This chapter discussed the various technologies and protocols associated with WAN networking. WAN networking is typically seen as a distinct function from LAN networking because WANs are almost exclusively centered around telephony, which is commonly disassociated from computing services in large information technology environments. Due to the ever-increasing demands to be "wired" all the time, however, this distinction is quickly disappearing. At the end of this chapter, you should have an understanding of the following concepts and terms:
The PSTN, T-carrier, SONET, and SDH digital transport systems
Packet-switched PSTN network technologies such as X.25 and Frame Relay
Asynchronous Transfer Mode and Broadband-ISDN
The HDLC and PPP data-link ...