Chapter 11 - Wide area networks. In this chapter, we first discuss point-to-point WANs, WANs that do not use switches. Then we discuss switched WANs. We focus especially on ATM, the dominant WAN technology. Finally, we discuss ATM LANs, LANs that use ATM WAN technology. | Chapter 11 Wide Area Networks Understand point-to-point WAN technologies: T-lines and SONET networks. Understand technology and why it is losing popularity. Understand Frame Relay technology and how it was designed to replace . Understand ATM technology and its importance in today’s market. After reading this chapter, the reader should be able to: OBJECTIVES Understand ATM LANs. POINT-TO-POINT WANs Figure 11-1 T-1 line A T-1 line has a data rate of Mbps Note: A T-3 line has a data rate of Mbps Note: Technical Focus: Fractional T-Lines Many subscribers may not need the entire capacity of a T- line. To accommodate these customers, telephone companies offer fractional T-line services, which allow several subscribers to share one line by multiplexing their transmissions. Figure 11-2 SONET SWITCHED WANs Technical Focus: Tunneling To use an network, an IP packet uses a technique called tunneling. Because does not allow IP packets to use their . | Chapter 11 Wide Area Networks Understand point-to-point WAN technologies: T-lines and SONET networks. Understand technology and why it is losing popularity. Understand Frame Relay technology and how it was designed to replace . Understand ATM technology and its importance in today’s market. After reading this chapter, the reader should be able to: OBJECTIVES Understand ATM LANs. POINT-TO-POINT WANs Figure 11-1 T-1 line A T-1 line has a data rate of Mbps Note: A T-3 line has a data rate of Mbps Note: Technical Focus: Fractional T-Lines Many subscribers may not need the entire capacity of a T- line. To accommodate these customers, telephone companies offer fractional T-line services, which allow several subscribers to share one line by multiplexing their transmissions. Figure 11-2 SONET SWITCHED WANs Technical Focus: Tunneling To use an network, an IP packet uses a technique called tunneling. Because does not allow IP packets to use their own network layer protocol, the IP packets are encapsulated in the network layer of the protocol. This can be compared to a car entering a tunnel. To an observer, the car disappears at one side of the tunnel and reappears at the other side. Likewise, an IP packet disappears at the entry point of an network and reappears at the exit point. Figure 11-3 Frame Relay network Figure 11-4 Frame Relay layers Technical Focus: DLCIs A Frame Relay network uses data link connection identifiers (DLCIs) which act as addresses. Each DLCI defines a channel between two adjacent devices (DTEs or DCEs). A path between a device at one end and another device at the other end is made of several DLCIs as shown in the following figure: A cell network uses the cell as the basic unit of data exchange. A cell is defined as a small fixed-sized block of information. Note: Figure 11-5 ATM multiplexing Figure 11-6 Architecture of an ATM network Technical Focus: VPIs and VCIs In an ATM network, .
