IP datagram has arrived with following partial information in the header (in…

Step 1: Look at the First Byte of the Header

First byte = 45 (Hex)

In IPv4, this byte contains:

• First 4 bits → Version

• Last 4 bits → IHL (Internet Header Length)

Step 2: Convert 45 to Binary

45 (Hex) = 0100 0101 (Binary)

So,

• Version = 0100 = 4 → IPv4

• IHL = 0101 = 5

Step 3: Interpret IHL Value

IHL represents the number of 32-bit words in the header.

Header Size =
IHL × 4 bytes

Step 4: Calculate Header Size

Header Size = 5 × 4 = 20 bytes

Final Answer:
The IP header size is 20 bytes.