sample midterm_solutions

15. Having a conversation with someone using a cellular phone is an example of _________ transmission. a. simplex b. full-duplex c. half-duplex d. analog e. digital Answer: B 16. The type of media usually installed on homes and businesses by the telephone company is called ____________. a. fiber optic cable b. coaxial cable c. twisted pair d. phone cable e. phone wire Answer: C 17. When all bits of a character are transferred one after another, the bits are transferred in ___________ mode. a. serial b. frequency division c. multiplexing d. parallel e. full complex Answer: A 18. Which of the following is a characteristic of sound waves that can be modulated to convert digital data into analog signals? a. phase b. attenuation c. bipolar d. bandwidth e. codec Answer: A 19. If the highest frequency of a circuit is 10KHZ and the lowest frequency is 900 Hz, the bandwidth available for this circuit is : a. 890 Hz b. 8900 HZ c. 9100 Hz d. 9Khz e. 890 KHz Answer: C

often. How well suited are these four protocols for this scenario? Provide a brief (one sentence) explanation of each answer. c. Now suppose the LAN must support both voice and data and you must choose one of these multiple access strategies in order to support both applications on the same network, with the understanding that voice calls are more important than data. Which would you choose and why? How would voice and data be sent in this scenario? That is, which access protocol would you use, or adapt/modify, and why? 33. Polling. Consider a broadcast channel with N nodes and a transmission rate of R bps. Suppose the broadcast channel uses polling (with an additional polling node) for its multiple access. Suppose the amount of time from when a node completes transmission until the subsequent node is permitted to transmit (that is, the polling delay) is t poll . Suppose that within a polling round, a given node is allowed to transmit at most Q bits. Further suppose node 1, initially with no bits to send, receives Q bits to send. What is the maximum time from when node 1 receives the bits until it can begin to send them? 34. Addressing. Suppose a client computer wants to access a web page on a web server. Assume that it knows all of the IP addresses and data link layer addresses in the network, except those for the web server itself. Describe how the client would obtain the IP address for the web server. 35. TCP/IP Protocol. Consider a planet where everyone belongs to a family of six, every family lives in its own house, each house has a unique address, and each person in a given house has a unique name. Suppose this planet has a mail service that delivers letters from source house to destination house. The mail service requires that (1) the letter be in an envelope, and that (2) the address of the destination house (and nothing more) be clearly written on the envelope. Suppose each family has a delegate family member who collects and distributes letters for the other family members. The letters do not necessarily provide any indication of the recipients of the letters. a. Describe a protocol that the delegates can use to deliver letters from a sending family member to a receiving family member. b. In your protocol, does the mail service ever have to open the envelope and examine the letter in order to provide its service?