Table of Contents
Working of the OSI ( Open System Interconnection )Model
OSI stands for “Open Systems Interconnection” and it is a conceptual framework for how an application communicates over a network. There are 7 layers in the OSI model and the layers represented in this layer are used to help users to understand what is happening within networking system.
What is OSI Model?
Before we get started on today’s blog, the OSI model layers are typically described from the top layer down. The layers are described as
7. Applications
6. Presentation
5. Session
4. Transport
3. Network
2. Data Link
1.Physical
These layers are provided by major operating systems, applications and networking hardware, which facilitates the transmission of signals over Ethernet, Fiber optic, Wi-Fi, and other wireless protocols.
We will describe the layers from the top down as the top layer is the “Applications” layer i.e. layer 7.
The Applications Layer:
This is the layer that is the most users interact with and will recognize. This layer provides the network services to the users. These services are protocols that work with the data that client is using. One of the protocols among them may be HTTP which can be used with different web browsers such as Google Chrome, Firefox, and Internet Explorer. Other examples of applications which also use Application layer are – Office, Outlook, and Skype.
All of those interactive applications provide services that allow the application layer to supply data to and receive data from the Presentation layer or layer 6.
The Presentation Layer:
It performs the uncomplicated tasks of syntax process or converting data from one format to another. For Example: Consider you are ordering something from an online store. These transactions typically require secured transmission which means that the data passing between this online store or the website application will transmit the encrypted data to the presentation layer that would need to be decrypted and processed. The Presentation Layer is responsible for translating the data from the top layer which is represented by application format to network format and vice versa. After that this presentation layer processes the data from one format to another, and then the information is then passed to the Session layer or the application layer, depending on whether the data is transmitting or receiving.
The Session Layer:
At Session Layer or layer no. 5, the construction, direction and inclusion of connections between devices occur. This layer supports different types of connections as well as it is responsible for authentication and reconnection, if the network interruption occurs.
After the Session layer is established the data then passes to or from the transport layer.
The Transport Layer:
The Transport Layer or the Layer no.4 is responsible for the transmission of data across network connections. This layer coordinates how much data to send, how fast, where it goes and these sorts of things. Of the most widely known protocol is internet application. These services may be provided by transmission control protocol or TCP and use Datagram Protocol UDP.
The additional capabilities like error recovery, data flow and re transmission can be supported by other protocols. Once the transport layer completes its functions, then the data is passed to or from the network layer.
The Network Layer:
The Network Layer or the layer no. 3 handles the routing of the data after the data arrives to this layer each frame of data is examined to conclude the data has reached to its ultimate target. The Network Layer sends data to the correct destination through an outgoing transmission and it also receives incoming transmissions as well.
The IP portion which stands for Internet Protocol of TCP/IP is the most commonly known network layer for the internet. This layer also manages the mapping between logical addresses and Physical addresses; for IP addresses this is accomplished through an Address Resolution Protocol or ARP. The data is then passed to the next layer which is the data link layer.
The Data Link Layer:
The Data Link Layer or layer 2 is considered the most complex layer among the other layers. This layer is often divided into sub layers called as Media Access Control (MAC) and Logical Link Control (LLC). The layers set up links across the Physical network. When this layer receives data from the Physical layer it checks for Transmission errors and then packages the Data frames from their this layer manages the physical addressing methods for the MAC or LLC layers.
The Data Link Layer then passes the data to the final layer present in OSI model which is the Physical Layer.
The Physical Layer:
The Physical Layer or layer 1 is the electrical or Physical layer of the model. This layer encompasses the network cables, card plugs, Cable Pinups, Wireless radio frequencies, connectors, Transceivers, Receives, repeaters, electric voltages etc. At the time of troubleshooting the problems this is typically the first place layer to start which checks is the device plugged in? Is the wireless card working? At this layer the model transmits the digital data from the source, sending devices, physical layer over network communication, media, which can be electrical, mechanical or radio to the receiving or destination devices physical layer.
The OSI model is a guide for developers to smooth the progress of developing communication products and software programs that will work in collaboration with the commonly established model. Once you understand the model you can then understand which protocols and devices would be compatible with one another?
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