Telephonic communications – Plural exchange network or interconnection – With interexchange network routing
Reexamination Certificate
2002-03-20
2004-08-10
Matar, Ahmad F. (Department: 2642)
Telephonic communications
Plural exchange network or interconnection
With interexchange network routing
C379S229000
Reexamination Certificate
active
06775375
ABSTRACT:
TECHNICAL FIELD
The invention relates generally to service and operations control for a telecommunications network, and more particularly to a service control and operations element system which performs and controls various functions of the telecommunications network.
BACKGROUND OF THE INVENTION
Management of modern telecommunications networks requires performing multiple functions, including call establishment and routing, fault management, call details recording used to compile customer bills, fraud detection and control, new services provisioning, post-dialing delay measurement and time synchronization. Currently, multiple systems within a telecommunications network perform these various functions.
In a telecommunications network, information in the form of signaling messages is exchanged between network elements involved in call establishment and control. Switches, databases and the like are used to carry out the information exchange.
Common channel signaling is an out-of-band technique for exchanging information over channels separate from those used to carry voice or data signals. One well-known signaling technique utilizes the Comite Consultatif International Telegraphique et Telephonique (CCITT) Signaling System no. 7 (SS7) protocol. In the interface between an AT&T network device and a Private Branch Exchange (PBX), a second well known signaling technique utilizes Q.931 protocol. In SS7 protocol, the messages are highly structured information fields of bits that are differentiated from each other by a length indicator. A detailed discussion relating to the format of the SS7 message and to the interrelation of SS7 and Q.931 protocols is given in the CCITT Blue Book,
Specification of Signaling System No.
7, Vol. 6 (1988). For a discussion of common channel signaling No. 7 protocol in general, see G. G. Schanger,
IEEE Journal on Selected Areas in Communication,
Vol. SAC-4, No. 3, pp. 360-65 (1986), and S. Suzuki et al.,
Review of the Electrical Communication Laboratories,
Vol. 28, No. 1-2, pp. 50-65 (1980) (each of which is incorporated herein by reference).
The network elements associated with a typical telecommunications network, such as the AT&T switched network, which are commonly traversed by a call include the following: (1) an originating switch node associated with the network, located in the geographic area of the calling party, which receives a call request message from a local exchange carrier or a competitive access provider, and is responsible for controlling the call set-up; (2) a terminating switch node, also associated with the network, but located in the geographic area of the called party, which connects the call to a local exchange carrier or a private branch exchange associated with the called party; (3) a via switch, used when a direct path between the originating switch node and the terminating switch node is not available because all direct trunks from the originating to the terminating switch nodes are busy, but an idle path exists which may be activated by using the via switch to reach the terminating switch node (for simplicity, references to via switches are omitted in the text and figures); (4) a service control point, which acts as a database that instructs the originating switch node as to the processing and routing of certain calls; and (5) signal transfer points, deployed in mated pairs, connected to the originating switch node, the terminating switch node, and the service control point by access links, used for transferring messages between network elements.
A typical call in North America has a called number of the form N0/1X NXX-XXXX, N being any number 2 through 9, 0/1 being either a 0 or a 1, X being any number 0 through 9, where the 10-digit code from left to right generally represents: a three-digit area code, a three-digit central office code, and a four-digit station number. The area code digits identify a geographic region in North America, the central office code digits identify the central office exchange serving the called party and the station code digits provide identification of the called party.
When the first three digits in the number are 800 or 900, however, the number is not directly associated with a geographic region. Some or all of the digits in an 800/900-type number normally must be translated into a physical destination by a service control point, which maintains a table of 800/900 numbers and the physical destinations associated with the numbers. Such a translation is referred to as a global title translation, and the tables maintained by the service control points are referred to as global title translation tables. The switches and/or signal transfer points maintain tables which identify which service control points serve which 800/900 numbers.
A signaling message flow for a typical call of the type 800 NXX XXXX or 900 NXX XXXX which traverses the various network elements is as follows.
An originating switch node receives a call request message, typically in the form of an initial address message, from a local exchange network or a competitive access provider serving the calling party. The originating switch node validates the message. If an error is detected in the message during the validation process, the call flow ends.
If no error is detected in the message, the originating switch node looks to its global title translation table to determine the identity of a service control point which can provide processing and routing instructions for the call. The global title translation table contains entries representing all numbers served by the network (e.g., 800 NXX XXXX or 900 NXX XXXX). For each dialed number, the table provides a service control point identification and a subsystem number identifying the application at that service control point. If the dialed number does not match an entry in the global title translation table, either the table is in error or the local exchange carrier switch or competitive access provider's switch misrouted the call.
Assuming a valid dialed number entry exists in the table, the originating switch node formulates a query message, also called a transaction capabilities application part message, requesting call routing and processing information. The originating switch node sends the query message to the service control point identified by the global title translation table. In some existing systems, a signal transfer point, instead of the originating switch node, looking at its own global title translation tables, routes a query message to the identified service control point.
After the service control point receives the query message, it formulates a response message containing instructions for processing and routing the call, and forwards the response message back to the originating switch node. If the service control point determines that it does not serve the dialed number received in the query message, the service control point will identify the error in the response message. Thus, the response message may contain instructions for processing and routing the call, or may be used to communicate that the call is being aborted because of an error detected at the service control point.
The originating switch node receives the response message and validates it. Assuming reception and validation of the response message is successful, the originating switch node proceeds to route the call. As part of the routing function, it sends the request message to a terminating switch node via a signal transfer point.
After the terminating switch node receives the request message from the signal transfer point and validates it, it forwards the request message to a local exchange carrier or private branch exchange serving the called party. If a private branch exchange serves the called party, however, the terminating switch node forwards, using Q.931 protocol, a set-up message (equivalent to the request message) to the private branch exchange. In both cases, the signaling in the forward direction for the call is thereby completed.
For a call terminating at a local exchange carri
Agdeppa Hector
AT&T Corp.
Matar Ahmad F.
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