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Unformatted text preview: CS176A - HOMEWORK ASSIGNMENT 2A Due: October 24 (By 11:59pm) Instructions Read each question carefully (there are 15 total)! Answer questions precisely--points will be taken off for unnecessary information. Turn in your assignment electronically (e.g., Plain Text, Word, or PDF). Questions 1. Which layers are in the OSI stack but not the TCP/IP stack? Session and Presentation. 2. A noisy (30 dB signal-to-noise ratio) 100 kHz channel carries 256 signal levels. What is the maximum date rate? (HINT: you'll need to consider both Nyquist and Shannon on this one.) Nyquist considers noiseless channel. The max bandwidth you would get based on Nyquist is: Bandwidth = 2*f*log_2(signal levels) = 1600kbps Shannon considers noisy channel. The max bandwidth based on Shannon would be: Bandwidth = f*log_2(1+SNR) = 1000kbps SNR = 10 log_10(Ps/Pn), for SNR = 30dB Ps = 1000*Pn So the maximum data rate of this channel is 1000kbps. 3. What are the two general categories of flow control for data link layer protocols? What are the major advantages and disadvantages of each? The two general categories for DLL flow control protocols are stop-n-wait and window-based. The window-based itself has two sub-categories: Go-Back-N and Selective Reject. In the stop-n-wait protocol a sender sends one packet at a time and waits for an ACK for this packet before sending another one. While good for assuring reliable transmission, stop-n-wait protocols are inefficient, because the time between sending separate packets is larger than with other protocols, thus the achieved throughput is not optimal....
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This note was uploaded on 02/19/2012 for the course ENGR 361 taught by Professor Drexel during the Spring '12 term at Bloomsburg.
- Spring '12