Although there are distinct differences between local and wide area networking equipment, data flow and networking techniques, there are also certain similarities between the two. In this section we will first focus our attention on obtaining an overview of equipment used to interconnect LANs. Once this has been accomplished we will turn our attention to the use of equipment which enables workstations on LANs to obtain access to mainframe computers.
Three additional popular types of servers are communications servers, database servers, and Web servers. A communications server has a number of connections to the public switched telephone network and/or to a packet network as well as a connection to a LAN. This enables persons beyond the boundary of the LAN to access the network via remote communications. A database server represents a special type of file server which structures the contents of files so that data can be rapidly retrieved. The third type of popular server is a Web server, which supports HyperText Transmission Protocol (HTTP) queries in the form of Uniform Resource Locator (URL) addresses and returns Web pages.
When we discuss the Internet later in this article, we will turn our attention to Web servers. It is important to note that most LANs contain several types of servers that have a predefined relationship to one another. For example, remote users may access a LAN via the use of a communications server in attempting to display a particular Web page by accessing a Web server. If the user needs to search for information or place an electronic order, his or her request may be forwarded from the Web server to the database server and the results sent back to the Web server for transmission to the user, with the functions of the communications server and database server normally transparent to the user.