Hitachi US7070447-001 Examples of Layer 2 devices are bridges and switches, Layer 3 Network Layer

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Fundamentals of Networking

The LLC sublayer defines the logical connection to the upper layer services based on a socket or Service Access Point (SAP). This allows two processes on the same network to maintain a “logical connection” with each other for the purpose of data exchange.

Examples of Layer 2 devices are bridges and switches.

Layer 3: Network Layer

This layer is where the network provides its routing functionality. The Network Layer uses a packet to transport data from one network to another. A 32-bit address is used to define the network’s logical location and is referred to as the network address or IP address.

Examples of Layer 3 devices are routers.

Layer 4: Transport Layer

This layer ensures reliable delivery of data between networks. All error checking, acknowledgments, retransmissions, and data sequencing are handled by the Transport Layer.

Layer 5: Session Layer

This layer provides for the ability for two processes on two different stations to form a connection for the purpose of communication with one another. This is often referred to as a dialogue layer. Host-to-host communication is established, managed, and terminated at this layer.

Layer 6: Presentation Layer

This layer converts the actual data that is being transferred into a readable and proper form.

Layer 7: Applications Layer

This layer provides network-based services to a user’s application. The application layer communicates with the end user via programs such as file transfers (FTP, TFTP), electronic mail (SMTP), and other applications.

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