exercise56概要.ppt

Exercises Review for Chapter 5 6 5.4 Give three examples of protocol parameters that might be negotiated when a connection is set up. 建立连接时可能协商的协议参数有哪些？举出3个。 The negotiation could set the window size, maximum packet size, data rate, and timer values. 5.5 Consider the subnet of Fig. 5-12(a). Distance vector routing is used, and the following vectors have just come in to router C: from B: (5, 0, 8, 12, 6, 2); from D: (16, 12, 6, 0, 9, 10); and from E: (7, 6, 3, 9, 0, 4). The measured delays to B, D, and E, are 6, 3, and 5, respectively. What is Cs new routing table? Give both the outgoing line to use and the cost. 6 5 DVR算法 来自邻居们的消息 B: (A5, B0, C8, D12, E6, F2); D: (A16, B12,C 6, D0, E 9, F10); E: ( A7, B6 , C3, D9, E0, F4). 自己测量的delays from C to B, D, and E are 6, 3, and 5, Going via B gives (A11,B 6, C14, D18, E12, F8). Going via D gives (19, 15, 9, 3, 9, 10). Going via E gives (12, 11, 8, 14, 5, 9). Taking the minimum for each destination except C gives C: (11, 6, 0, 3, 5, 8). (B, B, –, D, E, B) These are outgoing lines. 路由器C更新后的路由表说明：到A，最近距离为11，从B走；到B，距离为6，从B走；到C吗？就是我这里；……到F距离为8，从B走最近。 6 5 6 5 5.23 Suppose that instead of using 16 bits for the network part of a class B address originally, 20 bits had been used. How many class B networks would there have been? 假设B类地址用20bit作为网络号，而不是16bit，总共有多少个B类网？ 解答： With a 2-bit prefix, there would have been 18 bits left over to indicate the network.去除2bit类别号（“10”），还有20-2=18bit代表网络号 Consequently, the number of networks would have been 2^18 or 262,144. However, all 0s and all 1s are special, so only 262,142 are available. 2^18=262144,全0和全1是特殊地址，不分配给网络用，故共有262142个B类网 5.24 Convert the IP address whose hexadecimal representation 十六进制表示is C22F1582 to dotted decimal notation点分十进制 The address is 194.47.21.130. 5.25 A network on the Internet has a subnet mask of 255.255.240.0. What is the maximum number of hosts it can handle? 因特网上一个子网的掩码为255.255.240.0，它最多能容纳多少台主机？ A class B network on the Internet has a subnet mask