数据通信课件数据通信原理幻灯片.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. Dijkstra集中式算法： 算法举例（contd） 取D(1)中具有最小值的对应节点P1加入到集合N中, N= { P5,P4,P2,P3,P1}, 此时，节点都在N中，算法结束。 Dijkstra集中式算法： 连续的步骤，如下表： 10.6 Bellman-Ford分布式算法 分布式算法 每个节点在交互式的基础上和其邻节点交换代价和路由信息，直到这些节点的路由表到达最短路径的要求为止 Ford分布式算法（contd） Ford分布式算法也包括两个部分： 一个初始步骤 一个最短距离计算的步骤 这里，最短距离指一个给定节点和目标节点之间的距离 当所有节点都带有 1）一个表示它们到目标节点距离的标记以及 2）沿着最短路径到达目标节点要经过的下一个节 点的标记时，算法结束。 Ford分布式算法： 算法描述 每个节点v，都有(n,D(v))的标记。 D(v)代表该节点到目标节点的最短距离的当前值； n是截至目前得到的最短路径的下一个节点。 初始步骤： 设d是目标节点。 令D(d)=0，将所有其它节点标记为(.,∞) Ford分布式算法： 算法描述（contd） 最短距离计算步骤： 对所有节点的最短路径做标记：对每个节点v≠d： 使用v的每个邻节点w的当前D(w) 计算D(w)+l(w, v)，使得 D(v):