Solution

The correct answer is 20 bytes

EXPLANATION:

The header of the IP datagram given is in hexadecimal format.

Size of the header is 20 to 60 Bytes

Version = 4 bits = (0100)₂ (It is IPv4)

Header length = (0101)₂ to (1111)₂ = 5 bits to 15 bits

Total length = 2¹⁶ bits

Identification = 216 bits

Fragment Offset = 216 bits

Time to live = 2⁸ bits

Protocol = 28 bits

Header Checksum = 216 bits

SOLUTION:

IP Datagram = 45000054 00030000 2006.......

             4                   5                00                         0054

The first byte of the IP header contains two fields: the version and the Internet Header Length (IHL). In your case, the first byte is "45" in hexadecimal.

The first digit '4' is the IP version i.e., IPv4. The second digit '5' represents the Internet Header Length (IHL).

The IHL field is 4 bits long and specifies the header length in 32-bit words. '5' in hexadecimal is 5 in decimal, which means the header length is 5 words (32-bit or 4 bytes each).

So, the size of the header is 5 * 4 = 20 bytes.