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

Step 1: Write the header bytes in sequence
45 00 00 54 00 03 00 00 20 06 …

Step 2: Recall IPv4 header format (first few fields)

Step 3: Identify the Total Length field

From the given header:

45 | 00 | 00 54 | 00 03 | 00 00 | 20 | 06

So,

Total Length = 00 54 (Hexadecimal)

Step 4: Convert Hexadecimal to Decimal

00 54 (Hex) = 0x54

Now convert:

0x54 = (5 × 16) + 4
= 80 + 4
= 84

Step 5: Interpret the Meaning

The Total Length field specifies the size of the entire IP datagram, including:

• IP Header

• Data (Payload)

Final Answer:
The size of the IP datagram = 84 bytes.