Building the bridge: Devising an architecture to migrate voice-band calls to packet transport and multimedia services

One of the greatest challenges in the migration from a traditional telephony network toward a multiservices packet network is creating a packet-based infrastructure that will preserve the ubiquity, quality, and reliability of voice services while allowing the greatest flexibility for use of the new packet technologies. In practice, this means retaining current telephony-related services on new packet-based deployments. In this paper, we present an architecture model that can serve in the migration path to that infrastructure as well as in all-packet solutions. We recognize that most calls traverse multiple provider networks, which may use different transport technologies or call/service signaling protocols. Therefore, the next step is to create a transport-independent functional model for provider domains. This allows the solution to address, for example, introduction of new services separately from interworking between different transport technologies. The architecture model we present is one step away from physical implementations in equipment and can be used to model existing telephony equipment and protocols. Unlike protocol architectures, we do not define implementable entities such as Lucent Technologies' elemedia® H.323 gatekeeper or the Lucent Softswitch. The elements of our model can be combined to create such entities as appropriate and can also be used to design new ones. In the European Telecommunications Standards Institute (ETSI)/Telecommunications and IP Harmonization over Networks (TIPHON) project, the model is used for standardization.