When data communications started to invade the industry, equipment standardization was one of the main obstacles that investors faced. ISO and ITU-T faced this problem and proposed a protocol suite such that equipment manufacturing will be based on catering the requirements of the protocol such that a telecommunications company can utilize equipment of different providers. This set of standards has been dubbed Open Systems Interconnection and has seven layers.

The first layer called application is the one most visible to us. This layer details the execution or the job to be done and is written with a high-level language such as Java. This layer also details what form of succeeding protocols are to be used.

The second layer is the presentation layer. Ideally, this layer “gift-wraps” the data from the application layer. It provides data compression, conversion of high-level language into compatible form for next layer and data encryption.

The third layer is the session layer. This layer is responsible for network availability. Furthermore, it provides logical connection between entities such that data is transmitted securely between nodes. It also entails user authentication and network log-on and log-off. It determines what type of connection will be implemented. Session layer is characterized by synchronizing data flow for recovery and connection parameter negotiation.

The fourth layer, transport layer, ensures that data is reliably sent from one entity to another by administering signaling protocols, error checking and acknowledgment signals. Furthermore it also provides connection and connectioless-oriented services.

The fifth layer, network, is focused on routing data through multiple networks and subnetworks. It provides headers for the destination and source address if the data to be routed.

The sixth layer, data-link, manages the path of the data itself and ensures that data frames are synchronized and framed correctly. It also has the added feature of governing Ethernets.

The seventh layer, physical, manages the hardware or data communications equipment through which entitles communicate.

Posted 2010-12-14 and updated on Dec 14, 2010 6:11am by crisd

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