Pre-Congestion Notification Problem Statement
Nortel Networks
DiffServ mechanisms have been developed to support Quality of Service (QoS). However, the level of assurance that can be provided with DiffServ without substantial over-provisioning is limited. Pre- Congestion Notification (PCN) investigates the use of per-flow admission control to provide the required service guarantees for the admitted traffic. While admission control will protect the QoS under normal operating conditions, an additional flow pre-emption mechanism is necessary in the times of heavy congestion (e.g. caused by route changes due to link or node failure). This document provides a problem statement on the addition of flow admission control and flow pre-emption functionality to a DiffServ network, in particular for the support of real time services such as voice and video.