Telephonic communications – Plural exchange network or interconnection – With interexchange network routing
Reexamination Certificate
2002-09-26
2003-08-26
Hong, Harry S. (Department: 2642)
Telephonic communications
Plural exchange network or interconnection
With interexchange network routing
C379S221090, C379S221120, C379S224000
Reexamination Certificate
active
06611586
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to telephony and in particular to the art of using the Signaling System Number 7 (SS7) protocol to effect a database lookup by a Service Control Point (SCP) to assist in routing a toll call in a telephone network.
BACKGROUND OF THE INVENTION
The conventional telephone network, known as the Public Switched Telephone Network (PSTN), may be thought of as at least two different networks. The first of these networks is called an End Office (EO), and is typically operated by Local Exchange Companies (LEC), and the second—the network that carries toll traffic—is typically operated by an Inter-Exchange Carrier (IXC). These distinctions are used only for illustrative purposes. It may be the case, for example, that the same company serves as both the EO and the IXC. Additionally, the EO could be a wireline telephone company or a wireless telephone company, providing a subscriber loop via networks called Wireless Local Loops.
To complete a call that originates at an EO, a gateway switch functioning as an originating toll station (OTS) or a tandem-toll office (TO) is typically accessed. The OTS and the TO are ordinarily controlled by the IXC. Once the gateway switch takes control of the telephone call, the call can be completed without accessing the EO, which originated the call. In such a network, edge switches are used to concentrate customer traffic from EOs and feed it to a carrier network.
Other configurations of network interconnections are also possible. For example, a direct link to a carrier of toll traffic, such as an IXC or other carrier, can be established between a Customer Premise Equipment (CPE) located at a customer site and the gateway switch. In such cases, the IXC traffic that originates at the customer site is concentrated or “aggregated” by the CPE and routed via the toll carrier's trunks. These CPE vehicles that perform such traffic aggregation or gateway function between a customer site and the carrier network are also called edge switches.
An edge switch is a switch located at the edge of a network, typically the EO network or a CPE, where traffic from network nodes such as the EOs or CPEs crosses over to the toll or other carrier networks. The edge switch network configuration can be considered as a network comprising several subtending nodes causing the traffic to converge at a concentrator node. Thus, in a PSTN, the EO or the CPEs form the subtending nodes and the IXC toll tandem switches or other carrier vehicles act as concentrator nodes or gateways to the long-distance trunks. Thus, the subtending nodes or edges may be operated by one entity such as a LEC or a large customer such as a major bank or a government agency, whereas the concentrator or gateway may be operated by an IXC or a toll carrier or other entity. In other configurations, the edge switch vehicles could be operated by the toll carriers and the CPEs or the nodes that feed the traffic to the edge switches could be operated by the so-called nodal customers, such as large banks, or government agencies.
In the following discussion, reference is made to an “edge switch.” This reference should be understood to encompass all configurations of switching systems that could serve the purpose of establishing an interconnection between two switching networks, including, but not limited to, an EO switching system or a switching system such as a Private Branch Exchange (PBX) or other switch serving as a CPE. An example of an edge switching system is a class 5 system such as the Lucent® 5ESS™ switching system. The 5ESS™ is described by K. E. Martersteck, et al., in
AT
&
T Technical Journal
, Volume 64, No. 6, part 2, pp. 1305-1564 (July/August, 1985). Other examples of switching systems that could function as edge switches are the DMS-250™ switching system marketed by Nortel, Inc.; the EWSD™ switching system marketed by Siemens AG of Munich, Germany; the Lucent® DEFINITY™ PABX system; and the NEAX-51E™ switching system marketed by Nippon Electric Corporation of Japan.
Similarly, a reference in the following discussion to a “toll tandem” should be understood as encompassing any toll switching system or other similar vehicle that can determine the routing by either looking up from a traditional database or by interfacing with an intelligent network database such as a Service Control Point (SCP). The toll tandem switch may be, illustratively, an electronic program-controlled telephone switching system of the No. 4ESS™ design as described by A. E. Ritchie, et al., in the
Bell System Technical Journal
(BSTJ), Volume 56, No. 7 (September, 1977). The 4ESS™ switch performs multiple functions: as an originating switch, and as a toll tandem, and as a gateway to the SCP database. When it functions as an originating switch, the 4ESS™ switch is programmed to open a voice connection to a subscriber to play announcements, and receive input as touch-tone™ digits or other forms prior to routing a call on a network trunk. Thus, an originating switch such as a 4ESS™ is capable of engaging in a dialog with a subscriber to obtain additional information (e.g., authorization code for special calls).
A telephony Advanced Intelligent Network (AIN) comprises a network within the PSTN comprising switching systems such as the edge switches and the toll tandem switches, adjunct computer processors and other communicating components equipped with the capability to communicate using an out-of-band signaling method known as Common Channel Signaling (CCS). CCS is a high speed data link configured to carry network control information to and from various elements of the network. The AIN is described in detail in U.S. Pat. No. 5,247,571, which is incorporated herein by reference. For more information on intelligent telephony networks, see
The Intelligent Network Standards: Their Application to Services
(Igor Faynberg, Ed.), McGraw Hill Series on Telecommunications (November 1996).
The details of the usage of CCS to control and manage a telecommunications network are given in U.S. Pat. Nos. 5,515,427 and 4,277,649, both of which are incorporated herein by reference. An example of the CCS signaling method is CCS No. 7 which is also known as Signaling System 7, or SS7. SS7 is the name given to a suite of layered communication protocols that are used to access telephony databases, to establish and maintain telephone calls, and for other purposes. The part of the SS7 signaling protocol that is typically used by an AIN-equipped switching system to access telephony databases to obtain special instructions is called the Transaction Capabilities Application Part (TCAP).
U.S. Pat. No. 5,901,213, by Benhabib, et al., whose contents are also incorporated by reference, describes a virtual dedicated access by telecommunication subscribers to an IXC provided by way of an intelligent local EO that routes calls either to the IXC or to a local EO. The intelligent local EO itself advantageously performs inter-exchange processing of calls, as required, for calls that originate with, or terminate at, a customer rather than automatically route calls to the IXC for such inter-exchange processing, as was previously required.
In general, in an AIN, a switching system is equipped with at least one triggering device implemented as software, circuitry, or a combination of the two. The triggering device is configured to recognize the occurrence of certain types of phone calls (“trigger conditions”) and respond accordingly by handling such calls in a special way. Typically, to provide special handling in response to a trigger condition, the switching system suspends normal execution of the phone call, communicates with another network element to obtain special instructions, and handles that phone call according to the special instructions. In contrast, ordinary telephone calls do not require any special handling and therefore do not require special instructions from other network elements. Rather, in processing ordinary calls, local and toll tandem office switches function in a normal way and route such cal
Ibezim James A.
Kittredge Barbara Joanne
Mansell James J.
Peters Jr. Robert Yaeger
AT&T Corp.
Hong Harry S.
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