It 242 Osi Model

The OSI model relates to a network in multiple different ways but mainly through the lower 4 layers out of the 7 layers which make up the entire model. Out of the 7 layers that make up the OSI model a common network like WAN (Wide Area Connection) function mainly out of the lower three levels.

The three lower layers are the Physical (Layer 1), Data Link (Layer 2), and Network (Layer 3). Wan Protocols mainly operate in the lower two, the Data Link which is responsible for the transfer of data over the channel, and the Network which is responsible for addressing the routing between sub networks.

Two very common protocols that WAN might operate with is Point to Point protocol (PPP), and High-Level Data Link Control protocol (HDLC). HDLC is the protocol used to connect Point to Point serial devices. Point to Point in a WAN would be like two routers using a dedicated line connecting two routers together. TCP and UDP are other common protocols seen in layer four of the model.

The OSI layers that Routers and Switches operate on are layer 2-4.There are seven different layers in the OSI model. Routers reside in the lower three maybe four if you count the transporting protocol. Each layer has a different job, the first layer (physical) being the physical, which establishes your connection like your cables or other wiring. The second layer (data link) is where Switches and Ethernet operate at, third layer is where the IP address comes into play and routing protocols. The 4th layer (transportation) is the transportation of the message or data. Layers 5-7 are session presentation and application which basically finish out the connection and make it acceptable for the end user application. Layer 5 (session) establishes and manages the connection or terminates it. Layer 6 (Presentation) presents the data in a way that the end user will accept it in the final layer called the application layer, layer 7.

References

Schluting, Charlie. (January 13, 2005) The...