-计算机网络自顶向下方法第四版答案(英文版).docx
《-计算机网络自顶向下方法第四版答案(英文版).docx》由会员分享,可在线阅读,更多相关《-计算机网络自顶向下方法第四版答案(英文版).docx(118页珍藏版)》请在淘文阁 - 分享文档赚钱的网站上搜索。
1、Computer Networking: A Top-Down ApproachFeaturing the Internet, 4th EditionSolutions to Review Questions and ProblemsVersion Date: October 29, 2007This document contains the solutions to review questions and problems fbr the 4th edition of Computer Networking: A Top-Down Approach Featuring the Inter
2、net by Jim Kurose and Keith Ross. These solutions are being made available to instructors ONLY. Please do NOT copy or distribute this document to others (even other instructors). Please do not post any solutions on a publicly-available Web site. Well be happy to provide a copy (up-to-date) of this s
3、olution manual ourselves to anyone who asks.All material copyright 1996-2007 by J.F. Kurose and K.W. Ross. All rights reservedChapter 1 Review Questions1. There is no difference. Throughout this text, the words host and end system” are used interchangeably. End systems include PCs, workstations, Web
4、 servers, mail servers, Internet-connected PDAs, WebTVs, etc.2. Suppose Alice, an ambassador of country A wants to invite Bob, an ambassador of country B, over for dinner. Alice doesnt simply just call Bob on the phone and say, “come to our dinner table now. Instead, she calls Bob and suggests a dat
5、e and time. Bob may respond by saying hes not available that particular date, but he is available another date. Alice and Bob continue to send “messages back and forth until they agree on a date and time. Bob then shows up at the embassy on the agreed date, hopefully not more than 15 minutes before
6、or after the agreed time. Diplomatic protocols also allow for either Alice or Bob to politely cancel the engagement if they have reasonable excuses.3. A networking program usually has two programs, each running on a different host, communicating with each other. The program that initiates the commun
7、ication is the client. Typically, the client program requests and receives services from the server program.4. 1. Dial-up modem over telephone line: residential; 2. DSL over telephone line: residential or small office; 3. Cable to HFC: residential; 4. 100 Mbps switched Etherent: company; 5. Wireless
8、 LAN: mobile; 6. Cellular mobile access (for example, WAP): mobile5. HFC bandwidth is shared among the users. On the downstream channel, all packets emanate from a single source, namely, the head end. Thus, there are no collisions in the downstream channel.6. Current possibilities include: dial-up;
9、DSL; cable modem; fiber-to-the-home.7. Ethernet LANs have transmission rates of 10 Mbps, 100 Mbps, 1 Gbps and 10 Gbps. For an X Mbps Ethernet (where X = 10, 100, 1,000 or 10,000), a user can continuously transmit at the rate X Mbps if that user is the only person sending data. If there are more than
10、 one active user, then each user cannot continuously transmit at X Mbps.8. Ethernet most commonly runs over twisted-pair copper wire and thin” coaxial cable. It also can run over fibers optic links and thick coaxial cable.9. Dial up modems: up to 56 Kbps, bandwidth is dedicated; ISDN: up to 128 kbps
11、, bandwidth is dedicated; ADSL: downstream channel is .5-8 Mbps, upstream channel is up to 1 Mbps, bandwidth is dedicated; HFC, downstream channel is 10-30 Mbps and upstream channel is usually less than a few Mbps, bandwidth is shared.10. There are two most popular wireless Internet access technolog
12、ies today:a) Wireless LANIn a wireless LAN, wireless users transmit/receive packets to/from a base station (wireless access point) within a radius of few tens of meters. The base station is typically connected to the wired Internet and thus serves to connect wireless users to the wired network.b) Wi
13、de-area wireless access networkIn these systems, packets are transmitted over the same wireless infrastructure used for cellular telephony, with the base station thus being managed by a telecommunications provider. This provides wireless access to users within a radius of tens of kilometers of the b
14、ase station.11. A circuit-switched network can guarantee a certain amount of end-to-end bandwidth for the duration of a call. Most packet-switched networks today (including the Internet) cannot make any end-to-end guarantees fbr bandwidth.12. In a packet switched network, the packets from different
15、sources flowing on a link do not follow any fixed, pre-defined pattern. In TDM circuit switching, each host gets the same slot in a revolving TDM frame.13. At time to the sending host begins to transmit. At time = L/Rj, the sending host completes transmission and the entire packet is received at the
16、 router (no propagation delay). Because the router has the entire packet at time r7, it can begin to transmit the packet to the receiving host at time ti. At time 介=。+ UR2, the router completes transmission and the entire packet is received at the receiving host (again, no propagation delay). Thus,
17、the end-to-end delay is L/R + L/R?.14. A tier-1 ISP connects to all other tier-1 ISPs; a tier-2 ISP connects to only a few of the tier-1 ISPs. Also, a tier-2 ISP is a customer of one or more tier-1.15. a) 2 users can be supported because each user requires half of the link bandwidth.b) Since each us
18、er requires 1Mbps when transmitting, if two or fewer users transmit simultaneously, a maximum of 2Mbps will be required. Since the available bandwidth of the shared link is 2Mbps, there will be no queuing delay before the link. Whereas, if three users transmit simultaneously, the bandwidth required
19、will be 3Mbps which is more than the available bandwidth of the shared link. In this case, there will be queuing delay before the link.c) Probability that a given user is transmitting = 0.2d) Probability that all three users are transmitting simultaneously = jp3(l 一 p), 3=(0.2)3= 0 008. Since the qu
20、eue grows when all the users are transmitting, the fraction of time during which the queue grows (which is equal to the probability that all three users are transmitting simultaneously) is 0.008.16. The delay components are processing delays, transmission delays, propagation delays, and queuing dela
21、ys. All of these delays are fixed, except for the queuing delays, which are variable.17. Java Applet18. 10msec; d/s; no; no19. a) 500 kbpsb) 64 secondsc) 100kbps; 320 seconds20. End system A breaks the large file into chunks. To each chunk, it adds header generating multiple packets from the file. T
22、he header in each packet includes the address of the destination: end system B. The packet switch uses the destination address to determine the outgoing link. Asking which road to take is analogous to a packet asking which outgoing link it should be forwarded on, given the packefs address.21. Java A
23、pplet22. Five generic tasks are error control, flow control, segmentation and reassembly, multiplexing, and connection setup. Yes, these tasks can be duplicated at different layers. For example, error control is often provided at more than one layer.23. The five layers in the Internet protocol stack
24、 are - from top to bottom - the application layer, the transport layer, the network layer, the link layer, and the physical layer. The principal responsibilities are outlined in Section 1.5.1.24. Application-layer message: data which an application wants to send and passed onto the transport layer;
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 计算机网络 向下 方法 第四 答案 英文
限制150内