Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
1998-10-13
2002-12-03
Yao, Kwang Bin (Department: 2662)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
C370S356000, C370S401000, C379S220010
Reexamination Certificate
active
06490275
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates in general to a multimedia communications, and more particularly to a method and apparatus for improving call setup efficiency in multimedia communication systems.
2. Description of Related Art
Of the communication tools found in most offices today, such as E-mail, fax machines, pagers, and cellular phones, videoconferencing has yet to make the short list. However, this is changing, as companies move to take advantage of lower system costs and emerging new standards. For example, videoconferencing over an enterprise IP network is very appealing. It makes better use of an organization's finds rather than sinking additional investments in ISDN lines. Up to now, ISDN has been the only reliable way to connect video-enabled workstations and conference-room-based systems. However, the technology isn't readily available, and it's still expensive. Nevertheless, H.323-standard LAN-operable DVC (desktop videoconferencing) solutions are available.
The H.323 standards architecture specifies gateways and gatekeepers that enable connections among LAN-based DVC units, ISDN-connected H.320 units, analog telephone-connected H.324 devices, and ISDN and POTS telephones. One rapidly emerging branch of this market includes gateway and billing server systems devoted to Internet telephony.
The H.323 standard provides a foundation for audio, video, and data communications across IP-based networks, including the Internet. By complying to H.323, multimedia products and applications from multiple vendors can interoperate, thereby allowing users to communicate without concern for compatibility. H.323 will be the keystone for LAN-based products for consumer, business, entertainment, and professional applications.
More specifically, H.323 is an umbrella recommendation from the International Telecommunications Union (ITU) that sets standards for multimedia communications over Local Area Networks (LANs) that do not provide a guaranteed Quality of Service (QoS). These networks dominate today's corporate desktops and include packet-switched TCP/IP and IPX over Ethernet, Fast Ethernet and Token Ring network technologies. Therefore, the H.323 standards are important building blocks for a broad new range of collaborative, LAN-based applications for multimedia communications.
The H.323 specification was approved in 1996 by the ITU's Study Group 16. Version 2 was approved in January 1998. The standard is broad in scope and includes both stand-alone devices and embedded personal computer technology as well as point-to-point and multipoint conferences. H.323 also addresses call control, multimedia management, and bandwidth management as well as interfaces between LANs and other networks.
H.323 is the latest of the recommendations on the H.32X series which specifies standards for videoconferencing over a variety of networks. H.323 includes much of the work done since the approval of the H.320 recommendation in 1990, which is an specification for multimedia over circuit switched digital telephone networks. The H.32X is composed of the following recommendations:
H.320 allows videoconferencing over narrowband switched ISDN.
H.321 is for videoconferencing over broadband ISDN ATM LAN.
H.322 allows videoconferencing over Guaranteed bandwidth packet switched networks.
H.323 allows videoconferencing over non-guaranteed bandwidth packet switched networks.
H.324 is for videoconferencing over PSTN or POTS (the analog phone system).
The H.323 Protocol Stack supports many real time applications that the industry is eager to use through the Internet such as: Desktop Videoconferencing, Internet Telephony and Videotelephony, Collaborative Computing, Business Conference Calling, Distance Learning, Support and Help Desk Applications, etc. These applications already exist in the market, but most of them do not address the problem of how to run these applications over a packet switch network like the Internet and most corporate LANs which are based in the TCP/IP suite of protocols. With the pressure of the market to use this kind of applications over the Internet, H.323 emerges as a possible solution to the business needs.
H.323 defines four major components for a network-based communications system.
FIG. 1
illustrates a H.323 system
100
. In
FIG. 1
, the four major components of a H.323 system
100
are shown including their interaction with existing networks. These components interact with LANs that don't provide QoS. The four components include Terminals
110
, Gateways
120
, Gatekeepers
130
and Multipoint Control Units (MCUs)
140
.
These four elements
110
-
140
are specified only for the Application Layer of the Internet Layer Model. There is no specification about the lower layers (Transport, Network, Data link and physical layers). These characteristic makes H.323 flexible and allows H.323 devices to communicate with device of other networks.
H.323 Terminals
110
are the client software that runs in the end user computers that allow users to communicate in real time using all the power of multimedia. These terminals are also called Endpoints.
A Gateway
120
is a component of the H.323 specification that provides world wide connectivity and interoperability from LAN. That is, a Gateway
120
will allow computers connected to a LAN to communicate to regular phones
150
connected to the PSTN
152
, to digital phones
154
(H.320 terminals) connected to an ISDN network
156
. A gateway
120
also translates between different types of codecs used by different kinds of terminals, maps call signaling between Q.931 to H.225 and maps control signaling between H.242/H.243 to H.245.
In general, a Gateway
120
is a component that makes possible to interconnect a packet switched network with no QoS to other types of networks. If connections to different types of networks are not required, then a Gateway
120
is not required since terminals can communicate between them if they are on the same LAN. Terminals communicate with gateways using Q.931 and H.245 protocols.
A Gatekeeper
130
is an H.323 component that performs four basic functions:
Address Translation: It is the mechanism that allows to have different kinds addressing systems. For example, regular phone numbers (E.164 addresses) can be used in conjunction with e-mail addresses. The Gatekeeper
130
allows to communicate with terminals addressed in different ways.
Admission Control: The Gatekeeper
130
could reject calls from users. An user must be registered with the Gatekeeper
130
in order to complete a call.
Bandwidth Control: Networks managers can restrict the amount of bandwidth used for videoconference, which provide a way to control LAN traffic. The remaining of the bandwidth can be used then for web requests, e-mail, file transfers, etc.
Zone Management: The Gatekeepers
130
provide the functions of Address Translation, Admission Control and Bandwidth control for Terminals
110
, MCUs
140
and Gateways
120
registered with the Gatekeeper
130
in its zone of control. This zone is called H.323 zone.
The functions of the Gatekeeper
130
are included in the Gateway
120
by most vendors, although they are logically separated and they perform different kind of functions.
The Multipoint Control Unit (MCU)
140
is a logical device that supports conferences between three or more endpoints. The MCU
140
typically is integrated with the implementation of the gateway, so in most implementations the MCU
140
won't be a separate computer performing conferencing functions. Also, with a combined implementation of the functions of the MCU
140
with the functions of the gateway
120
, conferences among participants of different networks (LAN and PSTN) will have better performance than divided implementations.
Call setup in H.323 systems requires the exchange of several messages between several entity pairs. The sequence of message exchanges is specified by H.323 and depends upon the presence or absence of gatekeepers for the calling and/or called endpoint and
Altera Law Group LLC
Nguyen Hanh
Nokia Telecommunications Oy
Yao Kwang Bin
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