1.4 - Layers & Packet Switching

1.4 - Layers & Packet Switching

1. Layer Types

   • Layer 1: Data Link - This layer sends data over a physical network, like the Ethernet.
   • Layer 2: Network - Directs the data packets between network. This is where IP is used.
   • Layer 3: Transport - Controls the flow of data. This is where TCP is used.
   • Layer 4: Application - Turns data into applications or websites, whatever the data is told to do. The protocols used here are HTTP(S), FTP & SMTP.

2. Packet Switching

   • Step 1: Data is split into packets and numbered in order.
   • Step 2: Each packet is sent the fastest route across the internet by the routers. This means packets can take different routes and arrive out of order.
   • Step 3: The packet numbers are used to put them back into order.
   • Step 4: If packets are missing, a timeout message is sent. Once all have arrived, a receipt confirmation is sent to the device that sent them.

3. Network Protocols are divided into layers so that protocols with similar functions are grouped together.