OSI Model (Continued) - Network+ Certification Tutorial

Transport Layer

The Transport Layer provides reliable communications. It is responsible for ensuring session establishment and tear-down of virtual circuits, and hides the details of the network from the higher layers. Data at the Transport Layer is split into Segments. The corresponding devices are gateways.

Network Layer

The Network Layer provides the method for addressing and routing data through an internetwork. It routes data from one node to another. This is accomplished using logical addressing (as opposed to physical addressing). The corresponding devices are routers.

Data Link Layer

The Data Link Layer provides reliable error-free transfer of data across a physical network link. It also specifies the topology (such as Ethernet or Token Ring) and frames data accordingly.

The MAC (Media Access Control) address is involved in this layer. Data at his Layer is split into frames. The corresponding devices are bridges and switches.

Physical Layer

The Physical Layer manages the data onto the network media and taking it off. It is where the sending and receiving of bits takes place. It is where communication is direct with the communication media.

The Physical Layer specifications define characteristics such as voltage levels, changes of voltages, physical data rates, and physical connectors. The corresponding devices are hubs, repeaters, amplifiers, and transceivers.

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