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Network Layers and Protocols

OSI Model

Network Layers and Protocols

OSI Model

Layer Name Purpose Protocols mnemonic
Application Human Machine Interface – Where data is entered, Connects application to network DNS,HTTP,SMTP,POP3,FTP All
Presentation Data coded into 1s and 0s, or decoded, depending on file format JPEG,MIDI,TIFF,SSL,SSH People
Session Where secure sessions created, authentication takes place NetBIOS, Seem
Transport Error checking it conducted here. Chooses which transport protocol to use TCP,UDP,End-toEnd To
Network  Addressing and Routing IPV4,IPV6,IPSec Need
Data-Link This layer is where the data is prepared for sending Ethernet,PPP,ATM Data
Physical  Data is physically sent along a wire, fiber optic cable or radio waves. Ethernet, USB, Bluetooth,IEEE802.11 Processing

Activity – Watch the video below and fill out the worksheet (in the resources section) as you go through.



There are billions of network connected devices on the planet, each made at different times by different companies. In order for all these devices to communicate successfully with each other they all need to send, receive and process data in an agreed manner – a protocol.

Common Networking Protocols

IP / TCP – Internet Protocol  / Transfer Control Protocol

This protocol defines how packets are send over IP based networks.

IPV4 vs IPV6 – When Internet Protocol was designed very few institutions had networks or computers and so an address system of 32 bits was chosen as it was thought there would be enough addresses. (4,2 Billion addresses).

With the exponential growth of the internet and internet enabled devices, we are now running out of addresses available. A new system (IPV6) is being introduced that contains far more available addresses. 3.4×1038


HTTP / HTTPS – Hyper Text Transfer Protocol / Hyper Text Transfer Protocol Secure

This protocol defines how servers handle web request from users. This includes how to handle get/ post requests, as well as how to format error messages (such as 404 not found messages)


SMTP – Simple Mail Transfer Protocol

This is the protocol used when sending emails across the internet.


POP / POP3 – Post Office Protocol

This is the protocol used when retrieving emails



This is a protocol used for both sending and receiving email


FTP / FTP – File Transfer Protocol / File Transfer Protocol Secure

This protocol is used when sending and receiving files over the internet.

Packet Switching

Packet Switching

When large packets of data are send over the internet, they are split down in to smaller packets, with each packet being given a packet order number, and sent over the internet independently. The packets travel separately over the network, sometimes taking separate paths, and the packets are then reassembled at the other end. This allows for faster data transfer.