0 votes 0 votes Suppose that a message 1001 1100 1010 0011 is transmitted using Internet Checksum (4-bit word). What is the value of the checksum? Computer Networks computer-networks data-link-layer tanenbaum error-detection checksum + – ajaysoni1924 asked Mar 16, 2019 edited Mar 16, 2019 by ajaysoni1924 ajaysoni1924 7.3k views answer comment Share Follow See all 0 reply Please log in or register to add a comment.
18 votes 18 votes As we are asked for 4-bit checksum, so divide the data into 4 bit words and add all. 1001 + 1100 + 1010 + 0011 = 100010 We want 4-bit checksum, bring 10 down and so add 0010 + 10 = 0100 And checksum will be the complement of 0100 which is 1011 . Kapil answered Sep 14, 2016 edited Sep 21, 2016 by Kapil Kapil comment Share Follow See all 4 Comments See all 4 4 Comments reply Injila commented Jul 7, 2017 reply Follow Share You added four 4-bit words, how it produced a 6-bit output? 0 votes 0 votes Shweta Nair commented Nov 13, 2017 reply Follow Share 1001 + 1100 + 1010 + 0011 In decimal we can write this as, 9 + 12 + 10 + 3 = 34 Converting 34 to binary we get 100010 0 votes 0 votes Salla shivateja commented Jan 13, 2020 reply Follow Share why only two bits brought down? 0 votes 0 votes rajan31 commented Jul 3, 2022 reply Follow Share Because we want 4-bit checksum. but, 2-bits are extra. 0 votes 0 votes Please log in or register to add a comment.
4 votes 4 votes Add these numbers 1001+1100+1010+0011 you will get 0010 and a carry of 10 now add carry also in 0010 so 0010+10 =0100 now performs 1’s complement. you will get result as 1011 which is the required answer. Yash4444 answered Aug 14, 2020 Yash4444 comment Share Follow See all 0 reply Please log in or register to add a comment.
0 votes 0 votes Since we are asked for 4-bit checksum value so we take 4 bits pairs and add them together and if the result of them exceeds 4 bits we take it as carry and add it again. We repeat the steps until all the pairs are added. Then we take the 1’s complement of the result thus obtained. So, the checksum value is 1011. Ansh Sinha answered Jan 7 Ansh Sinha comment Share Follow See all 0 reply Please log in or register to add a comment.