Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
2000-05-03
2003-10-21
Yao, Kwang Bin (Department: 2667)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S410000
Reexamination Certificate
active
06636522
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to methods and applications of call redirection in packet-based multimedia communications networks.
BACKGROUND OF THE INVENTION
It is common in today's switch-based telephone networks to offer call redirection services such as call forwarding and call distribution, usually on a subscription basis. When a subscriber having a default DN (directory number) wants to activate call forwarding for example, the subscriber enters a forwarding DN, and a signalling procedure takes place between the subscriber's telephone and a network node which may be a telephone network switch, or an AIN (advanced intelligent network) based SSP (service switching point) for example. The network node then controls the redirection of calls initially directed towards the subscriber's default DN such that they are received at the forwarding DN. Such a centralized mechanism for providing features to subscribers requires a substantial investment in operations, administration, and maintenance functions.
The use of computing devices connected to an IP (internet protocol), ISDN (integrated serviced digital network) or ATM (asynchronous transfer mode) based LAN (local area network) or WAN (wide area network)) to assume multimedia communications roles has recently become increasingly widespread. Examples of this include voice communications and video conferencing communications over private intranets or the public Internet. It is desirable to be able to offer users of such multimedia communications media call redirection features which are similar to those which are available to normal telephone subscribers. For example, when an end-user having a computer normally connected to a default location with a normal address within a particular LAN moves to a different known location where he/she has access to another computer having a different address, it would be useful to be able to have multimedia calls placed to his/her normal address forwarded to the different address. A dedicated computing device or server may be used to provide the required call redirection capability to a number of end-users. This “server based” approach requires related operations, administration and maintenance functionality, requires address translation and related signalling from the end-user's computing device to the dedicated computing device, all of which adds complexity which may not be desirable from an administrative authority's perspective. In addition, having the call redirection functionality on a dedicated device offers limited end-user control and customization over how his/her calls are to be forwarded.
The Mobile IP Protocol (defined by the mobile IP work group within the IETF (Internet Engineering Task Force)) is an existing IP (Network) layer procedure for terminal mobility within the Internet/Intranet [Perkins, C., Editor, “IP Mobility Support”, RFC 2002, October 1996]. This protocol, however, requires the modification of a mobile host's IP stack to handle IP encapsulation or tunnelling, the modification of the home router's IP stack to support the functionalities of a Home Agent (i.e. encapsulating/decapsulating and tunnelling both call signalling and media packets to the destination c/o address), the existence of a Foreign Agent on the foreign network (router) to handle IP encapsulation/decapsulation and tunnelling at the far end, procedures to discover and register with Home Agents and Foreign Agents, and procedures to gain access to firewalls when the callee's mobile host is attached to a subnetwork behind a firewall.
Although comprehensive and currently gaining wide acceptance, the Mobile IP protocol requires modification to both the home network router's, foreign network router's and the mobile host's IP stack before being applied to realize terminal mobility. It provides very little end user control over how his/her calls are to be redirected, since call redirection is performed at the IP layer within the router.
SUMMARY OF THE INVENTION
It is an object of the invention to obviate or mitigate one or more of the above identified disadvantages.
According to a first broad aspect, the invention provides a personal mobility method for allowing a callee having a personal host connected to a packet based communications network at a home address to receive, at a foreign host connected to the network having a c/o (care/of) address, a multimedia call from a calling host originally directed towards the personal host, the method comprising the steps of: a) a call redirector application running on the personal host responding to a call setup request from the calling host with a call setup reply which includes the c/o address; b) the calling host sending a call setup request to the foreign host at the c/o address; and c) the foreign host sending a call setup reply, thereby completing the call signalling required to establish a link between the calling host and the foreign host.
According to a second broad aspect, the invention provides a terminal mobility method for allowing a callee having a mobile host normally connected to a packet based communications network at a home address to receive, at a their mobile host connected at a c/o (care/of) address, a multimedia call from a calling host originally directed towards their personal host, the method comprising the steps of: a) a call redirector application running on a shadow host intercepting a call setup request addressed to the personal host from the calling host with a call setup reply which includes the c/o address; b) the calling host sending a call setup request to the mobile host at the c/o address; and c) the mobile host sending a call setup reply, thereby completing the call signalling required to establish a link between the calling host and the mobile host.
According to a third broad aspect, the invention provides a call distribution method for distributing multimedia calls among a plurality of peer computing devices connected to a packet based communications network, each computing device having an address, one of the peer computing devices having a main address and being equipped with a call redirector application, the method comprising the steps of: a) the call redirector application running on the computing device having the main address responding to a call setup request from the calling host with a call setup reply which includes a redirecting address consisting of the address of one of the plurality of peer computing devices; b) the calling host sending a call setup request to the redirecting address; c) said one of the plurality of computing devices a call setup reply, thereby completing the call signalling required to establish a link between the calling host and the one of the plurality of computing devices.
According to a fourth broad aspect, the invention provides a call distribution method for distributing multimedia calls among a plurality of peer computing devices connected to a packet based communications network, each computing device having an address, one,of the peer computing devices having a main address and being equipped with a call redirector applications, the method comprising the steps of: a) the call redirector application running on the computing device having the main address responding to a call setup request from the calling host with a call setup reply; b) said one of the plurality of peer computing devices sending a call setup request to the computing device having the main address indicating that that device is available; c) the computing device having the main address responding with a call setup reply containing the address of the calling host; d) the one of the plurality of computing devices sending a call setup request to the calling host; e) the calling host responding with a call setup reply, thereby completing the call signalling required to establish a link between the calling host and the one of the plurality of computing devices; f) the calling terminal sending a disconnect message to the device having the main address
Frank Alan S.
Perinpanathan Nishanthan M. T.
Taylor Paul Thomas
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