The most common Layer 3, or network layer, protocols in use on LANs are Internet Protocol (IP), IPX, and AppleTalk. IP, sometimes called TCP/IP, is an open standard protocol that is defined and developed by an organization called the Internet Engineering Task Force (IETF). The standards that define IP are distributed in the form of Request for Comment (RFC) documents that are freely available from many sites on the Internet. IP, IPX, and AppleTalk are all routable protocols and thus effective for large-scale networking.
Nonroutable protocols such as NetBEUI, SNA, and the older LAT protocol pose serious scalability problems to a LAN because they require that all segments sharing resources be bridged together. Breaking up broadcast domains (network regions interconnected by repeaters or bridges) by using routable protocols leads to much more efficient networks.
There are other routable protocols in use on LANs, such as the Banyan Vines VIP protocol. Banyan Worldwide officially changed its name to ePresence Solutions in 2000 and dropped support for all Banyan products in 2001 to become a service-centered, rather than a product-centered, company. Thus, this protocol is effectively obsolete and should be avoided in any LAN architecture.
Sometimes you'll encounter a handful of other routable protocols, such as DECNET and OSI. DECNET was used primarily by equipment made by Digital Equipment Corporation. When that company broke up, most organizations that had ...