WO2000022780A1

WO2000022780A1 - Congestion protection tool for an intelligent network

Info

Publication number: WO2000022780A1
Application number: PCT/AU1999/000883
Authority: WO
Inventors: Hoerdur Matthiasson
Original assignee: Ericsson Australia Pty Ltd
Priority date: 1998-10-14
Filing date: 1999-10-14
Publication date: 2000-04-20
Also published as: AUPP649598A0

Abstract

A method of minimising congestion in an intelligent network during a mass participant telephony event, said intelligent network comprising a plurality of interconnected networks elements, said networks elements including at least one Service Control Point (SCP) (13) and a plurality of Service Switching Points (SSPs) (11), the method including the steps of: (a) determining (41) the available call-handling capacity of one or more of said network elements (11, 12, 13), (b) determining (52-57) event information characterising a new mass participant telephony event which is desired to be scheduled, (c) requesting (58) the scheduling of said new mass participant telephone event, (d) calculating (43) a predicted load placed on said one or more network elements during said new participant telephony event from said event information, (e) comparing (44) said predicted load to the available call-handling capacity of each of said one or more network elements during said new mass participant telephony event, and (f) authorising (46) the scheduling of said new mass participant telephony event if the predicted load is less than the available call-handling capacity of each of said one or more network elements.

Description

CONGESTION PROTECTION TOOL FOR AN INTELLIGENT

NETWORK

The present invention relates generally to tools for the protection of intelligent networks from congestion, and in particular to tools for the protection of intelligent networks from congestion during mass participant telephony events. The invention is applicable in particular to televoting services and it will be convenient to hereinafter describe the invention in relation to that exemplary application. It should be appreciated however, that the tool is not limited to that application, but is also applicable to teleshopping, radio or television contests and other intelligent network telephony services in which a large number of subscribers are likely to dial one or more pre-defined telephone numbers during a certain duration of time.

An intelligent network consists of a number of switching entities that combine to offer subscribers a specialised service such as televoting. The switching entities contain processing software to process calls according to the required service or application. Typically, an intelligent network contains a number of services switching points each connected to a public telecommunications network such as a public switched telephone network (PSTN), integrated services digital network (ISDN), packet switched public data network (PSPDN), mobile network or like telephony network. Each of the SSPs are connected to a service control point (SCP) which contains service specific applications software and customer or subscriber records. The SSP reacts to specific service triggers and initiates queries to the SCP over a common channel signalling network, such as the signalling system no 7 (SS7) network. The SCP acts upon the query from the SSP and returns a message containing the data and instructions required to complete the service. A service management system (SMS) is linked to the SCP and supports the administration of the customer records within the SCP.

Televoting is a particular service offered by an intelligent network in which callers may dial one or more pre-determined destination telephone numbers to register a vote or an answer in response to a choice or question initiated through a viewer or listener participation program conducted by a broadcaster, such as a television or radio network or the like. The owner or broadcaster of the program, hereinafter referred to as a subscriber, may provide an incentive to participants to call the pre-determined telephone numbers by offering prizes to selected callers. The televoting service is implemented in the intelligent network by having the subscriber load the SMS with parameters to finding the televoting event such as start time, end time, the destination numbers for each choice offered, announcements to be played to callers, etc. These parameters are downloaded into the SCP, which are in turn delivered to each SSP connected to the SCP, so that each SSP is programmed with these parameters. During an activated televoting service, incoming calls are received by the SSPs and handled in a sequential manner. The SSPs can then count the calls received and terminate a certain percentage by filtering. The remaining calls are allowed to be transferred to the SCP where they are stored in time sequence and remain eligible to win a prize in the contest.

In any given network it is currently possible for many televoting events to be scheduled for the same or overlapping time periods. The large number of telephone calls made by participants during each televoting event can lead to congestion of the intelligent network and a consequent inability of the network to satisfactorily complete one or more of the scheduled televoting events or other telephony functions. This problem would be aggravated if, instead of requiring subscribers to schedule televoting events via a central network operator, subscribers were to be provided with direct access to the SMS and an ability to schedule televoting events themselves. An aim of the present invention is to overcome or ameliorate this problem by proving a tool and method for protection of an intelligent network from congestion during a mass participant telephony event.

One aspect of the present invention provides a method of minimising congestion in an intelligent network during a mass participant telephony event, said intelligent network comprising a plurality of interconnected networks elements, said networks elements including at least one Service Control Point (SCP) and a plurality of Service Switching Points (SSPs), the method including the steps of: (a) determining the available call-handling capacity of one or more of said network elements, (b) determining event information characterising a new mass participant telephony event which is desired to be scheduled,

(c) requesting the scheduling of said new mass participant telephony event,

(d) calculating a predicted load placed on said one or more network elements during said new participant telephony event from said event information, (e) comparing said predicted load to the available call-handling capacity of each of said one or more network elements during said new mass participant telephony event, and

(f) authorising the scheduling of said new mass participant telephony event if the predicted load is less than the available call-handling capacity of each of said one or more network elements.

Conveniently, the intelligent network may further include a Service Management System (SMS), wherein the call-handling capacity of one or more of said network elements determined in step (a) is stored in a Network Protection Unit,

- said event information determined in step (b) is entered in said SMS , - a scheduling request and said event information are sent in step (c) from the

SMS to the NPTJ,

- the predicted load is calculated in step (d) in said NPU,

- the predicted load is compared to the available capacity of each of said one or more network elements in step (e) in said NPU, and - an scheduling authorisation signal is sent in step (f) from the NPU to the SMS if the predicted load is less than the available capacity of each of said one or more network elements.

The network elements may further include a plurality of telecommunications links between said at least one SCP and said plurality of SSPs. The said at least one SCP and said plurality of SSPs may each include processing means, the network elements further including one or more of said processing means. The network elements may further include one or more announcement devices for playing one or more prerecorded announcements to participants in said new mass participant telephony event.

The event information may include any one or more of the following: - announcement information characterising said recorded announcements,

- a start and stop time for said new mass subscriber telephony event, or

- a plurality of destination network addresses to which calls made during said new mass subscriber telephony event are to be routed.

During said new mass subscriber telephony event a predetermined number of calls handled by said SSPs during a gapping interval may be transferred from said SSPs to said at least one SCP, the event information including said predetermined number of calls and the duration of said gapping interval.

Another aspect of the invention provides a Network Protection Unit (NPU) for minimising congestion in an intelligent network during a mass participant telephony event, said intelligent network comprising a plurality of interconnected networks elements, said networks elements including at least one Service Control Point (SCP) and a plurality of Service Switching Points (SSPs), the NPU comprising:

- storing means for storing available call-handling capacity of one or more of said network elements, - signal input means for receiving a scheduling request signal and for receiving event information characterising a new mass participant telephony event which is desired to be scheduled,

- processing means for calculating a predicted load placed on said one or more network elements during said new participant telephony event from said event information and for comparing said predicted load to the available call-handling capacity of each of said one or more network elements during said new mass participant telephony event, and

- signal output means for generating a scheduling authorisation signal if the predicted load is less than the available call-handling capacity of each of said one or more network elements.

The following description refers in more detail to the various features of the present invention. To facilitate an understanding of the invention, reference is made in the description to the accompanying drawings where the tool and method of the present invention are illustrated in preferred embodiments. It is to be understood, however, that the tool and method of the present invention are not limited to the preferred embodiments as illustrated in these drawings. In the drawings: Figure 1 is a schematic diagram showing an intelligent network connected to a network protection unit according to the present invention;

Figures 2 and 3 are schematic representations of one embodiment of a method of minimising congestion in the intelligent network of Figure 1;

Figure 4 is a schematic diagram showing the network protection unit shown in Figure 1; and

Figure 5 is a graphical representation of the load placed upon the intelligent network of Figure 1 by various televoting events.

Referring now to Figure 1, there is shown a system 10 for selecting one or more winners in a televoting event. System 10 uses an intelligent network various network elements including a plurality of SSPs 11 connected via links 12 to an SCP 13. A service management system or SMS 14 is connected to the SCP 13 via a link 15. Each SSP 11 is connected to a public network through telecommunications links 16.

When a subscriber, such as a television network or radio network, wishes to conduct a televoting service or event in an intelligent network, event information or event parameters characterising the televoting service are input to the SMS 14, for example, through an interface device 17. Such event information includes the starting time and stop time between which the televoting event will be active, the televoting destination telephone numbers, the contents and duration of recorded messages to be delivered to callers at various stages throughout the event, the number of calls to be transferred from each SSP to the SCP during each gapping interval and the duration of that gapping interval.

The parameters are distributed to the SCP 13 and once the televoting service is implemented, the event information is in turn distributed from the SCP 13 to each SSP 11 so that each SSP 11 will be programmed to handle incoming calls from participants to the event or service. Services in intelligent networks are executable service logic programs (SLPs) that are defined in terms of functional components which are network call processing actions that direct internal network resources to perform specific actions. A service logic interpreter (SLI) executes SLPs and handles requests and responses exchanged between the various components of the intelligent network. A subscription to a televoting service by a television network or radio network is initiated by creating an instance of the SLP and connecting data to the service logic program instance (SLPI). The SLPI is implemented in the SCP 13 and controls the SSPs 11, being deployed and managed through the SMS 14. Through this mechanism, calls routed from the public network to the SSPs 11 can be controlled by the SCP 13.

Each SSP 11 receives calls to the televoting numbers from the public network over links 16. In the event that the contest is opened to a large proportion of the population, the telephone network may become congested and eventually collapse due to the number of calls be simultaneously received. To alleviate the possibility of collapse in this situation, each call received by the SSP 11 is firstly counted by first counter means 18, this counter means being incremented by 1 for each call received. The counter means 18 is set with a pre-determined value N so that only the Nth caller associated with the value N is routed through to the SCP 13 over links 15. All calls counted that have a counter value less than N are terminated with the announcement made by one of a group of announcement-and- digital-reception-devices (AST-DRs) 19, such as "Your vote has been registered. Unfortunately you have not been successful in reaching the next stage of the contest". After the call all calls are routed to the SCP 13, the respective counter means 18 of SSP 11 may be reset to zero to initiate a new incrementation of subsequent received calls.

The calls routed to the SCP 13 from each of the SSPs 11 are received by a second counter means 20 which increments by 1 for each call received. The calls thus received also have an announcement transmitted to them, such as "Your vote has been registered. Please wait as your call has been transferred to the next stage of processing in the contest". This message, again, is played by one of the AST-DRs 19 within each of the SSPs 11. The second counter means 20 is incremented until it reaches a counter value that matches a pre-determined number, designated as being the winner of the televoting event. Each call that has a counter value other than that pre-designated number is routed back to its respective SSP 11 and an announcement played to the caller by one of the AST- DRs 19, such as "Unfortunately you have not been successful in this televoting event. Thank you for your participation".

In the intelligent network shown in Figure 1, several potential capacity bottlenecks exist which can impair the functioning of the televoting event. These include the SCP, the plurality of SSPs, the traffic and signalling links, and the announcement and digital reception devices. All these resources are shared between various intelligent network services and to a certain extent with normal telephony traffic. Whilst most intelligent network services use these resources in a fairly predictable manner, mass participant telephony events do not behave in this way. Such events are planned and executed in limited periods of time and can generate traffic peaks during these periods. Furthermore, more than one mass participant telephone event can be executed at the same point in time, further adding to the strain on the network resources. For this reason, the system 10 in Figure 1 includes a network protection unit (NPU) 30, interconnected with the SMS 14. The NPU 30 is adapted to receive a scheduling request signal from the SMS 14, as well as event information characterising a mass participant telephony event which is desired to be scheduled. The NPU 30 compares the predicted load on the intelligent network from the mass participant telephony event to the available capacity of the intelligent network and sends either an authorisation or a rejection signal to the SMS 14, depending upon whether the intelligent network has sufficient capacity or not to successfully execute the telephony event.

The operation of the NPU 30 in conjunction with the various elements of the intelligent network of Figure 1 will now be explained with reference to Figures 2 and 3. In order for the NPU 30 to correctly function, the various elements of the intelligent network are firstly mapped and the capacity of each element determined. Accordingly, at step 40, the intelligent network operator maps the various elements of the intelligent network into the SMS 14 for subsequent transfer to the NPU 30. Firstly, the network operator identifies each of the intelligent network elements, including the number of SSPs, the type of processor used in the SSPs and the SCP, the available memory associated with the processor in the SSPs and the SCP, the number of TCAP/C7 links between each SSP and the SCP, the number of AST-DR devices associated with each SSP.

One example of the sort of information which may be mapped at this step is as follows:

Number of SSPs: 100

Processor within each SSP: APZ 212 11 Memory within the processor: 4 megabytes

Type of processor in the SCP: APZ 212 11

Available memory in the processor: 4 megabytes

Number of TCAP/C7 links between each SSP and the SCP: 1

Number of AST-DR devices per SSP: 4 At step 41, the available capacity of each identified network element is determined. This determination may take place in the NPU 30 or in the SMS 14. The available capacity of each intelligent network element is determined as follows: 1. SSP Information is stored in tabular form as to the traffic which can be executed by a range of microprocessors suitable for use in each SSP. In the above described example, information is retrieved from this table that the APZ 212 11 microprocessor is able to execute 870 milliseconds per second of effective traffic. Information may also be stored as to the load caused by background processors and traffic in the intelligent network. Typically this figure may be 500 milliseconds per second. In this case, the APZ 212 11 microprocessor in each SSP has an available capacity for executing traffic during the televoting event of 370 milliseconds per second.

The following imperical equations have been shown to represent an intelligent network call in a SSP:

LPCSSP - SSSP + TPCSTRANS + N EG LEG ⁺ EG LEG where:

LPC_SSP is load per call in an SSP

S_SSF is the base load from the invocation of the SSF (4.3 ms) N_TPC is the number of transactions per call (INAP/TCAP transactions) ST ANS is the loa ^* per transaction (6.5 ms) _LEG is the number of call legs created for a call L_LEG is the load from setup and release of a leg (4.9 ms) C_LEG is the load imposed by the charging applied to a call leg (2.7 ms) For a call that terminates in the SSP there are no transactions and only one leg is created. These calls will all be treated as PSTN access call (influences L_LEG) and charged by Toll Ticketing (worst case for C_LEG).

For an APZ 212 11 processor the load can then be calculated to be: LPC_SSP = 4.3 + 0 + 4.9 + 2.7 = 11.9 ms This information is stored in a memory device within either the SMS 14 or the NPU 30.

From this, it can be determined that the APZ 212 11 processor is able to handle 31 calls per second during the televoting event (an APZ 212 20 processor, however can handle four times that amount of traffic). The above calculation is valid for calls that are terminated in the SSPs.

This is the case for most calls made during a televoting event, and any calls routed to the SCP will not add significantly to this load. 2. S£E

Again, information is retrieved from a table within either the SMS 14 or the NPU 30 which indicates that the APZ 212 11 processor used in the SSP is able to execute 870 milliseconds per second of effective traffic, and that background processors and traffic of 500 milliseconds per second are to be expected during normal network operation. The processor thus has an effective capacity of 370 milliseconds per second for executing traffic from the televoting event. In addition, the memory associated with the processor is loaded by the number of subscriptions stored in the SCP. It can be estimated that each subscription occupies 250W16 (250 16 bit words). In the case where 1000 subscriptions are stored in the SCP, the memory consumption is then 250KW16 (approximately 0.5 megabits). The effective capacity of the memory associated with the processor in the SCP is therefore reduced to 3.5 megabits. 3. Links

Each call that is routed from an SSP to the SCP results in 450 objects of data being sent over the INAP/TCAP link. A normally dimensioned link set (0.3 Erlang) can handle 2400 octets per second. 4. AST-DRs Each such announcement device can play 64 simultaneous announcements.

Whilst the above described example includes intelligent network elements of SSPs, SCPs, links and AST-DRs, and various devices within these elements, it is to be appreciated that in other embodiments of the invention other network elements may be included. Moreover, the actual figures for the various capacities of the network elements provided above are merely one practical example of typical figures in intelligent networks which are currently available.

Having thus identified the intelligent network elements and determined the available capacity of each network element, the network protection unit 30 then determines the load placed on each intelligent network element by the processing of telephone calls during the mass participant telephony event. In order for this to take place, the subscriber of a desired telephony event must firstly provide the NPU 30 with event information characterising that televoting event. At step 52 in Figure 3, the subscriber provides the NPU 30, via the terminal 17 and the SMS 14, with the predicted number of telephone calls which will be received during the activated televoting event. A typical figure may be 2,000 calls per second.

At step 53, the subscriber enters the gapping interval, which is the time period during which a certain number of calls are to be transferred from the SSPs to the SCP during the televoting event. A typical figure may be one minute. At step 54, the subscriber enters the number of calls that are to be transferred from each SSP to the SCP during each gapping interval. A typical figure may be 10 calls per minute. At step 55, the subscriber enters the length of the announcement stored within each AST-DR to be played to participants in the televoting event. At steps 56 and 57 the subscriber also enters other information relating to the televoting event, such as the contest and voting telephone numbers, and the televoting event start and stop times. Other information relating to the processing of telephone calls during the televoting event may also be entered at this stage.

Having entered this information into the SMS 14 from the terminal 17, and having verified that this information is correct, the subscriber instructs the SMS 14 to send a scheduling request signal, at step 58, to the NPU 30 in order that the NPU 30 can determine whether the intelligent network will have sufficient available capacity to be able to successfully carry out the televoting event between the desired start and stop times.

Returning now to Figure 2, at step 42 the televoting request sent from the SMS 14 is received by the NPU 30. At step 43, the predicted load placed on each intelligent network element by the anticipated telephone calls received during the televoting event is calculated.

An example of the calculations performed within the NPU 30 is as follows: 1. SSP.

As explained previously, it has already been calculated that the processor within each SSP has an available capacity of 370 milliseconds per second, and the load per call in the SSP is 11.9 milliseconds. Accordingly, the NPU 30 calculates that each SSP can handle 31 calls per second.

From the information entered by the subscriber and provided to the NPU

30 from the SMS 14, it is known that the expected number of calls per second is 2,000. Since there are 100 SSPs within the intelligent network, the NPU 30 calculates that each SSP is likely to receive 20 calls per second during the televoting event.

During the handling of each telephone call by the SSP, approximately 26KW16/S (16 bit K words per second) of memory is occupied. For 20 calls per second this corresponds to a memory usage of 520KW16 (approximately 1 megabyte). 2. SCP

The following imperical equations have been shown to represent an IN call in an SCP:

LPCSCP ⁼ SSCF + NTPCSTRANS + NSPCSSIB where

LPC_SCP is load per call in an SCP

SSC_F is the base load from the invocation of the SCF (2.0 ms) N_Tpc is the number of transactions per call (3.5) STRAN_S i the load per transaction (5.6 ms)

NS_PC is the number of SIBs executed per call (59) S_S1B is the average load per SIB (0.2 ms)

For an APZ 212 11 processor the load can then be calculated to be: LPCSCP = 2.0 + 19.6 + 11.8 = 33.4 ms As previously explained, an APZ 212 11 processor can execute 870 milliseconds per second of effective traffic and, with a background and traffic processing load of 500 milliseconds per second, has an effective capacity of 370 milliseconds per second. This means that the processor is able to handle 11 calls per second. The NPU 30 calculates that with the intelligent network including 100

SSPs, each forwarding 10 calls to the SCP during each gapping interval of one minute, the SCP is expected to receive 16.7 calls per second. The NPU 30 compares this figure to the capacity of only 11 calls per second previously calculated, and, at step 44, determines that the intelligent network does not have the available capacity to successfully handle the televoting event characterised by the subscriber. In this case, a rejection signal is sent from the NPU 30 to the SMS 14, at step 45, instructing the SMS 14 not to activate the requested televoting service.

Had the NPU 30, on the other hand, determined that the SCP, had in fact, sufficient processing capacity to handle the expected number of calls, the NPU 30 would have then continued to examine the capacity of the remaining network elements.

In this case, the NPU 30 may then have examined the SCP memory. The memory consumption in the SCP is dependent upon two parts, firstly a fixed memory usage for each subscription (as described previously) and a second usage dependent upon the running televoting event. In the previously described example, with 1,000 subscriptions stored in the SCP, the fixed memory usage was 250KW16. The traffic dependent memory is estimated to be 20KW16/S which, with a maximum of 16.7 calls per second gives 334KW16 (approximately 0.67 megabytes). The total memory usage is therefore anticipated to be 1.17 megabytes. The NPU 30 determines that this figure is less than the available 4 megabytes of installed memory. 3. Links

As each SSP is expected to forward 10 calls per minute to the SCP, and each call results in 450 octets of data, there is anticipated to be 75 octets per second of data required to be transferred between the SSPs and the SCP. The NPU 30 compares this figure to the available capacity of 2,400 octets per second and determines that each link has more than enough capacity to be able to handle the anticipated number of calls. 4. AST-DRs

The NPU 30 calculates that as each announcement has a duration of 3 seconds and, as each SSP is expected to receive 20 calls per second, each SSP will be required to handle 60 simultaneous announcements. The NPU 30 compares this figure to the capacity of the four installed ANT-DR devices, which is 4 X 64 simultaneous announcements, and determines that the available capacity exceeds the required capacity to handle each of the incoming calls.

If the NPU 30 had determined that each network element had sufficient capacity to handle the expected load from the requested televoting event, an authorisation signal is sent from the NPU 30 to the SMS 14 at step 46. Turning now to Figure 4, there is shown a more detailed view of the NPU 30 of figure 1. In particular, the NPU 30 includes a microprocessor, for example the APZ 212 11 or APZ 212 20, as previously mentioned, here referenced 60. Associated with the microprocessor 60 are memory devices 61, 62, 63 and 64. The memory device 63 is used to store information characterising the televoting event received from the SMS 14. This information was previously entered by the subscriber during the steps 52 to 57 in Figures 3.

The memory device 64 is used to store information characterising the intelligent network and each of its elements. This information was entered by the network operator in the steps 40 and 41 of Figure 2. Both the memory devices 63 and 64 may be constituted by random access memory devices. The memory device 61 may be constituted by a read-only memory device and, programmed with instructions for the NPU to perform the various calculations described in relation to steps 43 to 46, and possibly 40 and 41, of Figure 2. The memory device 62 may be constituted by a volatile memory device for the temporary storage of data necessary in such calculations. In addition, the NPU 30 includes input/output devices 65 and 66 for receiving and sending information to and from the SMS 14, and an encoder/decoder device 67 for translating signals received from the SMS 14 into a format suitable for use by the microprocessor 60, and for generating the rejection and authorisation signals sent from the NPU 30 to the SMS 14 to either to allow or disallow the requested scheduling of a televoting event.

The "background" load of the various intelligent network elements may vary depending upon whether other mass subscriber telephony events have been programmed for activation during the same or overlapping times as a requested mass subscriber telephony event. As seen in Figure 5, a first televoting event programmed between the times tl and t3 may impose a certain load 70 on each of the network elements (in this case the SCP processor). A second televoting event will not be able to be programmed between the times t2 and t4 because the load of the second televoting event 71, when added to the first load 70 of the first televoting event, will exceed the capacity of that intelligent network element. However, if the televoting event is programmed at a later time, when the times t2 and t6, the same load 71 will be determined by the NPU 30 to be within the available capacity of that network element and the requested televoting event authorized to be activated.

Finally, it is to be understood that various modifications and/or additions may be made to the above described network protection unit and method for minimising congestion in an intelligent network during a mass subscriber telephony event without departing from the scope or ambit of the present invention.

Claims

1. A method of minimising congestion in an intelligent network during a mass participant telephony event, said intelligent network comprising a plurality of interconnected networks elements, said networks elements including at least one Service Control Point (SCP) and a plurality of Service Switching Points (SSPs), the method including the steps of:

(a) determining the available call-handling capacity of one or more of said network elements,

(b) determining event information characterising a new mass participant telephony event which is desired to be scheduled,

(c) requesting the scheduling of said new mass participant telephony event,

(d) calculating a predicted load placed on said one or more network elements during said new participant telephony event from said event information,

(e) comparing said predicted load to the available call-handling capacity of each of said one or more network elements during said new mass participant telephony event, and

2. A method according to claim 1, wherein said intelligent network further includes a Service Management System (SMS), and wherein

- the call-handling capacity of one or more of said network elements determined in step (a) is stored in a Network Protection Unit,

- said event information determined in step (b) is entered in said SMS , a scheduling request and said event information are sent in step (c) from the SMS to the NPU,

- the predicted load is calculated in step (d) in said NPU,

- the predicted load is compared to the available capacity of each of said one or more network elements in step (e) in said NPU, and

- a scheduling authorisation signal is sent in step (f) from the NPU to the SMS if the predicted load is less than the available capacity of each of said one or more network elements.

3. A method according to either of claims 1 or 2, wherein said network elements further include a plurality of telecommunications links between said at least one SCP and said plurality of SSPs.

4. A method according to any one of the preceding claims, wherein said at least one SCP and said plurality of SSPs each include processing means, and wherein said network elements further include one or more of said processing means.

5. A method according to any one of the preceding claims, wherein said network elements further include one or more announcement devices for playing one or more prerecorded announcements to participants in said new mass participant telephony event.

6. A method according to claim 5, wherein said event information includes announcement information characterising said recorded announcements.

7. A method according to any one of the preceding claims, wherein said event information includes a start and stop time for said new mass subscriber telephony event.

8. A method according to any one of the preceding claims, wherein said event information includes a plurality of destination network addresses to which calls made during said new mass subscriber telephony event are to be routed.

9. A method according to any one of the preceding claims, wherein during said new mass subscriber telephony event a predetermined number of calls handled by said SSPs during a gapping interval are transferred from said SSPs to said at least one SCP, and wherein said event information includes said predetermined number of calls and the duration of said gapping interval.

10. A Network Protection Unit (NPU) for minimising congestion in an intelligent network during a mass participant telephony event, said intelligent network comprising a plurality of interconnected networks elements, said networks elements including at least one Service Control Point (SCP) and a plurality of Service Switching Points (SSPs), the NPU comprising:

- storing means for storing available call-handling capacity of one or more of said network elements,

- signal input means for receiving a scheduling request signal and for receiving event information characterising a new mass participant telephony event which is desired to be scheduled,

11. A Network Protection Unit according to claim 10, wherein said network elements further include a plurality of telecommunications links between said at least one SCP and said plurality of SSPs.

12. A Network Protection Unit according to either of claims 10 or 11, wherein said at least one SCP and said plurality of SSPs each include processing means, and wherein said network elements further include one or more of said processing means.

13. A method according to any one of claims 10 to 12, wherein said network elements further include one or more announcement devices for playing one or more prerecorded announcements to participants in said new mass participant telephony event.

14. A Network Protection Unit according to claim 13, wherein said event information includes announcement information characterising said recorded announcements.

15. A Network Protection Unit according to any one of claims 10 to 14, wherein said event information includes a start and stop time for said new mass subscriber telephony event.

16. A Network Protection Unit according to any one of claims 10 to 15, wherein said event information includes a plurality of destination network addresses to which calls made during said new mass subscriber telephony event are to be routed.

17. A Network Protection Unit according to any one of claims 10 to 16, wherein during said new mass subscriber telephony event a predetermined number of calls handled by said SSPs during a gapping interval are transferred from said SSPs to said at least one SCP, and wherein said event information includes said predetermined number of calls and the duration of said gapping interval.