Functions of OSI and TCP/IP Layers Q.27

27In an IPv4 datagram, the M bit is 0, the value of HLEN is 10, the value of total length is 400 and the fragment offset value if 300. The position of the datagram, the sequence numbers of the first and the last bytes of the payload, respectively are

Option : C
Explanation : Since M bit is 0, so there is no fragments after this fragment. Hence this fragment is the “last fragment” Tow, H LEN defines t he length of Header in datagram. Since H LEN is 10 so size of header is 10 * 4 = 40B.
Length of data = Total length – Leader length = 400 – 40 = 360 B.
Few, fragment offset of data in original datagram is measured in units of 8B. So to find first Byte of this fragment,
first Byte/B = fragment offset
first Byte = 300 * 8 = “2400” B
since length of data is 360B
so last Byte on this datagram will be “2759” B

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