1. Field Of The Invention
This invention relates to computer systems and, more particularly, to methods and apparatus for automatically connecting computers to one of two available local area networks (LANs).
2. History Of The Prior Art
One of the significant movements in the computer industry has been toward interconnectivity of individual computers by local area networks. Initially, the desire was to allow the sharing of underused assets such as printers. More recently, the impetus has been the desire to share application programs and data and to enhance communication.
Whatever the reasons for their existence, LANs are proliferating. Typically, a LAN will be installed initially to provide connection between a small group of local computer users. The first LANs which were installed utilized coaxial cable as the physical wiring for the transmission of signals. Coaxial cable was necessary in order to reduce the noise and allow operation in the face of signal attenuation. As technology advanced and standards changed, it became possible to utilize twisted pair wiring as the physical connection to join the computers of a LAN together. Twisted pair wiring is preferred because it is less expensive and less expensive to install.
Often it is desirable to change computers from a coaxial network to a twisted pair network. During some interim period, it may be desirable to connect the computers to both networks. In a similar manner, it may become desirable to connect computers already joined in a local twisted pair network to another network in which the computers are joined by coaxial cable. In either case, it is possible that a number of individual computers will be physically connected simultaneously to two separate networks, a twisted pair network and a coaxial cable network. It is desirable that these computers be able to utilize either one of the two networks which is available and functioning so that if one network is not functioning communications will automatically be established on the other network.