WAN
Technologies
A WAN is a data communications network that
covers a relatively broad geographic area and that often uses transmission
facilities provided by common carriers, such as telephone companies. WAN
technologies generally function at the lower three layers of the OSI reference
model: the physical layer, the data link layer, and the network layer. The following articles provide information about the various protocols and technologies used in WAN environments:
Internet Protocols
The Internet protocols are the world's most
popular open-system (nonproprietary) protocol suite because they can be used to
communicate across any set of interconnected networks and are equally well
suited for LAN and WAN communications. The Internet protocols consist of a
suite of communication protocols, of which the two best known are the
Transmission Control Protocol (TCP) and the Internet Protocol (IP). The
Internet protocol suite not only includes lower-layer protocols (such as TCP
and IP), but it also specifies common applications such as electronic mail, terminal
emulation, and file transfer. This article provides a broad introduction to
specifications that comprise the Internet protocols. Discussions include IP
addressing and key upper-layer protocols used in the Internet. Specific routing
protocols are addressed individually later in this document. The following articles provide information about different IOS IP technologies:
Bridging and Switching
Bridges and switches are data communication devices that operate principally at Layer 2 of the OSI reference model. As such, they are widely referred to as data link layer devices. Several kinds of bridging have proven important as internetworking devices. Transparent bridging is found primarily in Ethernet environments, while source-route bridging occurs primarily in Token Ring environments. Translational bridging provides translation between the formats and transit principles of different media types (usually Ethernet and Token Ring). Finally, source-route transparent bridging combines the algorithms of transparent bridging and source-route bridging to enable communication in mixed Ethernet/Token Ring environments. Today, switching technology has emerged as the evolutionary heir to bridging-based internetworking solutions. Switching implementations now dominate applications in which bridging technologies were implemented in prior network designs. Superior throughput performance, higher port density, lower per-port cost, and greater flexibility have contributed to the emergence of switches as replacement technology for bridges and as complements to routing technology.
The following articles provide information about the technologies employed in devices loosely referred to as bridges and switches:
