The CVG, when processing a packet, is able to apply a variety of different policy controls to determine how the packet should be transmitted. These policy controls include selecting which interface a packet should be sent on, when a packet should be dropped, or when a packet should be duplicated. Examples of packet rules include:
- Prefer Wi-Fi: A packet may be routed over Wi-Fi, if the packet is part of a low priority flow which is not allowed to use the expensive mobile radio.
- Duplicate: A packet may be duplicated across all available interfaces, including Wi-Fi, 3G/LTE, plus any connected VehicleLink phones, if the packet is part of a critical flow (for example, a safety message indicating that the car has been in a collision).
- Discard: A packet may be dropped, if the packet is part of a low priority TCP flow, and there is not enough capacity for the existing high priority flows. In such a case the dropping of a few TCP packets will cause the TCP flows to back off (due to the behaviour of TCP), increasing the amount of the link that is available for the high priority flows.
These are just a few of the many possible ways to combine the policy actions of the CVG to implement Quality of Service while managing data flows intelligently.