There is a large world of IT terms and jargon. This is just part one of a small section of terms that every computer networking specialist or IT student needs to know in order to break into the out shell of this world. I learned the OSI Model while working with an Internet Service Provider as a Network Specialist.
The OSI Model is a layered sectioning of what the packets or data that travel over networks or the Internet must go through in order to be successfully accepted and understood. Below is the OSI Model listed from the Top Layer, which is the beginning of the two way transmission, and ending with the most basic level.
7 – Application Layer: This layer of the OSI model is the main interface for users. Think of it as the graphical layer of the OSI Model. This layer deals with User Interfaces like Firefox, Internet Explorer, Microsoft Outlook and other email accounts, Telnet, and FTP clients. This just scratches the surface of the many applications that Layer 7 can handle.
6 – Presentation Layer: This layer is the translator for the Application layer. Data transmitted over the internet using TCP/IP is not readable by the average user. It translates that data into ASCII code, as an example. This layer can also do encryption and decryption of data.
5 – Session Layer: This layer handles the connections that need to be established in order for networking to take effect. In order for two computers over a large network to communicate, there has to be a trusted or at least agreed upon line of communication. These connections are known as TCP Session, or maybe UDP Sessions. Also, this layer deals with the concept of Port Numbering.
4 – Transport Layer: Before the information can even dream about being sent over an open connection, the two computers must be sure that the information will be sent in a reliable fashion. This layer does this job by making sure the data has a level of integrity. This also makes sure the two computers are using the same protocols, like UDP, TCP, or SCTP.
3 – Network Layer: The Networking layer deals with the addressing and routing protocols of the model. This is sometimes also known as the logical layer. This is where IP addresses are attached to and read from the packets. This is usually attached to an IP packet in the header section.
2 – Data Link Layer: Now we are down to the last two layers. The Data Link layer is the layer responsible for reliable transmission of data over a medium. These mediums can be Ethernet, Fiber, or Copper Phone Wire. This layer can deal with Flow Regulation, Error Detection, and the framing of the Packets.
1 – Physical Layer: We have reached the bottom layer of the OSI Model. This layer is the most primitive layer to computers. I am speaking of course about Binary. This layer translates each bit of data from the binary code into a beep, for Ethernet or other Copper transports, or flash of light.
It is important to remember that each layer relies on the one below it. Now, for a small example of how the OSI Model works, I will give you a scenario. If I want to send an email to one of my classmates, I would start with Layer 7 and, after clicking the send button my browser or client, the other layers would take effect.
The layers would work from 7 down to 1. This would assure the data is broken down into a format for the correct transmission of the data. Then when the other computer sends the data, the data gets built back up starting from 1 and ending at 7. My classmate would then be able to read my email. It is kind of hard to believe that this is all done in a matter of milliseconds!