发布时间 : 星期六 文章计算机网络系统方法(英文版)课后习题及解答更新完毕开始阅读80fc960a0740be1e640e9a03
spanning tree algorithm.
15. Consider the arrangement of learning bridges shown in Figure 3.35. Assuming all are initially empty, give the forwarding tables for each of the bridges B1–B4 after the following transmissions:
■ A sends to C.
■ C sends to A.
■ D sends to C.
Identify ports with the unique neighbor reached directly from that port, that is, the ports for B1 are to be labeled “A” and “B2.”
17.Consider hosts X, Y, Z, W and learning bridges B1, B2, B3, with initially empty forwarding tables, as in Figure 3.36.
(a) Suppose X sends to Z. Which bridges learn where X is? Does Y’s network interface see this packet?
(b) Suppose Z now sends to X. Which bridges learn where Z is? Does Y’s network interface see this packet?
(c) Suppose Y now sends to X. Which bridges learn where Y is? Does Z’s net- work interface see this packet?
(d) Finally, suppose Z sends to Y. Which bridges learn where Z is? Does W’s network interface see this packet?
第四章
（4.1 4.2 4.3.1 4.3.5 4.5 节）
4.Suppose a TCP message that contains 2,048 bytes of data and 20 bytes of TCP header is passed to IP for delivery across two networks of the Internet (i.e., from the source host to a router to the destination host). The ?rst network uses 14-byte headers and has an MTU of 1,024 bytes; the second uses 8-byte headers with an MTU of 512 bytes. Each network’s MTU gives the size of the largest IP datagram that can be carried in a link layer frame. Give the sizes and offsets of the sequence of fragments delivered to the network layer at the destination host. Assume all IP headers are 20 bytes.
21.Suppose a router has built up the routing table shown in Table 4.14. The router can deliver packets directly over interfaces 0 and 1, or it can forward packets to routers R2, R3, or R4. Describe what the router does with a packet addressed to each of the following destinations:
(a) 128.96.39.10.
(b) 128.96.40.12.
(c) 128.96.40.151.
(d) 192.4.153.17.
(e) 192.4.153.90.