QoS Classification and Trust Boundaries
Trust boundaries are a critical element of the classification strategy of a QoS design.
Classification is the marking of packets so that the network core will know how to treat each packet as it comes along -- and it is a key component of a QoS design. This No Jitter Blog details QoS network design and discusses how to configure the endpoint to mark packet to have the network give each packet the right forwarding treatment in the network.
"Classification is a key component of a QoS design, and trust boundaries are a critical element of the classification strategy. Classification is the marking of packets so that the network core will know how to treat each packet as it comes along. Specific bits in the IP-header indicate the forwarding class of the packet, just like the priority stickers we put on packages that go in the mail. If the packet is a voice or video conferencing packet, it should have a priority sticker so it gets preferential treatment at each router hop along the path.
"The voice or video endpoint is usually capable of marking the packets, and the marking it uses is configurable so it will match the QoS design of the network. The endpoint is the right place to mark packets, because the endpoint is running the application and can easily distinguish between those packets that need preferential treatment (e.g. voice or video streams) and those that may need only a lower class of service (e.g. signaling packets) or no class of service (management, configuration or reporting interactions.) So it seems logical to configure the endpoint to mark packets, and then have the network use those markings to give each packet the right forwarding treatment in the network."