Packet header

Name:

Date:

Class:

Quick Questions

Shade in the A or B circle for each question.

1. Where is the packet header found in a packet?

A At the start of the packet, before the payload

B At the end of the packet, after the payload

2. Which of these is stored in a packet header?

A The destination address

B The file's actual contents

3. What is the packet number in the header used for?

A To put the packets back in the right order

B To encrypt the data in the packet

4. Why does the header contain the destination address?

A So the receiver knows how fast the packet travelled

B So the router knows where to send the packet

5. What does the originator's address in the header show?

A The IP address of the router that will receive it next

B The IP address of the device that sent the packet

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1header: dest=192.168.1.20		Aheader = [dest, from, packet_no]
2header: packet_no=4		Bheader: from=10.0.0.5
3The header holds the originator's address so the receiver knows which device sent the packet		CThe packet number field, which lets the receiving device put packets back in the correct order
4A packet header contains control information (destination, originator and packet number), not the data itself		DThe destination address field, which tells routers where the packet must be delivered
5packet = [payload, header, trailer]		EThe header is in the wrong place. It is the first part of a packet, so it must come before the payload.
6header = [email text, dest, from]		FThe header does not hold the data being sent. The message content belongs in the payload, and the header should include the packet number.

Definitions

packet header

Fill in the Blanks

Complete each line of code by filling in the missing parts.

packet = ______ + payload + trailer

header = [___________, originator, number]

header = [destination, __________, number]

header = [destination, originator, ______]

SORT packets BY packet.header.______

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A header = first part of packet

B header = control information

C header holds the file content

Question 2

A packet.header.dest = 'B'

B packet.header.origin = 'A'

C packet.trailer.number = 3

Question 3

A packet 4 arrives

B READ payload for packet number

C place packet 4 in order

Question 4

A header = LAST part of packet

B payload = the data itself

C trailer = LAST part of packet

Question 5

A router reads the packet header

B it finds the dest address

C it sends packet to the origin

Answer Key

Packet header

Section A: Quick Questions

A — At the start of the packet, before the payload

A — The destination address

A — To put the packets back in the right order

B — So the router knows where to send the packet

B — The IP address of the device that sent the packet

Section B: Match the Pairs

header: dest=192.168.1.20 → The destination address field, which tells routers where the packet must be delivered

header: packet_no=4 → The packet number field, which lets the receiving device put packets back in the correct order

The header holds the originator's address so the receiver knows which device sent the packet → header: from=10.0.0.5

A packet header contains control information (destination, originator and packet number), not the data itself → header = [dest, from, packet_no]

packet = [payload, header, trailer] → The header is in the wrong place. It is the first part of a packet, so it must come before the payload.

header = [email text, dest, from] → The header does not hold the data being sent. The message content belongs in the payload, and the header should include the packet number.

Section C: Definitions

packet header — The first part of a packet. It holds control information: the destination address, the originator's address and the packet number, used to deliver and reassemble the packet.

Section D: Fill in the Blanks

packet = header + payload + trailer

header = [destination, originator, number]

SORT packets BY packet.header.number

Section E: Spot the Error

C — The header holds control information such as the destination address. The file content is the payload, not part of the header.

C — The packet number is stored in the packet header, not the trailer. It should be packet.header.number = 3.

B — The packet number is part of the header, so the computer must read the header. The payload only holds the data.

A — The header is the FIRST part of a packet. The trailer is the last part.

C — The router uses the destination address in the header to send the packet onward. It should send the packet to the destination, not back to the origin.