Introduction to Cyber Security(VI): The OSI Model.

Introduction to Cyber Security(VI): The OSI Model.

NETWORK LAYER

Network: This is a medium or process in which many nodes can be connected (an interconnected system of computers), on which every node has an address (IP and MAC) and which permits every other node connected to it the permission to transfer messages.

Node: This is any computer that is hooked or connected to a computer network

NETWORK LAYER

This is the third layer of the OSI Model.

This is the layer that deals with the structuring and managing of a multi-node network, including addressing, routing and traffic control. It is the layer that defines which physical path the data will take. It is responsible for packet forwarding including intermediate routing. Some of the functions of the network layer are;

There is a relation between the network layer and the TCP/IP protocol but, that will be discussed later on. Most people tend to think they are the same but the TCP/IP is just a subset of the network layer because it only describes one part of the network layer, the internet.

Another function of the network layer is that it is responsible for the fragmentation and assembly of the IPV4 packets that are larger than the smallest MTU of all the intermediate links packets paths to their destination.

Now, on the network layer, various protocols operate at it, some are;

  • CLNS, Connectionless-mode Network Service

  • DDP, Datagram Delivery Protocol

  • EGP, Exterior Gateway Protocol

  • EIGRP, Enhanced Interior Gateway Routing Protocol

  • ICMP, Internet Control Message Protocol

  • IGMP, Internet Group Management Protocol

  • IPsec, Internet Protocol Security and many more.

So with that, we will be moving into details about the network layer soon and more.