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Posted By Azker

Network Layers (OSI Model) :: Explained [Part 2]

Have you missed the 1st part.. Read -> PART 1

Assuming you’ve read Part 01, I’m continuing to explain by expanding this article.. 🙂

Alright!! I hope you’ve got to learn something about OSI model as we now going to learn about the networking layers which defines this model. As I’ve explained, there are seven layers in this model. So, we will go through one by one with an example for you all to understand or to get a basic idea of what each layer does.

Network Layers (OSI Model)

[box] 01. Physical Layer – This is the very first layer which comes to play on a network layer as it detesmines the topology for the network. It also converts bits into electrical signals. This is the layer where DATA’s are physically moved across the DATA interface. It actually deals with the bits as explained (which means the 1’s & 0’s bits)…

Functions of a physical layer – Defines the physical topology for the network, Completely undertake the hardware requirements, Also does the encoding & decoding part, Then the DATA transmission & reception. [/box]

[box]02. Data Link Layer – This is the second layer which specifies the organization of data into frames and how to send frames over a network. As the DATA’s are seen as frames, there will be only a destination address and a source address in a frame. This can be named as a MAC address or a physical hardware address.

Functions of a Data link layer – providing physical address (MAC), Arbitration (media access control happens in this), Identifying encapsulated DATA’s, Error checking (by looking at the FCS field). [/box]

[box]03. Network Layer – This is the second layer which specifies addressing assignments and how packets are forwarded. Simply all the DATA’s transmitted in this layer is seen as packets. This layer is very important one, as we get to learn about IP addressing (IPv4 & IPv6) & it’s classes.  

Functions of a Network layer – assigning the network (IP) address to the packets, mapping the network (IP) to the physical address (MAC), determining the best path to the packets by using routings. [/box]

[box]04. Transport Layer – This layer sites between the network and session layer, and also it takes the responsibility to deliver messages between the network host. The transport layer also provides the acknowledgement of the successful data transmission and sends the next data if no errors occurred.

Functions of a Transport layer – Ensuring there is no loss of DATA’s (while transferring DATA’s there can be congestion..etc. Due to such reasons this layer guarantees end-to-end error free delivery of the entire message and not just a part of it). [/box]

[box]05. Session Layer – This layer defines on how to establish, synchronize, maintain & end the session. Basically, this layer controls dialogues between two processes by determining which can transmit & receive in a point during the communications.

Functions of a Transport layer – Determining the direction in which DATA flows as there are three type; simplex, half-duplex & full-duplex. [/box]

[box]06. Presentation Layer – Specifies how to represent data. This layer provides independence from data representation (e.g., encryption) by translating between application and network formats.

Functions of a Presentation layer – Does Translation (on the network if there are two different systems or type such as mac and unix; where the charactors sent to both PC’s are different, this layer represent DATA’s accordingly), Compressing DATA’s, Encrypting DATA’s using various securities. [/box]

[box]07. Application Layer – The last ever layer on the networking model. This specifies how a particular application uses a network. Or I could say, users are basically interacting with this layer as user-end applications are been used here.

Functions of a Presentation layer – nothing more than the user interactions, end-user applications are been circulated. [/box]


Note: This layers which were numbered from 1 – 7 has to go from bottom to top. Please refer the below screen for more….
[lbfenix img=”http://i985.photobucket.com/albums/ae337/darocker077/the-osi-reference-model.jpg”]


More… If you can identify or you remember the layers names, then here’s a simple sentence which can help you naming those layers simply from bottom to top.

All Proffesionals Should Take Note During Presentation

This explanation is the simplest explanation ever we can give you to understand the networking process. If you need more advanced than this, please refer wikipedia or any other websites by googling… We make things simply here.. so the users understand the scenarios, that is more than enough for us.

An IT professional living far away from the pearl of Indian ocean. A Telecom nomad moved towards networking & hospitality IT building elegant resort in the romantic island of Maldives. An open-source fanatic, a geek and yes! a minion fan. I prefer football & popcorn ^_^

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