Interoperable routing for IN and IP telephony

This paper discusses the problem of interoperability of Internet protocol (IP) telephony and switched-circuit networks (SCN) in the area of routing information. We describe and analyze a solution for directory-based routing. We will present an architecture based on a distributed database on the SCN and the IP network. The aim of the solution is to provide efficient service management, close to optimal routing for all calls including calls to 800- and cellular numbers and personal number portability between both the network technologies. The solution is based on similar, but differing in detail, approaches for each network. In the IP network, we use the telephony routing over IP (TRIP) protocol developed by Internet Engineering Task Force (IETF). Additionally, the described architecture is open for inclusion of the telephone number mapping (ENUM) protocol that is under development. For the circuit-switched network, we suggest a new protocol called circuit telephony routing IP (CTRIP). The protocol provides a distributed method for synchronizing routing information between databases. Furthermore, we propose numbering gateways for transferring number information between the two network types. We utilize the server cache synchronization protocol (SCSP) as the common element for data synchronization and replication among distributed entities. We also discuss briefly the design of a test implementation of the proposed infrastructure functions and protocols under development in our laboratory. In conclusion, we propose designing a common interoperable routing information infrastructure for the emerging hybrid SCN/IP telephony network. (C) 2001 Elsevier Science B.V. All rights reserved.