Feature transparency in a telecommunications network

Details Feature transparency in a telecommunications network Feature transparency in a telecommunications network

1998-06-30

2003-11-18

Chin, Wellington (Department: 2664)

Multiplex communications

Pathfinding or routing

Combined circuit switching and packet switching

C370S465000

Reexamination Certificate

active

06650632

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to telecommunications and more particularly to signaling systems that communicate information about features of services and calls in virtual private networks.
BACKGROUND OF THE INVENTION
Many corporations and other enterprises are installing private networks to interconnect their facilities to provide voice and data communications. Private networks typically include a number of private branch exchanges (PBXs) or other telephone switches that are linked together. Each PBX, which supports a private network or subnetwork of its own, is typically responsible for telecommunications services in a geographically restricted area, for example, at a particular building or campus occupied by the enterprise. In contrast to a public switched telephone network (PSTN), which is operated by a common carrier, a private network is generally characterized by access limits or restrictions, for example, by designating particular telephones or telephone numbers for internal communications only. As enterprises expand to include an increasing number of offices and sites, they need to link together the PBXs and private networks across wider geographical areas.
FIG.
7
(
a
) depicts one way of linking private networks
700
and
710
together by installing a fixed, point-to-point private line
720
between the two private networks. For purposes of illustration, private network
700
includes a PBX
702
and two (2) telephones
704
and
706
, and private network
710
also includes a PBX
712
and two (2) telephones
714
and
716
. A fixed, point-to-point private line
720
is coupled between PBX
702
of private network
700
and PBX
712
of private network
710
. Accordingly, a user of telephone
704
in private network
700
can call telephone
714
over fixed, point-to-point private line
720
in private network
710
.
One drawback for an enterprise in interconnecting private networks at different sites with fixed, point-to-point private lines becomes apparent when the sites are widely separated. For example, to install a fixed, point-to-point private line beyond the boundaries of an office building or campus is often too expensive. When the sites are in different cities or different countries, the cost may become prohibitive. Accordingly, public telephone carriers offer “virtual private networks” to their customers.
A virtual private network is a combination of public and private networks, in which the public portion of the virtual private network carries local and long distance communications between various private networks. In a virtual private network, as illustrated in FIG.
7
(
b
), the customer uses the telephone carrier's public network
730
to interconnect its geographically separated private networks
700
and
710
. The network dialing plans, routing schemes, and switches of the public network
730
, however, are configured in such a manner that the customer's service appears to be carried over a private network connection. Such a configuration can actually involve the use of several interconnected networks, each of which use may employ a different signaling protocol.
One benefit of private networks over public networks is that they can provide features and services that are unavailable in public networks. A feature is a unit of functionality that is incrementally added to a network to provide an additional service to users of the network. Many PBXs that implement private networks employ various protocols to support a rich set of features. For example, DPNSS, a PBX protocol popular in the United Kingdom, offers Call-Back-When-Free, Three-Way-Calling, Call-Forwarding, and many other special features.
Many private networks, however, implement features that are generally not supported by the protocols used within common public networks and, hence, in common virtual private networks. Protocols or messages that include feature requests not supported by the public network are typically filtered out or otherwise lost at an access point in the public network, because the unsupported feature has no analogue in the signaling message structure of the public network. Although some protocols employed by public networks reserve some space in signaling messages for passing user-defined information, the available space is typically insufficient for directly supporting many features common in private networks. Consequently, calls placed from such a private network across the public network portion are usually limited to the lowest-common denominator, often Plain Old Telephone Service (POTS), thereby destroying the appearance of a wide area virtual private network.
Based on the foregoing, there is a clear need for mechanisms that permit use of advanced calling features in a virtual private network, even when the public telephone network that implements the virtual private network does not support, or have a protocol capable of supporting, features of the private network.
Further, there is a need for a method of transmitting signaling messages over a virtual private network that request features not supported by a public network that implements the virtual private network.
SUMMARY OF THE INVENTION
These needs, and other needs that will become apparent from the following description, are addressed by the present invention, which comprises, in one aspect, an auxiliary communication network connection to transmit publicly non-supported features between sites in a virtual private network connected by a public communication network. Use of the auxiliary communication network enables messages to be passed between the virtual private networks sites without having to filter out or otherwise downgrade messages due to limitations in the protocols used by the public network. Consequently, users of the virtual private network gain feature transparency, which is the virtual appearance of a full-featured private network from end to end notwithstanding the lack of capabilities of the public communication network used for call establishment.
Since public communication networks often employ complicated and sophisticated routing techniques, there is also a need for a way to establish the auxiliary network connection without duplicating the routing logic of the public network. According to another aspect, the auxiliary connection is initiated through the auxiliary communication network from the destination site to the originating site, after the destination site in the virtual private network has received a connection request message from the originating site through the public network. Preferably, the auxiliary connection is established based on an identifier of the originating site passed within a user-defined space of the connection request message. Consequently, the auxiliary connection for handling features can be established regardless of how the original call is routed through the network.
Accordingly, one aspect of the invention relates to a call feature transmission apparatus for use with a first private network that is connected to a second private network by a communication network. The communication network employs a protocol incapable of supporting at least one feature supported by the first private network and the second private network. The apparatus comprises a first communications interface coupled between the first private network and the communication network so as to communicate information between the first private network and the communication network. The apparatus also includes a second communications interface coupled between the first private network and an auxiliary network so as to communicate messages in the protocol that use the at least one feature. A processor is coupled to the first communications interface, the second communications interface, and a memory. The memory contains one or more instructions which, when executed by the processor, cause the processor to intercept a message directed from the first private network to the second private network, determine whether the message uses the at least one feature, and in respo

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