Of the three types of cable that can be used for Ethernet connections, unshielded twisted pair, which currently occupies just 16% of the market will soon be coming into its own. Ratification of the 10Base-T standard for unshielded twisted pair, finalised by the Institute of Electrical & Electronic Engineers in October, was the icing on the cake for companies selling 10Base-T-based products and which have been singing its praises all along. Those include Advanced Micro Devices Inc, Sunnyvale, California, which recently launched its Ethernet controller chip, the 32-bit ILACC, David Systems Corp, Mountain View, California which has a whole host of 10Base-T hardware lined up for the New Year and BICC Data Networks Ltd which has been marketing its Etherconnect hub for over a year. The main alternative to unshielded twisted pair is coaxial cable, far and away the most popular way to make Ethernet connections. There are several differences between the two, but the most important is the difference between the topologies they employ – the so called Star topology of 10Base-T compared to the Bus topology of unshielded twisted pair. A Star topology fits in with the concept of Structured Networking – planning networks in advance so that they are flexible, easier to maintain and easier to fix if a node goes down. It involves the designing networks on a floor by floor basis, with a connecting fibre backbone and a wiring closet on each floor containing any Ethernet distribution products such as an RS323. From the closet radiates the individual wiring for each terminal, so if one node goes down, it does not affect the rest of the network. Conversely, a Bus topology uses one cable running past every terminal, making faults hard to detect and disruptive to fix. Jeff King of BICC Data Networks says that although coaxial still dominates the market there is a definite shift away from it, and research by Advanced Micro Devices suggests that by 1992 worldwide ships of unshielded twisted pair will overtake coaxial – at the moment coaxial is twice that of unshielded twisted pair. Other forecasts, from International Data Corp for example, say that by 1992 twisted pair installations will claim 46% of the Ethernet market, which, overall, is set to double by 1994 to $8,000m.
