service quality management over ip

7/27/2019 Service Quality Management Over Ip

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SOLUTION

JUL 2008.

ISSUE 4239

SQM over IP

hile IP-based telecommunicationshave emerged as a prevalent industrytrend, new technologies bring bothproblems and risks. Service quality

management (SQM) over IP is one o the issueshindering the evolution to IP. Its causes lie withtwo key aspects o IP technology: the statisticalmultiplexing o IP services and the dynamic routingo IP networks.

For instance, due to the statistical multiplexing

o IP services, monitored network KPI remainsnormal even when service quality is badly afected.his means that we ail to trace the root causeand ulill our service level agreement (SLA) withcustomers. Non-connection-oriented IP orwardingand dynamic routing disturb ault location; aultsspread across the network like a wild ire, causingthe buttery efect, and this greatly impacts networkreliability.

China Mobile, or example, constructed its IP-based toll tandem oce project rom 2004 till theend o 2007, culminating in 750 routers, 141 trunk

media gateways (MGs), and 76 sotswitches.he toll tandem oices bear 88% o intra- andinter-province traic, which at peak times reaches150MErl.

However, network operation and maintenance(O&M) aces a range o problems: 1) Service qualitycannot be associated with network perormanceindexes, which ail to reveal how greatly servicequality is aected; 2) It is diicult and time-consuming to locate aults ater services have beenaected. For instance, the recovery time or theMG and the BICC server are between 20 and 30

minutes and 1 to 2 hours respectively. he abovetwo problems must be addressed beore we apply IP-based end oces to mobile networks.

As technologies develop, subscr iber s se rv iceexperience requirements are increasingly stringent,which urges operators to implement more eectiveintranet and service quality control measures. Chinaelecom has set its perormance index standards orits NGN bearer network to ensure high quality servicedelivery and evaluate maintenance perormance. able 1lists some o the perormance indexes.

Service requirements are even stricter oroperators subscribers. B, or example, promises the

ollowing SLA terms to enterprise subscribers:1. A compensatory reund o one days ee or

each day that services are delayed.2. Multi-level customer classiication regarding

network reliability, ranging rom 97.00% to99.999%. B promises rapid ault response andrecovery time that are shortened in line with acustomers priority. I contractual agreements arebreached, customers can claim a signicant amounto nancial compensation.

3. Network delays o less than 40ms in Europeand between 50ms and 500ms in other regions.

4. A jitter range o 2.53.5ms in Europe and2.510ms in other regions.5. A ne tw or k pa ck et los s ra te rang in g rom

0.050.15% in Europe and 0.150.25% in otherregions.

his places pressure upon our trust in the IPtransormation process o telecom i we are unable toprovide efective solutions to SQM problems. Withthe increase in services delivered over IP, IP networksare in turn becoming more heavily relied, and systemconstruction risks are ampliied simultaneously.Operators and equipment vendors have no choice

By Zhang WeiOVER IPService Quality Management

W

Service quality management over IP


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Huawei Technologies

JUL 2008.

ISSUE 42 4

SOLUTION

Disassembled E2E network performance indexes of the highest QoS level (Designed Values)

Network performance parameter User E2E index Network E2E indexDisassembled index

CPE and User Terminal IP MAN A CN2 IP MAN B CPE and User Terminal

Upper limit of unidirectional average delay 145 ms 85 ms 30 ms 20 ms 45 ms 20 ms 30 ms

Upper limit of unidirectional average jitter 8 ms 4 ms 5 ms 3 ms 1 ms 3 ms 5 ms

Upper limit of unidirectional packet loss 1.2/100 2/1000 5/1000 1/1000 5/10000 1/1000 5/1000

Table 1 Disassembled end-to-end network indexes with the highest QoS level in the China Telecom NGN

but to ace these problems and establishsolutions.

SQM solution

he ability to realize a quantiiable IPnetwork is crucial in Huaweis IP bearernetwork SQM solution, as measurabilityorms the basis o manageability. A datatest packet deriving rom specic protocolscan be created. We can supervise anduniy IP network and typical service bearerquality via lexible measuring modes,which periodical ly coll ec t and analyzedata. he resulting statistics providedirect inormation regarding networkoptimization, and shed light on the causeand occurrence tendency o perormance

deterioration or urther exploration.A combined test and status evaluation

o aected services can rapidly diagnosethe root cause o a ault, and acilitate itstimely correction in order to minimizesubsequent impact.

he SQM solution has an analogwith health exam in that the diagnosesp a r amet e r s a r e sp ec i i ed . Qua l i t y supervision resembles regular medicalexams. Hence, problems can be detectedear ly on, and a hol i s t ic p icture ohealth can be provided. In theory, the

eectiveness o a routine examination isenhanced by a broader criteria range andhigher requency, the eatures or both owhich require de ining in terms o costand viability. A ault diagnosis resemblesan irregular medical diagnosis in that theunderlying root cause is identied ater aspecic problem has arisen. Tis requiresa series o diagnostic chain that allowsremedies to be eventually tailored andimplemented.

While a probing-based solution cannot

apparently solve all quality supervision

and ault d iagnosis i s sues , Huaweisolution employs an active probingmechanism that maximizes its directnessand simplicity. Generally a system thatemploys the statistical mode is passiveand based on services and users, whilethe probing-based solution eaturesexibility, minimized statistical data, anda simple and rapid calculation mode. TeHuawei IP bearer network SQM solutionmainly adopts active probing to regularlysupervise network/service quality andlocate typical aults. It also combines theexisting association model to correlatedirectly related passive collection indexes.hese passive collection indexes includebandwidth usage and QoS measurements.he SQM solution utilizes the industrys

mature data abstraction, convergence,and mining platorm to give operators anentire system that is able to exibly analyzedata and reect both network quality andactual user experience.

Quality supervision of theservice bearer network

Whi l e t he I P bea re r n e t work i sinsensitive to control and orward layerservices, it strongly inluences service

quality. raic is segmented into packetsor transmission over the network withthe result that some network layerunitary indexes are unable to completelyrepresent user service experiences. Servicesare transmitted over the network via anemulation service transmission protocol.We can calculate the actors afected by thebearer network segment or a particularservice, and determine the impact thatthe bearer network segment has on servicequality during transmission. Subsequently,

we are able to determine whether the IP

bearer network is able to meet customersSLA requirements.

he voice service is the main sourceo operators revenue and thus VoIPmust prioritize voice service quality.he traditional detection indexes in thenetwork layer are unable to provide VoIPservice quality mapping so that the impacto a ault on services cannot be measured.As a result, we need to convert the indexesinto a general descriptive language oservice quality. In this regard, the meanopinion score (MOS) standard evaluatesvoice service quality across the industry.

MOS scores end-to-end voice servicequality rom 0 to 5, with 5 being thehighest. Voice quality deteriorates whenthe voice service begins at user A, travels

through terminals and networks, andreaches user B. Once users are aware ovoice quality deterioration, operatorsshould locate the segment that mostseriously afects quality. In these terms, theIP bearer network segment is vital.

Generally, the bearer network segmentsMOS value must exceed 4.0 so as toguarantee relatively reliable end-to-endvoice quality. I the MOS value is less than3.6, the bearer network is signiicantlyafecting voice quality and we are unableto provide users with high-quality services

due to encoding, decoding, and otherinuences.

o ensure voice service qual i ty,operators usually transmit voice streamsin the VPN dedicated to the IP bearernetwork. So ar, the mature solution is toinject voice streams based on a particularcoding protocol into the speciied VPN.Ac co rd in g to KP Is su ch as de lay andpacket loss, MOS impairment is calculatedby the ormula dened in IU- G.107.Hence, the extent to which service

quality is afected by the network can be


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SOLUTION

JUL 2008.

ISSUE 4241

calculated.he solution also works or other

services, and its long-term supervisoryc a p a b i l i t y g i v e s o p e r a t o r s a u l lunderstanding o their networks andservices operat ional s tatus , whichs t imu la t e s t he e a r l y and a c c u r a t edeployment o customized precautions andnetwork optimization measures.

Fault diagnosis on the IPbearer network

Fault diagnosis is extremely complexon the IP bearer network. Currently,two ault diagnosis modes exist. Te rstmode involves constantly optimizingdevices OAM protocols and improvingthe detection mechanism; detecting deviceand network interconnection aults; and

reporting alarm details so maintenanceengineers can accurately and quickly locateaults. Although theoretically expedient,existing standards or this mode are notcomplete, and the automatic associationwi th s er v ice bear ing i s not ea sy toimplement.

he second mode i s a s o l lows :O&M engineers employ the detectiontool to quickly locate a ault point, andprecautionary measures relating to possibleservice aults identiied by the quality

supervision system are put in place. heconcept underpinning the second modeautomates the diagnostic methodology orO&M engineers by utilizing external systemsand the association model to correlate aultypoints on the device hierarchy according tothe impact on services. Te second mode isefective and basically meets requirements orswit ault location.

Multiple vendors devices are involvedin the networking o most networks.According to the second ault diagnosismode, we might employ a combinationo internal and external probes to meetdierent vendors device detect ionrequirements. Fault location has twostages. In the irst, the ault scope isdened through nding out a device nodeor node group to narrow down the aultscope. In the second stage, a ault librarysystem based on representative scenarios

is ormed. Further operationssuch asassociation detection, status checking,and cause identiicationdirectly locatethe ault route, and thus realize intelligentault diagnosis. Tis mode greatly shortensault correction times and curtails OPEX.

Experience is the motherof wisdom

Huawei ully understands the IP

network and continues to accumulate richO&M experience in this eld. Huawei hasdeeply analyzed the problems acing ChinaMobile in its IP bearer network O&M,and in response has tailor-made an overallSQM solution. he solution employs abuilt-in probe to detect the bearer networkend-to-end perormance indexes andlocate aults based on the OAM protocol.External probes are installed on third-partydevices and on numerous access devicesessential or end-to-end quality evaluation.

he SQM solution establishes thequality supervision association model,whi ch in tu rn is bas ed on sta nda rd s,experience, and experiment results.Moreover, the model can be customizedaccording to customer requirements. Te

system boasts a sound association modelor a carried VoIP service that relatesthe extent to which a bearer networkinuences end-to-end voice quality.

o locate a ault, we must rst establisha cooperative mechanism between theservice and bearer networks via a serieso diagnostic tools. When any problemhappens to the service network, detectionbegins immediately to determine whethera ault is occurring on the bearer orservice network itsel. I a ault occurs onthe bearer network, the SQM system is

notiied to start the diagnostic low. heaulty point can be quickly located throughthe OAM mechanism and the layeredassociation. Te ow gives the position othe ault, and reduces the ault locationtime. Te predicted duration or locating aBICC interruption ault can be shortenedto around 10 minutes with cooperation othe core network.

Huawei is cooperating with InoVistato establish a complete SLA supervisionand punishment system or the Italian B

branch. his system enables the operatorto accurately supervise service quality orboth high-end (gold, silver, and copper)and general customers. A supervisoryplatorm or service guarantees is thenbuilt between operators and users.

he SQM solut ion is s t i l l beingperected. As urther applied to operatorsnetworks, it will help them realize greaterO&M eciency and considerably reduceOPEX.

Editor: Xu [email protected]

Service quality management over IP

service quality management over ip

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