An SD-WAN User Network Interface or SD-WAN UNI is the demarcation point between the responsibility of the Service Provider and the responsibility of the Subscriber. The SD-WAN UNI is on the boundary between the Subscriber Network and the Service Provider Network. The basic unit of transport at the SD-WAN UNI is the IP Packet.
Formally, the UNI is a reference point. The term UNI is often used to also refer to the network connection between the Subscriber Network and the Service Provider Network, but the actual location of the reference point is important because it defines where the Service Provider’s responsibility starts and also because service performance is defined from UNI to UNI.
MEF 70 Requirements:
An SD-WAN UNI MUST be dedicated to a single Subscriber.
An SD-WAN UNI MUST be dedicated to a single SD-WAN Service Provider.
An IP Packet that crosses the UNI from the Subscriber to the Service Provider is called an Ingress IP Packet, and the UNI is the Ingress UNI for that IP Packet. Similarly, an IP Packet that crosses the UNI from Service Provider to the Subscriber is called an Egress IP Packet, and the UNI is the Egress UNI for that IP Packet. These are shown in Figure 1:
Terminology warning: Since SD-WAN is an overlay service, the terms Ingress and Egress can also be (and often are) applied to IP packets crossing the Underlay Connectivity Service UNIs. This can create ambiguity and confusion. In this document their use only refers to packets crossing the SD-WAN UNI as shown in Figure 1.