Seven Layers OSI

The seven layers of networking is sometimes referred to the OSI Model, Open System Interconnection. Networking is broken down by traveling through several layers or protocols. This process is broken down into seven layers; Application Layer, Presentation Layer, Session Layer, Transport Layer, Network Layer, Data Link Layer, and Physical Layer. When a person communicates to another person on a network the information passes through these layers. It begins at the Application Layer, works its way through to the Physical Layer and then back up to the Application Layer.

(7) Application Layer- This layer is where the end-user (computer user) begins the communication process. At this layer user authentication is identified and protocols like FTP, TELNET, E-MAIL, and other file transfer protocols begin with the user starting the process.

(6) Presentation Layer - This layer is where encryption occurs. This layer converts the file and/or information into a language (format) that the remaining layers can read and handle without any compatibility problems.

(5) Session Layer - This layer is where the communication is coordinated. Applications are managed in this layer. This layer manages the exchange of information by creating and terminating all communication between the application layer at both ends.

(4) Transport Layer - This layer is responsible for ensuring the data completes it's transmission to the other user. It's also responsible for flow control and error recovery.

(3) Network Layer - This layer is where the routing and switching takes place. Packet sequencing, addressing, congestion control, and internetworking happen at this layer. Logical paths are created at this level to allow users to communicate to each other. This layer utilizes IP addresses.

(2) Data Link Layer - This layer is where packets (information) is broken into bits through encoding and decoding. At this layer you have two sections; Media Access Control (MAC), and Logical Link Control (LLC). The MAC section is where packets (information) is gathered and gets permission to transmit the data. The MAC section is where your computer's MAC address is located to allow proper delivery to a specific system (computer). The LLC section controls synchronization, flow control, and error checking.

(1) Physical Layer - This layer is where your hardware such as ethernet cable, Network Interface Cards, etc., provide the transmission through electrical impulse, light, and radio waves. This layer is the hardware means of sending and receiving data (information).