What is a WAN? Wide-area network definition and examples

WANs connect smaller networks across long distances, and their architecture, protocols and technologies have evolved to their latest incarnation, SD-WAN.

Wide-area networks: What WANs are and where they’re headed
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People want to connect to all of their apps all of the time from all of their devices no matter where they are. And they pretty much can, thanks to wide-area networks (WANs).

At its core, a WAN is a network of networks. The Internet itself is a giant WAN, and how you connect to it can be as diverse as through an Ethernet cable, coaxial cable, or a cellular radio signal.

Your office network, home Wi-Fi, cellphone, smartwatch, doorbell camera and vehicle-based Internet connection are just endpoints on a vast global WAN that is constantly evolving to carry more traffic, and to carry that traffic faster as the demands for near-instantaneous access to resources increase.

How is a WAN different from a LAN?

A Local Area Network (LAN) is confined to a relatively small area. In the business world, LANs are generally limited to a single building or a small campus. In a LAN topology, all the devices that end users need to access are connected by switches and routers. Your home Wi-Fi is also a LAN, where you can connect multiple devices, including laptops, desktops, printers and smart home devices via a central router.

When your network requires access to resources that are not available on the LAN, an external link is added to the router. So, while a LAN connects you to local resources on your network, a WAN connects multiple networks together to share resources.]

In the case of a company that has a corporate headquarters and multiple branch offices scattered around the world, the WAN connects multiple LANs, While LANs typically connect end users through Ethernet technology, WANs can employ a variety of transport methods.

What is a private WAN?

LANs are typically maintained by an organization’s IT staff, but WANs are typically reliant on physical connections provided by the major telecommunication carriers. There are different ways to transport WAN data, each with benefits, drawbacks, and costs.

A private WAN is implemented with leased data lines. The service provider maintains the network (through multiple interconnects and vendors, if necessary) to create a continuous link between the network endpoints. Leased lines provide consistent symmetric upload and download speeds. Since the service provider reserves specific infrastructure for a private WAN, it is usually the most expensive option. Should there be damage at any point in the link you will likely see an interruption in service, making it necessary for you to plan for redundancy.

What is a cloud WAN?

As employees moved to remote locations and applications moved to the cloud, organizations began shifting to a cloud-based WAN approach that takes advantage of a mesh of networks to provide highly redundant connectivity anywhere in the world.

For example, Amazon offers AWS Cloud WAN, a managed service that customers can use to build and manage a global network that connects resources running across your cloud and on-premises environments, including branch offices, data centers, and Amazon Virtual Private Clouds (VPCs).

What is an MPLS WAN?

An MPLS network is managed end-to-end by a single service provider such as Verizon or AT&T, using an already existing set of physical networks to create a virtual path through them. The Transmission Control Protocol/Internet Protocol suite (TCP/IP) breaks the data stream into smaller chunks, or packets, that are sent independently and reassembled at the destination endpoints of the network.

Each packet contains a payload and an identifying header that includes destination and reassembly information. Every packet is verified at the destination and, if successful, an acknowledgment is returned to the sender. Should verification fail, a request is sent back to the point of origin to be re-transmitted.

Data packets on an MPLS network are labeled and routed based on that pre-defined path for fast transport speeds across the network. An MPLS cloud uses multiple physical networks and is able to change routes to take advantage of the best bandwidth or to bypass problems. Traffic can be shaped through Quality of Service (QoS) parameters, such as video and Voice over IP Telephony (VoIP), to improve performance by application. While less expensive than leased lines in a Private WAN, MPLS can be expensive compared to connecting directly to the internet.

What is an internet-based WAN?

Instead of paying a premium for a leased line or MPLS connection, organizations can also simply connect directly to the internet through an Internet Service Provider (ISP).

A straight internet connection gives you access to the vast number of network nodes that comprise the largest WAN ever built. The downside is that there is no specific authority controlling the quality and reliability of the data path through the internet.

Data packets must be inspected for destination addresses at each routing hop and are delivered on a best-effort basis. This is fine for many applications such as emails that do not have issues with latency between the sender and receiver, but could be problematic for apps that require low latency.

Also, since the internet is a distributed public network, there is a greater chance of data packets passing through the servers of bad actors looking to collect or corrupt your data. Unlike MPLS or leased lines, it is critical to use encryption on all traffic.

The internet is ubiquitous and readily available from multiple sources, making it the cheapest option available to build your WAN upon.

What is a managed cloud WAN?

Vendors are also offering managed cloud WAN services, which include global connectivity, the ability to set policies for the entire global network from a single policy control point and a single management dashboard that allows organizations to monitor WAN features such as connectivity, routing, performance, access control and applications. A managed cloud WAN enables organizations to connect all on-prem sites and branch offices.

What is a wireless WAN?

A wireless WAN deploys cellular broadband radio devices to connect with a series of radio towers, referred to as cells, which act as base stations to convert the wireless data packets that travel across private or cloud WANs. (It is also possible to connect multiple devices to perform point-to-point communication using a wireless transportation layer.)

The wireless network infrastructure is designed to support millions of connections across a nationwide footprint. As the endpoint transceiver passes beyond the range of a cell, the network automatically hands the connection off to the next, providing uninterrupted connectivity. Since the cellular network is already established, a wireless WAN can be deployed quickly and relatively inexpensively.

One of the more common uses for this type of WAN is to connect Internet of Things (IoT) devices that collect and process data. For example, the parking meter you pay is connected via a wireless WAN to collect your payment and check your authorization to stay in the space. As newer 5G technology rolls out, its higher bandwidth promises to allow mission-critical data exchanges, such as those used by self-driving cars.

What does the modern WAN architecture look like?

It is important to understand the type of data you are working with on your WAN. You will build something different if transporting highly sensitive or low latency-dependent data.

At the WAN’s core, you will have connections from all the differing types of transports that allow traffic to route where it is most efficient and cost-effective. If you need highly secure, fast, and consistent connectivity, a private WAN should be an option.

For most of your traffic that requires reliable data delivery, such as content delivery, VoIP, or video conferencing, an MPLS connection will provide a secure, redundant, and consistent connection less expensively than with a leased Line. You will also be able to shape your network traffic by assigning QoS parameters to ensure that critical services get priority.

Finally, add Internet connectivity to direct your non-critical traffic to the lowest-cost route available. It also opens you to allowing user connectivity from anywhere through tunneling. The most common tunnel is the Virtual Private Network (VPN). VPN connections encrypt data to keep it private as it travels over public networks like the internet.

You can also establish a point-to-point VPN connection to act as a redundant link for leased lines as an inexpensive insurance policy in the event of service disruptions. The VPN is encrypted and, while slower, will provide a temporary solution in a disaster.

Sitting between the internet and your network will be a firewall that blocks any traffic that you haven’t explicitly allowed; an extra layer of protection on top of the VPN.

Wireless connectivity into your WAN will come from endpoints needing to connect over a cellular network, such as a smartphone accessing an application through a secured website or by first connecting to a VPN that allows access to resources such as database servers or storage devices.

WAN management and optimization

The speed of light limits the speed of data across the WAN, as data packets travel on fiberoptic cables. The greater the distance between the endpoints, the longer it takes data to make the trip, and while a few hundred milliseconds seem like nothing to us humans, they are an eternity to modern computing infrastructures.

It is also worth noting that while things seem to be happening simultaneously on the network, data packets are actually moving sequentially along the wire. As more devices use the network, problems such as congestion and dropped packets can introduce performance problems.

WAN optimization addresses these problems with features such as deduplication (reducing redundant data transmission), compression (reducing the size of data), and caching (storing commonly used data closer to the endpoint).

A technique called traffic shaping establishes QoS parameters that prioritize network packets for time-sensitive applications such as voice and video over less time-sensitive traffic such as email, thus improving overall performance.

What is SD-WAN?

WAN management is both a time consuming and labor intensive effort. Software-defined WAN ( SD-WAN) helps by employing software to monitor the performance of all available WAN connections and choosing the most efficient route by traffic type.

For example, smooth video playback requires that packets be delivered in order. Putting this traffic on a busy link like the internet can slow the delivery of packets, so SD-WAN would direct these packets over the leased line or MPLS.

Email, which is not subject to poor user experience if packets arrive later, can use the public Internet. SD-WAN software accounts for each type of link and shifts the traffic to the best path based on cost and performance characteristics.

SD-WAN technology is a critical component of any networking strategy, with a $3.25 billion market in 2021 that is expected to grow 30% in 2022, according to DataVagyanik, a market intelligence firm.

Future of WANs

WAN technology has come a long way since the early days of circuit-switched telephone lines and 2400 baud modems. Today, leased lines, wireless, MPLS, and the public internet makes it possible for you to videoconference on demand from your telephone to anyone around the world, backup your data to another city, manage the operations of a self-driving vehicle, and work from any place you can get a radio signal.

WANs aren’t just limited to Earth. NASA and other space agencies are working to create a reliable "interplanetary internet," which aims to transmit test messages between the International Space Station and ground stations. The Disruption Tolerant Networking (DTN) program is the first step in providing an internet-like structure for communications between space-based devices, including communicating between the Earth and Moon, or other planets.

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