Juniper Certification | JNCIA-Enterprise Routing & Switching | Day-2 OSI Model

OSI Model

Now we will move on to OSI model reference that is Open System Interconnection these networks that provides guide lines that provides to communicate with computers over network. These are not specific procedure or protocols because these functioning by step by step process that must be completed at each layer that the computer communicate over a network.

Physical Layer

The lowest layer of the OSI Model is concerned with electrically or optically transmitting raw unstructured data bits across the network from the physical layer of the sending device to the physical layer of the receiving device. It can include specifications such as voltages,  pin layout, cabling, and radio frequencies. At the physical layer, one might find “physical” resources such as network hubs, cabling, repeaters, network adapters or modems.

Data Link Layer

At the data link layer, directly connected nodes are used to perform node-to-node data transfer where data is packaged into frames. The data link layer also corrects errors that may have occurred at the physical layer.

The data link layer encompasses two sub-layers of its own. The first, media access control (MAC), provides flow control and multiplexing for device transmissions over a network. The second, the logical link control (LLC), provides flow and error control over the physical medium as well as identifies line protocols.

Network Layer

The network layer is responsible for receiving frames from the data link layer, and delivering them to their intended destinations among based on the addresses contained inside the frame. The network layer finds the destination by using logical addresses, such as IP (internet protocol). At this layer, routers are a crucial component used to quite literally route information where it needs to go between networks.

Transport Layer

The transport layer manages the delivery and error checking of data packets. It regulates the size, sequencing, and ultimately the transfer of data between systems and hosts. One of the most common examples of the transport layer is TCP or the Transmission Control Protocol.

Session Layer

The session layer controls the conversations between different computers. A session or connection between machines is set up, managed, and termed at layer 5. Session layer services also include authentication and re-connections.

Presentation Layer

The presentation layer formats or translates data for the application layer based on the syntax or semantics that the application accepts. Because of this, it at times also called the syntax layer. This layer can also handle the encryption and decryption required by the application layer.

Application Layer

At this layer, both the end user and the application layer interact directly with the software application. This layer sees network services provided to end-user applications such as a web browser or Office 365. The application layer identifies communication partners, resource availability, and synchronizes communication.

These 7 layers that are like set of building blocks are arranged in order and in fact that these seven layers are also we can say as "network stack". Like this game shown below ;

 

Network Protocol

This process of communication are done when it is actual communication occurs. A protocol has a formal set of rules or procedures that computers must understand, accept and use also able to talk to each other over network. When it comes to OSI model that how a data should flow down the model or stack. When a lower case says something to upper case that an information or package as data which carries and adds to it's own header and if needed a footer. We understand that how a network logically organized or designed..
   
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