数据通信课件笫11章因特网协议和应用幻灯片.ppt

* Emphasize: Highlight the fixed values that start each class address. The first octet rule states that when an address falls into a specified range, it belongs to a certain class. Students should soon be able to recognize the address class of any IP address on sight. Note: If time or interest permits, you can use the initial bit patterns in the first octet and show how a class of IP network derives the range of network numbers for that IP address class. * Purpose: This figure presents an overview of host and network address conventions. Emphasize: In the example, and refer to the wires at each end of the router. Explain how the routing table is used. Entries in the routing table refer to the network only. The router does not know the location of hosts—it knows the location of networks. . * Layer 1 of 2: Purpose: This exercise verifies that the students understand IP address classes, network numbers, and host numbers. Give the students time to list the address class, network, and host number for each IP address in the table. Review the correct answers interactively. The answers are given in the following figure. * Layer 2 of 2: Purpose: This answers to the exercise are given in the figure. Note: Students can also find the answers to this exercise in the “Answers” appendix. * Purpose: This figure introduces the protocols used at the transport layer. Emphasize: TCP is one protocol within the protocol suite of TCP/IP. TCP is an acknowledged transport-layer protocol. However, TCP has a large header so there is much overhead. UDP is unacknowledged. By eliminating all of the acknowledgement mechanisms, UDP is fast and efficient. UDP does not divide application data into pieces. Reliability is assumed to be handled by the upper-layer protocols, by a reliable lower-layer protocol, or by an error-tolerant application. UDP does have a smaller header and less overhead. * Purpose: This figure explains how TCP uses port numbers to connect applications. Emphasi