2. Computer Networking 网络课件 双语教学 模拟实验 计算机网络教研室

3. Department of Computer Networking Application Chapter 13 Wide Area Network(WANs) 1 The first section 2 Exercises 3 Online lecture

4. www.gxmu.edu.cn LAN SECURITY:  Proxy Server– acts as an intermediary between the internet and net- equipped computers  Password policies  A sign-off policy  The encryption of data sent on a LAN or stored on servers  Regular backup of the server disks  Downloading  Scanning of viruses Chapter 13 Wide Area Network(WANs)

5. www.gxmu.edu.cn VIRTUAL PRIVATE NETWORKS (VPN) Chapter 13 Wide Area Network(WANs)

6. www.gxmu.edu.cn A corporate VPN using the Internet Chapter 13 Wide Area Network(WANs)

7. www.gxmu.edu.cn HOME NETWORKING and COMPONENTS OF A HOME NETWORK Ethernet Wireless Networks Phone Line Networks Power Line Networks Chapter 13 Wide Area Network(WANs)

8. 课后习题 D 、 All of the above 1. Which of the following routing techniques are used in WANs? （ ）. D A 、 dynamic routing B 、 distributed routing C 、 static routing Show Answer Reset Next × × × √ Exercises Chapter 13 Wide Area Network(WANs)

9. 课后习题 D 、 All of the above. 2. Delays in networks can come from （ ）. D A 、 propagation B 、 switching C 、 queuing Show Answer Reset Next × × × √ Exercises Chapter 13 Wide Area Network(WANs)

10. 课后习题 B 、 frame relay 3. Which of the following was developed to overcome the overhead of packet switching and provide more efficient data transmission? （ ） B D 、 RS-232 A 、 X.25 C 、 circuit switched systems Show Answer Reset Next × × × √ Exercises Chapter 13 Wide Area Network(WANs)

11. 课后习题 C 、 a 53-byte transmission unit 4. In the context of ATM, a cell is （ ）. C D 、 the place where the designer is kept for specifying an overly complex network design A 、 the geographic boundary of the network B 、 the boundary of the area in which voice traffic can be handled Show Answer Reset Next × × × √ Exercises Chapter 13 Wide Area Network(WANs)

12. 课后习题 D 、 All of the above. 5. VPNs （ ）. D A 、 can handle traffic relatively securely B 、 can restrict outside packets from entering the VPN C 、 are usually quite cost effective Show Answer Reset Next × × × √ Exercises Chapter 13 Wide Area Network(WANs)

13. 课后习题 1. A packet switching system breaks a message into ______ and sends each one through the network independently. packets Answer Exercises 2. Alternate _______ are important so that message traffic can continue to be sent through the network even when the primary route has failed or otherwise become unusable. routes Answer 3. Packet switching is a form of __________ because messages from different nodes are interspersed on a circuit at any point in time. multiplexing Answer Chapter 13 Wide Area Network(WANs)

14. 课后习题 4. A _________ is a packet that contains its destination address and is handled independently by the network. datagram Answer Exercises 5. A centralized router in a network represents a single point of _______ and if it fails the entire network may be down. failure Answer 6. __________ routing sends all messages to every node on the network. broadcast Answer Chapter 13 Wide Area Network(WANs)

15. 课后习题 7. A _________ determines the best way to route to use when sending a message through a network and sends it on its way. router Answer Exercises 8. ___________ can occur in a network when the message volume exceeds the capacity of a part of the network. congestion Answer 9. _________ can occur at a node when messages arrive faster than they can be forwarded or processed. queuing Answer Chapter 13 Wide Area Network(WANs)

16. 课后习题 10. A ____________ network divides a message into variable length frames for transmission through the network. frame relay Answer Exercises 11. A frame relay network has approximately __________ (how much) of the overhead of a basic packet switching network. one quarter Answer 12. Packet switching operates on lines of _____ speed.any Answer Chapter 13 Wide Area Network(WANs)

17. 课后习题 13. Frame relay was designed to operate on _________________ speed lines. high OR multi-megabit Answer Exercises 14. A high speed transmission service that an organization may want to consider using for establishing a MAN within a city, and which is based on optical fiber as the transmission medium is called ________. SONET Answer Chapter 13 Wide Area Network(WANs)

18. www.gxmu.edu.cn Chapter 13 Wide Area Network(WANs)