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Unformatted text preview: Homework 2 Student name: Son Tran (o ) Student ID: 2007-23576 Class: Data Networks - 2008 2.30 - Answer: (a) Stuffed bits are in bold and strikethrough: 011011111 0011111 101011111 11111 01111010 (b) Flags are in bold and underlined; stuffed bits are in x: 01111110 11111 x 110011111 x 011111 x 11111 x 1100 01111110 1011111 2.31 - Answer: The modified destuffing rule starts at the beginning of the string and destuffs bit by bit. A zero is removed from the string if the previous six bits in the already destuffed portion of the string have the value 01 5 . For the particular example: 011011111 x 111111011111 x 1 01111110 2.32 - Answer: Considering following two cases: (a) 01 5 x . If the original string is 01 5 x , then it is possible to avoid stuffing a bit, because the unstuffed version of this string could never be mistaken for the string 01 6 0. Because our flag contains a 1, however, every string of 0s in the frame will always be terminated by a 1. This case could never arise. (b) 01 5 x 1. If the original string is 01 5 x 1, then we must stuff a bit. This follows from a bit of formal inductive reasoning. We start with the string 01 5 01. If we don't stuff a bit, then it will be impossible for the receiver to disambiguate this string from the string 01 6 01, which we know must be stuffed. Therefore, we must stuff the string 01which we know must be stuffed....
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- Spring '08