2) (14 pts) Answer the following short answer questions. a) (2 pts) Suppose that setting up a call requires reserving 3 link segments. Each segment is available with probability 0.3. What is the probability that a call request can be completed? b) (2pts) Explain where the following fits in the OSI reference model: In WWII, a teleprinter transmits a message over radio (telex-on-radio, TOR). c) (2 pts) Recall that HDLC protocol applies bit stuffing. (Note that HDLC uses 01111110 as the frame marker.) And please mark the stuffed bits and errored bits in the following data payload bit sequence: 110101111101011111101011111110 d) (3 pts) For a message M = 00110100111101, we use 2-dimensional parity code to derive the error detection code. Suppose 7-bit words are used. If even parity is being used, derive the error detection code.

e) (2 pts) What is the efficiency (the percentage of effective data in the overall data) of 4B/5B encoding? How about 8B/10B? f) (3 pts) Suppose a sliding window algorithm is implemented using a SWS=3 and a RWS = 4, will 6 sequence numbers (i.e. 0,1,2,3,4,5) be sufficient to correctly distinguish all packets that are received? Explain your answer. (for example, an old sequence number of 0 is not mistaken for a new sequence number of 0.) Use a diagram if necessary.

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