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  1. N. Beijar, Distribution of Numbering Information in Interconnected Circuit and Packet Switched Networks, Master's thesis, Helsinki University of Technology, 2002 (pdf)(bib)
    Abstract: 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.