This framework defines a method of providing Explicit Congestion Control to real-time inelastic traffic like voice and video through the use of session admission control and preemption mechanisms. This approach uses the Pre-Congestion Notification Marking (PCN) 
mechanism. PCN marking is deployed in routers to measure and convey two levels of onset of congestion with the SIP controlled endpoints responding to the marking. This approach is different from what is defined in An edge-to-edge Deployment Model for Pre-Congestion Notification , as here the admission and preemption control function resides in the application (either in the endpoint or the application server that controls the endpoint. This framework is focused on using Session Initiated Protocol (SIP) as the application signaling protocol but other application signaling protocols could be extended for this purpose.
|Publisher||Internet Engineering Task Force (IETF)|