7 votes 7 votes A IP packet has arrived in which the fragmentation offset value is $100,$ the value of $\textsf{HLEN}$ is $5$ and the value of total length field is $200.$ What is the number of the last byte? $194$ $394$ $979$ $1179$ Computer Networks computer-networks ip-packet isro2014 + – ajit asked Sep 23, 2015 • edited Dec 4, 2022 by Lakshman Bhaiya ajit 9.7k views answer comment Share Follow See all 0 reply Please log in or register to add a comment.
Best answer 16 votes 16 votes Data length $ = 200 – 4 \times 5=180$ Starting number of the first byte of fragment $ = 100\times8=800$ Number of the last byte $ = 800+179 = 979$ $\mathbf{Ans}\;\textbf C$ Pooja Palod answered Sep 23, 2015 • edited Nov 1, 2021 by `JEET Pooja Palod comment Share Follow See all 11 Comments See all 11 11 Comments reply Show 8 previous comments shraddha priya commented Mar 6, 2019 reply Follow Share @ayush palak @Raju Kalagoni But shouldn't data be a multiple of 8? Here data size is 180, which is not a multiple of 8. 1 votes 1 votes Raju Kalagoni commented Aug 8, 2019 reply Follow Share @shraddha priya, data need not be a multiple of 8. it doesn't make sense to have data always in multiple of 8. We should always be in a position to send data across network either in multiple of 8 or not. 1 votes 1 votes commenter commenter commented Jan 3, 2020 reply Follow Share @shraddha priya Data should be a multiple of 8 in cases where there are more than 1 fragmented packets and all the packets except the last packet must be a multiple of 8. If there is only one packet or the packet is last fragmented packet then it need not be a multiple of 8. 1 votes 1 votes Please log in or register to add a comment.
4 votes 4 votes $\mathbf{Option \;C}$ Total Length=$200$ Data field excluding header=$ 200-20 = 180(0 \dots 179)$ No of byte ahead from this packet is $ = 100\times8 = 800$ so last byte = $800+179=979$ Paras Nath answered Sep 10, 2016 • edited Nov 1, 2021 by `JEET Paras Nath comment Share Follow See all 0 reply Please log in or register to add a comment.
3 votes 3 votes Header Payload An IP packet looks like this. Header Length = $5*4=20$ So, Payload = $200-20=180$ Fragmentation offset = $100*8=800$ The last byte would be $180 + 800$th = $980th$ but since we number everything from 0 in computer science, it'll be $979th$ JashanArora answered Dec 8, 2019 JashanArora comment Share Follow See all 0 reply Please log in or register to add a comment.
0 votes 0 votes Here in this case answer should be 979. eshita1997 answered May 8, 2021 eshita1997 comment Share Follow See all 0 reply Please log in or register to add a comment.