Through the various forms of media that Ethernet has evolved, the topology of the network has also been able to change and improve. Moving from a bus-like technology, Thick Coax, to Thin Coax, to the star-like configurations in use today, using Twisted Pair.
In the early instantiations, Thick Coax, was used. This required very inflexible, heavy, expensive coax cable (Big Orange). Connections to the coax were done via a mechanical tap that was expensive, unreliable, and cumbersome to install. Likewise the thick, orange coaxial cable had to run close to the system to be connected.
Later, Thin Coax, or CheaperNet, was developed. Many of the drawbacks of Thick Coax were addressed; less expensive, more flexible, more reliable BNC connections, but still had some of the drawbacks of Thick Coax.
With the development of differential, telephone wire, signaling technology, the preferred media for connections has become Twisted Pair. The much less expensive, more flexible, CAT-3 and CAT-5 cabling has enabled reliable connectivity of virtually any computer anywhere.
While the technology, and media, for Ethernet has changed over the years, the need of compatibility, or interoperability, has remained. Since not all networks can be upgraded to the latest technology instantaneously, it is not uncommon to have multiple network media within one organization.
