link to gnugk site
insert from site:
OpenH323 Gatekeeper - The GNU Gatekeeper
The GNU Gatekeeper (GnuGk) is a full featured H.323 gatekeeper, available freely under GPL license. It forms the basis for a free IP telephony system (VOIP). Please read the manual and the FAQ for general information what a gatekeeper does or take a look at some VOIP and H.323 books to get into the subject.
The GNU Gatekeeper is very stable. It is being used commercially by many organizations to provide VOIP services. They provide executables for Linux, Windows, FreeBSD, Solaris and MacOS X
- can be run as a Windows service
- accounting and call authorization via SQL database, Radius, file or external application
- flexible call routing
- number rewriting (calling and called)
- support for NAT traversal
- full H.323 proxy
- TCP interface to applications
- CTI functions (eg. VOIP call-center, call transfers)
- gatekeeper clustering support (neighbors, parent/child, alternates)
- H.235 security
- graphical user interface
- and it's free, including source code
The interoperability list shows a lot of equipment GnuGk has been used with.
In addition to the general settings explained in the manual there are some specific configuration notes how to configure gateways from some major vendors for use with GnuGk.
More coming soon. I will be adding scripts and option examples. I am working on a few examples, and we now operate our own GNU gateway ourselves.
GNU gateway is based on H.323. Link
What is ITU-T Recommendation H.323? Why have the worlds largest carriers deployed and continue to deploy H.323? H.323 is the first and remains the most powerful international multimedia communications protocol standard, bringing the convergence of voice, video, and data. Built for the packet-based network, H.323 has found a strong home in IP networks, making it the leader in VoIP.
As with other carrier-grade communication protocols, H.323 is a standard published by the International Telecommunications Union. It was approved by the world governments as the international standard for voice, video, and data conferencing, defining how devices such as computers, telephones, mobile phones, PDAs, wireless phones, video conferencing systems, etc., communicate to bring a whole new experience to the user.
H.323 borrows from both the traditional PSTN protocols and the Internet-related standards. By leveraging from both circuit-switched and packet-switched protocol standards, H.323 is able to smoothly integrate with the PSTN, while at the same time send multimedia communications over such mediums as the Internet.
H.323 originated in the mid-'90s as a logical extension of the circuit-switched multimedia conferencing work being done within the ITU-T. Because of this heritage, H.323 interoperates well with a very large installed base of video conferencing equipment. However, H.323 introduced much more capability than was introduced by previous protocols. It brought with it the ability to integrate with the Internet and the World Wide Web (WWW), as well as interface with the PSTN, to provide a range of applications from wholesale transit of voice, pre-paid calling card services, residential voice/video services, enterprise voice/video services, and much more.
With H.323, users at remote locations are able to hold a video call and edit a document together-in real-time over the Internet-using their personal computers. Not only that, but H.323 allows the users to customize their phones or phone services, locate users, transfer a call, or perform any number of other tasks by using an HTTP interface between the H.323 client and a server on the network. H.323 fully embraces the power of the Internet. From the outset, designers of H.323 wanted to create a protocol that would serve well as the Next Generation Network protocol. H.323 significantly lowers the cost of communications and facilitates the rapid creation of many new kinds of services that were never before possible. In addition, H.323 enables endpoints to perform tasks that were previously only possible for centralized servers to perform. H.323 breaks away from the "old technology" model and introduces an intelligent endpoint capable of initiating and accepting calls without dependency on centralized network elements. However, recognizing the business requirements for centralized control in the service provider and enterprise markets, H.323 also allows for centralized control over the endpoint when desired. The level or extent to which a carrier or enterprise wishes to exert control is entirely up to them.