Telephonic communications – Plural exchange network or interconnection – With interexchange network routing
Reexamination Certificate
2000-02-14
2003-10-28
Smith, Creighton (Department: 2742)
Telephonic communications
Plural exchange network or interconnection
With interexchange network routing
C379S221080
Reexamination Certificate
active
06639981
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the routing of signaling messages in a communications network, such as the public switched telephone network (PSTN), or a voice over internet protocol (VOIP) network. More particularly, the present invention relates to methods and systems for routing signaling messages associated with ported subscribers in communications network.
BACKGROUND ART
Local number portability (LNP) gives telephone service subscribers the ability to change local service providers without changing their directory numbers. More specifically, the generic term LNP is actually representative of three basic number porting scenarios: service provider portability which allows subscribers to change local service providers without changing their phone number; service portability, which allows subscribers to change from one type of service to another (e.g., analog to integrated services digital network (ISDN) without changing their phone numbers; and geographic portability, which allows subscribers to move from one physical location to another without changing their phone numbers.
In the current, non-LNP environment, a telephone number performs two basic functions: it identifies the customer, and it provides the network with information necessary to route a call to that customer. Local number portability solutions separate these two functions, thereby providing the means for customers to keep the same directory number when changing local service providers. By separating these two functions, LNP gives customers the flexibility to respond to pricing and service changes offered by rival carriers. Accordingly, it is anticipated that LNP will promote local-exchange competition, which in turn will benefit all customers, as has already been the case with the long-distance market. As LNP solutions are implemented, competition in the local-exchange market is expected to drive down the cost of service, encourage technological innovation, stimulate demand for telecommunications services, and boost economic growth.
A number of interim number-portability methods, such as remote call forwarding and direct inward dialing exist today. However, these methods have several disadvantages: longer call set-up times, increased potential for call blocking, continued reliance on the incumbent local exchange carrier's (LEC's) network, loss of feature functionality, as well as substantial on-going costs to the new local service provider. Among the more long-term LNP solution approaches currently being offered, triggered LNP technology is the most relevant to a discussion of the present invention.
Triggered LNP Solutions
Triggered LNP solutions, as indicated by the name, require that both the “new” and “old” local service providers implement a trigger function in their respective end offices. The “old” service provider switch (often referred to as the donor switch) administers an LNP trigger on the ported subscriber's directory number. When activated, this trigger causes the end office switch to formulate an LNP query that is subsequently launched into the SS7 network. This LNP query is ultimately delivered to an LNP database that contains information related to service provider associated with the dialed number. More particularly, the LNP database performs a lookup based on a portion of the called party dialed digits. A location routing number (LRN) is returned by the LNP database which identifies the end office of the service provider currently serving the called party. The LRN value is then sent back to the end office that originated the LNP query. Upon receipt of the LRN containing message, the originating end office proceeds with call setup and teardown operations using the LRN as a destination address for all subsequent messages associated with the call.
Shown in
FIG. 1
is an example of a telecommunications network, generally indicated by the numeral
100
, that employs a triggered LNP solution similar to that described above. Telecommunications network
100
includes an originating end office (EO)
110
, a recipient terminating EO
112
, a donor terminating EO
113
, a tandem switching office
114
, a signal transfer point (STP)
116
, a service control point (SCP) based LNP database
118
, a calling party
120
, and a called party
122
. In this example, it is assumed that called party
122
has had local phone service ported from a service provider that owns EO
113
to a service provider that owns EO
112
. Consequently, it is implied that the service responsibility for called party
122
was transferred from the donor EO
113
to the recipient EO
112
at some point in the past. As such, EO
112
is now assumed to service called party
122
.
As such,
FIG. 1
illustrates a simplified signaling message flow sequence associated with the setup of a call from calling party
120
to called party
122
. When calling party
120
goes off-hook and dials the telephone number associated with called party
122
, originating EO
110
analyzes the dialed digits and recognizes that the dialed number falls within an exchange that contains ported subscribers. Consequently, the originating EO
110
formulates an LNP query message M
1
and sends this query message to the STP
116
. Those skilled in the art of SS7 telecommunication networks will appreciate that such LNP queries and responses are typically in the form of Transaction Capabilities Application Part (TCAP) protocol signaling messages. As the TCAP protocol is well known and widely employed in the communication networks presently contemplated, a detailed discussion of the TCAP signaling protocol is not included herein.
Returning now to the message flow shown in
FIG. 1
, LNP query message M
1
is received by the STP
116
and subsequently routed to the SCP-LNP database node
118
as LNP query message M
2
. The LNP query message M
2
is processed by SCP-LNP database node
118
, and an LNP response message M
3
is formulated and sent back to STP
116
. It should be appreciated that LNP response message M
3
contains a Location Routing Number (LRN) associated with the recipient EO
112
, which is the EO currently servicing Called Party
122
. Tandem office
114
is particularly significant from a call setup standpoint, in that a voice trunk connection through tandem
114
will ultimately be required in order to establish a voice circuit with the terminating EO
112
that is currently serving the called party
122
. LNP response message M
3
is received by the STP
116
and subsequently routed to the originating EO
110
, as LNP response message M
4
. The originating EO
110
processes the LNP response message M
4
, and uses the LRN information contained therein to formulate and send a call setup message M
5
. Once again, those skilled in the art of SS7 telecommunication networks will appreciate that such call setup messages are typically of ISDN user part (ISUP) format, and as the ISUP signaling protocol is well known and widely employed in the telecommunications industry, a detailed explanation of this protocol is not provided herein.
Signaling System #
7, by Travis Russell, copyright 1998, McGraw-Hill Publishing, the disclosure of which is incorporated herein by reference in its entirety, provides a detailed explanation of TCAP and ISUP signaling protocols.
Returning to
FIG. 1
, STP
116
receives message M
5
and subsequently message transfer part (MTP) routes the message to tandem office
114
as message M
6
. Tandem office
114
examines and processes the message and formulates a message M
7
. Message M
7
is sent to STP
116
, which in turn MTP routes the message to terminating EO
112
as message M
8
. Those skilled in the art of telecommunications network operations will appreciate that additional call setup and teardown messages, not shown in
FIG. 1
, may be necessary to administer a complete a telephone call between the calling party
120
and the called party
122
. The signaling message flow shown in
FIG. 1
is intended only to generally illustrate a conventional LNP translation process. As these addition
Collard Colleen McGinnis
Cox David Paul
Dunn, Jr. Randal Latta
Ravishankar Venkataramaiah
Jenkins & Wilson, P.A.
Smith Creighton
Tekelec
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