EP0640269A1 - Procede de regulation du trafic dans un reseau de telecommunications - Google Patents

Procede de regulation du trafic dans un reseau de telecommunications

Info

Publication number
EP0640269A1
EP0640269A1 EP93910183A EP93910183A EP0640269A1 EP 0640269 A1 EP0640269 A1 EP 0640269A1 EP 93910183 A EP93910183 A EP 93910183A EP 93910183 A EP93910183 A EP 93910183A EP 0640269 A1 EP0640269 A1 EP 0640269A1
Authority
EP
European Patent Office
Prior art keywords
exchange
trunk
threshold
network
routes
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP93910183A
Other languages
German (de)
English (en)
Inventor
Ian Barry 3 The Old Cottages Crabtree
Charles Arnold Woodside Cottage Swaine
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
British Telecommunications PLC
Original Assignee
British Telecommunications PLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB929210173A external-priority patent/GB9210173D0/en
Priority claimed from GB929210172A external-priority patent/GB9210172D0/en
Application filed by British Telecommunications PLC filed Critical British Telecommunications PLC
Publication of EP0640269A1 publication Critical patent/EP0640269A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04MTELEPHONIC COMMUNICATION
    • H04M3/00Automatic or semi-automatic exchanges
    • H04M3/22Arrangements for supervision, monitoring or testing
    • H04M3/36Statistical metering, e.g. recording occasions when traffic exceeds capacity of trunks
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04QSELECTING
    • H04Q3/00Selecting arrangements
    • H04Q3/64Distributing or queueing
    • H04Q3/66Traffic distributors

Definitions

  • This invention relates the control of a telecommunications network which includes at least one local exchange connected by routes to one or more parent trunk exchanges each being one of a plurality of trunk exchanges interconnected by trunk routes and to telecommunications networks so controlled. It is particularly concerned with the detection of focused overloads in such networks.
  • a local exchange is associated with a home exchange, through which incoming calls to the local exchange are routed, and a security exchange, through which outward calls from the local exchange are routed, in normal operation.
  • the security exchange is so called because it can also be used to route incoming calls to the local exchange if the home exchange fails.
  • the security and home exchanges are collectively referred to as the parent exchanges of the local exchange. Exchanges other than the parent exchanges are referred to as far-end trunk exchanges of the local exchanges.
  • NTM Near real-time network traffic management
  • BT' s trunk network in the United Kingdom currently handles approximately six million call attempts per hour during the busy periods which is equivalent to 1, 700 call attempts per second.
  • any networl- difficulties are detected and controlled as quickly a ⁇ possible.
  • difficulties are often encountered by network traffic managers due to abnormal traffic patterns which can be caused by events such as 'phone-ins, tele-votes and public holidays (for example Christmas Day and New Year's Eve/Day). In all these cases traffic in the network varies widely from the normal level, sometimes quite spectacularly, and the network must be controlled to maintain the best overall network performance.
  • BT' s Network Traffic Management System currently receives statistics on upwards of 37,000 routes from 490 exchanges in the UK every five minutes, which measurement period was chosen to be a long enough period to be able to obtain a statistically reliable measurement of the network performance whilst being short enough to allow effective real-time control of the network.
  • the information received by the NTMS is processed to provide CCITT recommended parameters.
  • the parameter values are compared with thresholds to determine if any difficulties exist on the monitored network elements.
  • the first indication of a network problem is when an ' exception' is displayed on a wall-board, or on a graphical interface at an individual manager' s workstation, at a Traffic Management Centre.
  • Exceptions are those parameter values, calculated from network element measurements, which deviate sufficiently from a predetermined threshold for that value. The exceptions are ranked in a priority order with the top 20 displayed.
  • some exceptions do not necessarily indicate a difficulty as thresholds are percentage-based and set a value which ensures all potential difficulties are captured. This results in exceptions being displayed that are occasionally spurious or insignificant. The exceptions therefore need to be examined in more detail to determine if a real difficulty exists and whether it warrants any action.
  • the NTMS provides near real-time surveillance and monitoring of the network' s status and performance. It provides the network traffic managers with information to enable them take prompt action to control the flow of traffic to ensure the maximum utilization of the network in all situations.
  • the NTMS allows network traffic managers to look at the raw statistics as well as derived generic parameters and to compare traffic patterns over the last few measurement periods to isolate any trends.
  • An On-Line Traffic Information System takes the measurement of statistics from the NTMS system and processes them to provide summarised historical data for daily and weekly traffic patterns. This system allows the network traffic managers to examine historical traffic patterns to detect any radical shifts in traffic.
  • a data management system provides the network traffic managers with an up-to-date copy of the routing tables at all trunk exchanges. This information is used to check the routes to which calls can be routed, which controls are in force and the routing algorithms being used.
  • ACE All Circuits Engaged
  • a method of controlling a telecommunications network which includes at least one local exchange connected by routes to one or more parent trunk exchanges each being one of a plurality of trunk exchanges interconnected by trunk routes, is characterised in that the method comprises applying focused overload controls to the trunk exchanges of the network when the Bids per Circuit per Hour (BCH) along the primary traffic routes from a parent trunk exchange to the local exchange exceed a first threshold and the magnitude of a decrease in the average Answer Seizure Ratio (ASR) on the trunk primary traffic routes to the parent exchange over a measurement period exceeds a second threshold.
  • BCH Bids per Circuit per Hour
  • ASR Answer Seizure Ratio
  • a primary traffic route is the route first tried for a call in a network, all alternative routes then being secondary.
  • the BCH parameter gives a normalised indication of the number of call attempts down a particular route and will generally stay at a normal value well below the maximum BCH that can be handled by the exchanges under normal conditions but will tend to move to and above that value during a focused overload. These normal values provide a maximum expected BCH range of the routes in the network.
  • the BCH will also rise due to an increase in country ⁇ wide traffic to a large number of subscribers served by a given local exchange, for example when a disaster befalls an area, but this will not necessarily result in a focused overload if a sufficiently high number of calls continue to be connected.
  • the inclusion of the test of the ASR in the present invention serves to distinguish between these two scenarios.
  • the first threshold can be set according to the normal maximum expected value of the BCH parameter on the route that can be properly handled by the network. It has been found that in a focused overload the BCH parameter rises very sharply reaching a peak in the first five minutes followed by an exponential drop to the normal level over the following forty minutes.
  • the maximum expected value of Seizures per Circuit per Hour (SCH) is approximately 60 divided by tfc- * ; average call length which at 2 to 3 minutes gives a normal maximum expected BCH for BT' s UK network of about 20 to 30 with the normal value at most about 10.
  • the first threshold is towards the high end of the above maximum expected BCH range. In this case a value of 30 can be used.
  • the ASR has been found to drop very sharply in the event of a sudden focused overload and it remains low for about 15 minutes before slowly returning to its normal value.
  • the second threshold can therefore be conveniently set equal to the normal daily excursion which for BT' s UK network is approximately 10%.
  • a 10% drop in the average Answer Seizure Ratio (ASR) on the trunk primary traffic routes into the home exchange over a single measurement period is very significant and can therefore be used to detect the focused overload condition.
  • focused overload controls can be applied to the trunk exchanges of the network only when the increase in the average value of the BCH along the trunk primary traffic routes into the respective parent exchange over a measurement period exceeds a third threshold.
  • a network may be controlled according to the present invention by an apparatus to which is input the network parameters and which provides control information to the network controller when the focused overload condition has been detected so that the network manager can apply the method of the present invention to the network.
  • the network can be controlled automatically on detection of the focused overload to apply the method of the present invention without the intervention of a network manager.
  • the focused overload controls to be applied to the network may be call gapping applied to the home trunk exchanges or to one or more of the far-end trunk exchanges of the local exchange, for example.
  • the focused overload controls can be removed, ie that the focused overload problem has been overcome. It has been found that it is satisfactory to remove the focused overload controls once the BCH from the home exchange to the local exchange falls below a fourth threshold, which threshold is preferably 5. Once it has been determined that the focused overload controls can be removed, the focused overload controls applied to the exchanges of the network are removed either by a network manager or automatically by a network controlling apparatus. In this way local focused overload controls can be overidden once it has been determined globally that the problem has been solved.
  • a method of controlling a network which includes at least one local exchange connected by routes to one or more parent trunk exchanges each being one of a plurality of trunk exchanges interconnected by trunk routes, in which call gapping is applied to one or more of the exchanges of the network on detection of a focused overload at an exchange, the method being characterised in that call gapping of numbers of a local exchange is applied either: a) to an associated parent exchange whenever the Bids per Circuit per Hour (BCH) from the parent exchange to the local exchange is greater than a fifth threshold and the Answer Seizure Ratio (ASR) on primary traffic routes from the parent exchange to the local exchange has stayed below a sixth threshold for the duration of a measurement period; or b) to a far-end trunk exchange of the local exchange whenever the ASR from the far-end trunk exchange to a parent trunk exchange of the local exchange has stayed below a seventh threshold for the duration of a measurement period.
  • BCH Bids per Circuit per Hour
  • ASR Answer Seizure Ratio
  • a method according to the second aspect of the present invention can be used advantageously, whether or not in combination with a method according to the first aspect of the present invention.
  • the advantage lies in the increased flexibility available. If call gapping is applied to the home trunk exchange, it has effect on all routes in to that home trunk exchange for the local exchange. If it is applied at the far-end trunk exchanges, it is possible to select one or more of the far-end trunk exchanges which is or are contributing heavily to the focused overload, and call gap only that one exchange, or those selected trunk exchanges. When applying call-gapping to one or more of the far- end trunk exchanges, a less sensitive test than that used for the application of local focused overload controls has been found to be appropriate.
  • the seventh threshold can conveniently be set to be about equal to the average normal ASR for exchanges in the network so the exchanges are regulated to allow the associated ASRs to move back to this value.
  • the fifth, sixth and seventh thresholds will in general need to be determined by analyzing the normal values for the particular network to be controlled in accordance with the above general principles.
  • the local controls are preferably removed progressively as the problem is resolved at different parts of the network.
  • the call gapping is removed from a parent trunk exchange once the ASR and Percentage Occupancy (OCC) have stayed above an eighth threshold and below a ninth threshold, respectively, for the duration of a measurement period.
  • the percentage occupancy is the total traffic in Erlangs, divided by the number of in-service circuits on a route.
  • the eighth and ninth thresholds can be set to equal the highest normal ASR and OCC for exchanges in the network which for BT' s UK network are in the order of 80% and 60%, respectively.
  • the call gapping is preferably applied to a far-end trunk exchange until the ASR to the home exchange has stayed above rhe eighth threshold for the duration of a measurement period.
  • the extent of call gapping applied can be a fixed amount, for example 5 second call gapping, but will preferably be selected according to the prevailing conditions based on prior knowledge of the call handling capability of the subscriber being called or from general experience of the network manager.
  • thresholds can be selected according to the characteristics of the particular network to which the present invention is to be applied. If the normal time variation of the parameters being monitored is known, the threshold values could be adjusted accordingly to provide a more consistent alert of a focused overload and to reduce the chance of a normal increase in traffic triggering a false indication of a problem.
  • Figure 1 is a schematic representation of a network controllable by the method of the present invention
  • FIG. 2 is a schematic representation of a control system for implementing the method of the present invention.
  • Figure 3 is a schematic representation of a control system for implementing the method of the present invention using direct control of a network by a computer.
  • a telecommunications network comprises a number of digital main switch units (DMS ⁇ s) - trunk exchanges - of which only five are shown for clarity and are referenced 102, 104, 106, 108 and 110.
  • DMS ⁇ s digital main switch units
  • Subscribers' customer premises equipment of which only two are shown referenced 112 and 114, are connected to the trunk exchanges 102 to 110 via respective digital local exchange (DLE) 116 and 118.
  • DLE digital local exchange
  • the DLE 116 is connected to the DMS ⁇ 102 through which incoming calls to the subscribers attached to the DLE 116, including subscriber 112, are routed.
  • the DMS ⁇ 102 is commonly referred to as the home trunk exchange for the DLE 116.
  • the DLE 116 is also connected to the DMS ⁇ 104 through which outgoing calls from the DLE are routed. This is usually called a security exchange as incoming calls to the exchange 116 can be routed through it should the DMSU 102 fail.
  • the DMS ⁇ 108 is the home exchange for the digital local exchange 118.
  • the home and security exchanges associated with a DLE are collectively referred to as the parent exchanges of that DLE.
  • the digital local exchange 116 may not be able to handle the calls and in extreme cases the DLE might also go into overload. This will block unrelated traffic in the area around the destination exchange. This is what is called a focused overload which needs to be controlled if congestion is to be avoided.
  • FIG. 2 shows a network control system implementing the method of the present invention.
  • the network of Figure 1 is denoted by box 202. Every five minutes, which is the measurement period of the network of Figure 1, a set of statistics is generated by the digital exchanges of the network 202 which is processed by an NTMS system 204 to provide generic measurement values including those of the CCITT recommendation. These parameters are input to a run ⁇ time system 206 which applies rules to the received parameters from the NTMS 204 by means of an appropriately coded expert system.
  • the run-time system 206 provides recommendations to aid a network traffic manager 208 detect and control focused overload problems in the network 202 according to embodiments of the present invention.
  • the run-time system 206 employs a three phase cycle in which recommendations for focused overload control actions are passed to the network traffic manager 208.
  • the run-time system 206 monitors each local exchange and determines when the BCH along the route from the home trunk exchange of a local exchange exceeds 30 and in which the BCH averaged over trunk primary traffic routes to that home exchange have increased by 40% since the last measuring period. When these conditions are satisfied the run-time system supplies a recommendation to the network traffic manager 208 to apply focus overload controls and in particular, in this embodiment, call gapping to the parent trunks of the local exchange or to far-end trunks of the local exchange affected - assumed for the purposes of the following description to be local exchange 116 of Figure 1.
  • the run-time system 206 can provide recommendations to the network traffic manager 208 on applying a specific, local focused overlaod controls to the trunk exchanges 102 to 110 to the network 202 according to the present invention.
  • the parent trunk exchange 102 of the local exchange 116 will be subjected to call gapping to numbers of the local exchange 116 once the ASR from the parent trunk exchange to the local exchange 116 has remained at less than 20% for the duration of a five minute measuring period and the BCH along the route from the parent trunk exchange to the local exchange 116 is greater than 10.
  • the run-time system 206 can alternatively recommend call gapping to numbers of the local exchange 116 at a far- end trunk exchange 106 to 110 of the local exchange 116 when the ASR along the route from the far-end trunk exchange to a parent exchange 102, 104 of the local exchange 116 falls below 45%.
  • the run-time system 206 will also recommend to the network traffic manager 208 when the call gapping at a given trunk exchange should cease. Advice is given to remove call gapping from a parent trunk exchange 102 of the local exchange 116 once the ASR to the local exchange 116 is greater than 50% and the OCC along the route from the parent trunk exchange to the local exchange 116 is less than 80% for the measuring period, and to remove the call gapping of the far-end trunk exchanges 106 to 110 of the local exchange 116 once the ASR along the route from the far-end trunk exchange to the parent exchange 102 of the local exchange 116 once again rises above 45%.
  • the run-time system 206 can alternatively also recommend that all focused overload controls are removed once the BCH along the route from a local exchange' s home exchange to that local exchange is less than five. This ensures that all controls will be removed under a relevant, overriding condition. It is envisaged that the run-time system 206 may directly control the network to apply the method of the present invention as shown in Figure 3 but at present it is expected that it will be necessary to use a network traffic manager 208 to implement of the method of the present invention to allow overriding of the recommendations at his or her discretion.
  • the method of the present invention has been simulated on a computer representation of BT' s UK telecommunications network in which the run-time system 206 comprises a PROLOG-based expert system coded with the rules necessary to provide the recommendations described above in response to the appropriate CCITT parameters from the NTMS 204.
  • the particular system employed was a QUINTUS PROLOG expert system run on a Sun Sparc station. Parameters generated during real network activity were recorded for the entire GB network for four, 5-minute measurement periods and stored as a data file on the computer.
  • a C-language program provide an interface between the raw parameters in the computer file and the expert system in that as the expert system required information about the network, the C-language program calculated the data from the raw parameters.
  • the particular thresholds adopted in order to determine when a focused overload condition is likely to occur and when the various call gapping controls are to be applied and relaxed will be set according to the particular network 202 to which the method is to be applied.
  • the present invention is not restricted to any particular values of threshold adopted in the above described specific embodiment.

Landscapes

  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Monitoring And Testing Of Exchanges (AREA)

Abstract

Procédé de régulation du trafic dans un réseau de télécommunications comprenant au moins un central local relié, par des voies d'acheminement, à au moins un central interurbain de rattachement, chaque central interurbain de rattachement faisant partie d'une pluralité de centres de rattachement reliés entre eux par des voies d'acheminement de rattachement. Ledit procédé consiste à exercer une régulation de surcharge concentrée sur au moins un central de rattachement du réseau lorsque les tentatives de prise par circuit et par heure (BCH) le long d'une voie primaire d'acheminement de trafic allant d'un central interurbain de rattachement au central local dépassent un certain seuil et que l'amplitude de diminution du taux de prise de réponse (TPR) moyen, sur la voie primaire d'acheminement de trafic interurbaine allant jusqu'au central de rattachement, dépasse, sur une période de mesure, un autre seuil. Les régulations de surcharge concentrées sont appelées régulations d'espacement d'appel, et la période de mesure dure approximativement cinq minutes.
EP93910183A 1992-05-12 1993-05-12 Procede de regulation du trafic dans un reseau de telecommunications Withdrawn EP0640269A1 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
GB929210173A GB9210173D0 (en) 1992-05-12 1992-05-12 Method of controlling a telecommunications network
GB9210173 1992-05-12
GB9210172 1992-05-12
GB929210172A GB9210172D0 (en) 1992-05-12 1992-05-12 Method of controlling a telecommunications network
PCT/GB1993/000972 WO1993023962A1 (fr) 1992-05-12 1993-05-12 Procede de regulation du trafic dans un reseau de telecommunications

Publications (1)

Publication Number Publication Date
EP0640269A1 true EP0640269A1 (fr) 1995-03-01

Family

ID=26300864

Family Applications (1)

Application Number Title Priority Date Filing Date
EP93910183A Withdrawn EP0640269A1 (fr) 1992-05-12 1993-05-12 Procede de regulation du trafic dans un reseau de telecommunications

Country Status (5)

Country Link
EP (1) EP0640269A1 (fr)
JP (1) JPH08500219A (fr)
CA (1) CA2135633C (fr)
SG (1) SG52408A1 (fr)
WO (1) WO1993023962A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR0169035B1 (ko) * 1996-05-30 1999-01-15 양승택 확장된 서비스 필터링 기법을 이용하여 지능형 정보제공 시스템과의 상호작용을 통해 제공되는 전화투표 서비스에서의 대량집중호 처리방법

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9323962A1 *

Also Published As

Publication number Publication date
SG52408A1 (en) 1998-09-28
WO1993023962A1 (fr) 1993-11-25
CA2135633C (fr) 1998-07-14
JPH08500219A (ja) 1996-01-09
CA2135633A1 (fr) 1993-11-25

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