QoS support in IP multimedia subsystem using DiffServ

IP multimedia subsystem (IMS) is a 3GPP Rel. 5 standardized control domain for multimedia services. The IMS is an application environment that uses the PS domain as a bearer service. In this paper UMTS packet switch domain will be described as IMS packet-based access network. The IMS provides services for any type of IP communication whether it is voice or video telephony, video streaming, instant and multimedia messaging, multimedia gaming or virtual-reality. It is obvious that all of that services, especially real time services require end-to-end QoS support. This paper presents some aspects of provisioning QoS in the IMS environment based on differentiated services (DiffServ), relatively simple but scalable IP-based QoS technology. This requires proper choices of QoS mapping, router configuration, and admission control. The major network elements responsible for providing QoS support (GGSN, PCF, MGW, edge routers) based on DiffServ are also described in the paper.