Multiplex communications – Channel assignment techniques – Messages addressed to multiple destinations
Reexamination Certificate
1998-06-24
2004-06-22
Nguyen, Steven H. D (Department: 2665)
Multiplex communications
Channel assignment techniques
Messages addressed to multiple destinations
C370S261000, C370S351000
Reexamination Certificate
active
06754224
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to call signaling and, more specifically, however, to using multicast call signaling in a packet network.
Conducting voice communications over a packet network is desirable because companies typically use 50% or less of available network bandwidth. Therefore, putting company voice traffic on the same packet network used to transmit data can save long distance charges and allow for greater communication options. Sending voice data on IP networks is therefore extremely desirable when there is a guaranteed bandwidth.
Call signaling techniques in packet networks traditionally route signaling data serially, or sequentially, such that a response is sought from only one endpoint at a time. If a first endpoint fails to respond to the request, then the request is sent to a second endpoint. If no response is obtained from the second endpoint the request is sent to a third endpoint, and so on. A conventional telephony call forwarding technique is used to connect with a user at any one of multiple locations-such as attempting to contact someone whether they are at the office by an office phone, at home by a home phone, or away from home and the office by a cell phone or a pager—operates as follows. First, the telephony system attempts to reach the desired party at the office by signaling (calling) the office phone. If no response is obtained at the office, the system calls the home phone. If no response is received from the home phone, then the cell phone is signaled. Finally, the pager is contacted if no response was obtained from any of the previous devices. When a response is finally obtained, either from a live-person contact, from an answering machine, or from any other type of coverage device (i.e., voice mail), the signaling sequence stops and no further devices are signaled.
Unfortunately, not only does this system consume a great deal of time trying to track down the desired party, it also breaks down when there is an answering machine or voice messaging device at one of the endpoints. When the answering machine or voice mail system establishes a connection with the caller, the call forwarding process stops and the desired contact must be obtained by calling each phone number manually.
Another problem related to sequential call signaling involves conference calling. Conference calls generally require that each party be contacted separately. Specifically, one party is typically called and put on hold while the next party is contacted. This process continues until all of the desired parties are finally contacted. Again, this method is time consuming and burdensome. Scalability is also a significant problem because all of the work done in contacting the desired parties is done at the initiating endpoint.
The existing audio transport protocol used in IP networks H.323 is derived from traditional telephone networks and is not highly scalable in packet networks or even Local Area Network (LAN) environments. Telephony based protocols are also complex and bulky and require centralized control. Thus, these traditional audio transport protocols are not easily implemented in low cost devices such as cable modems, phones, and pagers because of the intensive processing requirements.
Therefore, a need remains for a scalable and easily implemented packet-based call signaling system that contacts multiple communications devices at the same time. The industry would also benefit from a call signaling system that allows multiple parties to be contacted for participation in a conference call, without the need to separately call each desired party.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a call signaling system that allows multiple endpoints to receive a call setup request.
Another object of the present invention is to provide a method of call signaling that allows multiple parties to be contacted without having to independently call each party.
A further object of this invention is to provide a scalable system for call signaling multiple endpoints.
The present invention is a call signaling system that takes advantage of multicasting technology. The invention sends signaling data in packets having multicast addresses so that multiple endpoints are contacted while sending only one setup signal.
By using a multicast address for telephony signaling, telephone calls can be sent to several telephony devices (i.e. an office phone, a cell phone, a home phone, a pager, etc.), all at the same time. A live-person contact can therefore be sought in several locations simultaneously, eliminating the prior art need for contacting each location sequentially or independently. Furthermore, the invention allows conference calls to be accomplished faster because each of the desired parties can be contacted at the same time, eliminating the need for sequential, independent phone calls to each party.
To achieve these desired results, the invention synthesizes multicasting with call signaling to perform multicast call signaling. Several network endpoints subscribe to and thereby become members of a telephony multicast group. The subscribing endpoints then send call signaling packets (call setup requests) using a multicast address to each of the other members of the multicast group. Each of the subscribing endpoints is notified of a signaling state for each of the other members of that group. Therefore, when one member becomes active (i.e., transmits a call setup request), each of the other members becomes aware of this and can activate devices that notify a user. Of course, the multicast group can also still be used to carry the voice and/or video data in addition to the signaling data.
The invention is more scalable than prior art systems other than the transmission of the telephony call setup request from the originating endpoint, the network and the receiving endpoints do most of the call processing. This approach allows for more distributed processing and accordingly allows for more powerful and scalable implementations.
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Cisco Technology Inc.
Marger Johnson & McCollom PC
Nguyen Steven H. D
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