What is a WAN?

A wide-area network (WAN) is the technology that connects your offices, data centers, cloud applications, and cloud storage together. It is called a wide-area network because it spans beyond a single building or large campus to include multiple locations spread across a specific geographic area, or even the world. For example, businesses with many international branch offices use a WAN to connect office networks together. The world’s largest WAN is the internet because it is a collection of many international networks that connect to each other. This article focuses on enterprise WANs and their uses and benefits.

What is the purpose of a WAN connection?

Wide-area networks (WANs) are the backbone of enterprise today. With the digitization of resources, companies use WANs to do the following:

  • Communicate using voice and video.
  • Share resources between employees and customers.
  • Access data storage and remotely back up data.
  • Connect to applications running in the cloud.
  • Run and host internal applications.

WAN technology innovations help organizations access information in a secure, fast, and reliable way. WANs are important for business productivity and continuity.

What is WAN architecture?

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.

What are WAN protocols?

Wide-area network (WAN) protocols, or networking protocols, define the rules of communication across any network. The following are some examples:

Frame relay

Frame relay is an early technology that packages data in the form of frames and transmits it over a private line to a frame relay node. Frame relay works on layers 1 and 2 and facilitates information transfer from one LAN to another over multiple switches and routers.

Asynchronous transfer mode

Asynchronous Transfer Mode (ATM) is also an early WAN technology that formats data into 53-byte data cells. ATM network devices use time-division multiplexing, which converts digital signals into fixed-sized cells, transmits them, and then reassembles them at their destination.

Packet over SONET/SDH

Packet over SONET/SDH (POS) is a communication protocol that defines how point-to-point links communicate when using optical fiber.


The Transmission Control Protocol/Internet Protocol (TCP/IP) defines end-to-end communication by specifying how data should be packetized, addressed, transmitted, routed, and received. IPv6 is the latest version of the most commonly used method.

What are local area networks?

Local area networks (LANs) are the building blocks of a WAN. A LAN consists of interconnected computers and other devices limited to a small place, such as a building, school, or office.


LANs are smaller networks with limited capacity but higher speeds. They are easier and more cost effective to design, set up, and manage. They are private networks that typically use a single connection technology.

On the other hand, WANs connect LANs together. A single WAN can have many different types of networking technologies to communicate across LANs. Its communication speed is slow, but its capacity is high. Because a WAN is a large network, you may find it more complex to set up and manage.

How does a WAN work?

Enterprises have resources running in different on-premises data centers, branch offices, and virtual private clouds (VPCs). To connect these resources, enterprises use multiple network connections and internet services. Since companies cannot build their own network infrastructure across multiple geographical boundaries, they typically rent it from a third-party service provider.

The following are some common types of connections:

Leased lines

A leased line is a direct network connection that you can rent from a large network provider, such as an ISP. It can connect two LAN endpoints together. Leased lines are not necessarily physical lines. They may be virtual connections that the service providers implement over other network infrastructure.


Tunneling is a way to encrypt data packets as they move over the public internet. In tunneling, you use an internet connection to access enterprise servers in another country. But you send them as encapsulated packets, forming your own virtual private network (VPN).

Multiprotocol label switching

Multiprotocol Label Switching (MPLS) is a technique that routes data traffic based on predetermined labels. It attempts to route critical data traffic across shorter or faster network paths, improving network performance. It works between Open Systems Interconnection (OSI) layers 2 and 3. You can use it to create a unified network across existing infrastructure, such as IPv6, frame relay, ATM, or ethernet. You can use MPLS leased lines or MPLS with VPNs to create efficient and secure networks.

Software-defined WAN

Software-defined wide-area network (SD-WAN) is the further evolution of MPLS technology. It abstracts the MPLS functions into a software layer. Because SD-WAN works over commodity broadband internet connections, it can often reduce networking costs and provide greater flexibility than a fixed connection.


MPLS can slow down cloud integration because it routes traffic through corporate headquarters, which act as central choke points. On the other hand, SD-WAN is cloud-aware and integrates much better with modern cloud infrastructure. SD-WAN is also cost effective. It can work over MPLS so you can use bandwidth more efficiently on expensive MPLS lease lines.

What is WAN optimization?

Wide-area network (WAN) optimization is a collection of techniques that improve WAN performance metrics such as throughput, congestion, and latency. WAN design, technology choices, and traffic flow arrangements all affect WAN performance. The following are some common techniques for WAN optimization.

Traffic flow management

Traffic flow management includes techniques that minimize the amount of data sent over the network. Here are some examples:

  • Caching frequently stored information on local servers
  • Identifying and eliminating redundant data copies for data backup and disaster recovery applications
  • Compressing or zipping data files

Protocol acceleration

Some WAN protocols are chatty—that is, they may require a lot of back-and-forth data communication for a single request. For example, both client and server may send acknowledgment data back to confirm that they have received data. Protocol acceleration bundles chatty protocol communications to lower the number of data packets on the network.

Rate and connection limits

Network administrators can limit the number of open internet access links, the number of users, and the amount of bandwidth each user can access at a time. For example, they can set rules to prevent employees from streaming videos on the enterprise WAN.

Network segmentation

Traffic shaping controls data flow for specific applications, which divides network bandwidth optimally between applications. The network operator can choose to prioritize certain critical applications to improve their performance.

How can AWS help you with WAN management?

AWS Cloud WAN is a fully managed service to build, manage, and monitor your global wide-area networks (WANs). It provides a central dashboard for making connections between your branch offices, data centers, and virtual private clouds (VPCs) in just a few clicks. It generates a complete view of your on-premises and AWS networks to help you monitor network health, security, and performance. You can also use network policies to automate network management and security tasks from one location.

You gain these benefits:

  • Use your choice of local network providers to connect to AWS, and then use the AWS global network to connect your locations and VPCs.
  • Save time by automating routine networking tasks, such as adding new connections, branch locations, and VPCs.
  • Track network traffic, view the health of your network, improve performance, and minimize downtime.

Get started with Cloud WAN by creating an AWS account today.

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