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),
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.
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.