An Open Source H.323-SIP Gateway as Basis for Supplementary Service Interworking
Key: ADG+01-1
Author: Ralf Ackermann, Vasilios Darlagiannis, Manuel Goertz, Martin Karsten, Ralf Steinmetz
Date: April 2001
Kind: In proceedings
Book title: Proceedings of the 2nd IP Telephony Workshop, New York
Abstract: IP telephony is currently evolving from a more or less still experimental towards a carrier grade service which has the potential of extensive use both within the Internet as well as in Intranets. Currently we see the two signaling protocol families H.323 and SIP existing and further evolving simultaneously. For both, efforts are done to not only establish basic calls but to enable so called Supplementary Services. This is generally considered one precondition for replacing the functionality of existing conventional PBXs on top of a standard protocol. Nevertheless solutions that support more then just basic call scenarios are at the moment still often based on proprietary protocols or protocol extensions. Since we assume that both H.323 and SIP are going to coexist for a longer future period, gateways between both protocol families are of large interest and research, standardization and development activities have been spent on those. As part of an industry research cooperation we have (independently from other efforts) developed and deployed a fully Open Source H.323/SIP gateway. The paper shows its concepts and describes its use as a powerful reference implementation basis for further development targeting at the mapping and gatewaying of Supplementary Services. Our gateway's modular, flexible and extensible architecture as well as the usage of scripting functionality both for configuration as well as internal protocol processing enables the usage of different basic software components (e.g. protocol stacks) in a fast prototyping way. We consider this especially important, since the existing freely available stacks (such as OpenH323) do not support H.450 or SIP Supplementary Services at the moment.
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