Computer Science : S2 : L1 : Data Packet

—----------------------------------------------------------------------------------------------------------------------Section 2 : Data Transmittion

Lesson 1 : Data Packet

When data is sent over a long distance the data is normally broken up into smaller data packets. 

Advantages : 

• Easier to control

• Each packet can take its own route

Disadvantages : 

• They require careful construction and additional information so they can be reassembled correctly

• They can get lost

Packet Structure : 

Packet Header 

• Destination IP Address

• Sender's IP Address

• Packet number 1 of 5

Payload

• The actual content to be transmitted

Trailer 

• Marks the end of a packet

• Error checking method

At each stage in transmission there are nodes that contain a router. A router receives a data packet and based on the information from the header it decides where to send it next. Each router determines which route the packet needs to take.

Packet switching is a five stage process : 

1) A data transmission is broken down into packets. 

2) Each packet is assigned a number before being sent.

 3) Each packet can take its own destination based on congestion 

4) Routers are responsible for controlling the route each packet takes.

5) Packets arrive at the final IP address out of order and once the final packet arrives the are reordered correctly