ECE438-Final-Study Notes - CS/ECE 438: Communication...

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CS/ECE 438: Communication Networks Final Study Guide The class Final examination will be held in 1 14 Transportation Building from 1 :30p.m. to 4 :30p.m. on Wednesday, 12/14. The exam will begin and end promptly. Please arrive before 1 :30p.m. to allow everyone to settle into their seats before the test begins. The exam will be condu cted in a closed-book format , but you'll be allowed 2 sheets of notes . The final will contain ve parameterized problems and one set of short-answer question s . Each parameterized problem will consist of multiple parts. The short questions are simple-answer or true-or-false questions. On the final , you must show all work and reasoning, writing both work and solution legibly, and should box all answers. If the course staff cannot read a solution, no credit will be given. You are encouraged to study in groups for the final . Short-Answer Questions 1. Give two good reasons to allow branching—that is, the ability to support multiple protocols above and below any given protocol—in protocol graphs. 2. Explain one advantage of abstracting networked communication into multiple layers. 3. H ow is 802.11 similar to Ethernet protocol? How do they differ? 4. Why is DNS load balancing useful? 5. Explain the relationship between SMTP and MIME. 6. Explain why the mail access protocol (such as POP3 or IMAP) is needed. 7. Consider an HTTP client that wants to retrieve a Web document at a given URL. The IP address of the HTTP server is initially unknown. The Web document at the URL has one embedded GIF image that resides at the same server at the original document. What transport and applicatoin-layer protocols behinds HTTP are needed for this scenario? 8. What is the difference between persistent HTTP with pipelining and persitent HTTP without pipelining? 9. Why do HTTP, FTP, SMTP, POP3, and IMAP run on top of TCP rather than on UDP? 10. What is a value-result argument? 11. Explain how the Last-Modi ed and Expires elds are used in HTTP. 12. Draw a protocol graph for the Internet, including at least the following: ATM, Ethernet, FDDI, FTP, HTTP, IP, TCP, TFTP, and UDP. 13. Why does TCP begin by multiplicatively increasing its congestion window? What is “slow” about this approach? 14. What is a key problem with stop-and-go protocols? 15. Suppose an application generates chunks of 40 bytes of data every 20 msec, and each chunk gets encapsulated in a TCP segment and then an IP datagram. What percentage of each datagram will be overhead, and what percentage will be application data?
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16. Describe the problem solved by reliable data transport. 17. Explain the main drawback of the stop-and-wait reliable data transport algorithm. 18. Name the four components that uniquely specify a TCP connection and state the length of each component in bits.
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This note was uploaded on 02/08/2012 for the course ECE 438 taught by Professor Luo during the Fall '08 term at University of Illinois, Urbana Champaign.

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ECE438-Final-Study Notes - CS/ECE 438: Communication...

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