Gartner Research

SIP Trunking: More than Legacy PSTN Connection Replacement

Published: 29 September 2009

ID: G00203808

Analyst(s): Mark Cortner


The availability of Session Initiation Protocol (SIP)-based access services to the public switched telephone network (PSTN) enables enterprises to leverage investments in Voice over Internet Protocol (VoIP) technology and eliminate time-division multiplexing (TDM)-based trunks and gateways. But not all SIP trunking services are created equal; they range from the simple substitution of Integrated Services Digital Network (ISDN)-based to IP-based access services to intelligent network routing services. In this updated report, Senior Analyst Mark Cortner includes new perspective on the state of the SIP trunking market and analysis of its role in an enterprise's future telephony and unified communications (UC) plans.

Table Of Contents

Summary of Findings


  • Definition of SIP Trunking
  • IP-Enabled PSTN Access
  • Enhanced Call Routing Services
  • IP-PBX and Service Provider Interoperability
  • Demarcation and Security Issues
  • The Business Value of SIP Trunking
  • Market Impact
    • Service Provider Impact
    • IP-PBX Vendor Impact
  • Recommendations
    • Leverage SIP Trunking to Reduce Voice Networking Costs
    • Evaluate Enhanced Call Routing Services
    • Assess Implications to Network Survivability Plans
    • Demand SIP Trunking Interoperability Certification

The Details

  • What Is SIP Trunking?
  • SIP Trunking Architecture and Implications
    • SIP Trunking Architecture: Enterprise PBX Component
    • SIP Trunking Architecture: Demarcation Device
    • SIP Trunking Architecture: The Trunk
  • SIP Trunking QoS and Reliability


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