7 layers of osi models

Mr . Sathish Kumar . M

Department of Electronics and Communication Engineering

I’ve learned that people will forget what you said, people will forget what you did, but

people will never forget how you made them feel. –Maya Angelou

NETWORK LAYERS

A network can be one computer connected to the Internet, or two or more computers connected to each other (and possibly to the Internet as well). In a wireless (Wi‑Fi)network, the computers are connected by radio signals instead of wires or cables.

What is Wireless Networks….?

• ISO International Standards

Organization

• OSI Open Systems Interconnect

• Introduced in 1978 and revised in 1984.

• Formulates the communication process into structured layers.

• There are seven layers in the model, hence the name the 7-Layer model.

ISO-OSI

7. Application

6. Presentation

5. Session

4. Transport

3. Network

2. Data Link

1. Physical

7 LAYERS

Physical Layer The physical layer of the OSI model defines connector and

interface specifications, as well as the medium (cable) requirements. Electrical, mechanical, functional, and procedural specifications are provided for sending a bit stream on a computer network.

Data Link Layer• Allows a device to access the network to send and receive

messages offers a physical address so a device’s data can be sent on the network

• Works with a device’s networking software when sending and receiving messages

• Provides error-detection capability

• Network interface cards

• Ethernet and Token Ring switches

• Bridges

Network Layer• The network layer controls the operation of the subnet,

deciding which physical path the data should take based on network conditions, priority of service, and other factors.

• To make it easier to manage the network and control the flow of packets, many organizations separate their network layer addressing into smaller parts known as subnets. Routers use the network or subnet portion of the IP addressing to route traffic between different networks. Each router must be configured specifically for the networks or subnets that will be connected to its interfaces.

Transport Layer• Purpose of this layer is to provide a reliable mechanism for

the exchange of data between two processes in different computers.

• Ensures that the data units are delivered error free.

• Ensures that data units are delivered in sequence.

• Ensures that there is no loss or duplication of data units.

• Provides connectionless or connection oriented service.

• Provides for the connection management.

• Multiplex multiple connection over a single channel.

Session Layer• Session layer provides mechanism for controlling the dialogue

between the two end systems. It defines how to start, control and end conversations (called sessions) between applications.

• This layer requests for a logical connection to be established on an end-user’s request.

• Any necessary log-on or password validation is also handled by this layer.

• Session layer is also responsible for terminating the connection.

• This layer provides services like dialogue discipline which can be full duplex or half duplex.

• Session layer can also provide check-pointing mechanism such that if a failure of some sort occurs between checkpoints, all data can be retransmitted from the last checkpoint.

Presentation Layer

• The presentation layer, is responsible for how an application formats the data to be sent out onto the network. The presentation layer basically allows an application to read (or understand) the message.

• Encryption and decryption of a message for security

• Compression and expansion of a message so that it travels efficiently

• Graphics formatting

• Content translation

• System-specific translation

Application Layer

• Application layer interacts with application programs and is the highest level of OSI model.

• Application layer contains management functions to support distributed applications.

• Examples of application layer are applications such as file transfer, electronic mail, remote login etc.

TCP/IP Model

Application LayerApplication programs using the network

Transport Layer (TCP/UDP)Management of end-to-end message transmission,

error detection and error correction

Network Layer (IP)Handling of datagrams : routing and congestion

Data Link LayerManagement of cost effective and reliable data delivery,

access to physical networks

Physical LayerPhysical Media

Thank You……!