An SD-WAN (Software-Defined Wide Area Network) is a category of solutions that enables central management of wide area networks (WANs).
SD-WANs are based on the concept of software-defined networking (SDN), which presumes that network management does not depend on data transmission technologies or specific network devices, but rather relies on application-aware policies.
What are wide area networks (WANs)?
WANs are networks that extend over large areas and provide a connection between geographically distant objects. For example, the Internet is a WAN because it joins users from all over the world. A network of a business that has subsidiaries in several cities and corporate cloud services is also a WAN. In traditional WANs, local network devices manage traffic.
How SD-WANs work
SD-WAN solutions are virtual networks built on the communication channels that transmit data between remote nodes of the WAN (for example, between a company’s subsidiaries).
The data-transmission technologies SD-WANs support include:
- Wireless (3G, 4G LTE, and 5G),
- Satellite,
- Fiber-optic,
- Cable,
and combinations thereof; and they enable the quick redistribution of traffic among those technologies so as to balance load and fulfill other needs. SD-WAN solutions also support the combination of various data transmission standards, including IP, MPLS, ATM, and others; and they can direct traffic through dedicated communication channels as well as through public communication channels such as the Internet.
SD-WAN architecture
The Metro Ethernet Forum (MEF), as part of the MEF 70 standard, which outlines the requirements for the SD-WAN category of services, details the following service components:
- SD-WAN UNI (SD-WAN User Network Interface): The demarcation point between an organization’s local network and its SD-WAN service provider’s area of responsibility;
- Underlay Connectivity Services (UCS): The connectivity services used by the SD-WAN. UCSs include communication channels such as Ethernet and wireless Internet, data transmission technologies such as MPLS, and so on. An SD-WAN provider can give a customer access to its UCSs or use the customer’s infrastructure;
- SD-WAN Edge: The network functions that connect the SD-WAN UNI and UCS;
- SD-WAN Virtual Connection (SWVC): A logical network that brings together the organization’s various SD-WAN UNIs;
- SD-WAN Virtual Connection End Point: The location where the policies controlling the application data flows are applied;
- Tunnel Virtual Connection (TVC): Data transmission paths using various UCSs.