Wide Area Networks

- Overview

In its simplest form, a wide area network (WAN) is a collection of local area networks (LANs) or other networks that communicate with each other. A WAN is essentially a network of networks, and the Internet is the world's largest WAN.

A WAN is a computer network that connects multiple locations over a large geographic area, such as a city, country, or even the entire world. A WAN is made up of smaller networks, such as LANs, that allow devices in different locations to communicate with each other.

Businesses and governments use WANs to connect offices, data centers, and other sites that are far apart. They provide organizations with important functions such as resource sharing, data exchange, and centralized application access.

The Internet is the world's largest WAN, made up of many interconnected international networks. Your modem uses its WAN port to send and receive information over the Internet.

- How Did WANs Begin?

The first known wide area network was created by the United States Air Force in the late 1950s to connect sites in the Semi-Automatic Ground Environment (SAGE) radar defense system. A vast network of dedicated telephone lines, phones, and modems connected these sites together.

The foundation of the IP-based Internet began with the Advanced Research Projects Agency Network (ARPANET), the first wide area packet switching network with distributed control and the first to implement the TCP/IP protocol suite.

ARPANET initially connected the University of California, Los Angeles (UCLA), Stanford Research Institute (now SRI International), the University of California, Santa Barbara (UCSB), and the University of Utah.

- Traditional WANs

A wide area network (WAN) is a telecommunications network that extends over a large geographical distance for the primary purpose of computer networking. WANs are often established with leased telecommunication circuits. Business, education and government entities use WANs to relay data to staff, students, clients, buyers, and suppliers from various locations across the world. In essence, this mode of telecommunication allows a business to effectively carry out its daily function regardless of location. 

Many technologies are available for WAN links. Examples include circuit-switched telephone lines, radio wave transmission, and optical fiber. New developments in technologies have successively increased transmission rates. However, the traditional WAN function was to connect users at the branch or campus to applications hosted on servers in the data center. This doesn't work in a cloud-centric world.

WANs face important operational challenges, including network congestion, packet delay variation, packet loss, and even service outages. Modern applications such as VoIP calling, videoconferencing, streaming media, and virtualized applications and desktops require low latency. 

Bandwidth requirements are also increasing, especially for applications featuring high-definition video. It can be expensive and difficult to expand WAN capability, with corresponding difficulties related to network management and troubleshooting.

- The Challenges in Traditional WAN

Traditional WANs face challenges like: high cost due to dedicated leased lines, complex configuration and management, limited flexibility to adapt to changing network demands, poor performance for cloud applications due to static routing, difficulty in troubleshooting issues, and potential security vulnerabilities due to reliance on static configurations.

Essentially, they struggle to efficiently manage traffic across diverse locations with dynamic needs, often resulting in high latency and suboptimal application performance.

Key problems about traditional WAN challenges:

• Static Routing: Traditional WANs often use static routing, meaning routes are manually set and cannot adjust dynamically based on network conditions, which can lead to inefficient traffic flow and delays.
• Limited Bandwidth Management: Difficulty in prioritizing critical traffic, causing congestion and impacting performance for important applications.
• High Cost: Relying on dedicated leased lines can be expensive, especially when scaling to multiple locations.
• Complex Management: Manual configuration and troubleshooting of network devices across different sites can be time-consuming and challenging.
• Poor Cloud Integration: Inefficient routing for cloud-based applications due to static configurations, resulting in latency issues.
• Security Concerns: Potential vulnerabilities arise from static configurations and limited visibility into network traffic.

One major problem with Traditional WANs is the lack of oversight of the traffic moving through a network, which means high-value tasks could experience latency because they're competing for capacity with low-value tasks.

- Different Types of WAN Technologies

• Circuit-switched: Creates a dedicated physical connection between two endpoints for a communication session
• Packet-switched: A type of WAN technology
• Cell-switched: A type of WAN technology
• Leased line WAN: A private connection between two sites for reliable data transfer
• MPLS: Routes traffic based on labels rather than IP addresses
• Point-to-point protocol: A type of WAN technology
• Ethernet private line (EPL): A type of WAN technology
• Metro Ethernet: A point-to-point Ethernet data networking service that connects locations within a metropolitan area
• Ethernet over Synchronous Optical Network (SONET): A secure point-to-point WAN connectivity technology
• Dedicated internet access (DIA) WAN: A high-speed, private connection between a physical location and the internet
• Broadband internet WAN: A shared connection that distributes bandwidth among all users

A WAN connects offices, data centers, cloud applications, and cloud storage together across a geographic area or the world. The internet is a common example of a public WAN, which connects devices belonging to different organizations.