CCNA第一章练习.docx

网际互联A receiving host has failed to receive all of the segments that it should acknowledge. What can the host do to improve the reliability of this communication session?A. Send a different source port number.B. Restart the virtual circuit（重启虚电路）.C. Decrease the sequence number（序列号）.D. Decrease the window size.通过使用流量控制（默认时TCP使用窗口机制），接收方主机能够控制发送方主机。通过减小窗口尺寸，接受方主机能够降低发送方主机的发送速率，从而使得接收方主机的缓冲区不会产生溢出。2. Which fields（字段） are contained within an IEEE Ethernet frame header?(Choose two.)A. Source and destination MAC addressB. Source and destination network addressC. Source and destination MAC address and source and destination network addressD. ECS field一个Ethernet 帧有源MAC地址和目的MAC地址、Ether-Type字段(用来识别网络层协议)、数据和FCS字段(用来保存CRC的结果)。3. Which layer（层） 1 devices can be used to enlarge the area covered by a single LAN segment（局域网部分）?(Choose two.)A. Switch（交换机）B. NIC（网卡）C. Hub（集线器）D. Repeater（中继器）E. RJ45 transceiver并不是你真的想扩大冲突域，但是集线器(多端口中继器)会产生一个大的冲突域。4. Segmentation（分隔） of a data stream（数据流） happens at which layer of the OSI model?A. Physical（物理层）B. Data Link（数据链路层）C. Network（网络层）D. Transport（传输层）传输层从高层接收大的数据流，并将它们分为小一些的数据块，称其为数据段。5. Which of the following describe router functions?(Choose four.) A. Packet switching（包交换）B. Collision preventionC. Packet filtering（数据包过滤）D. Broadcast domain enlargementE. Internetwork communication（互联网络通信）F. Broadcast forwardingG. Path selection（路径选择）路由器提供数据包转发(交换)、包过滤、国际网络通信和路径选择功能。6. Routers operate at layer ____. LAN switches operate at layer ___. Ethernet hubs operate at layer ____. Word processing operates at layer ____.A. 3,3,1,7B. 3,2,1,noneC. 3,2,1,7D. 2,3,1,7E. 3,3,2,none路由器工作在第3层，局域网交换机工作在第2层，以太网集线器工作在第1层。文字处理程序Word会与应用层借口通信，但确实并不工作在第7层，因此答案是“none”。7. When data is encapsulated（封装）, which is the correct order?A. Data, frame, packet, segment, bitB. Segment, data, packet, frame, bitC. Data, segment, packet, frame, bitD. Data, segment, frame, packet, bit封装顺序8. Why does the data communication industry（数据通信行业） use the layered OSI reference model?(Choose