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INTERO - InterOperability Mechanisms for IN/IP Telephony

Journal papers


Conference papers

Jose Costa-Requena, Ignacio Gonzalez Olias, Raimo Kantola, Nicklas Beijar: Autoconfiguration mechanism for IP Telephony Location Servers SCN-IP Telephony convergence

IP Telephony is clearly the service that converges data and real time voice, video over IP networks. This paper shows that the convergence for this specific service is feasible. Nevertheless, it shows that certain technologies trends needs to be solved. The smoothly transition from switched telephony over IP networks can be achieved. This paper analyses a suitable architecture and presents specific enhancements to be implemented in the existing IP Telephony routing protocols. The appropriate auto-configuration and replication mechanism in the proposed architecture will facilitate the data synchronisation across switched and IP technologies. This will promote the convergence of services into IP networks in a seamless manner.

Keywords: Location Servers, Synchronisation, TRIP, SCSP, IP Telephony, Routing, Auto-configuration.


Nicklas Beijar, Distribution of Numbering Information in Interconnected Circuit and Packet Switched Networks, Espoo 2002

Because of the introduction of Internet Protocol (IP) telephony and the increasing complexity of the telephony networks, the burden of managing routing information is growing. Number portability, which allows users to change operators, locations and services without changing their numbers, is now being required in many countries. An automatic approach of generating and distributing routing information is motivated.
    This master’s thesis examines the issue of how a routing protocol can be used to distribute numbering information in an interconnected circuit and packet switched network. An architecture based on the Telephony Routing over IP (TRIP) protocol for distributing routing information is developed.
    The first part introduces some of the theory and literature related to the subject. The principles of routing telephone calls on the circuit switched network and IP networks are presented. The TRIP protocol and ENUM (tElephone NUmbering Mapping) directory are major issues, since they form the base for the architecture. Number portability and its implementations are described.
    In the second part, the solution is developed. The architecture is defined and some scenarios are presented. A new protocol named CTRIP (Circuit Telephony Routing Information Protocol) is developed as a counterpart to TRIP for the circuit switched network. The attributes and messages of CTRIP are defined. The TRIP protocol is extended with some new optional attributes. Further, the process of converting routing information between TRIP and CTRIP is defined. A new network element named numbering gateway is introduced. To some extent, the ENUM directory is integrated into the solution. Finally, some applications and scenarios based on the solution are discussed.

Keywords: Routing, Routing protocol, Number portability, TRIP, CTRIP, ENUM, NP, VoIP

Ignacio González Olías, Security and Auto-configuration of Location Servers for IP Telephony, Espoo 2002

IP networks were designed to provide an effient and robust mechanism for transferring data between remote computers. Initially, the information exchanged was mostly computer related data: text documents, files, web content, etc. However, the increasing popularity of this kind of networks is encouraging the development of new services and applications that take advantage of the existing infrastructures.
    One of the emerging applications is IP telephony, a new service aimed to allow end users to complete voice calls over IP networks. This a clear example of how a service that was traditionally offered using a different technology, i.e. public switched telephone networks (PSTN), has been adapted to the IP networks.
    Since the migration from one approach to another can not take place overnight, both technologies will be interacting for a period of time. This interaction generates new interoperability problems that must be addressed. Data and signalling conversion between both networks is performed by special entities called gateways.
    We focus our study on the architecture that solves the problem of gateway location. The Telephony Routing over IP (TRIP) protocol is responsible for distributing gateway availability information between different administrative domains, while the Server Cache Synchronization Protocol (SCSP) performs the required database replication.
    This document presents security and auto-configuration modules for the TRIP/SCSP architecture. The former is aimed to ensure that the data exchange takes place in a secure way, while the latter improves the scalability, reliability and availability of the system.
    We also include some test results to show how the addition of security services to protect SCSP traffic affects the performance of the protocol.

Keywords: interoperability, gateway location, TRIP, SCSP, replication, security, auto-configuration.

Antti Paju, Number Portability in Interconnected Circuit and Packet Seitched Networks, Espoo 2002

Number portability is quite a topical issue in several countries including Finland. In Finland the communications regulatory authority (FICORA) has ordered the GSM numbers to be portable from an operator to another from 1st of July 2003 onwards. As VoIP (Voice over IP) is getting more common, a need arises to port subscribers from the SCN to the IP network so that a ported-out subscriber can still keep his/her number. For a customer, the technological transition is not any reason to change his/her telephone number. Number portability enhances competition in the telecom markets and improves customer satisfaction. When a subscriber moves, his/her number does not have to be changed. Changing the telephone number can cause e.g. significant advertising costs to business customers. So, number portability is very useful for both business and residential customers.
    Nowadays, number portability is managed with IN technology (Intelligent Network). IN based number portability has several drawbacks. This thesis tries to fix them by introducing a new solution, which still uses the existing IN technology some way. The management of number portablility is treated as an application, which is created using standards interfaces and definitions. This thesis rejects the approach of routing the call into the donor's network first. The aim is, that the call is routed directly into the network where the called party is located. Number portability requires a number translation service, which resolves the logical directory number into a routing number, or to be more specific into a routing address. Interoperability requires common numbering between the SCN and IP networks. Due to the structure of PSTN, E.164 numbering is used in both SCN and IP networks.
    The solution utilizes relational databases for efficient database management. They provide very scalable data structures and tools for automatic data integrity management. ODBC (Open Database Connectivity) is selected as the access inteface to relational databases. ODBC makes the solution portable to many commercial and non-commercial SQL databases. As a result, we get a service, which is independent on the carrier network, and the scalability of which knocks previous database management solutions of number portability into a cocked hat.


Full papers are either in PostScript or PDF format.

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