Which h.323. protocol handles signaling

These are not IP devices. It is not necessary to Configure them in SmartConsole. Manages a collection of H. A Gatekeeper converts phone numbers to IP addresses and can provide Security Gateway services as well. Provides interoperability between different networks.

The Gateway translates between the telephony protocol and IP. Allows a Q. Allows a RAS port to be opened, and then dynamically opens a Q. Allows only RAS ports. Cannot be used to make calls. If this service is used, no Application Intelligence Checks payload inspection or modification as NAT translation are made.

Applies only to Security Gateways R Address Translation —Translates H. Admission Control —Controls endpoint admission into the H. In order to achieve this, the gatekeeper uses these:.

See the H. Bandwidth Control —Consists of the management of endpoint bandwidth requirements. In order to achieve this, the gatekeeper uses these H.

Zone Management —The gatekeeper provides zone management for all registered endpoints in the zone, for example, the control of the endpoint registration process. Call Management —With this option, the gatekeeper maintains active call information and uses it to indicate busy endpoints or redirect calls. Bandwidth Management —With this option, the gatekeeper can reject admission when the required bandwidth is not available.

Call Control Signaling —With this option, the gatekeeper can route call-signaling messages between H. Alternatively, it allows endpoints to send H. RAS is the signaling protocol used between gateways and gatekeepers. The RAS channel is opened before any other channel and is independent of the call setup and media transport channels.

The ITU H. This port initiates the Q. When a gatekeeper is present in the network zone, H. The method chosen is decided by the gatekeeper during the RAS admission message exchange. It is used to negotiate channel usage and capabilities such as:. Thisis the processes by which H.

If an H. This is a UDP datagram addressed to the well-known destination port and transmitted in the form of an IP multicast with the multicast group address A reject message contains the reason for the rejection and can optionally return information about alternative gatekeepers.

Auto discovery enables an endpoint to discover its gatekeeper through a multicast Gatekeeper Request GRQ message. Because endpoints do not have to be statically configured for gatekeepers, this method has less administrative overhead.

A gatekeeper can be configured to respond only to certain subnets. It never remains silent. If a gatekeeper is not available, the gateway periodically attempts to rediscover a gatekeeper. If a gateway discovers the gatekeeper has gone off-line, it ceases to accept new calls and attempts to rediscover a gatekeeper.

Active calls are not affected. Registration occurs after the discovery process. The iNOW! Profile has also been extended to include interoperability between gatekeepers and other endpoint. Compliant products and services are certified by IMTC. Several software vendors have developed H. These software modules allow developers of H. Vendors that offer H. Many hardware and software companies have set up their own interoperability labs to test their and other vendors products and services.

NetMeeting, a H. The vision of H. These goals have not yet been achieved. From a business point of view a technology cannot succeed solely on the basis of lower operational costs. It must also provide additional value and performance in the form of ease of use and improved feature set for it to supplant a well-entrenched technology such as PSTN. Several ITSPs exist today e.

Global interoperability is still a problem. Furthermore, the features and quality of service being offered is often inferior to POTS. The first is the lack of interoperability of endpoints especially gateways from different vendors. And the second is the poor scalability of H. As such, it is well positioned to offer services to ITSPs, ISPs, and traditional telephone companies to route their multimedia traffic over its packet-based network. It had earlier signed similar service deals with Priceline.

The quality of video on public networks like the Internet is poor. For example, in IP networks H. Development of more efficient codecs will also play an important role in improving quality. Enterprise IT managers are also reluctant to deploy H. Security of H. Concerns over privacy has prevented businesses from moving over to H.

Part of the problem was resolved with H. However, many products have not implemented the security recommendation. In this section several key developments and trends that are shaping H. This is the question IP telephony vendors are asking.

Analysts often make an analogy between H. Although the share of SIP will increase H. Moreover, the investment in H. SIP and H. The greatest growth in H. Integration and development of new services is also an advantage.

Furthermore, H. Small business and home users put more emphasis on quality, value, and features. They are less concerned with interoperability with legacy systems and security. This is the market where H. Adoption will increase in the coming years as the price-performance ratio improves. This is also the market where SIP can make a significant impact. Version 2. The focus has shifted from LANs to larger networks such as the Internet and the challenges associated with it.

Work is also being done to add mobile communication capability to H. Another initiative is the preparation of an implementation guide for H. Interoperability issues and security are on-going initiatives. For documents on current developments in H. An analysis of H. An extensive listing of vendors and their products is also maintained at IPTelephony.

Multipoint control units MCU are needed when dozens of endpoints participate in a multimedia conference like in a virtual corporate meeting. There are two different configurations or architectures in which MCUs are available: server-based or rack mounted.

Rack-based MCUs use proprietary hardware and software to provide the necessary functionality. In the following paragraphs key features of five currently available MCUs are described. For a detailed comparative review of these products see [Brown99]. Depending on the proximity of the gateway to the PSTN where a call is placed the savings can be significant. For example, Net2Phone provides a rate of 3. Flat rate charges are often adopted. Key H.

It is a broad and flexible specification that caters to the needs of both enterprises and individuals. The goal of H. Work is on-going in improving the H. Finds SGCP better. Overview of upcoming video coding standards H. Presents an architecture for IP telephony that is scalable and capable of supporting thousands of subscribers.

Gateways are a bottleneck for IP to circuit-switch telephony. Authors propose a decentralized architecture. Discusses the new supplementary services architecture in H.

Supplementary services allows additional services to be built on top of H. Describes a technique that allows mobile telephony by integrating mobile IP addressing and the facility of dynamic conference joining already provided in H. Discusses the signaling and control message protocols A brief overview of all conferencing standards H. Detailed with coverage of IP telephony, H.

Compares call setup time, complexity, flexibility, functionality, security, transport neutrality, etc. Covers Version 1. Good reading. Good for beginners. Dual rate speech coders for multimedia communication transmitting at 5.