(12) United States Patent
`Yaakov
`
`USOO6748433B1
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 6,748,433 B1
`Jun. 8, 2004
`
`(54) METHOD AND SYSTEM FOR
`CONTROLLING QUALITY OF SERVICE
`OVERATELECOMMUNICATION
`NETWORK
`
`(75) Inventor: Yaron Yaakov, Lapid (IL)
`(73) Assignee: Ectel, Ltd., Petach Tikva (IL)
`(*) Notice:
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 720 days.
`
`(21) Appl. No.: 09/613,461
`(22) Filed:
`Jul. 10, 2000
`(30)
`Foreign Application Priority Data
`Jul. 12, 1999
`(IL) ................................................ 13O895
`(51) Int. Cl. .............................................. G06F 15/173
`(52) U.S. Cl. ....................... 709/224; 709/223; 709/236;
`370/241; 370/401
`(58) Field of Search ................................. 709/200-203,
`709/223-224, 236-238,246; 370/224–230,
`241, 395.2, 395.21, 401–402
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`5,883,819 A 3/1999 Abu-Amara et al. ........... 716/1
`6,055,571 A * 4/2000 Fulp et al. .................. 709/224
`6,308.216 B1 * 10/2001 Goldszmidt et al. ........ 709/224
`6,385,204 B1 * 5/2002 Hoefelmeyer et al. ...... 709/401
`6,446,122 B1
`9/2002 Rawat et al. ............... 709/224
`6,466,985 B1 * 10/2002 Goyal et al. ................ 709/238
`6,631,135 B1 * 10/2003 Wojcik .........
`... 370/395.21
`6,636,516 B1 10/2003 Yamano ..................... 370/401
`6,647,412 B1 * 11/2003 Strandberg et al. ......... 709/223
`
`
`
`SERVICE
`
`OTHER PUBLICATIONS
`ITU-T (International Telecommunication Union- Telecom
`munication Standardization Sector of ITU), p. 861, (02/98)
`(14pgs.).
`PAMS (Perceptual Analysis Measurement System), the Brit
`ish Telecom Brochure (4 pgs.) No Date.
`ITU-T (International Telecommunication Union- Telecom
`munication Standardization Sector of ITU), G.107, (12/98),
`(25 pgs.).
`Simon Broom et al., “Getting the Message, Loud and
`Clear-Quantifying Call Clarity.”, British Telecommunica
`tions Engineering, vol. 17, pp. 66-72, Apr. 1998.
`* cited by examiner
`Primary Examiner Bharat Barot
`(74) Attorney, Agent, or Firm- Nath & Associates; Harold
`L. Novick
`ABSTRACT
`(57)
`A method, a System and equipment for determining quality
`of telecommunication Service over a telecommunication
`network, which provide: (a) obtaining data on quality of
`service over a number of routes in the network by
`determining, for each route, N parameters p, each reflecting
`either a quality of transmission of a particular Service
`through said route or a Statistical characteristics of Said
`route's availability to a subscriber, and (b) building an
`objective quality Score (OQS) for each of the routes, the
`OQS being a multi-profile quality estimation equation pre
`Senting a Sum of N said parameters p, taken with respective
`weight functions W(p) thereof. Based on the Score, one or
`more routes can be selected in the network (for example, for
`routing), which have the OQS value not lower than a
`predetermined OQS.
`
`22 Claims, 3 Drawing Sheets
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`U.S. Patent
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`Jun. 8, 2004
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`U.S. Patent
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`Sheet 3 of 3
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`US 6,748,433 B1
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`1
`METHOD AND SYSTEM FOR
`CONTROLLING QUALITY OF SERVICE
`OVERATELECOMMUNICATION
`NETWORK
`
`FIELD OF THE INVENTION
`The present invention relates to a method and a System for
`controlling quality of Service over a network, and in
`particular-Over a packet Switched data network, Such as
`over IP (Internet Protocol).
`BACKGROUND OF THE INVENTION
`It is widely known, that modem telecommunication net
`WorkS comprise different interconnected domains, for
`example a PSTN (Public Switched Telephone Network)
`which was originally designed for handling Voice calls, and
`a packet Switched network which, by its nature, is data
`oriented. Nowadays, all kinds of Services or transmission
`types (e.g., voice, fax or data) are transmitted through the
`combined networks and are inevitably Subjected to many
`factors which affect the quality of Service expected by a
`particular Subscriber. The above-mentioned factorS Stem not
`only from the nature of a particular network domain, but also
`(and to the great extent) from the growing traffic load in the
`modem telecommunication networkS.
`In packet Switched networks, real time Services Such as
`voice, fax, real-time video conference (e.g., packetized
`voice signals of Voice over IP), are mixed with data Signals
`and, as a result, Suffer from degradation that is not encoun
`tered in the regular circuit-switched networks (e.g., PSTN).
`The degradation may occur due to such known packet
`networks problems, as packet loSS, packet delay and packet
`delay variation (so-called jitter) which are known as specific
`criteria of data transmission quality.
`While in the PSTN the voice channels are assigned to a
`constant, assured bandwidth, in packet Switched networks
`the bandwidth varies dynamically, depending on data and
`Voice traffic in the network. In order to ensure a given quality
`of the Voice Signal, a Service provider in the packet Switched
`network must assure both a minimum bandwidth at all times,
`and keep the three criteria mentioned above within given
`limits. For example, it becomes difficult to carry on a voice
`conversation if the packet delay exceeds 200 ms.
`While for data traffic control in the packet switched
`networks it may be enough to monitor Some performance
`criteria Such as the packet delay, in the case of Voice traffic
`various parameters combine in an infinite number of poS
`Sible combinations So that, there is no simple correlation
`between these parameters and the actual Voice quality heard
`by the caller.
`Voice networks have traditionally been tested by injection
`of test sentences at one (transmitting) end, and having this
`Sentence heard and its clarity Subjectively graded by a group
`of people at the other (receiving) end of the path. The test
`result is called a Mean Opinion Score (MOS) and ranges
`from 1 (poor) to 5 (excellent).
`To convert this obviously subjective method to an objec
`tive one, real measurements of quality should Serve the basis
`for conclusions. To this end, two main approaches were
`proposed. The first one can be classified as an intrusive
`approach, which is based on comparison of a transmitted
`Signal to the same received signal, and examining the
`difference. There are a number of models enabling to arrive
`to the MOS results using the above comparison, for example
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`2
`PSQM model (described in the International ITUT standard
`Q862) and PAMS model developed by British Telecom
`(BT). It should be noted, that PAMS is the only model which
`takes into account problems in the quality of Service which
`may be brought to data networks by phenomena Such as
`packet delay, packet loss, jitter, etc. The Second approach is
`a non-intrusive approach based on measuring physical
`parameterS Such as noise, delay, echo etc., and improving
`thereof up to a Satisfactory level. A number of models exist,
`for example E-model of ITUT standard body and a CCI
`(Call Clarity Index) developed in BT Presently, there is no
`Such a non-intrusive model, which would take into account
`problems of quality degradation due to data networkS.
`Nowadays, voice Services providers which utilize packet
`Switching in their networks, cannot assure the desired Voice
`quality to their customers in advance, Since the Voice quality
`of Service is not monitored in the networks to the extent
`allowing that.
`On the other hand, fully loaded networks suffer from
`Shortage of lines, and very often the quality of Service (with
`respect to voice, fax and data) is reduced due to low
`connectivity in the network and low availability of destina
`tion points.
`None of the relevant methods and systems known to the
`Applicant describes or Suggests any combined Quality of
`Service estimation mechanism for a network, which would
`enable integral monitoring of the quality of Service, and
`control of the quality of service to be provided.
`SUMMARY OF THE INVENTION
`It is therefore the object of the present invention to
`provide a method of determining quality of the telecommu
`nication Service over a telecommunication network based on
`a novel, combined estimation of quality of Service for this
`network. A further object of the invention is to provide a
`method, a System and an equipment for monitoring and
`controlling the quality of Service in the network, based on
`the combined estimation thereof. The invention is most
`effectively applicable to modem telecommunication net
`Works including packet Switched networks.
`The above main object can be achieved by a method of
`determining quality of telecommunication Service over a
`telecommunication network, the method including the fol
`lowing Steps:
`a) obtaining data on quality of Service over a number of
`routes in the network by determining, for each route, N
`of parameters p, each of Said parameters p, reflecting
`either a quality of transmission of a particular Service
`(transmission type) through said route or a statistical
`characteristics of Said routes availability to a
`Subscriber,
`b) building an objective quality score (OQS) for each of
`Said routes, the OQS being a multi-profile quality
`estimation equation presenting a Sum of N Said param
`eters p, taken with respective weight functions W(p)
`thereof.
`It is further proposed, that the weight functions W(p)
`reflect a preferred profile of the quality of Service in Said
`network and are presented as positive numbers in the range
`0s W(p)s 1 selected so that M values of said weight
`functions W(p) are more than 0, (Ms N), and the sum of the
`Selected values of the W(p) is equal to 1.
`Preferably, the method also comprises Step (c):
`c) Selecting one or more routes having the OQS value not
`lower than a predetermined OOS value for further
`routing the telecommunication Services there-through.
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`US 6,748,433 B1
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`3
`It should be mentioned, that for effecting control of the
`Service quality, an additional Step is to be effected, i.e. the
`Step of routing the telecommunication Services over Said one
`or more Selected routes.
`It is understood, that said particular Service (transmission
`type) is one of components in a non-limiting list comprising
`Voice, fax and data.
`The mentioned equation can be presented in the following
`form:
`
`4
`In another possible version, the weight functions W(p) of
`the quality of Service can be Selected by a client in order to
`form its own profile of service. The client uses the weight
`functions for estimating various options of the Service
`profile and further choosing the most reasonable one.
`In both mentioned versions a so-called service level
`agreement (SLA) can be signed (accepted) between the
`Service provider and the client, which agreement comprises
`both the selected weights and the selected OQS parameter.
`In practice, the client Selects the mentioned M parameters
`with the weight functions thereof (i.e., the parameters which
`are important for the Services of interest), thereby selecting
`the preferred profile of service. The service provider esti
`mates OOS for a variety of routes using the profile of service
`obtained from the Subscriber, for proposing variants of the
`“total' quality to the subscriber. The subscriber is then
`invited to select a preferred OQS value(s). Upon doing that,
`the Service provider accepts its obligation to route all the
`Services of this particular Subscriber along those routes
`which have been found to Satisfy the required total quality
`of Service OOS.
`It should be appreciated that the above method may
`terminate with a step (d) of routing the Services over one or
`more routes which have been Selected at Step (c).
`However, the method may further comprise a step (e) of
`monitoring the quality of Service in real time and comparing
`it with the predetermined value OQS.
`Preferably, the Step (e) comprises obtaining data on qual
`ity of Service over a particular Selected route in the network
`by determining M of Said parameters p, and building an
`objective quality score (OQS) for said route, the OQS being
`a multi-profile quality estimation equation presenting a Sum
`of M said parameters p, taken with Said weight functions
`W(p).
`Those skilled in the art understand that in such telecom
`munication networks as PSTN and ATM the routing is
`accomplished in a fixed way. It means, that if the routes
`Selected at Step (c) are then found to Supply the quality of
`Service lower than was expected, the Situation can be
`improved only physically, for example by effecting repairs
`in the network. In other words, the monitoring allows for
`obtaining the updated information about channels quality
`which might be useful for the purposes of the equipment
`maintenance and improvement of the Service.
`It is known, that for IP domains the situation is different,
`i.e. the routing is more flexible. In view of this, the method
`may comprise a feedback feature, i.e.
`Step (e) additionally comprises real-time monitoring the
`OQS of a plurality of routes in the network, and a step
`of near real-time re-routing the telecommunication
`Services to those routes which are characterized by
`OQS value not lower than the predetermined value; the
`re-routing is provided in case that the Selected route has
`the OQS lower than the predetermined value.
`For example, the real-time monitoring the OQS of a
`plurality of routes in the network with respect to a particular
`transmission type may be provided in the following way:
`obtaining data on quality of Service concerning Said
`particular transmission type from a plurality of points
`in the network, distributed therein,
`processing the obtained data to determine a corresponding
`current value of p, parameter for Said plurality of
`points, and
`defining in Said network a number of alternative trans
`mission paths for Said transmission type, each having a
`particular current value of the parameter p.
`In one particular version of the method, Said parameter p,
`is the Voice Quality of Service parameter QoS, and said
`network comprises a packet Switched network Such as IP
`network.
`
`wherein:
`OQS is the objective quality score estimation
`pi-a value of a parameter “i' in a particular route in the
`network
`W(p)-weight function of the parameter
`(in one
`Simple particular case W.(p) may be a constant coef
`ficient of the parameter “i”)
`N is the number of parameters defined for the network.
`The above-mentioned parameters preferably comprise at
`least the following five (N=6) characteristics of the quality
`of Service for particular transmission types and the network
`of interest:
`p-is a voice Quality of Service parameter QoS which
`can be estimated using at least one of the following
`methods known in the prior art: CCI (Call Clarity
`Index), PAMS (Perceptual Analysis Measurement
`System), PSQM (as defined in the international ITUT
`Standard Q-862), E-model, etc.,
`P is a Fax Quality of Service parameter estimated, for
`example, according to a Statistically obtained ratio
`between a number of errors during a fax transmission
`and a number of pages in the fax, or other methods, for
`example based on checking a coded message enclosed
`in a particular fax packet.
`P is a Data Quality of Service parameter which can be
`estimated based on Such a widely known transmission
`parameters as Packet delay, Packet loSS and Packet
`delay variation (jitter);
`P is Line Availability in the network, which parameter
`can be calculated using Statistical parameters of physi
`cal reliability of a line, i.e., MTBF (MeanTime
`Between Failure) and MTTR (MeanTime to Repair);
`Ps is Connectivity of the network which may be
`obtained from Statistically calculated parameterS ASR
`(Answer Seizure Ratio) and NER (Network Effective
`neSS Ratio) estimating a number of Successful calls
`with respect to a number of the initiated calls, and calls
`provided by the destination network portion, respec
`tively;
`Pi—is a Service Availability parameter, Statistically
`reflecting ratio is of the responses “busy' or “not
`available' to the inquiry calls, with respect to the
`requested destination numbers or Sites.
`In one version of the method, the weight functions W.(p.)
`of the quality of Service can be Selected by a Service provider
`for forming a number of profiles of services to be offered to
`clients.
`The mentioned pair of a Service provider and a client may
`reflect various combinations, for example a Service provider
`and a particular customer (Subscriber); two Service providers
`being inter-carriers, a Service provider and a “clearing
`house'; a clearing house and a network provider and the
`like.
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`S
`It should be noted that more than one p can be determined
`and monitored according to the above version. The
`re-routing of the particular transmission type Signal can be
`thus effected via those of Said transmission paths having
`current values of Said at least one p, parameter being not
`lower than said Selected W(p)p.
`The method comprising feedback enables the Service
`provider to fulfill the obligations according to the Service
`Level Agreement (SLA) proposed to a customer by assuring
`a desired end-to-end quality of Service in the network.
`Further, the method may include a step of quality related
`call billing, where a call is billed taking into account the
`quality actually delivered or preliminarily ordered. It is
`natural that any combination of the parameter p, with its
`weight function W(p) having values from 0 to 1 can be
`asSociated with an appropriate price function. Based on this,
`the OQS estimation can be reflected by a specific price range
`offered by the service provider. Similarly, the SLA signed
`between the service provider and the subscriber reflects not
`only the profile of service the subscriber has selected, but
`also the prices associated with this profile. Alternatively or
`in addition to the SLA, the caller may indicate the level of
`quality/cost desired in real time (for example, for an inter
`national voice call he/she may request a higher QoS than for
`a national long distance call).
`The method would enable the service providers to offer
`Voice, fax and data transmission Services of various quality
`ranges and at appropriate prices, beginning from full price
`high quality Services up to premium Services.
`According to a Second aspect of the present invention,
`there is also provided a System for determining and moni
`toring quality of Service in a telecommunication network.
`The System for determining a quality of Service estimate
`in a network may comprise:
`a plurality of test units capable of collecting data for
`determining value of at least one quality of Service
`parameter p, with respect to a particular transmission
`type at various points in Said network, Said parameter
`p, being one of N quality of Service parameters;
`a Server computer adapted to communicate with Said test
`units for receiving therefrom the collected data on Said
`at least one parameter at Said respective points of the
`network, Said Server computer being capable of defin
`ing a number of transmission paths (routes) in the
`network, each having its own Said quality of Service
`parameter p.
`Preferably, the Server computer is adapted to communi
`cate with the test units collecting data on at least one
`additional quality of Service parameter of Said N quality of
`Service parameters, and, based on the collected data con
`cerning the points and the parameters, the Server computer
`being capable of building an objective quality Score (OQS)
`for a number of routes in the network, wherein the OOS is
`a multi-profile quality estimation equation presenting a Sum
`of N Said parameters pi taken with respective weight func
`tions W(p) thereof.
`According to the preferred embodiment of the System,
`Said plurality of test units are also capable of monitoring Said
`at least one parameter p, in real time, while Said Server
`computer adapted to define in real time a number of trans
`mission paths each having its own current value of quality
`of Service parameter p.
`In one particular embodiment of the System, where the
`Voice QoS parameter p is monitored, it enables the Service
`provider to measure the audio quality of individual pack
`etized voice channels (voice transmission paths) “buried” in
`a data communications traffic.
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`US 6,748,433 B1
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`6
`Preferably, the Server computer is also capable of ranking
`said paths according to their p, parameter. Such an ability
`can be used for various purposes, for example: for reporting
`on poor quality of particular channels, for further routing a
`particular transmission type incoming the packet network,
`and/or for assigning different tariffs to the paths with dif
`ferent ranks of p.
`According to one exemplary embodiment of the System,
`wherein the packet Switched network cooperates with a
`gateway circuitry where an analog voice Signal is packetized
`and routed, the above-mentioned gateway circuitry com
`prises a Service provider's network element responsible for
`routing Said Voice Signals, and the Server computer is
`capable of providing Said element with information on the
`defined transmission paths and respective values of their
`voice quality of Service p(QoS) parameter, thereby enabling
`the routing of the Voice Signals via those of Said transmission
`paths having predetermined values of the QoS parameter.
`Actually, in this embodiment the System for monitoring
`becomes a System for providing improved Voice Service in
`a packet Switched network.
`The mentioned service provider's network element where
`the analog voice Signal is packetized and routed (as well as
`the element where the packetized voice Signal is
`de-packetized and passed to its destination) may constitute
`a Voice over IP (VoIP) gateway or gatekeeper.
`The above-mentioned Server computer, and an equipment
`kit including at least one Such Server computer and,
`optionally, a number of the described test units-form
`additional aspects of the present invention.
`For example, a Server computer can be designed for
`determining a quality of Service in a network, the Server
`computer being designed for communicating with a plurality
`of test units for receiving therefrom data on quality of
`Service parameters p, at various points of the network, based
`on the collected data concerning the points and the
`parameters, the Server computer being capable of building
`an objective quality score (OQS) for a number of routes in
`the network, wherein the OQS being a multi-profile quality
`estimation equation presenting a Sum of Said parameters p,
`taken with respective weight functions W(p) thereof...,
`wherein
`each of Said test units being adapted to determine value of
`at least one quality of Service parameter p, with respect
`to a particular transmission type.
`The Service computer can definitely be used for monitor
`ing the quality of Service, and for routing in the network
`based on the OOS estimation.
`Further features of the system will become apparent from
`the following description of the preferred embodiments.
`BRIEF DESCRIPTION OF THE DRAWINGS
`The method and the System according to the invention
`will be further explained with reference to non-limiting
`examples illustrated in the attached drawings in which:
`FIG. 1 is a pictorial representation of a System for
`controlling quality of service over a PSTN network.
`FIG. 2 is a pictorial representation of a System for
`controlling quality of Service over a data network Such as IP
`network.
`FIG. 3 is a pictorial representation of a system for
`real-time monitoring of a Voice Quality of Service over the
`IP network.
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`FIG. 1 illustrates a system implementing the described
`method, for controlling the quality of service in a PSTN
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`7
`network being an example of to the network with conven
`tional (fixed) routing. Other examples of Such a network can
`be an ATM (Asynchronous Transport Mode) network and a
`cellular telephone network.
`The network 10 shown in the figure is a conventional
`PSTN network with an out-of band signaling network 12,
`Such as a widely known signaling System SS7. Two end
`points 14, between which the telecommunication Service is
`provided, are equipped with access units 16. The left-hand
`end point 16 is, for example a Central Office PSTN Switch
`having a plurality of E1/T1 output lines. A call following via
`one of the lines is transmitted via a number of middle layer
`Switches 18 to the E1/T1 lines of the right-hand endpoint 14,
`and then to its access unit 16. The quality of service of the
`network 10 will be estimated for the end-to-end communi
`cation. To this purpose, at least two opposite acceSS units 16
`are provided with Remote Test Units (RTU) 20 for intrusive
`quality monitoring which are Switched in the access lines
`and are capable of obtaining particular quality parameters
`from messages of a particular call transmitted there-between
`over the network (to be more exact, the parameters are
`determined by comparison transmitted Signals to the
`received ones). The RTU20, for example, can be manufac
`tured similar to the monitoring unit Quali.NetTM of ECTel(R),
`Israel. The System also comprises a number of non-intrusive
`Monitoring Systems (MS) 22 for PSTN which are capable of
`obtaining data on a particular transmission type (Service)
`from E1/T1 lines of end points 14, and also signaling data
`from the Signaling network 12, for producing therefrom a
`number of quality parameters with respect to a particular call
`and a particular route (transmission path). The MS 22 can be
`similar to the ECTel’s product QualiView. Data obtained by
`the probes 20 and 22 is processed by a Quality Management
`Server (QMS) 24 controlled by a central processor (control
`unit CU) 26. The collected data is received by a Data
`Collector 28 where CDRs (Call Detail Records) are built and
`values of the parameters p, are determined for the route
`under examination. The weight functions W(p) preliminar
`ily introduced into a so-called block 30 (also serving for
`Storing Service Level Agreements) are used for calculating
`the value of OQS for the route (transmission path) under
`examination by unit 32, based on the equation (1). Results
`of the OOS estimation for a number of routes is further
`displayed by a monitor 34. The checking Stage of the method
`is finished. The telecommunication Services can be then
`permanently routed, via those transmission paths (routes)
`which demonstrate a Suitable value of OOS. Real time
`monitoring of the quality of Service can be provided in a
`Similar way just for the purpose of displaying whether the
`expected level of quality (stored in the block 30) corre
`sponds to the real level (obtained from block 32).
`FIG. 2 illustrates another System implementing the
`described method, i.e., a System for controlling the quality of
`Service in a network comprising a packet Switched network
`(in this figure, an IP network). Units similar to those
`illustrated in FIG. 1, will be marked with similar numbers.
`The network 40 comprises a PSTN network and a IP
`network 42, connected by two Media Gateways 44. The
`gateways 44 are controlled by a Gatekeeper 46 and a Media
`Gateway Control 99 (MGC) unit 48. The MGC 48 interacts
`with the Signaling network 12 (two parts thereof are shown)
`via Signaling Gateways 50.
`In this particular embodiment, each of the Gateways 44 is
`connected at one end to E1/T1 lines of the PSTN Switch 14
`and the access unit 16, while at the other end to the IP
`network 42. Monitoring Systems (MS) 22 are therefore
`non-intrusively placed at the E1/T1 inputs of the gateways
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`US 6,748,433 B1
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`8
`44 to collect data both from these inputs, and the Signaling
`network 12. Monitoring Systems (MS) 48 are connected
`between the gateways 44 and the IP network 42 and capable
`of collecting and processing both the transmission type data
`and the Signaling data which is exchanged in the IP network
`while a particular call is executed.
`In this particular embodiment, a Quality Management
`Server (QMS) 25 collects data from all types of probes (RTU
`and MS blocks 20, 22 and 48). It should be noted, that the
`types of probes to be included in the System are usually
`Selected according to the client's profile of Service, i.e., all
`types of the probes are not required by default. The Data
`Collector 28 builds CDRs on particular calls in respect of
`particular initial routes in order to obtain values of quality
`parameters p, for these routes. The Objective Quality Score
`OQS is then calculated by the unit 32 based on the weight
`functions W(p) obtained from the block 30 which serves for
`Storing the preferred profiles of quality of Service for dif
`ferent subscribers (and also for further storing the OQS
`values corresponding to the SLAS of particular Subscribers).
`The OOS value of a particular route can be displayed by a
`display 34, with a reference to a OQS according to the SLA.
`Additionally, block 50 is provided for real-time comparing
`the OQS with the OQS according to the SLA in the moni
`toring regime. The unit 32, as well as units 28, 30 and 50 are
`controlled by the central processor (CU) 26. The control
`System illustrated in this figure enables obtaining feedback
`concerning the OQS parameter in near real-time and effect
`ing re-routing of the telecommunication Services. In
`particular, if block 50 issues a signal that the value of OOS
`is lower than a predetermined value stored in the SLA unit
`30, this signal activates two interacting management Sys
`tems 52 and 54. For example, a Network Manager 52 and a
`Policy Based Manager 54 can be provided, capable of
`controlling the Media Gateways 44 and routers (not shown)
`in the IP network for re-routing a particular telecommuni
`cation service via routes for which the OOS value is not
`lower that the predetermined OQS.
`After a SLA is signed between the Service provider and
`the Subscriber, each packet issued by a Gateway is provided
`with a specific code incorporated in its particular portion (for
`example, in a header) and indicating its routing Schedule (for
`example, a particular architecture of the network may Sup
`port the described function by a protocol Diffserv).
`In this embodiment, the Police Based Manager is respon
`Sible for routing each and every packet arriving from a
`Gateway according to this code. However, if a re-routing is
`required by the QMS 25, the routing code comprised in the
`appropriate packets is changed with the aid of the Network
`Manager 52 to direct the packets through a Suitable available
`route; the Policy Based Manager 54 will be therefore
`correspondingly informed on the change.
`Such Suitable available routes can be found, in near
`real-time, by Statistically processing the data collected by
`the Data Collector 28.
`An example of determining Such routes (transmission
`paths) is illustrated in FIG. 3. As before, similar blocks will
`be marked with similar reference numbers. The system 100
`is intended for providing quality Service over a packet
`Switched network comprising two sub-networks: PSTN and
`IP network 42. For the sake of simplicity, in this particular
`embodiment the System is considered to monitor only the
`Voice over IP quality in the data network i.e., ac