Chapter 11: Wide-Area Networks and the Internet

Transcription

1 Chapter 11: Wide-Area Networks and the Internet MULTIPLE CHOICE 1. MAN stands for: a. Manchester Access Network c. Metropolitan-Area Network b. Multiple-Area Network d. Multiple Access Network 2. Packet switching is based on: a. store-and-forward c. real-time delivery b. switched circuits d. all of the above 3. SNA stands for: a. Standard Network Access c. Standard Network Architecture b. Small Network Access d. Systems Network Architecture D 4. The number of layers in ISO OSI is: a. 3 c. 7 b. 5 d The lowest-level layer in ISO OSI is called the: a. physical layer c. cable layer b. link layer d. transport layer 6. Bad frames are usually detected by the: a. frame layer c. error-check layer b. physical layer d. link layer D 7. A virtual circuit is set up by the: a. user c. network b. link layer d. frame 8. Frame Relay: a. is faster than X.25 c. allows for variable length packets b. does less error checking than X.25 d. all of the above D

2 9. ATM stands for: a. Asynchronous Transfer Mode c. Asynchronous Transmission Model b. Asynchronous Transmission Mode d. Automatic Test Mode 10. A bridge: a. separates a network into "collision domains" b. looks at the address of each packet c. operate at the data-link level d. all of the above D 11. IP stands for: a. Internet Process c. Interconnect Protocol b. Internet Protocol d. Interconnect Procedure B 12. TCP stands for: a. Transmission Control Process c. Transfer Connection Protocol b. Transmission Control Protocol d. none of the above B 13. Together, TCP/IP consists of: a. 5 layers c. an application and a process b. 7 layers d. datagrams 14. IP is a: a. connection-oriented protocol c. connectionless protocol b. virtual circuit d. non-robust protocol 15. The "lifetime" of a packet in an IP network: a. is essentially forever b. depends on elapsed time since transmission c. depends on number of "hops" between nodes d. is approximately 200 milliseconds 16. UDP stands for: a. User Datagram Protocol c. User Data Packet b. User Data Protocol d. Universal Data Packet 17. HTTP stands for: a. High-speed Transmission Test Procedure

3 b. High-Level Transfer Test Procedure c. Hypertext Transmission and Transport Procedure d. Hypertext Transport Protocol D 18. HTTP allows the use of: a. dumb terminals c. browsers b. file transport d. none of the above 19. HTML stands for: a. Hypertext Markup Language c. Hypertext Transfer-Mode Layer b. Hypertext Transfer-Mode Level d. High-speed Transfer-Mode Language 20. HTML allows: a. telneting c. web page layout b. high-speed file transfer d. all of the above 21. FTP stands for: a. File Transfer Protocol c. File Test Procedure b. File Transport Protocol d. Fast Transport Packet 22. FTP is used to: a. transfer files between a server on the network and a user b. test files to see if their data has been "corrupted" c. transport packets at maximum speed through the network d. none of the above 23. SMTP stands for: a. Short Message Transport Protocol c. Simple Mail Transport Protocol b. Simple Message Transport Protocol d. Secondary Mail Transfer Procedure 24. ISP stands for: a. Internet Service Protocol c. Internet Service Procedure b. Internet Service Provider d. none of the above B 25. The standard Internet address (or URL) is: a. a 32-bit binary number c. running out of available values b. four groups of base-ten numbers d. all of the above

4 D 26. DNS stands for: a. Domain Name Server c. Domain Numbering System b. Domain Name System d. Domain Naming System 27. A DNS: a. has become obsolete on the Internet b. translates words to numbers c. stores all domain addresses d. describes the Internet address-naming procedure B 28. An intranet connected to the Internet is often protected by: a. a DNS c. a "firewall" b. a "brick wall" d. the use of "spoofing" protocols 29. OSI stands for: a. Open Systems Interconnection c. Open Systems Internet b. Open Standard Interconnection d. none of the above COMPLETION 1. A -Area Network would extend typically across a city. Metropolitan 2. A -Area Network could extend across a nation. Wide 3. A dedicated telephone line can be on a monthly basis. leased 4. The use of digital circuit- lines is cheaper than dedicated lines. switched 5. Packet switching is done on a store-and- network. forward 6. A is a hierarchy of procedures for implementing digital communications.

5 protocol 7. Voltage levels on a cable are specified at the layer. physical 8. Bad frames are usually detected at the layer. data-link 9. Setting up a path through the network is done by the layer. network 10. The X.25 protocol was developed by the. CITT 11. In X.25, the data-link layer is called the layer. frame 12. In X.25, the network layer is called the layer. packet 13. The physical route of a circuit changes each time it is used. virtual 14. Frame Relay requires channels with low rates. bit-error 15. Compared to X.25, Frame Relay does error checking. less 16. All ATM frames contain just bytes Small frame size and a high-speed channel allow -time communications. real 18. simply regenerate and retransmit packets in a network. Repeaters

6 19. look at the address inside a packet to decide whether or not to retransmit it. Bridges 20. decide the best network path on which to forward a packet. Routers 21. TCP/IP goes back to the of the 1970s. ARPANET DARPANET 22. Between ISO OSI and TCP/IP, was used first. TCP/IP 23. A protocol does not track packets after they are sent. connectionless 24. HTTP allows the use of that jump to other pages on the web. hyperlinks 25. The Internet "backbone" mostly uses high-speed cables. fiber-optic 26. A translates words in an Internet address to numbers. DNS 27. Intranets usually connect to the Internet through a for security. firewall 28. Voice over is telephony done over the Internet. IP 29. " " is another term for real-time transmission over the Internet. Streaming 30. Most people gain access to the Internet by subscribing to an. ISP

7 SHORT ANSWER 1. Name the three parts of an IP address as used on the Internet. Network number, Subnet number, Host number 2. Why is a logical channel called a "virtual" circuit? A logical channel is a way of keeping track of which two nodes on the network have messages for each other. The actual physical path can change while packets are being sent. Virtual means it behaves like direct circuit between 'A' and 'B', but it is not a direct circuit. 3. Why is it faster to send packets of a fixed size compared to packets of variable size? The processing required to store and forward packets of different lengths is greater than that required for packets of a fixed length. More processing implies more time per packet, which implies fewer packets per second through the network. 4. Why are the tasks involved in digital communications divided into layers in a protocol stack? Why not just have one layer that does it all? Divide and conquer: it reduces complexity to a manageable job. One big layer could not be adapted to newer media etc as easily as a system of independent layers. Think of subroutines in a computer program. 5. What is a "hop"? Every time a packet is forwarded on to the next store-and-forward node in the network, it is considered to be one "hop". 6. What does it mean to say a packet has a lifetime measured in hops? Each packet contains a number representing the maximum number of allowed hops. At each hop, this number is reduced by one. When it gets to zero, the packet is deleted from the network. 7. Why should packets have a lifetime? If they didn't, then the number of "lost" packets traveling around the network would continuously increase. At some point, there would be no bandwidth left to carry real traffic.