← Years 5–6 Digital Systems

Data packets

A small chunk of data with the sender, destination and order number attached. Packets travel a network by different routes and are put back in order at the destination.

Part of: 5-6 Digital Technologies Vic Curric - Digital Systems & Security — Module 34, 7-8 Digital Technologies Vic Curric - Digital Systems and Security — Module 34, 9-10 Digital Technologies Vic Curric - Digital Systems and Security — Module 7, IGCSE Computer Science 0478 — 2.1 Data Transmission Types and Methods — Module 5, ACARA Digital Technologies Years 7–8 — Wired and Wireless Networks — Module 38

Understanding Data packets in Years 5–6 Digital Systems

What it does: This packet shows all four parts: the sender, the destination, the order number and the chunk of data. The packets arrive in a mixed-up order because they travelled by different routes, and the order numbers are used to put them back in sequence. Large data is broken into small packets so it can travel across the network efficiently. The destination information on each packet tells the network where to deliver it. A packet is one small piece of a larger message, and it carries labels so it can be delivered and put back in the right place.

Common mistakes: A dictionary needs a colon between each key and its value. The destination should be written as "to": "PC" so it is attached to the packet. Packets must be put back in order using their order numbers. reverse() only flips the list to [2, 1, 3]. It should be arrived.sort() to get [1, 2, 3].

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This module's key terms are also in a printable crossword (Modules 31–40) and word search (Modules 21–52).

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Learning
Duo
How does a large file travel across a network?
It is split into small packetsIt is sent as one giant block
Matches
A whole 5 MB photo is sent as one single piece through the network
↓
Data is not sent as one big piece. It is split into small packets that travel separately and are reassembled at the destination.
Applying
Meanings
Term
packet
Meaning
A small chunk of data with the sender, destination and order number attached. Packets travel a network by different routes and are put back in order at the destination.
Practice
message = Hello Sam
Testing
Gaps
: "PC1", destination: "PC2"}
Check Answer
Spots
1pkt = {"num": 1, "to" "PC"}
2print(pkt["num"])

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Quick Questions

1. How does a large file travel across a network?
A. It is sent as one giant block
B. It is split into small packets ✓
Large data is broken into small packets so it can travel across the network efficiently.
2. Which information is attached to a packet?
A. Only the file name and the colour of the cable
B. Sender, destination and order number ✓
Each packet carries the sender, the destination and an order number, along with a piece of the data.
3. Why does each packet have an order number?
A. So the packets can be put back in the right order ✓
B. So the packets can be made bigger
Packets may arrive out of order, so the order number lets the destination reassemble them correctly.
4. Do all packets from one message have to take the same route?
A. No, packets can take different routes ✓
B. Yes, they must all take the same route
Each packet can travel by a different route across the network and still reach the same destination.
5. Where are the packets put back together?
A. At the destination ✓
B. At each router along the way
Packets are reassembled at the destination device, using their order numbers.

Match the Pairs

packet → A small chunk of data with the sender, destination and order number attached
packet 3 of 5 → The order number tells the destination where this piece fits when the data is reassembled
Each packet carries the sender, the destination, an order number and a piece of the data → {from: 'Maya', to: 'School', order: 2, data: 'llo'}
Packets can take different routes but are reassembled in order at the destination → arrive: 3, 1, 2 -> sort by order -> 1, 2, 3
A whole 5 MB photo is sent as one single piece through the network → Data is not sent as one big piece. It is split into small packets that travel separately and are reassembled at the destination.
Packets 3, 1, 2 arrive, so the message is read as 3, 1, 2 → The packets must be put back in order using their order numbers before the message is read, so it should be read as 1, 2, 3.

Key Term

packet
A small chunk of data with the sender, destination and order number attached. Packets travel a network by different routes and are put back in order at the destination.

Fill in the Blanks

1. packet = {data: "Hi", order: 1, sender: "PC1", destination: "PC2"}
Hint: Type the field name that says which device the packet came from.
2. packet = {data: "lo", sender: "PC1", destination: "PC2", order: 2}
Hint: Type the field name that stores the packet's place in the sequence.
3. packets = split(message) send(packets[1], route_a) send(packets[2], route_b)
Hint: Type the function name that breaks a message into small packets.
4. arrived = [packet3, packet1, packet2] message = sort(arrived, by=order)
Hint: Type the function name that puts the arrived packets back in sequence.
5. if received == total: message = join(sorted_packets)
Hint: Type the function name that joins the ordered packets into the whole message at the destination.

Spot the Error

Question 1
A pkt = {"num": 1, "to" "PC"}
B print(pkt["num"])
C print(pkt["to"])
Line A — A dictionary needs a colon between each key and its value. The destination should be written as "to": "PC" so it is attached to the packet.
Question 2
A arrived = [3, 1, 2]
B arrived.reverse()
C print(arrived)
Line B — Packets must be put back in order using their order numbers. reverse() only flips the list to [2, 1, 3]. It should be arrived.sort() to get [1, 2, 3].
Question 3
A message = HELLO WORLD
B first = message[0:5]
C second = message[5:11]
Line A — Text data must be inside quotes to be a string. It should be message = "HELLO WORLD" before it is split into packets.
Question 4
A routes = ["A", "B"]
B for route in routes
C print("Via", route)
Line B — A for loop line must end with a colon. It should be for route in routes: so each packet can be shown taking a different route.
Question 5
A def make_packet(data, n, to):
B me = "Laptop"
C return [n, me, data]
Line C — The packet is missing its destination. Every packet needs the order number, sender, destination and data, so the line should be return [n, me, to, data].

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