2.1 The estructure of a data packet

2.1 The structure of a data packet

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2. Data transmition

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Multiple Choice

If you have a package with dimensions 100x100, can it fit through a door that is 50x50?

• Yes

• No

• I am the package.

• I am the door

As same as the small door, the internet cables and radio wave have a bandwidth, which is like the size of the door.

The Problem of Large Files

​Data to transfer

​Internet bandwidth

The bandwidth limits the amount of data that can be transfer through internet.

The Problem of Large Files

​Data to transfer

​Internet bandwidth

The data in a file to be transmitted, it is broken down into very small units called packets.

Solution: Breaking Data into Packets

​Internet bandwidth

Each packet of data contains three different sections:

Solution: Breaking Data into Packets

​Internet bandwidth

Header
Payload
Trailer

Multiple Choice

What are the three different sections of a packet?

• header, payload, trailer
• data, checksum, sequence
• start, middle, end
• header, body, footer

Packets

Header
- destination address. (for who)
- packet number (later use to rebuild the data)
- originators address (the source or from who)

Payload
Trailer

Multiple Choice

What information does the packet header contains?

• Source and destination MAC addresses
• Data payload and checksum
• Source and destination IP addresses and the packet number

• Transmission speed and error rate

All devices connected to the internet have an IP address.

Knowing a device's IP address is like knowing its location. This allows you to send information to that specific device.

Destination address

Go to the start or press the Windows Key.
Type "cmd" and press Enter key to open the command line.
Type the command > ipconfig
Check your IP address with your classmates.

Happy Bonus Practice

Each data packet in the file is given a packet number

Packet Number

​Internet bandwidth

1

2

3

Reorder

Reorder the following binary numbers:

• 0001

• 0010

• 0011

• 0100

• 0101

1

2

3

4

5

• 1
• 2
• 3
• 4
• 5

The originators or the source address is also normally an IP address.

Originators address

The actual data

Payload

The actual data.

"Hello, What's up?"

Payload

​Internet bandwidth

Hello,

What's

up?

Two pieces of information:

1. Marker to indicate that it is the end of the packet.
2. Data for error detection.

Trailer

Match

Match the descriptions to parts of a packet

• Packet Identification

• Destination address

• Source address

• Payload

• Error detection bits (Trailer)

Gives each packet an ID so it can be identified when it is to be put back together

Location of the recipient's computer

Location of the sender's computer

Data carried by the packet

Data used to check whether the packet has been received correctly

• Gives each packet an ID so it can be identified when it is to be put back together

• Location of the recipient's computer

• Location of the sender's computer

• Data carried by the packet

• Data used to check whether the packet has been received correctly

Open Ended

What information does the packet header contain?

Open Ended

Which part of the data packet is the actual data from the file?

Open Ended

Why does data need to be broken down into packets to be transmitted?