The H.323 Gatekeeper Call Transfer Function Of The Realization And Research

gnugk is a C++ implemention of H.323 Gatekeeper, which provides almost all Gatekeeper functions defined by H.323, and its source code is open under the terms of GPL.The design, overall structure and calling related details of gnugk are covered within this paper. 3 kinds of call forwarding operations, i.e. CFU, CFB and CFNR, are added to gnugk by imposing direct modifications to the source code.With respect to devices already deployed, the upgraded ones should be as compatible as well and the modifications invoked by the upgrade should be as small as well. If so, not only the previous investment is protected, but also the duration to upgrade and testing are shortened and the possibility for bugs to come with the upgrade is lowered.While the call forwarding function is deing designed, the communication methods and signalling processes defined in H.323 are fully respected, so there is no impact to the compatibility of gnugk with other H.323 endpoints. Furthermore, just the Gatekeeper itself is invoked in the improvment, so once completed, existing H.323 terminals are able to make use of this functionality at once and there is no need for them to be modified and the functionality of the whole system is upgraded smoothly. A interface is also provided for the administrator to control the call forwarding.