (thin) ethernet? > >You mention that you run the twisted pair back to a central hub. Does >this mean a separate connection to each office from the hub? > > Tim Well here at Bell we have hundreds of users PCa and SUN workstations connected with UTP (Unshielded Twisted Pairs). The performance is better than coax (from what I have read on the tech side of things) because each concentrator amplifies and corrects/filters the signals. Now we can support both TRN and Ethernet on the same concentrator. There is even Network management support. I could go on and on, but if you have the money (this harware costs much more that wire) and you have problems to solve, find out more about this equipment from Synoptics. -- Dave Sellers Computer Systems Advisor Network Operations (Support Systems) Bell Canada, 393 University Ave., Toronto, Ont., (416) 978-1311
henry@zoo.toronto.edu (Henry Spencer) (01/21/91)
In article <6314@ecs.soton.ac.uk> tjc@ecs.soton.ac.uk (Tim Chown) writes: >What exactly is "twisted pair" and what are its performance >characteristics when compared against conventional (thin) ethernet? More formally, it's "unshielded twisted pair", more or less high-quality phone wiring. It runs at the same speed as all other Ethernet, 10 Mbps. Distance is limited to something like 100m, as I recall. >You mention that you run the twisted pair back to a central hub. Does >this mean a separate connection to each office from the hub? Yes. Twisted-pair is point-to-point, not bussed. This means more wire. But it's cheap wire, possibly even already-installed wire. And the star configuration has the enormous advantage that foulups are often confined to a single host, instead of ruining network connectivity for an entire bussed cable with dozens of hosts on it. It still looks like regular Ethernet to the hosts; the hubs are just electrical connection points, so to speak, not routers, so everybody still hears all packets. -- If the Space Shuttle was the answer, | Henry Spencer at U of Toronto Zoology what was the question? | henry@zoo.toronto.edu utzoo!henry
kwe@bu-it.bu.edu (Kent England) (01/23/91)
In article <6314@ecs.soton.ac.uk>, tjc@ecs.soton.ac.uk (Tim Chown) writes: > > You mention that you run the twisted pair back to a central hub. Does > this mean a separate connection to each office from the hub? > 10BaseT or twisted pair Ethernet requires a star configured topology, but other media, like thin coax or AUI cables, can be used to achieve a star topology. Many users will accept 10BaseT since the wire is already installed or they believe that it will be cheap to install, so they seredipitously receive a star topology without having to learn why they need it. Insist on a star topology for one simple reason: When you have one end of a cable in your hand in the user's office, only a star topology allows you with reasonable assurance to know where the other end is and what it is connected to. This sounds trivial, but it is not and that is why almost everyone with field experience has adopted the idea of *structured* wiring (aka star topologies). Remember that star topologies can be configured into rings and busses as needed, so star topologies are also popular in installing fiber backbones and fiber wiring. Not every wiring plan in the world is a star or should be so (the national fiber optic network comes to mind), but most so-called horizontal wiring is becoming star or structured. Topology is the key, not the medium. 10BaseT takes advantage of the topology to do such things as link status, but that could be done with star-wired thin-net, too. FDDI-to-the-desktop will also benefit from star topology, no matter what medium you end up using. --Kent