An architecture for the transport of IP telephony services

Abstract

The transport infrastructure to VoIP traffic is moving toward a multiple service platform of high-speed routers interconnected by optical network SDH/WDM. A multiple-service network allows operators to attend to clients through optimization of resources, differentiated quality of service and traffic engineering. This article describes a scalable architecture for the transport of IP telephony services based on MPLS and DiffServ as complementary solutions to provide QoS in access, collector portion, and core of the network. This work presents the state of the art of the protocols related with quality of service, routing and traffic engineering in the IP Telephony field. First we examine the network elements and their functionality inside each protocol, with a focus on the environment of the two workgroups, ITU-T and IETF. Finally we discuss the necessary changes for the introduction of MPLS (Multi Protocol Label Switching) as a significant strategy for the transport of IP telephony services, due to its capacity to emulate the orientation to connection provided by ATM technology. Moreover it offers scalability, low cost, and the possibility of automatization of several aspects of the traffic engineering function - such as the bearer capacity for VoIP, thereby providing more predictable, and even constrained QoS. © Springer-Verlag Berlin Heidelberg 2001.