IP datagram has arrived with following partial information in the header (in…
2023
IP datagram has arrived with following partial information in the header (in hexadecimal)
45000054000300002006……
How many more routers can the packet travel to?
- A.
22
- B.
26
- C.
30
- D.
32
Attempted by 192 students.
Show answer & explanation
Correct answer: D
Solution:
Step 1: Write the header bytes in sequence45 00 00 54 00 03 00 00 20 06 …
Step 2: Recall IPv4 Header Field Positions
Byte Position | Field |
|---|---|
1st byte | Version + IHL |
2nd byte | Type of Service |
3rd–4th bytes | Total Length |
5th–6th bytes | Identification |
7th–8th bytes | Flags + Fragment Offset |
9th byte | Time To Live (TTL) |
10th byte | Protocol |
Step 3: Identify the TTL Field
From the header:
45 | 00 | 00 54 | 00 03 | 00 00 | 20 | 06
So,
TTL = 20 (Hexadecimal)
Step 4: Convert TTL from Hexadecimal to Decimal
20 (Hex) = 2 × 16 + 0 = 32
So,
TTL = 32
Step 5: Interpret TTL Meaning
TTL indicates the maximum number of routers (hops) the packet can pass through.
Each router decreases TTL by 1.
Therefore, the packet can still travel through 32 routers before being discarded.
Final Answer:
The packet can travel 32 more routers (hops).
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