An IP datagram has arrived with the following partial information in the header (in
hexadecimal): 45000054 00030000 2006 . . . a. What is the header size? b. Are there any options
in the packet? c. What is the size of the data? d. Is the packet fragmented? e. How many more
routers can the packet travel to? f. What is the protocol number of the payload being carried by
the packet?
Solution
VER HLEN Service Total ID Flag & TTL Protocol
type length Frag offset
4 5 00 0054 0003 0000 20 06...
a.What is the size of the header? 5x4bytes = 20 bytes
b. Are there any options in the packet? no
c.What is the size of the data? Length of data = Total length – HLEN = 84 – 20 = 64 bytes
d. Is the packet fragmented? No
e. How many more routers can the packet travel to? TTL = 20 which means the the number of
hops (router, computer or device along a network) the packet is allowed to pass before it dies ,
thus 20 hops, or 20 routers. The last router will discard the datagram.
f. What is the protocol number of the payload being carried by the packet? 06 TCP
(Transmission Control Protocol)
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