An $IP$ router with a $\text{Maximum Transmission Unit (MTU)}$ of $1500$ bytes has received an $IP$ packet of size $4404\text{ bytes}$ with an $IP$ header of length $20\text{ bytes}$. The values of the relevant fields in the header of the third $IP$ fragment generated by the router for this packet are:
"Total length of the datagram" field is of 16 bits and "Fragmentation Offset" field is of 13 bits. 2^16-1 cannot be represented using 13 bits therefore 2^16/2^13=8, 8 is the scaling factor and that's why offset is divided by 8.
1st Fragment's Offset :0
2nd Fragment's offset = Previous Fragment's Offset +(Data bytes of prev fragment/8) and so on.
If they ask what is the length of Internet header length(IHL)?
IHL has 4 bit field and we have IP header length = 20bytes
answer would be 20/4 = 5 where 4 as scaling factor saw somewhere.
please explain this?
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