The physical layer implementations vary depending on the distance of the equipment from the services, the speed, and the type of service itself. Serial connections are used to support WAN services such as dedicated leased lines that run Point-to-Point Protocol (PPP) or Frame Relay. The speed of these connections ranges from 2400 bits per second (bps) to T1 service at 1.544 megabits per second (Mbps) and E1 service at 2.048 megabits per seconds (Mbps).

ISDN offers dial-on-demand connections or dial backup services. An ISDN Basic Rate Interface (BRI) is composed of two 64 kbps bearer channels (B channels) for data, and one delta channel (D channel) at 16 kbps used for signaling and other link-management tasks. PPP is typically used to carry data over the B channels.

With the increasing demand for residential broadband high-speed services, DSL and cable modem connections are becoming more popular. For example, typical residential DSL service can achieve T1/E1 speeds over the existing telephone line. Cable services use the existing coaxial cable TV line. A coaxial cable line provides high-speed connectivity matching or exceeding that of DSL. DSL and cable modem service will be covered in more detail in a later module.

Interactive Media Activity Drag and Drop: WAN Physical Layer Implementation After completing this activity, the student will be able to identify the components in the WAN physical layer.

   

Web Links WAN Speeds http://www.webwisdom.com/edu_content/ cps640fall00/ lectures/module3/WAN/ sld008.htm