Hi, this is your host Habib's Korea and in our first lesson I will be talking about the communication reference model also known as OSI model. Please note that all the OSI model acts as a reference model and not as an implementation model. I will explain to you the implementation model in the next lesson or psi stands for open system interconnection. international standards organization known as ISO came forward to standardize network communication in the year 1970. and resolve the problem for the consumers to interoperate different hardware devices using common standard. I will talk about each layer. So, let's start physical layer is the layer one of the OSI model.

The data is In the form of bits ones and zeros, it defines the type of media used to communicate over the network. Examples are physical cables properties of the physical cables like voltages, signals, devices that operate at the at the layer one our hub hubs, repeaters modems and Nic cards. communication can happen in many ways. simplex communication, which is also known as one directional, like broadcast messages, half duplex communication Wi Fi can operate at half duplex as you know, which means that the data can be sent and received only at a given time. When the media is condition free, full duplex data can be sent and received at the same time. data link layer is the layer two of the OSI model the data is in the form of frames.

Frames are subdivided into two LLC known as the logical Link Control. It manages communication between devices in the same network. Mac, which is the media access control, it's actually the physical address of a device. bridges and layer two switches operate at this layer. Ethernet frame relay Token Ring ftdi are the protocols used in this layer. network layer is the layer three of the OSI model.

The data is in the form of packets, IP is given to devices. These IPS are the logical addressing of the devices routing of the packets between the sender and the receiver At this layer, layer three switches, routers firewalls all operate at this layer. transport layer is the layer four of the OSI model. The data is in the form of segments. Transport Layer uses two protocols, TCP and UDP. TCP is a reliable communication protocol, whereas UDP is unreliable communication protocol mainly used by voice functions like flow control and congestion avoidance is handled by transport layer.

There is the layer fifth of the OSI model. session management between sending and receiving devices happens at this layer. session layer synchronization happens by using sequence numbers. presentation layer is the layer six of the OSI model. It is responsible for formatting the data like JPEG or PNG MPEG compression of data happens to improve the transfer rate at this layer. encryption of the data happens at this layer to improve security.

Application layer is a layer seven of the OSI model. It is the interface for the applications running on the computers to provide services like the DNS HTTP, FTP. As we come to an end of this lesson, the OSI model picture is in front of you. physical data link and the network layers are known as the media layers. And the topmost layer transport session presentation application layer are known as the host layers. Please remember the picture as we continue to our next lesson, and I'll see you there.

Thank you