IP-centric conferencing offers flexibility

IP-centric conferencing - offering real-time, multimedia voice, video and data conferencing over packet-based networks - is less complex to implement than ISDN-based solutions.

Nevertheless, network executives have to ensure the necessary infrastructure is in place to support IP conferencing, or select an application service provider who can provide conferencing services.

In order for participants to communicate over an IP network, all devices and equipment need to be interoperable.

In terms of standards, H.323 was the first that the International Telecommunication Union (ITU) developed to enable real-time communication over packet-based IP networks. H.323 is the most widely deployed standard for IP. Session Initiation Protocol (SIP), introduced by the Internet Engineering Task Force (IETF), is a relatively new signaling protocol that is growing in popularity.

Whereas H.323 was designed initially for interactive multimedia communication, SIP was designed initially for voice-over-IP applications. The IETF's Media Gateway Control Protocol (MGCP) and MEGACO/H.248 (IETF and ITU) are complementary protocols to both SIP and H.323. MGCP and MEGACO/H.248 interface between "intelligent" media gateway controllers and "dumb" media gateways.

A key point for future growth of IP-centric conferencing is the interworking of all these protocols, allowing for seamless, end-to-end connectivity between all types of endpoint and network devices.

An IP-centric conferencing network includes:

Gatekeeper or call agent: Manages, controls and monitors network resources and usage. To compensate for the nonintuitive underlying IP address system, devices such as H.323 gatekeepers provide address translation and directory server services. Gatekeepers can provide an array of services, such as call routing, call transfer and forwarding, line hunting, Lightweight Directory Access Protocol and DNS support, as well as billing support.

IP networks are fundamentally different from ISDN networks. IP networks have a distributed and flexible architecture that spans a LAN, WAN and/or the Internet. The IP infrastructure is location- and service provider-independent. The inherent scalability of IP allows bandwidth to be increased, equipment to be added and services to be improved without making fundamental changes to the infrastructure.

A critical factor for successful IP-centric conferencing is sufficient bandwidth to maintain satisfactory levels of voice, video and data transmission. Another important factor for successful conferencing is quality of service (QoS), the guaranteed quality of the media being delivered. On packet networks, QoS depends on a set of transmission parameters such as delay, jitter and bandwidth that is assigned to selected traffic on the network.

The IP network has it own set of management and administration issues. Conference management facilities are required to configure the services and properties of any conference. These can include allocated bandwidth, load balancing, cascading, supported coder/decoders, transcoding priorities, continuous presence, video switching and far-end camera control. A conference can be reserved or initiated on the fly. As IP conferencing be comes more tightly integrated with the Web and Web-based applications, Web-based management tools will provide a comprehensive single system view of all users, sites, equipment, features and services.

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Gamaroff is director of technical documentation at RADvision. She can be reached at shirley@radvision.com.