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VoIP Interconnection Challenges

For further information please contact:

Adam Kapovits
Programme Manager
Wieblinger Weg 19/4
69123 Heidelberg, Germany

Project Information
What is this Project about?

Service Providers are in the process to migrate their PSTN (Public Switched Telephone Network) service to IP networks. A major challenge and key to the success of this process is to preserve global reachability, ie. subscribers should be able to place calls to any destination with a level of perceived QoS (Quality of Service) similar to the one experienced in current PSTN networks.

This global reachability, which allows extending the scope of IP-based telephony services beyond the scope of a single administrative domain, can be implemented by deploying several Points of Presence around the world or in a more realistic way by settling several interconnection agreements with other Service Providers. Inevitably, the dynamics of establishing new interconnection agreements should be intensified, depending on the PSTN migration rate as implemented by the Service Providers, so as to be able to convey traffic to remote telephony destinations which are not attached to their IP Telephony Administrative Domain (ITAD). The current bilateral model is not always valid and/or feasible, because:

  • Emergence of new VoIP actors: A large amount of interconnection agreements should be settled in order to reach destinations managed by these new actors. The number of required agreements is drastically increasing and is probably close to the current number of BGP domains, which is 17000. This means that scalability is a real show stopping weakness of the centralised model if a Service Provider wishing to place calls with all telephony destinations and without using PSTN or other PLMN.

  • Unlike PSTN, customers are not anymore identified only by an E.164 identifier. New telephony identifiers have been promoted within IETF (Internet Engineering Task Force)). These Identifiers are commonly known as URIs (Uniform Resource Identifier) and are similar to DNS (Domain Name System) aliases. Consequently, no geographical localisation is conveyed in such schemes. Inevitably, this will impact telephony routing processes.

In addition to these challenges, telephony service offerings should meet other requirements such as QoS, high availability and robustness. These requirements are not only valid for the “Service Layer” but also for the “Network/Transport Layer” which is not necessarily managed and controlled end-to-end by the same entity. For these reasons, new means to drive the inter-domain routing selection process should be investigated and implemented for the delivery of QoS-enabled Telephony services across several IP telephony domains.  

What are the main objectives of this Project?

The study has the following objectives:

  • Identify a set of session-based services to be covered

  • Identify both “Customer” and “Service Provider” requirements in order to offer global conversational services

  • Propose VoIP Interconnection Model

  • Elaborate Interconnection Business Model

  • Provide a techno-economic analysis of the proposed interconnection model

  • Sketch “high-level” solutions to:

  • Promote dynamic telephony routing;

  • Ensure synchronisation between service layer and IP network layer. This includes Media Layer interactions

  • Ensure QoS-enabled VoIP Services

  • Provide against congestion for inter-provider telephony service offerings

  • Enhance the robustness and the availability of inter-provider telephony service offerings

  • Enforce security means within an inter-provider telephony context

  • Activate Inter-Provider Service Monitoring

  • Drive inter-provider Billing and accounting models

  • Enlist persistent technical challenges and problems
Project Results
Deliverable Title  No Issue date
White Paper: “Promoting Telephony over IP Interconnection Models at Large” D1 Cancelled
Inter-Provider Telephony over IP: Requirements, Hurdles, Business Model, Interconnection Models and Service Engineering Issues” (Word document) D2 June 2009
Inter-Provider Telephony over IP: Requirements, Hurdles, Business Model, Interconnection Models and Service Engineering Issues” (PowerPoint presentation) D3 June 2009