Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1998-11-03
2002-10-22
Nguyen, Chau (Department: 2663)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S410000, C370S522000, C370S352000
Reexamination Certificate
active
06470020
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the integration of stimulus signalling protocol communication systems with message protocol communication systems.
2. Description of the prior art
Stimulus signalling protocols and message protocols are two methods for transferring information over a communications network. Stimulus signalling is typically used for connecting simple (dumb) terminals to a more powerful host. Message protocols are typically used to connect between such hosts. Equipment has typically been developed and manufactured for use with either stimulus signalling protocol systems or message protocol systems but not both. Both types of protocol have different advantages and disadvantages and previously, in order to exploit the advantages of both protocols, users have needed to install equipment for each type of protocol or employ the use of a protocol conversion device. Such protocol conversions are complex and time consuming to develop and maintain.
An example of a stimulus signalling protocol is P-Phone which is a proprietary protocol developed by Northern Telecom Limited. P-Phone is typically used in telecommunications networks and equipment has been developed for use in this type of system. P-Phone is used for Northern Telecom's DMS support of Centrex services. Simple terminals, for example, “business handsets” have been developed for use in this type of system. The term “business handset” is used herein to refer to any type of terminal in a communications network which has a number of input devices such as keys and buttons. A business handset usually also has display capabilities but this is not essential.
FIG. 1
shows an example of a business handset which has a display panel
100
, telephone hand piece
101
, a message waiting lamp
102
, a number of function keys
103
, and a number of indication lamps
104
.
When a user makes an action using the business handset shown in
FIG. 1
, for example by pressing a button on the handset, a signal is sent from the terminal to a node in the communications network to which the terminal is connected. Whenever an individual keypress is made an individual transaction occurs between the terminal and a node to which it is connected. For example, when a telephone number is entered in order to make a telephone call to a third party (called party) the digits are sent one at a time in separate transactions. Each individual key press constitutes a transaction. This illustrates how, a stimulus signalling protocol (also referred to as a stimulus response protocol) is a method of sending messages in a communications network whereby individual digits or other items of information are sent individually.
As discussed above an alternative to a stimulus signalling protocol is a message protocol. In a message protocol, a collection of related signalling information is sent as a discrete unit. For example, a called party number is sent as a single message together with additional call set-up information, clearing information or other additional information. An example of a message protocol system is the ITU-T H.323 multimedia conferencing standard.
Systems conforming to the H.323 standard allow audio and video telephony calls to be provided and also allow cross-platform application interworking which may be between similar computer architectures such as desktop computers, or completely different implementations such as dedicated video phone.
One problem is that systems and equipment that have been developed for use in stimulus signalling protocol communications systems are not compatible with message protocol systems. Two separate sets of equipment are required in order to make use of both systems. For example,
FIG. 2
shows a stimulus signalling protocol communications system according to the prior art.
A user at location
26
has access to a business handset
23
and a computer
24
on his desk. The business handset is connected to a stimulus signalling protocol communications system, in this case a public switched telephone network (PSTN)
21
. The computer
24
is connected to the Internet
22
. A second user at location
25
also has a computer
24
and a business handset
23
which are connected similarly. The first user may use his computer
24
to send messages to the second user over the Internet
22
using a message protocol system but the stimulus signalling protocol business handset
23
cannot be used to send information over the Internet
22
. Also, each user has two items on his desktop. This means that purchase and installation costs are increased and space is used.
For a stimulus signalling protocol such as the P-Phone signalling model, it is necessary that an “always up” connection is available between the terminal and an exchange or host. An “always up” connection is permanently active so that the terminal and exchange or host are always able to send and receive information over the connection at all times. This requirement is a result of the way that stimulus signalling protocol systems work. Stimulus signalling protocols were originally developed to facilitate the introduction of relatively “dumb” terminal units such as business handsets. These units needed to be simple because the overhead of both host and terminal message processing were significant factors in runtime efficiency of the overall switch. This was achieved in stimulus signalling protocols such as P-Phone by maintaining a state mapping of the terminal in the exchange. This enables host initiated state transitions to be reflected at the terminal so that all transfers whether from host to terminal or terminal to host are always initiated from the host. This allows central processor unit (CPU) occupancy and message throttling to be implemented centrally and for the runtime efficiency of the overall exchange (switch) to be improved. Central processor unit occupancy involves determining how busy the central processor unit is and message throttling is a method whereby some traffic is diverted in the event that the central processor unit is busy. However, an “always up” channel is required (i.e. a channel that is always open and available for use). For example, consider the situation when a voice mail message is left at the host and a message waiting indicator needs to be illuminated on the terminal. If an “always up” channel from the host to the terminal is not present then the message waiting lamp is not lit and the event is missed.
As already mentioned, the H.323 multimedia conferencing standard is an example of a message protocol system. The H.323 standard is an umbrella recommendation from the International Telecommunications Union (ITU). It sets standards for multimedia communication over packet based networks, including the Internet, which may not provide a guaranteed Quality of Service. H.323 entities may provide real-time audio, video and/or data communications. Support for audio communications is mandatory, while data and video services are optional. By complying with H.323 requirements the aim is that multimedia products and applications produced by different manufacturers can interwork and allow users to communicate without concern for compatibility. For example, H.323 establishes standards for compression and decompression of audio and video data streams, ensuring that equipment from different manufacturers can be used to receive and decompress the same information. The standard also establishes a common call set-up and control protocols.
H.323 defines four major components for a network based communications system: terminals, gateways, gatekeepers and multipoint control units (MCUs). Terminals are the user end-points on the communications network that provide realtime two way communications. All H.323 terminals must support voice communications; video and data are optional. H.323 specifies the modes of operation required for different audio, video, and/or data terminals to work together.
An H.323 gateway is an element that provides a connection or interface from the H.323 network to a non-H.323 commu
Barker Iain William
Jarvis Peter Karel
Tubb David John
Lee Andy
Lee Mann Smith McWilliams Sweeney & Ohlson
Nguyen Chau
Nortel Networks Limited
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