A packet has arrived in which the offset value is 200, the value of HLEN is 6 and the value of the total length field is 120. What is the number of the first byte and the last byte?

(Offset = 200, HLEN = 6, Total Length = 120)

You’re given three values.
Offset = 200
HLEN = 6
Total Length = 120

Now let’s break this down step by step.

First, remember that the fragment offset is measured in units of 8 bytes.

So the starting byte is

First byte = 200 × 8 = 1600

Now move to HLEN.
HLEN is given in units of 4 bytes.

Header length = 6 × 4 = 24 bytes

Now find the data length inside this fragment.

Data length = Total Length - Header Length 

= 120 - 24 = 96 bytes

So this fragment carries 96 bytes of actual data.

Now calculate the last byte.

Last byte = First byte + Data length - 1 

= 1600 + 96 - 1 = 1695

Final Answer

• First byte = 1600

• Last byte = 1695

Offset	HLEN	Total Length	Header Length	Data Length	First Byte	Last Byte
200	6	120	24	96	1600	1695