Audio Web Conferencing

NetMeeting is not currently compatible with H.323 gatekeepers. However, this will change in the future, so it is important that you consider them, as well as gateways, when planning NetMeeting audio web conferencing installations.

An H.323 gatekeeper is a server that manages bandwidth and conferences. Many incorporate LDAP (Lightweight Directory Access Protocol) and ILS (Internet Locator Server) support, as well, but a gatekeeper is not just a directory service. NetMeeting's optional client-level bandwidth controls are one way to limit a conference's load on a network. This is handy for throttling Internet connections, but it does not prevent overloads on intranets where many conferences are likely to occur.

The addition of a gatekeeper means that H.323 clients place conference calls via the gatekeeper. The gatekeeper is involved in the initial call setup and call completion, and the gatekeeper can reject a call if the current number of calls or their load on the network exceeds the configured threshold. Conference call loads are based primarily on audio or video conferencing that uses a fixed bandwidth, making tracking relatively easy for the gatekeeper. All the gatekeeper needs to do is add the bandwidth to what's currently in use when connections is made, and remove it when the connection is terminated. This is actually the simplest case with point-to-point conferences over a network that has a fixed bandwidth, such as a 10BaseT Ethernet network implemented with hubs. The equation becomes more complicated when switching networks, as well as WAN links, are involved. In this case, the gatekeeper must be programmed with the network topology as well as with the location of workstations.

H.323 gateways are servers used to bridge the gap between H.323 clients and other conferencing protocols, such as the ISDN-based H.320 and the modem-based H.324 point-to-point protocols. Gateways can also provide connections to proprietary conference clients. A gateway could even provide audio conferencing for voice calls over a telephone. For example, some conference participants might be using a room-based conferencing system, others might be using workstation-based systems, and some might be using conventional telephones.

Unlike the H.323 gatekeeper, the H.323 gateway is actively involved throughout a conference-not just for the initiation and termination. Information passes through the gateway between the clients. Conferences that operate through a gateway are bandwidth-limited by the slowest part of the connection. Like a gatekeeper, a gateway can also limit the number of calls and the bandwidth used for each call.

Gatekeepers and gateways are key features needed for widespread use of computer conferencing on any type on a network. They provide the control and the connections necessary for general use. Without them, the network manager can- not manage the bandwidth utilization on the network or provide links to the outside world.

Eventually, gatekeepers and gateways will be as common as file, print, and application servers. Conferences between clients on different networks will be common, and audio and video conferencing will finally be a standard method of communication that is also integrated with the telephone system. That time is not too far away.