What is WAN? – Wide Area Network Explained – AWS

Wide-area network (WAN) architectures are based on the Open Systems Interconnection (OSI) model that conceptually defines and standardizes all telecommunication. The OSI model visualizes any computer network to work in seven layers. Different networking technologies operate on each of these different layers and together make a working WAN.

We will show you these layers in a top-down approach and provide an example to help you understand them:

Layer 7 – Application layer

The application layer is closest to the user and defines how the user interacts with the network. It contains the application logic and is unaware of the network implementation. For example, if you have a calendar booking system in your enterprise, this layer manages booking logic such as sending invitations, converting time zones, and more.

Layer 6 – Presentation layer

The presentation layer prepares data for transmission across the network. For example, it adds some encryption so that cybercriminals watching your WAN can’t hack your sensitive meeting data.

Layer 5 – Session layer

The session layer manages the connections or sessions between local and remote applications. It can open, close, or terminate the connection between two devices. For example, your booking system is located on a web server in the central office, and you are working from home. The session layer opens a connection between your computer and the web server after authentication. This connection is a logical connection, not an actual physical connection.

Layer 4 – Transport layer

The transport layer defines the functions and procedures for data transmission. It classifies and dispatches the data for transfer. It may also package the data into data packets. For example, when you visit the booking site, the Transmission Control Protocol (TCP) manages communication by sorting it into request and response packets.

Layer 3 – Network layer

The network layer manages how the data packets travel through the network. For example, it defines the rules for packet routing, load balancing, and packet loss.

Layer 2 – Data link layer

The data link layer is responsible for establishing communication rules or protocols on the physical layer operations. For example, it decides when to start or terminate a direct connection. This layer function forwards packets from one device to another until they reach their destination.

Layer 1 – Physical layer

The physical layer manages the transfer of raw data in the form of digital bits, optical signals, or electromagnetic waves across the different network transmission media, such as optical fibers and wireless technologies.