Advantages of Reference Models

• Advantages of using the OSI layered model include, but are not limited to, 
the following:
• Allows multiple-vendor development through standardization of 
   network components.

• Allows various types of network hardware and software to communicate.

• Prevents changes in one layer from affecting other layers, so it does not       hamper development.

Internetworking Models

• In 1977, the International Organization for standardization (ISO)created the Open Systems Interconnection (OSI) Reference Model.

• OSI Layer is meant for Networking manufacturers and developers to provide them a standard based on which they can make their products.

• All OSI Layers are independent from each other, which makes introducing changes easier as no other layers are effected.

The Layered Approach

• A reference model is a conceptual blueprint of how communications should take place. It addresses all the processes required for effective communication and divides these processes into logical groupings called layers

• When a communication system is designed in this manner, it’s known as layered architecture.

Computer network elements

End devices
Devices that have the resources to share with others, or devices that are used by the end users to access the shared resources.
Examples of the end devices are a ‘PC’, a ‘laptop’, a ‘printer’ and a ‘server’. 
             

Networking devices
Devices that are used to connect between end devices.
Examples of networking devices are a ‘hub’, a switch’ and a ‘router’. 

What is a computer network?

A computer network is a collection of devices connected to each other, in order to allow every device to share its resources with other devices, and access other devices shared resources. In most cases, this connection is made via electrical cables that carry the information in the form of electrical signals. But in some cases, other types of connections are used. For example, fiber-optic cables let computers communicate at extremely high speeds by using impulses of light. Wireless networks let computers communicate by using radio signals, so the computers aren’t restricted by physical cables.

 

Internetworking Basics

• Breaking up a larger network into a number of smaller ones is called network segmentation, and it’s accomplished using routers, switches, and bridges.

• Possible causes of LAN traffic congestion are:

• Too many hosts in a broadcast domain
• Broadcast storms
• Multicasting
• Low bandwidth