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Claims  |
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We claim:
1. A network comprising:
local communication links;
a trunk circuit;
at least two separately located central office switching systems
interconnected via the trunk circuit for selectively providing switched
call connections between at least two of the local communication links;
a signaling transfer point for routing signaling messages; and
signaling links coupling the signaling transfer point to the central office
switching systems, said signaling links being separate from the local
communication links and the trunk circuit;
wherein the signaling transfer point comprises:
(1) a data switch for switching messages between the signaling links,
(2) a database storing call processing data associated with a plurality of
the local communication links for control of call processing through one
or more of the central office switching systems, and
(3) a program controlled processor: (A) recognizing that a call satisfies a
predetermined condition in response to at least one call related signaling
message from one of the central office switching systems which is
processing the call, and obtaining call processing information from the
database, and transmitting a signaling message containing the call
processing information to the one central office switching system to
control subsequent processing of the call, and (B) controlling the data
switch to route a further signaling message relating to a call not meeting
the predetermined condition from one signaling link to another signaling
link.
2. A network as in claim 1, wherein:
the communication links are telephone links; and
the central office switching system are telephone switches.
3. A network as in claim 2, wherein a plurality of the telephone links are
telephone lines.
4. A network as in claim 1, wherein the signaling transfer point is adapted
for sending and receiving signaling system 7 (SS7) compliant signaling
messages.
5. A network as in claim 1, wherein the data switch comprises a packet data
switching fabric.
6. A network as in claim 1, wherein:
the network further comprises a service control point, separate from the
central office switching systems and coupled to the signaling transfer
point via a signaling link, said service control point comprising a
database storing call processing data associated with a plurality of the
local communication links for control of call processing through one or
more of the central office switching systems; and
the program controlled processor recognizes that the predetermined
condition is not met with regard to another call related signaling
message, and in response thereto the signaling transfer point routes said
another signaling message to the service control point.
7. An intelligent signaling transfer point comprising:
interface modules for providing two-way data communications to a plurality
of common channel interoffice signaling links coupled to switching offices
of a communication network;
a data switch for switching messages between the interface modules;
a database storing call processing data associated with a plurality of
local communication links of the communication network for control of call
processing through one or more of the central office switching systems;
and
a program controlled processor: (A) recognizing a predetermined condition
regarding at least one call related signaling message from one of the
central office switching systems which is processing a call, in response
thereto obtaining call processing information from the database, and
transmitting a signaling message containing the call processing
information to the one central office switching system to control
subsequent processing of the call, and (B) controlling the data switch to
route a further signaling message not meeting the predetermined condition
from one signaling link to another signaling link.
8. An intelligent signaling transfer point as in claim 7, wherein the data
switch comprises a packet data switching fabric.
9. An intelligent signaling transfer point as in claim 7, wherein the
interface modules and the data switch are adapted for sending and
receiving signaling system 7 (SS7) compliant signaling messages.
10. A network comprising:
local communication links;
a trunk circuit;
at least two separately located central office switching systems
interconnected via the trunk circuit for selectively providing switched
call connections between at least two of the local communication links;
a service control point, separate from the central office switching
systems, comprising a database storing call processing data associated
with a plurality of the local communication links for control of call
processing through one or more of the central office switching systems;
a signaling transfer point for routing signaling messages; and
signaling links coupling the signaling transfer point to the central office
switching systems and to the service control point, said signaling links
being separate from the local communication links and the trunk circuit;
wherein the signaling transfer point comprises:
(1) a data switch for switching signaling messages between the signaling
links
(2) a database storing call processing data associated with a plurality of
the local communication links for control of routing of signaling messages
related to services provided to the plurality of the local communication
links through the data switch; and
(3) a program controlled processor controlling the data switch to route at
least some incoming signaling messages from signaling links through to
other signaling links, and in response to at least some other signaling
messages meeting predetermined criteria, formulating responsive messages
in accord with call processing data stored in the database and sending the
responsive messages through signaling links.
11. A network as in claim 10, wherein:
the communication links are telephone links; and
the central office switching systems are telephone switches.
12. A network as in claim 11, wherein a plurality of the telephone links
are telephone lines.
13. A network as in claim 10, wherein the signaling transfer point is
adapted for sending and receiving signaling system 7 (SS7) complaint
signaling messages.
14. A network as in claim 10, wherein the data switch comprises a packet
data switching fabric.
15. A network comprising:
local communication links;
a trunk circuit;
at least two separately located central office switching systems
interconnected via the trunk circuit for selectively providing switched
call connections between at least two of the local communication links;
signaling links coupled to the central office switching systems and
carrying interoffice signalling messages, said signaling links being
separate from the local communication links and the trunk circuit; and
a signaling transfer point comprising a message routing fabric and a
database, for receiving the signaling messages over the signaling links,
transmitting signaling messages meeting at least one first predetermined
condition from a signaling link coupled to one of the central office
switching systems to a signaling link coupled to another of the central
office switching systems; and in response to a signaling message from one
of the central office switching systems meeting at least one second
predetermined condition formulating a response message based on
information from the database and transmitting the response message over a
signaling link to the one central office switching system.
16. A network as in claim 15, wherein:
the communication links are telephone links; and
the central office switching systems are telephone switches.
17. A network as in claim 16, wherein a plurality of the telephone links
are telephone lines.
18. A network as in claim 15, wherein the signaling transfer point is
adapted for sending and receiving signaling system 7 (SS7) compliant
signaling messages.
19. A network as in claim 15, wherein the data switch comprises a packet
data switching fabric.
20. A network as in claim 15, further comprising a services control point,
separate from the central office switching systems and coupled to the
signaling transfer point via a signaling link, said services control point
comprising a database storing call processing data associated with a
plurality of the local communication links and providing information for
control of call processing through one or more of the central office
switching systems in response to at least some of the signaling messages
meeting at least one first predetermined condition.
21. In a network comprising:
local communication links;
a trunk circuit;
at least two separately located central office switching systems
interconnected via the trunk circuit for selectively providing switched
call connections between at least two of the local communication links;
a signaling transfer point for routing signaling messages; and
signaling links coupling the signaling transfer point to the central office
switching systems, said signaling links being separate from the local
communication links and the trunk circuit,
a method of processing a call comprising:
receiving the call over one of the local communication links at one of the
central office switching system;
transmitting a query message containing information relating to the call
and address information over one of the signaling links to the signaling
transfer point;
accessing a database in the signaling transfer point based on at least a
portion of the information contained in the query message to retrieve call
processing information;
based on the call processing information, if a condition is met, then
routing the query message based on the address information; and
based on the call processing information, if the condition is not met, then
formulating a response in the signaling transfer point and sending the
response over one of the signaling links to the one central office
switching system.
22. A method as in claim 21, wherein the network comprises a telephone
network.
23. A method as in claim 21, wherein said at least a portion of the
information contained in the query message relates to a calling party.
24. A method as in claim 23, wherein the condition is an outgoing call
screening criteria selected by the calling party.
25. A method as in claim 21, wherein said at least a portion of the
information contained in the query message relates to a called party.
26. A method as in claim 25, wherein the condition is an incoming call
screening criteria selected by the called party.
27. A method as in claim 21, wherein the address information relates to a
remote database containing call processing information.
28. In a network comprising:
local communication links;
a trunk circuit;
at least two separately located central office switching systems
interconnected via the trunk circuit for selectively providing switched
call connections between at least two of the local communication links;
a signaling transfer point for routing signaling messages; and
signaling links coupling the signaling transfer point to the central office
switching systems, said signaling links being separate from the local
communication links being separate from the local communication links and
the trunk circuit,
a method of processing calls comprising:
receiving a first call over one of the local communication links at one of
the central office switching system;
recognizing a predetermined condition of the first call as a trigger;
in response to recognition of the trigger, transmitting a query message
containing information relating to the first call over one of the
signaling links to the signal transfer point;
accessing a database in the signaling transfer point based on at least a
portion of the information contained in the query message to retrieve call
processing information;
formulating a response in the signaling transfer point based on the call
processing information;
sending the response over one of the signaling links to the one central
office switching system;
processing the first call in accord with the response; and
processing a second call that does not meet the predetermined condition
without accessing the database.
29. A method as in claim 28, wherein the network comprises a telephone
network.
30. A method as in claim 28, wherein said at least a portion of the
information contained in the query message relates to a calling party.
31. A method as in claim 28, wherein said at least a portion of the
information contained in the query message relates to a called party.
32. A method comprising:
receiving a signaling message at a transfer point from a first node of a
signaling network, said signaling message comprising content information
relating to processing of a call through a communication network and
routing information;
analyzing said content information;
if the analyzed content information satisfies a first predetermined
condition, transmitting the signaling message including said content
information from the transfer point through the signaling network to a
second node of the signaling network in accord with the routing
information; and
if the analyzed content information satisfies a second predetermined
condition, accessing call processing data stored in a database in the
transfer point to formulate a response message, and transmitting the
response message from the transfer point through the signaling network to
the first node of the signaling network.
33. A method as in claim 32, wherein the signaling message is a data packet
in signaling system 7 protocol format.
34. A method as in claim 33, wherein the second predetermined condition
relates to predetermined Transaction Capabilities Applications Protocol
content information in the signaling message.
35. A method as in claim 33, wherein the first predetermined condition
relates to predetermined Integrated Services Digital Network User Part
content information in the signaling message.
36. A method as in claim 35, wherein the second predetermined condition
relates to predetermined Integrated Services Digital Network User Part
content information in the signaling message.
37. A method as in claim 33, wherein the second predetermined condition
relates to predetermined Integrated Services Digital Network User Part
content information in the signaling message.
38. In a communication network having a plurality of interconnected central
office switching systems at different locations, each of said central
office switching systems connected through a plurality of local subscriber
lines to subscriber stations, a voice network portion comprising voice
communication paths for interconnecting two of said subscriber stations
through at least one of said central office switching systems, a common
channel signaling network portion comprising signaling paths
interconnecting said central office switching systems through at least one
signaling transfer point (STP) and a services control point (SCP)
including a data base, a method for controlling call completion to one of
said subscriber stations comprising the steps of:
in response to each call to a number associated with the one subscriber
station, launching a query message addressed to the SCP through the common
channel signaling network portion;
receiving each query message at the STP and in response thereto
incrementing a call count value;
for each query message, comparing the call count value to a predetermined
value stored in the STP;
only when receipt of one query message results in the call count value
equaling the predetermined value, forwarding the one query message to the
SCP;
in response to the one query message, accessing call processing information
stored in the SCP;
transmitting a response message containing the call processing information
to one of the central office switching systems to complete a call
corresponding to the one query message to the one subscriber station.
39. A method as in claim 38, further comprising:
for each query message wherein the call count value does not equal the
predetermined value, formulating in the STP a response message indicating
a call station busy status and transmitting the response message
indicating a call station busy status to one of the central office
switching systems to supply a busy signal to a caller. |
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Claims |
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Description |
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TECHNICAL FIELD
The present invention relates to a Common Channel Interoffice Signaling
system, an intelligent packet switching system used therein as a signal
transfer point and methods of operation thereof for conditional processing
of signaling messages to provide intelligent network type control of an
associated communications network.
ACRONYMS
The written description uses a large number of acronyms to refer to various
services, messages and system components. Although generally known, use of
several of these acronyms is not strictly standardized in the art. For
purposes of this discussion, acronyms therefore will be defined as follows
:
Address Complete Message (ACM)
Advanced Intelligent Network (AIN)
Answer Message (ANM)
Application Service Part (ASP)
Backward Indicator Bit (BIB)
Backward Sequence Number (BSN)
Call Processing Record (CPR)
Common Channel Signalling (CCS)
Common Channel Interoffice Signalling (CCIS)
Customer Identification Code (CIC)
Cyclic Redundancy Code (CRC)
Destination Point Code (DPC)
Fill in Signal Unit (FISU)
Global Title (GTT)
Initial Address Message (IAM)
Integrated Service Control Point (ISCP)
Integrated Services Digital Network (ISDN)
Intelligent Peripheral (IP)
Intelligent Signaling Transfer Point (ISTP)
ISDN User Part (ISDN-UP)
International Standards Organization (ISO)
Link Service Signaling Unit (LSSU)
Message Signaling Unit (MSU)
Message Transfer Part (MTP)
Multi-Services Application Platform (MSAP)
Open Systems Interconnection (0SI)
Operations, Maintenance, Application Part (OMAP)
Origination Point Code (OPC)
Plain Old Telephone Service (POTS)
Point in Call (PIC)
Point in Routing (PIR)
Service Control Point (SCP)
Service Information Octet (SIO)
Service Management System (SMS)
Service Switching Point (SSP)
Signaling Connection Control Part (SCCP)
Signaling Link Selection (SLS)
Signaling System 7 (SS7)
Signaling Point (SP)
Signaling Transfer Point (STP)
Subsystem Number (SSN)
Transaction Capabilities Applications Protocol (TCAP)
BACKGROUND ART
All telecommunications systems having multiple switching offices require
signaling between the offices. The classic example relates to telephone
networks. Telephone networks require signaling between switching offices
for transmitting routing and destination information, for transmitting
alerting messages such as to indicate the arrival of an incoming call, and
for transmitting supervisory information, e.g. relating to line status.
Signaling between offices can use `in-band` transport or `out-of-band`
transport.
In-band signaling utilizes the same channel that carries the communications
of the parties. In a voice telephone system, for example, one of the
common forms of in-band signaling between offices utilizes multi-frequency
signaling over voice trunk circuits. The same voice trunk circuits also
carry the actual voice traffic between switching offices. In-band
signaling, however, tends to be relatively slow and ties up full voice
channels during the signaling operations. In telephone call processing, a
substantial percentage of all calls go unanswered because the destination
station is busy. For in-band signaling, the trunk circuit to the end
office switching system serving the destination is set-up and maintained
for the duration of signaling until that office informs the originating
office of the busy line condition. As shown by this example, in-band
signaling greatly increases congestion on the traffic channels, that is to
say, the voice channels in the voice telephone network example. In-band
signaling also is highly susceptible to fraud because hackers have
developed devices which mimic in-band signaling.
Out-of-band signaling evolved to mitigate the problems of in-band
signaling. Out-of-band signaling utilizes separate channels, and in many
cases separate switching elements. As such, out-of-band signaling reduces
congestion on the channels carrying the actual communication traffic.
Also, messages from the end users always utilize an in-band format and
remain in-band, making it virtually impossible for an end user to simulate
signaling messages which ride on an out-of-band channel or network.
Out-of-band signaling utilizes its own signal formats and protocols and is
not constrained by protocols and formats utilized for the actual
communication, therefore out-of-band signaling typically is considerably
faster than in-band signaling.
Out-of-band signaling networks typically include data links and one or more
packet switching systems. Out-of-band signaling for telephone networks is
often referred to as Common Channel Signaling (CCS) or Common Channel
Interoffice Signaling (CCIS). Most such signaling communications for
telephone networks utilize signaling system 7 (SS7) protocol. An SS7
compliant CCIS network comprises data switching systems designated
Signaling Transfer Points (STPs) and data links between the STPs and
various telephone switching offices of the network.
In recent years, a number of new service features have been provided by an
enhanced telephone network, sometimes referred to as an Advanced
Intelligent Network (AIN). AIN type call processing relies heavily on
signaling communication via the CCIS network. In an AIN type system, local
and/or toll offices of the public telephone network detect one of a number
of call processing events identified as AIN "triggers". For ordinary
telephone service calls, there would be no event to trigger AIN
processing; and the local and toll office switches would function normally
and process such calls without referring to the central database for
instructions. An office which detects a trigger will suspend call
processing, compile a call data message and forward that message via a
CCIS link to an Integrated Service Control Point (ISCP) which includes a
Multi-Services Application Platform (MSAP) database. If needed, the ISCP
can instruct the central office to obtain and forward additional
information. Once sufficient information about the call has reached the
ISCP, the ISCP accesses its stored data tables in the MSAP database to
translate the received message data into a call control message and
returns the call control message to the office of the network via CCIS
link. The network offices then use the call control message to complete
the particular call.
An AIN type network for providing an Area Wide Centrex service was
disclosed and described in detail in commonly assigned U.S. Pat. No.
5,247,571 to Kay et al., the disclosure of which is entirely incorporated
herein by reference. AIN type processing in such a system is controlled by
the ISCP, which typically is operated by the local exchange carrier.
Similar intelligent services, particularly advanced 800 number services,
may be offered by other carriers. Existing 800 number call processing
utilizes a central 800 database (CMSDB) in a Service Control Point (SCP),
to control switching operations through multiple end offices. Local and/or
toll offices of the network detect dialing of an 800 number, suspend call
processing, compile a call data message and forward that message via a
CCIS link to the 800 database in the SCP. The SCP accesses stored data
tables identified by the dialed 800 number to translate the received
message data into a call control message, including a plain old telephone
service (POTS) type destination telephone number. In this system, if the
SCP does not currently store the destination number corresponding to a
particular 800 number, the SCP will obtain the destination number from a
national 800 database referred to as a Service Management System (SMS).
The SCP transmits the call control message to the office of the network
via CCIS link, and the network offices use the POTS destination telephone
number in the call control message to complete the particular call.
Examples of 800 number call processing routines are disclosed in U.S. Pat.
No. 4,191,860 to Weber, U.S. Pat. No. 4,611,094 to Asmuth et al. and U.S.
Pat. No. 4,611,096 to Asmuth et al.
The intelligent call processing provided by the ISCP and SCP type
centralized databases facilitates a wide range of services, many of which
can be customized to meet the needs of individual subscribers. To service
a large number of customers in this manner, particularly where every call
to or from every intelligent service subscriber receives query and
response processing through a centralized database, places a heavy
signaling burden on the interoffice signaling network. Also, typically, a
query and response cycle between a switching office and a remote database
requires approximately 600 microseconds. Although this time appears short
to a person placing a call, the delay is quite long in terms of electronic
or computer processing capabilities by the switching offices. During this
waiting time, resources of the switch that launched the call are sitting
idle, reserved for the call but waiting for the response from the
database. When multiplied by millions of calls, the waiting time burdens
switching office resources that otherwise could be processing other calls
and thereby generating additional revenue. As the number of intelligent
services utilizing the query and response procedure continues to increase,
the need for a more rapid technique to provide the necessary control
information to the switching offices becomes increasingly acute.
Also, the various intelligent services provided through earlier systems
have relied on `triggers` set in the individual switching offices.
Occurrence of a call processing event recognized as a trigger causes the
switching office to formulate a special application message in Transaction
Capabilities Applications Protocol (TCAP). Triggers must be set in many
individual offices, and each such office must formulate the specialized
type messages. Upgrading individual switching offices to perform these
functions is expensive.
DISCLOSURE OF THE INVENTION
The present invention overcomes the above noted problems by providing a
database, storing call processing control information, in a signaling
transfer point (STP) of the interoffice signaling network. The STP also is
adapted to trigger access to records within that database in response to
signaling messages when certain conditions are met. As such, the STP
becomes an intelligent node of the network, i.e. an Intelligent Signaling
Transfer Point (ISTP)
A network implementing the present invention includes local communication
links, one or more trunk circuits and at least two separately located
central office switching systems. The trunk circuits interconnect the
central office switching systems. The network selectively provides
switched call connections between at least two of the local communication
links. The network also includes a signaling transfer point (STP) for
routing signaling messages and signaling links coupling the signaling
transfer point to the central office switching systems. The signaling
links are separate from the local communication links and the trunk
circuit.
In accord with one aspect of the present invention, the STP includes a data
switch for switching messages between the signaling links. A database
stores call processing data associated with a plurality of the local
communication links for control of call processing through one or more of
the central office switching systems. A program controlled processor in
the STP recognizes a predetermined call related condition with regard to a
signaling message from one of the central office switching systems that is
processing the call. In response, the processor obtains call processing
information from the database and transmits a signaling message containing
the call processing information to the one central office switching system
to control subsequent processing of the call. In view of the inclusion of
the database and the intelligent processing, the STP becomes an ISTP.
In this manner, the ISTP may screen signaling messages and formulate and
return response messages in some cases, without the query going to a
distant node of the network to formulate and return a response. For
example, the network may include a service control point (SCP). As noted
above, the transmission of messages to the SCP and waiting for a response
ties up network resources. The ISTP therefore responds faster to the
messages under certain conditions and passes only a limited number of
messages, i.e. those meeting specific conditions, to the SCP for
processing.
As another example, the ISTP may provide screening services based on
messages normally transmitted between switching offices during call set-up
processing. The screening criteria is established within the database in
the ISTP. If the ISTP determines that a first condition is met, e.g. a
call should not be completed in view of criteria defined by the
subscriber, then the ISTP transmits a busy status indication to the
originating office. If the ISTP determines that a second condition is met,
e.g. a call should be completed in view of criteria defined by the
subscriber, then the ISTP passes the signaling message on to the
terminating office for normal call set-up processing. The screening
functionality can apply to outgoing calls from a subscriber's line or to
incoming calls to a subscriber's telephone number. Triggers for this type
of screening are set in the ISCP, not in the individual switching offices.
Also, certain calls may trigger a query to the STP itself. In this type of
operation, a switching office processing a call detects an AIN type
trigger event. That office sends a query message through the signaling
network to the ISTP. The ISTP uses at least some information from the
query message to access a call processing record in the database within
the ISTP and formulate an appropriate response message. The ISTP transmits
the response message back to the switching office, and that office uses
information from the response message to continue its processing of the
particular call.
Additional objects, advantages and novel features of the invention will be
set forth in part in the description which follows, and in part will
become apparent to those skilled in the art upon examination of the
following or may be learned by practice of the invention. The objects and
advantages of the invention may be realized and attained by means of the
instrumentalities and combinations particularly pointed out in the
appended claims.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a simplified block diagram of a Public Switched Telephone Network
and its SS7 signal control network, helpful in explaining the present
invention.
FIG. 2 depicts the protocol stack for SS7 and comparison thereof to the OSI
model.
FIG. 3 illustrates in graphic form the layout of an SS7 protocol message
packet.
FIG. 4 illustrates in graphic form the layout of the routing label portion
of the SS7 protocol message packet shown in FIG. 3.
FIG. 5 is a functional block diagram of an Intelligent Signaling Transfer
Point (ISTP) in accord with the present invention.
FIG. 6 is a simplified flow diagram of the message processing operations of
the ISTP in accord with the present invention.
FIG. 7 is a simplified flow diagram of one specific call processing type
service by the network of FIG. 1 in accord with the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention provides customized processing of signaling messages
at a packet switching node of a signaling network, to achieve intelligent
routing of calls through offices of a communication network. The concepts
of the present invention may apply to a variety of out-of-band signaling
networks. The preferred embodiment, however, relates to improvements in an
SS7 compliant common channel interoffice signaling system used in a public
switched telephone network. In such an implementation, signaling packets
are routed through one or more Signaling Transfer Points (STPs). At least
one STP includes or connects to an associated database of call processing
records (CPRs) and serves as an ISTP in accord with the present invention.
The database associated with the ISTP provides instructions for processing
the signaling messages to provide customized call processing services
through the communication network. The call processing records effectively
specify how the ISTP should process a message under certain predetermined
conditions, to provide a subscriber one or more selected service features.
For example, the ISTP may pass a query message relating to one
subscriber's service under a first condition (e.g. at a first time). Some
other network node formulates a response and sends the response back
through the ISTP. Under other conditions (e.g. at other times), the ISTP
will itself process the query message and provide an appropriate response
message. The inclusion or association of the database with the ISTP
eliminates the delay incurred by forwarding queries to a separate database
and waiting for the response to return to the ISTP for subsequent
transport to the switching office which launched the query.
Another advantage of the use of the database in the ISTP is that the
processing by the ISTP need not always rely on specialized triggers and
specialized TCAP messages. During processing of many normal calls, an
originating office will transmit a signaling message intended for a
terminating office, i.e. serving the line of the called party. The ISTP
can trigger access to the internal database in response to such messages
and formulate certain responses, to provide the customized processing
without the delay for transmission to and from the distant terminating
office.
To facilitate understanding of the present invention, it will be helpful
first to review the architecture and operation of a telephone network
having CCIS capabilities.
Referring to FIG. 1 there is shown a simplified block diagram of a switched
traffic network and the common channel signaling network used to transport
the signaling messages that control call processing by the switched
traffic network. Although the signaling message routing of the present
invention will apply to other types of networks, in the illustrated
example, the network is a telephone network.
In the illustrated example, the network includes a number of end office
switching systems 11 and 17 providing connections to local communication
links coupled to end users telephone station sets. Typically, the
communication links are telephone lines (solid lines), although skilled
artisans will recognize that other links could be used, such as broadband
links, wireless links, etc. The network also includes one or more tandem
switching systems 13 providing trunk to trunk connections between offices
(bold solid lines). For convenience, only one tandem office 13 is shown.
As such, the first telephone network consists of a series of switching
offices interconnected by voice grade trunks.
Bach switching office has SS7 signaling capability and is conventionally
referred to as a signaling point (SP) in reference to the SS7 network. One
or more of the each switching offices 11, 13 and 17 may also be programmed
to recognize identified events or points in call (PICs). In response to a
PIC, such an office 11, 13 or 17 triggers a query through the signaling
network, for example to a Service Control Point (SCP) 19 for further
instructions. Switching offices having such trigger and query capability
are referred to as Service Switching Points (SSPs). As discussed more
later, the SSPs may also address queries to the Intelligent Signaling
Transfer Point (ISTP) 15. The SCP 19 may be part of an integrated services
control point (ISCP) of the type disclosed in the above discussed Kay et
al. Patent.
The end office and tandem switching systems typically consist of
programmable digital switches with CCIS communications capabilities. One
example of such a switch is a 5ESS type switch manufactured by AT&T; but
other vendors, such as Northern Telecom and Seimens, manufacture
comparable digital switches which could serve as the SSPs and SPs. The SSP
type implementation of such switches differs from the SP type
implementation of such switches in that the SSP switch includes additional
software to recognize the full set of AIN triggers and launch appropriate
queries.
The illustrated network also includes a common channel interoffice
signaling (CCIS) network. The CCIS network includes at least one
Intelligent Signaling Transfer Points (ISTP) 15 and data links shown as
dotted lines between the ISTP(s) and the various switching offices 11, 13
and 17. A data link also connects the ISTP 15 to the SCP 19. The structure
of an exemplary ISTP in accord with the present invention will be
discussed in more detail below, with regard to FIG. 5.
FIG. 1 shows one telephone line and associated telephone station connected
to end office switching system 17 serving a radio station 18. One specific
example of a call screening service discussed in detail below, relates to
allowing only one call satisfying a predetermined threshold value to be
completed to the line to the radio station 18. The network of FIG. 1 will
also provide connections to other types of systems, such as voice mail
system 21 and one or more intelligent peripherals or `IPs` (not shown).
Although shown as telephones in FIG. 1, the terminal devices can comprise
any communication device compatible with the local communication line.
Where the line is a standard voice grade telephone line, for example, the
terminals could include facsimile devices, modems etc.
Commonly assigned copending application Ser. No. 08/248,980, filed May 24,
1994, entitled "Advanced Intelligent Network with Intelligent Peripherals
Interfaced to the Integrated Services Control Point" (attorney docket no.
680-076) provides a more detailed disclosure of an AIN type network,
including the structure of an SSP switch and the structure of an IP, and
the disclosure of that application is incorporated herein in its entirety
by reference.
An end office switching system 11 or 17 shown in FIG. 1 normally responds
to a service request on a local communication line connected thereto, for
example an off-hook followed by dialed digit information, to selectively
connect the requesting line to another selected local communication line.
The connection can be made locally through only the connected end office
switching system but typically will go through a number of switching
systems. For example, when a subscriber at station X calls station Y, the
connection is made through the end office switching system 11, the tandem
office 13 and the end office switching system 17 through the telephone
trunks interconnecting the various switching offices.
In the normal call processing, the central office switching system responds
to an off-hook and receives dialed digits from the calling station. The
central office switching system analyzes the received digits to determine
if the call is local or not. If the called station is local and the | | |
