Wide-Area Networks

A wide-area network (WAN)  is essentially a network of networks: a collection of LANs or other networks that communicate with one another. Today, there are several types of WANs that touch virtually every aspect of modern life. The internet as a whole is a huge, international WAN.

Data transmission takes place via packet switching whereby  a message is broken into several parts, called packets, that are sent independently, in triplicate, over whatever route is optimum for each packet and reassembled at the destination. A router is a networking device typically used to interconnect LANs to form a wide area network (WAN) and as such is referred to as a WAN device. IP routers use IP addresses to determine where to forward packets. An IP address is a numeric label as

The first known WAN was created by the U.S. Air Force in the late 1950s to interconnect sites in the Semi-Automatic Ground Environment (SAGE) radar defense system. An enormous network of dedicated phone lines, telephones, and modems linked the sites together.

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 network to implement TCP/IP protocol suite. This began by interconnecting the University of California, Los Angeles (UCLA), the Stanford Research Institute (now SRI International), the University of California, Santa Barbara (UCSB), and the University of Utah.

• X.25: In the 1970’s, the International Telegraph and Telephone Consultative Committee (CCITT, now ITU-T) developed the X.25 protocol. It is the oldest packet-switched data communication protocol (method to group data into packets) and was used until 2015. It uses a point-to-point architecture that served to connect remote terminals to mainframes. It operated over analog channels leased from telephone companies.
• Frame Relay: In the 1980’s, Frame Relay became an alternative to X.25 providing increasing speed. By improving voice and video performance, it was largely adopted by enterprises in the US while X.25 remained the standard in Europe. Frame Relay transmits data in variable-size units called “frames” over a virtual circuit-based connection. It does not perform any error correction such as retransmission of data, and leaves error checks to terminals. If an error is detected, the packet is simply dropped.
• ATM: Asynchronous Transfer Mode or ATM was developed in the late 1980’s and early 1990’s. It differs from Frame Relay by transferring fixed size cells (53 bytes). Also, ATM provided error correction unlike Frame Relay and was faster (up to 622 Mbps compared to 45 Mbps for Frame Relay). However, ATM didn’t get the expected success due to the better price performance of internet-protocol based products as well as the size of cells (53 bytes) that was not efficient.
• MPLS: Multiprotocol Label Switching (MPLS) was developed in the late 1990’s as a more flexible and scalable alternative to ATM. MPLS routes packets based on labels and not IP addresses. It can be used with any networking protocol, including Ethernet, ATM, and Frame Relay. Even though MPLS provides scalability and performance, it fails shorts to support modern cloud architectures as SaaS traffic needs to be backhauled to the data center for security inspection, impacting application performance.
• SD-WAN: Developed in the 2010’s, it can combine heterogeneous links, including MPLS, broadband internet and 5G through network virtualization, providing redundancy and improved performance. It allows organizations to reduce MPLS dependency by leveraging low-cost internet connections. With SD-WAN, branch offices can also better manage SaaS traffic by avoiding sending cloud traffic back to the data center. SD-WAN is also part of SASE (Secure Access Service Edge), ensuring secure access to cloud applications, from anywhere and any device.

Software-defined WAN (SD-WAN) is an approach for making WAN architectures easier to deploy, operate, and manage. It relies on virtualisation, application-level policies and overlay networks, and onsite SD-WAN devices and software platforms.

Latency and bandwidth constraints often cause performance issues in enterprise WANs. WAN optimisation use a variety of techniques, including deduplication, compression, protocol optimization, traffic shaping, and local caching. These techniques improve packet delivery and traffic control, in turn allowing network bandwidth to grow or shrink dynamically as needed.

SD-WAN technology and WAN optimisation can be used separately or together. Some SD-WAN vendors are adding WAN optimisation features to their products.

A WAN router, also known as an edge router or border router is a device that routes data packets between WAN locations, giving an enterprise access to a carrier network.  Several WAN protocols have been developed over time, including Multiprotocol Label Switching (MPLS), ATM, and Frame Relay.

Packet switching is a method of data transmission in which a message is broken into several parts, called packets, that are sent independently, in triplicate, over whatever route is optimum for each packet, and reassembled at the destination.

TCP/IP stands for Transmission Control Protocol/Internet Protocol. It is a protocol suite of foundational communication protocols used to interconnect network devices on today’s Internet and other computer/device networks.