Pelos

VoIP Network Design for Service Providers

A look at the challenges involved in designing a converged network to support VoIP and other applications
How service providers can manage migrating existing voice services or building new managed IP networks

This white paper addresses:
• The complexities of VoIP network design • Designing a framework to support VoIP migrations • The uniqueperformance, restoration and reliability requirements of voice services

Contents
Introduction .......................................................................................3 Framework.........................................................................................3
IMS Architecture .........................................................................................4 ServiceProvider VoIP Architecture .............................................................5 A Multi-Service MPLS Network ..................................................................6 Multiple Classes of Service ..........................................................................6 Multiple Domains........................................................................................7Bearer Network Design.......................................................................9
Generic MPLS Network Design Process.......................................................9 Supporting VoIP in Generic MPLS Network Design Process .....................12 Design Steps ..............................................................................................14

Signaling NetworkDesign.................................................................15 QoS Design ......................................................................................17
The Integrated Services (IntServ) model...................................................17 The Differentiated Services (DiffServe) QoS model .................................18 Supporting Intra-Enterprise VoIP Traffic...................................................20 QoS for Signaling Traffic............................................................................20

Conclusions......................................................................................21 Acronyms .........................................................................................22 About the Authors...........................................................................23
Jayant G. Deshpande.................................................................................23 David J. Houck ..........................................................................................23

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Introduction
Driven by competitive pressure and the desire for new service generating opportunities, major ServiceProviders (SP) have begun rolling out VoIP (Voice over IP) services to business and consumer markets. The challenge is to design the network to support VoIP service requirements for strict connectivity, latency, jitter, packet loss, and reliability objectives that are normally expected from the (circuit-switched) PSTN services. In addition the network design must support new voice applications – thatare made possible by the new converged voice/data network. SPs are either migrating voice services from the circuit switched networks to their existing data networks, or building new managed IP networks to support voice and other applications. In all cases, these data networks need to be carefully designed to support their most important and challenging application – VoIP. Some of the keycomponents of network design for supporting VoIP are: • Topological design: Core network topology, softswitch and router placement, and backhaul. Design for reliability and scalability. • Capacity design: Softswitches, routers, facilities, servers, and other network elements to support voice traffic and signaling. • Signaling network design: Interconnecting voice end points independent of their access...