Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: Connection controller for managing media paths between
terminal devices residing in different network domains
s FIELD OF THE INVENTION
The invention relates to communication devices, in
particular to a connection controller for the management
of media paths. The invention also extends to a terminal
proxy useful for controlling the flow of media signals
originating or arriving at a terminal device residing~~in a
communications network.
BACKGROUND OF THE INVENTION
is
Circuit switching and packet switching are different
and well-known methods for establishing a connection
between two terminal devices to permit the exchange of
uoice or data signals. In the dial-up telephone network,
for example, a caller's line goes to a switching center or
switch, where the actual connection is made to the called
party. In the case of a circuit-switch network, a
permanent connection is set-up and maintained for the
duration of the call. 'In contrast, the packet-switched
2s network does not establish a permanent connection, rather
the information to be transmitted is assembled in packets
that are sent over a channel dedicated to the connection
only for the duration of the packet transmission.
Communications systems that are currently available
in the marketplace, that support both circuit-switched and
packet-switched domains, use call processing and media
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path management logic that is very much dependent upon the
nature of the terminal devices involved in the call. This
is obviously undesirable since the call processing logic
must be designed to support a variety of signaling
protocols to accommodate a wide range of terminal devices.
Against this background it clearly appears that a
need exists in the industry to develop a communications
system that supports both circuit-switched and packet-
switched domains where the call processing and/or media
path management logic is de-coupled from the specific
signaling protocols of the individual terminal devices.
SUMMARY OF THE INVENTION
is
In a broad aspect, the invention provides a terminal
proxy for controlling media signals originating or
arriving at a terminal device residing in a packet
switched network domain. The proxy server has a first
interface for communicating with the terminal device using
a terminal device protocol, a second interface for
communicating with a.remote entity using a protocol other
than the terminal device protocol, and an interoperation
functional unit in communication with the first interface
and with the second interface. The interoperation
functional unit is operative to effect manipulations on
signaling information received by the interfaces from the
terminal device and the remote entity, respectively, to
allow the terminal device and the remote entity to
interoperate for effecting management of the flow of media
signals originating or arriving at the terminal device.
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The terminal proxy presents an advantage in that it
allows de-coupling the management of the media signals
from the signaling protocol of the terminal device.
In a specific and non-limitative example of
implementation, the remote entity with which the terminal
proxy communicates is a media path server. The media path
server can set-up a media path between two or more
terminal devices residing in a packet switched network. A
terminal proxy is associated with each terminal device.
The media path server communicates with each terminal
proxy by using a common protocol. In particular, when a
media path is to be set between two terminal devices
remote from one another, the media path server sends
signaling information to the terminal proxies of the
respective terminal devices. In turn, the terminal proxies
manipulate or convert the signaling information to allow
the media path server and the terminal devices to
interoperate.
For the purpose of this specification, the expression
"terminal device" should be given a broad interpretation,
and should not be limited to a communication device, such
as a telephone, that a user would normally employ to
communicate with a remote party. "Terminal device" can
include any device capable of providing telephony-related
services to a user, a gateway that connects two different
network domains, such as a gateway between a Private
Branch Exchange (PBX) and the Public Switched Telephone
Network (PSTN) or a gateway between two packet switched
networks, or a media gateway that forms a point of
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interaction between a packet switched network domain and a
circuit switched network domain. "Terminal device" can
also include the device that is the point of interaction
between two PBX systems, among many other possibilities.
Under a second broad aspect, the invention provides a
connection controller for the management of. media paths
between two or more terminal devices. These devices can be
in the same switching domain or reside in different
switching domains. For example, one terminal could reside
in a packet switched network and another terminal device
could reside in a circuit switched network. The
connection controller includes an input for receiving
signaling information indicative of a need of a media path
between two or more terminal devices. The connection
controller also includes one or more packet switched sub-
systems responsive to the signaling information to effect
management of the packet switched network leg, and one or
more circuit switched sub-system also responsive to the
signaling information to effect management of the circuit
switched network leg.
Under a third broad aspect, the invention includes a PBX
that has a call manager and a connection controller. The
connection controller is responsible for the management of
media paths during call sessions between terminal devices
set-up by the call manager. The call manager sends
signaling information to the connection controller that is
independent of the connection type of the terminal
devices. "Connection type" refers to where or how terminal
devices are connected or reside. The terminals can be
connected to or reside on one of multiple circuit-switched
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networks or one of multiple independent packet switched
networks.
BRIEF DESCRIPTION OF THE DRAVtlINGS
5
A detailed description of examples of implementation
of the present invention is provided hereinbelow with
reference to the following drawings, in which:
Figure 1 is a block diagram of a PBX that spans two
different network domains. In the block diagram the
arrows in solid lines represent logic signaling paths.
The arrows in dashed lines represent media paths.
Figure 2 is a detailed block diagram of a connection
controller of the PBX shown in Figure 1;
Figure 3 is a detailed block diagram of a terminal
proxy shown in Figure 2; and
Figure 4 is a block diagram of a terminal proxy in
accordance with a variant.
In the drawings, embodiments of the invention are
illustrated by way of example. It is to be expressly
understood that the description and drawings are only for
purposes of illustration and as an aid to understanding,
and are not intended to be a definition of the limits of
the invention.
3b
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DETAILED DESCRIPTION
An example of implementation of the present invention
is illustrated in figure 1 that depicts a PBX system 10
associated with terminal devices residing in a circuit-
switched network and terminal devices residing in a
packet-switched network. More particularly, the PBX
system 10 has four main functional units, namely a call
manager 12, a connection controller 14, an array of media
gateways 16 (individual media gateways are designated by
16a, 16b, 16c, etc.) and a time switch 18. It should be
noted that a plurality of time switches 18 can be provided
if a single time switch cannot provide enough resources in
terms of switching capacity. Also, a plurality of time
switches 18 can be provided to support circuit switched
devices residing in different circuit switched networks to
which the PBX 10 connects.
The PBX system 10 spans two types of network domains
that differ from one another by the manner in which a
connection between terminal devices involved while a call
session is made. The first domain is a circuit-switched
domain, while the second domain is a packet-switched
domain. The PBX system 10 is associated with a number of
terminal devices that reside in a circuit-switched network
15 that is part of the circuit-switched domain. It should
be appreciated that- the PBX system 10 can be associated
with several independent circuit-switched networks, all
being part of the circuit-switched domain. For example,
Figure 1 shows five typical terminal devices, namely three
devices 35, 37 and 39 that provide telephony related
services to users, a gateway 43 that forms a point of
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interaction between the PBX 10 and the PSTN and a point of
interaction 45 between the PBX 10 and another PBX system.
The PBX 10 is also associated with a plurality of
terminal devices 38, 40, 41 and 47 that reside a packet-
s switched network 34 that forms part of the packet-switched
network domain. As mentioned above in connection with the
circuit-switched domain, the PBX system 10 can be
associated with several independent packet-switched
networks, all being part of the packet-switched domain.
The terminal devices 38, 40 and 41 provide telephony-
related services to users. The terminal device 47 is a
gateway that forms a point of interaction between the
packet switched network 34 and another packet-switched
network. Finally, note that the media gateways 16a, 16b,
16c, etc., also constitute terminal devices that are
controlled by the PBX.
The time switch 18 is an entity that routes media
signals properly to complete the media signal paths during
a call session between terminal devices that involves the
circuit-switched network 15. As mentioned earlier, the PBX
system 10 may be provided with an array of time switches
18 to augment the resources of the PBX 10 when required,
or to service independent circuit-switched networks.
The media gateways 16a, 16b, 16c, etc., form points
of interaction between the circuit-switched network 15 and
the packet-switched network 34. A media gateway 16a, 1~6b,
16c, etc., is responsible for performing the necessary
media signal conversions such that parties involved in a
call session terminating in different network domain types
can hear what each other is saying. For example, media
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signals into the circuit-switched network 15 are in the
form of Pulse Coded Modulation (PCM) signals. When such
PCM signals are delivered to a media gateways 16a, 16b,
16c, etc., they are converted into discrete data packets
that are sent to the packet-switched network 34 for
delivery to the terminal device 38, 40, 41 or 47 that
terminates the call session in the packet-switched network
34. Advantageously, the media gateway 16a, 16b, 16c,
etc., will encode the audio information to compress it in
order to reduce the bandwidth requirements. Any suitable
encoding algorithm can~be used for this purpose. For
media signals into the reverse direction, the media
gateway 16a, 16b, 16c, etc., converts data packets into a
suitable encoding algorithm for circuit switched
connections, for example PCM, that is passed .to the
circuit-switched network 15. If the media signals into
the reverse direction are encoded, the media gateway 16a,
16b, 16c, etc., will decode them into a suitable encoding
algorithm for circuit switched connections, for example,
PCM format.
The call manager 12 includes a call .processing
functional unit 42 and a plurality of terminal agents 44.
A distinct terminal agent 44 is associated with each
terminal device 35, 37, 39, 43, 45, 38, 40, 41 and 47.
The call processing functional unit 42 is software
implemented and performs high level call processing
services such as call set-up, feature invocation, voice
mail, among many others.
The terminal agents 44 are software implemented
entities that manage the . operations of the terminal
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devices 35, 37, 39, 43, 45, 38, 40, 41 and 47. For
example, the terminal agent 44 of the terminal device 38
could be designed to track call states, feature states and
the user interface operation of the terminal device 38.
Although Figure 1 shows the call manager 12 as a
single entity, it should be appreciated that the call
manager 12 could be designed as a distributed architecture
system where the different components, such as the call
processing functional unit 42 and the terminal agents 44,
are remote from one another. Individual Call Processing
Functional Units can also be linked to form to form a
larger distributed system.
The connection controller 14 is responsible for
managing media paths involving the terminal .devices 35,
37, 39, 43, 45, 38, 40, 41, 47 and 16a, 16b, 16c, etc.,
during call sessions handled by the call manager 12. The
call manager 12 controls the operation of the connection
controller 14 by sending signaling information to the
connection controller. This signaling information is
independent upon the connection type of terminal device
being controlled.
Figure 2 illustrates in greater detail the structure
of the connection controller 14. The connection
controller 14 includes a central connection unit 48, a
circuit-switched sub-system 50 and a packet-switched sub-
system 52. In the example shown, each sub-system 50, 52
is associated with a corresponding network, namely
circuit-switched network 15 and the packet-switched
network 34. When the PBX 10 connects to devices residing
in different or independent networks under the same domain
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type, for instance two or more circuit-switched networks,
the connection controller may be provided with a plurality
of sub-systems, each sub-system associated with a
corresponding network. Accordingly, it should be
5 understood that the connection controller 14 is not
limited to only a single sub-system per network domain
type.
The central connection unit 48 has an input 46
through which signaling information sent from the call
10 manager 12 is received. The central connection unit 48
has an overall controlling responsibility for the
operation of the connection controller 14. The purpose of
the circuit-switched sub-system 50 is to manage the
portion of the media path during a call session that
resides in the circuit-switched network 15. Similarly,
the purpose of the packet-switched sub-system 52 is to
manage the portion of the media path during a call session
that resides in the packet-switched network 34. During a
call session where the terminal devices reside in the same
network, only the sub-systems 50-52 associated with that
network will be activated. The other sub-systems 50-52
will remain inactive.
The packet-switched sub-system 52 includes a media
path server 54 and a plurality of terminal proxies 56.
Each terminal proxy 56 is associated with a terminal
device that resides in the packet-switched network 34. In
the example shown in the drawings, there is one terminal
proxy 56 for each terminal device 38, 40, 41, 47 and 16a,
16b, 16c etc. The media path server communicates with the
terminal proxies 56 by using a common protocol. This
signaling is done independently of the specific signaling
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protocols of the terminal devices 38, 40, 41, 47 and 16a,
16b, 16c etc.
One of the functions of the media path server 54 is
to mediate with various terminal devices that are to be
connected by a media path such as to allow the media
signals to be properly exchanged. For example, when
terminal devices exchange encoded voice information, and
each terminal device can implement a plurality of
encoding/decoding algorithms, one of the functions of the
media path server is to designate for each terminal device
the encoding/decoding algorithm to use such that there is
compatibility.
It should be noted that the connection controller 14
could include a plurality of media path servers, each
media path server controlling a set of terminal proxies.
Also, the connection controller 14 may have a distributed
architecture such that its various components are remote
from one another. The components of the connection
controller 14 are software implemented. As such these
components can be executed on computing platforms that are
remote from one another without departing from the spirit
of the invention.
Figure 3 illustrates a terminal proxy 56 in greater
detail. The terminal proxy 56 includes an interface 58
that communicates with the media path server 54 by using
any suitable signaling protocol. The media path server 54
communicates with each terminal proxy 56 by using the same
signaling protocol. For the purpose of convenience, the
signaling protocol between the media path server 54 and
the terminal proxy 56 will be referred to as "media path
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server signaling protocol".
The terminal proxy 56 includes an interface 60 that
communicates with the terminal devices 38, 40, 41, 47 and
16a, 16b, 16c etc., by using signaling protocols that are
terminal device specific. The terminal proxy 56 further
includes an interoperation functional unit 62 whose task,
broadly stated, is to effect the necessary manipulations
on data exchanged between the entities (media path server
54, terminal devices 38, 40, 41, 47 and 16a, 16b, 16c
etc.,) such that the two entities can functionally
intemperate. For example, the interoperation functional
unit 62 can perform some basic signaling information
translation such that signaling information received in
the media path server protocol is converted into signaling
information in the protocol of the specific terminal
devices 38, 40, 41, 47 and 16a, 16b, 16c, etc.
It should be expressly noted that "interoperation" is
not limited to signaling information translation as it can
encompass a number of other functions. For the purpose of
this specification, "interoperation" implies conversion of
data, either protocol conversion or logical conversion
such as to allow messages from one entity to be understood
and/or implemented by another entity.
Although not essential, it is advantageous to provide
the interoperation functional unit 62 with the capability
to either query the terminal devices 38, 40, 41, 47 and
16a, 16b, 16c etc., for information such as what are its
specific functionalities or capabilities, or store a
profile that holds this information. The profile as to
the specific functionalities or capabilities of the
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terminal devices 38, 40, 41, 47 and 16a, 16b, 16c, etc.,
can be transmitted to the media path server 54 that can
use this information in setting up the media path leg in
the packet switched network 34.
The terminal proxies 56 can be software implemented.
As indicated earlier, the terminal proxies 56
abstract the media path server functions from the terminal
device specific signaling protocols. The terminal proxies
56 can be designed to be generic or terminal device
specific. A generic terminal proxy 56 has an
interoperation functional unit 62 that has the capability
to effect signaling information translation from the media
path server protocol into a variety of possible terminal
device specific protocols. Also, the terminal device
interface 60 is designed to communicate with a variety of
possible terminal devices that use different signaling
protocols. In contrast, a terminal proxy 56 that is
terminal device specific can work with a specific terminal
device.
20' Figure 4 illustrates~a variant of the terminal proxy
70. The terminal proxy 70 can perform the functions of
the terminal proxy 56 described earlier. In addition, it
can also perform translation of signaling information
directed/reeeived from a terminal device, that is used for
purposes other than media signals control. Such signaling
information can be used for call processing functions, for
example. This feature allows the terminal proxy 70 to
interoperate with the terminal agents 44, to abstract the
operations of the call manager 12 from the terminal device
specific signaling protocols.
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The terminal proxy 70 has, in addition to the
components of the terminal proxy 56, a call manager
interface to communicate with the call manager 12 using a
call manager protocol. An interoperation functional unit
66 performs the necessary data manipulations such that
signaling information from the call manager can be made
compatible with the signaling protocol of the terminal
device, and vice-versa. The interoperation functional
unit 66 communicates with the terminal device interface
60 .
In a possible variant, a single interoperation
functional unit can be provided to handle signaling
information for both media path management and call
processing functions.
The following detailed examples will help to
illustrate the operation of the PBX system l0 in greater
detail.
1) Example 1 (call session between terminal devices in the
circuit-switched network):
a) A user at terminal 35 wants to call a user at
terminal device 39;
b) The user at terminal device 35 goes off-hook or
performs another action (such as depressing a button
on the terminal device 35) that indicates that a call
session is desired;
c) The terminal agent 44 detects the off-hook condition
(or other action) and starts collecting information
input by the user identifying the remote party to be
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called. Such information can be the directory number
dialed on the terminal device 35;
d) The terminal agent 44 communicates with the call
processing functional unit 42 and then with the
5 terminal agent 44 of the terminal device 39 to signal
that a call session with the terminal device 35 is
desired;
e) The terminal agent 44 of the terminal device 39
signals to the terminal agent 44 of the terminal
10 device 35 that the call session is accepted;
f) The call manager 12 then signals the. connection
controller 14 to set-up a media path to connect the
terminal devices 35 and 39. This signaling
information is independent of the connection type of
15 the terminal devices 35 and 39, accordingly
immediately after the signaling information is
received~the connection controller 14 does not "know"
that the terminal devices 35 and 39 are both in the
circuit-switched network 15;
g) Based on the identifiers of the terminal devices 35
and 39 transmitted by the call manager 12, the
connection controller determines their connection
type. For instance, the connection controller 14 may
query the terminal devices 35 and 39 (or their
terminal proxies) involved 'in the call session to
determine where they reside. Alternatively, the
connection controller 14 communicates with another
entity in the PBX or even external to the PBX that
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can indicate the type of terminal devices based on
their identifiers;
h) Under this example, the connection controller 14
determines that both terminal devices 35 and 39
reside in the circuit-switched network 15.
i) The central connection unit 48 signals to the
circuit-switched sub-system 5.0 to establish a media
path between the terminal devices 35 and 39;
j) The circuit-switched sub-system 50 signals the time
switch 18 to set-up a media path between the terminal
devices 35 and 39;
k) During the call session the packet-switched sub-
system 52 is idle. .
2) Example 2 (call session between one terminal. device in
the circuit-switched network and one terminal device in
the packet-switched network). Steps (a) to (f) are the
same as above except that the call session is to be
established between the terminal device 35 and the
terminal device 38:
g) Based on the identifiers of the terminal devices 35
and 38 transmitted by the call manager 12, the
connection controller determines their connection
type;
h) Under this example, the connection controller 14
determines that terminal device 35 resides in the
circuit switched network 15 and terminal device 38
resides in the packet-switched network 34;
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i) The packet-switched sub-system 52 allocates a media
gateway, say media gateway 16a;
j) The central connection unit 48 signals to the
circuit-switched sub-system 50 to establish a media
path leg between the terminal device 35 and the media
gateway 16a;
k) The central connection unit 48 signals to the packet
switched sub-system to establish a media path leg
between the media gateway 16a and the terminal device
l0 38;
1) The media path server 54 sends signaling information
to the terminal proxy 56 of the media gateway 16a to
inquire about its capabilities;
m) The signaling message in (1) above is converted by
the terminal proxy 56 associated with the media
gateway 16a, in a message that the media gateway l~
can understand;
n) The media gateway 16a issues a response message and
that message is converted by the terminal proxy 56
associated with the media gateway 16a such that the
media server can understand the message;
o) The steps (1) to (n) are repeated with the terminal
proxy 56 associated with the terminal device 38;
p) Assume that, the media path server 54 has been advised
that the media path server can encode/decode voice
signals according to algorithms A, B, and C, while
the terminal device can encode/decode voice signals
according to algorithms C and E;
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q).The media path server 54 selects encoding/decoding
protocol C for compatibility;
r) The media path server 54 sends signaling information
to the terminal proxies 56 of the media gateway 16a
and of the terminal device 38 such as to set the
media gateway 16a and the terminal device 38 to use
the encoding/decoding algorithm C. Alternatively, the
logic of the media path server 54 and the logic of
the terminal proxies 56 can be configured such that
it is the terminal proxies 56 that perform the actual
selection of the encoding/decoding algorithm. The
media path server in this case acts as a go-between
mostly re-transmitting messages from one terminal
proxy 56 to another terminal proxy 56.
s) At this point, the media path between the terminal
device 35 and the terminal device 38 is ready.
The various components of the PBX, such as the
connection controller 14, and the terminal proxies 56, are
implemented in software. More particularly, the software is
a program element contained on a computer readable storage
medium. The program element is executable on a suitable
computing platform to provide the functionality of the
connection controller l4 and the functionality of one or
more terminal proxies 56. Alternatively, the connection
controller 14 and a terminal proxy 56 can be implemented in
hardware or a combination software/hardware, without
departing from the spirit of the invention.
Although various embodiments have been illustrated,
this was for the purpose of describing, but not limiting,
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the invention. Various modifications will become apparent
to those skilled in the art and are within the scope of
this invention, which is defined more particularly by the
attached claims.
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