When one or more of the Underlay Connectivity Services in an SD-WAN Service is an Internet Service, some Application Flows can be forwarded directly to the Internet rather than delivered to another SD-WAN UNI. This capability is called Internet Breakout and it is assigned to an Application Flow by Policy (see section 8.5.4). The most common case is for the Application Flow to be forwarded to an Internet UCS that is connected to the SD-WAN Edge where the Ingress UNI (for the IP Packet) is located. This is called Local Internet Breakout.
An example of Local Internet Breakout is shown in Figure 4. An ingress IP Packet at site B is forwarded across the UCS UNI for UCS #1 (the Internet), but instead of being sent over one of the TVCs, it is forwarded directly to an Internet-connected destination.
Figure 4 – Local Internet Breakout
If an Application Flow is assigned a Policy that indicates Internet Breakout and access to the Internet is not available at the SD-WAN Edge containing the Ingress UNI for the IP Packet, the Service Provider may deliver the packet over a TVC to another SD-WAN Edge for "breakout" to the Internet, but this is outside the scope of this document.
A UCS, such as an Internet UCS, is a service with a subscriber and a provider, and it is likely that there are service parameters that are agreed on by those parties, but that service agreement is separate from the SD-WAN Service agreement. Therefore, there is no need for the SD-WAN Subscriber and the SD-WAN Service Provider to agree on any SD-WAN Service Attribute values for the Internet Access Service (beyond the Application Flow recognition and Policy assignment). However, there are Internet Service parameters that need to be exchanged between the SD-WAN Subscriber and the SD-WAN Service Provider such as: