Iptv performance monitoring


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Iptv performance monitoring

  1. 1. Abstract:IPTV End-to-End Service Providers are spending millions of dollars in rolling out IPTV services. In order to deliver profitablePerformance services in this competitive market service provider should focus on reliability and service quality. ToMonitoring gauge end-user experience they should deploy end-to- end proactive performance monitoring solution for IPTV. Monitoring should be done at various identified interfaces, servers, network elements for user impacting impairments from Super-headend to Set-NTSS CSU Top-Box. Trouble alarms raised need to be addressed before they accumulate and impact end-user experience. Following a proactive approach forAuthor monitoring will help service provider in earlyPriya Gupta, Senior Technical Associate detection and resolution of faults. The ability to do soChitresh Markanda- Principal Consultant-Tech will help in improving end-user experience and in turnArvind Bhosale- Senior Consultant-Tech increase service provider revenue.Naveen Sharma - Senior Solution Architect © Tech Mahindra Limited 2010
  2. 2. Contents 1.  Introduction ......................................................................... 2 2.  Components of IPTV Architecture ....................................... 2  2.1  Super Headend & Video Hub office.............................. 3  2.2 Core Network................................................................ 4  2.3 Access Network ............................................................ 4  2.4 Home Network ............................................................... 5 3.  Need for performance monitoring and its benefits ............... 5 4.  Approach for performance monitoring ................................. 6 5.  Performance Metrics in IPTV............................................... 7 6.  QoE in IPTV ...................................................................... 10 7. Summary ........................................................................... 12 8. References ......................................................................... 12 9. Abbreviations ...................................................................... 12  1
  3. 3. 1. IntroductionIPTV is use of broadband network for delivery of broadcast television, VoD and rich media content overIP network. IPTV is one facet of Triple Play (VoIP, IPTV and Data services) and Quadplay (also includesmobile services) services. It is a game changing technology as it provides end-users a two-waycommunication in the delivery of broadcast television. IPTV offers with interactive services like VoD,Trick Plays like rewind and pause of live broadcast, PVR, time shifting etc. In this growing technologymany telecom service providers are now offering services like Triple/Quadplay in an attempt to gaingreater market share.According to 2010 IPTV Global Forecast by MRG, Inc number of global IPTV subscribers will growfrom 41.2 million at the end of 2010 to 101.7 million in 2014 at a compound annual growth rate of 25.3%.The global IPTV market is US$17.5 billion in 2010 and is forecasted to grow to US$46 billion in 2014 ata compound annual growth rate of 27% by 2014.In general, Quality of Service(QoS) metric measures the performance of the system from networkperspective. This measure ensures all network elements, protocols and related service operate as expected.Quality of Experience(QoE), however relates to overall acceptability of service as perceivedsubjectively by end user. ”QoE is a measure of an end-to-end performance levels from the userperspective and an indicator of how well this system meets the user needs”.In this arena of fierce competition, IPTV service providers have to compete with there counterpartsoffering IPTV services and Cable & Satellite TV providers. To be successful, they have to meet andexceed today’s high standards of a reliability and service quality. Service Quality is a primary reason forcustomer churn and dissatisfaction. Hence end-to-end performance monitoring plays a very crucial role inany successful rollout and management of IPTV offerings. 2. Components of IPTV ArchitectureMajor Components of Architecture of IPTV includes 1. Super Headend 2. Video Hub Office 3. Core Network 4. Access Network 5. Home Network   2 © Tech Mahindra Limited 2010
  4. 4.  Figure-1: IPTV Architecture Stack 2.1 Super Headend & Video Hub office closest to the clients. Figure-2 shows major functions performed by headend. IPTV Service providers acquire television programs from many different sources like Satellite, off air receivers and encode them into MPEG-4 AVC H.264 /SMPTE VC-1. Good compression of video is required in order to transmit good quality video for SDTV/HDTV to customers having bandwidth constraints in access network. The compressed signal will then be encrypted using DRM Technology. Then video stream is packetized in RTP packets forFigure -2: IPTV Headend distribution.SHE component is responsible for acquiring This system is also responsible for streaming oftelevision signals and videos, processing and RTP packets, storing video contents anddistributing it to customer through VHO. IPTV supporting personalized and interactive servicesnetwork generally contains one SHO and like nPVR, TV time shifting. Figure-3 alsomultiple VHOs, where national services are shows various protocols that are used foracquired at the SHO and regional, local services delivering IPTV.and video on demand services are acquired andintegrated at each of the VHOs. The contentdistribution systems are located in the VHOs 3
  5. 5. Figure-3: IPTV Protocol StackSHO consists of various elements like:- Servers: - Content Acquisition Server (EPG listing, VOD Assets, VOD Metadata), Content Distribution Servers, Middleware Servers, Video Hub Office Servers (VHO servers), Advertisement Server, CA/DRM Servers, Database Servers and Servers to integrate with service provider OSS & BSS systems. Receivers:- High Definition/ Standard Definition program receiver, Analog receiver, Analog to Digital Receiver, Satellite Receivers and Off Air receive system etc Others: - Advanced Video Encoders, Ad Splicer, IRD, IP Service Router and SDI Switch etc                             2.2 Core NetworkCore Network of IPTV needs to be re-engineered to support carriage of large volumes of video contentfrom SHO to Access network. Major technologies that can be used in IPTV core network are ATM overSONET/SDH, IP over MPLS and Metro Ethernet. It consists of elements like:- Core Network elements: - Router, DNS, DHCP servers, directory servers, Load balancers and IP Switch etc.2.3 Access NetworkIn order to deliver good quality video to end user “The Last Mile” must be capable of supporting thebandwidth required to carry a video on IP. IPTV roughly requires 2 Mbps for a SD content/channel and 6-12 Mbps for HD content/channel in MPEG-4 format of compression. With fiber, bandwidth in local loopis not an issue since Fiber can easily carry even multiple SDTV or HDTV channels in MPEG-4 formats.However, providing fiber to all customers is a complex undertaking as it is costly and may involvesredesign of existing infrastructure. Thus currently broadband technology (ADSL2+ and VDSL) seems tobe the most economical means of deployment of real time video services. Figure-4 shows accesstechnology infrastructure for IPTV. Various Access Network elements are:- Access Network elements :- DSLAM ports, ONT, ONU or DSL modems and Residential Gateways etc4 © Tech Mahindra Limited 2010
  6. 6. 2.4 Home NetworkHome Network becomes increasingly important as IPTV Service Providers are looking to offer IPTVservices to their subscribers. The bandwidth of network within the home will be critical factor to assuregood delivery of IPTV service to the subscribers. Service providers need to provide IPTV service byutilizing existing wiring (power lines, phone lines, coax cables and wireless technologies) that areavailable at subscriber premises. This area needs more attention since nearly 40% of video issues occur inthe home (as reported by Video Quality Study by MRG).Figure-4 shows various home networkingtechnologies that service provider might use for delivering IPTV are Ethernet/Cat-5, HomePlug,PhoneLine, MoCA and HPNA. Home Network Elements:-Set Top Box (STB), Routing Gateway, PC Client and TVFigure-4: Access and Network Infrastructure IPTV 3. Need for performance monitoring and its benefitsWhile service providers are spending millions of dollars in rolling out IPTV service, spend on proactiveend-to-end monitoring of IPTV cannot be overlooked. Need for proactive monitoring of IPTV services is centered on delivering reliable and profitable services in this highly competitive market. Focus on reliability and quality of IPTV services will be key to growth and long term survival of the service provider. Since service quality is a primary reason for customer churn and dissatisfaction. Therefore service provider should meet customer’s expectation of service quality. Most operators are using some form of monitoring solution but are highly dissatisfied as they do not have end-to-end visibility of IPTV stack-from headend through network to customer premises. Also with existing solution they are not able to gauge end user quality of experience. End-to-End monitoring of IPTV will give service provider complete knowledge of outage, its scope and magnitude. This knowledge will allow them to act proactively rather than reactively to any outage. 5
  7. 7. Benefits of monitoring Services can be made available with required QoS performance Reacting to outage before customer complaints and thus improves QoE Reduce Customer churn Increase customer satisfaction Increase average revenue per user(ARPU) 4. Approach for performance monitoringMonitoring of IPTV is done in order to detect user impacting impairment as early as possible. Manyfactors can degrade video quality that may lead to user impacting impairments. Achieving the desired highservice availability with required QoS performance in such a complex and dynamic system requirescontinuous monitoring and performance analysis. Following a proactive approach for monitoring will helpservice provider to detect and respond to problems before an end user is even aware that problem hasoccurred. For performing end-to-end monitoring following approach is recommended. The flow ofapproach is also shown in Figure-5.Monitoring PointsIn order to have a complete unified view, IPTV stack should be monitored at all interfaces with alldevices, servers and network elements that are present between Super-headend to subscriber. Some ofinterfaces that are suggested by ITU-T G.1081 are also marked in Figure-1. Suggested monitoring points(shown in Figure-1) and interfaces are listed below:-M1:- Between egress of Content Provider and ingress of Super-HeadendM2:- Domain Border between SHO and Core NetworkM3:- Domain Border between Core Network and Access NetworkM4:- Domain Border between Access Network and Home NetworkM5:- Between STB and TVServers: - Content acquisition server, Content distribution server, Advertisement Server etc. Few of theseare listed in section 2Devices: - Routers, DSLAM and Encoders etcNetwork: - Access Network and Home Network etcPerformance MetricsListed in the section-5 are some of major monitoring performance parameters that need to be monitoredby service provider for delivering good quality video to customers.How to do MonitoringMonitoring can be done by putting probes or agents on all servers, devices and network elements fromSHO through distribution network to customer premises equipments. Probes located in servers willmonitor performance parameters of servers. Probes on network will monitor video stream quality forvarious impairments. Probes should be able to analyze transactions, signals and video flows and raisealarm when thresholds of various performance parameters are breached.6 © Tech Mahindra Limited 2010
  8. 8. Correlation engineThis system should be able to correlate the alarms as far as possible that are coming from differentmonitoring points. It should also be able to generalize the problem and then send those global alarms todashboard. Correlation of different alarms will not only help in problem location but will also help inearlier fault diagnosis and its resolution.Unified dashboardService providers should have a unified dashboard that is going to pull all performance metrics fromdifferent demarcated points suggested above in IPTV. This dashboard will enable service provider tohave end-to-end visibility of what is happening in their IPTV stack from headend to STB. This dashboardwill also enable to view alarms and to drill down at various levels of granularity from regional networklevel to subscriber level. This visibility will enable them to react to any outage even before customercomplains.Figure-5: Performance Monitoring Flow 5. Performance Metrics in IPTVFigure-6 Performance Metric in IPTV 7
  9. 9. Major performance parameters that need to be monitored for IPTV are as follows:-Monitoring Source Stream Quality: - At SHO/VHO programs streams obtained from various externalsources are aggregated. It is very necessary to monitor source quality of Audio/Video streams received atSHO/VHO. If Source quality is not good service provider will not be able to deliver good quality video tocustomer.Coding Parameters for Audio/Video: - Media streams received at SHO/VHO are processed i.e.encoded, transrated etc. Encoding has a significant impact on video quality. Efficiency of encoding aids inbandwidth efficiency while preserving the video quality. Due to measures taken to conserve bandwidthcertain impairments are inevitably introduced. Various parameters that affect QoE due to digitization andcompression are :- Codec standard used, bit rate, CBR , frame rate, GoP Structure and its length, Motionvector search range, Video rate shaping, Frame Width, height, Frame rate, interlacing and Slices per I-frame, Video Reference Clock rate etc. As recommended by Broadband Forum TR-126 provisional videoapplication layer performance objectives for broadcast SDTV & HDTV are Bit rate Threshold values SDTV broadcast Video 1.75 Mbps CBR HDTV Broadcast Video 10 Mbps CBR VOD SDTV 2.1 Mbps CBRMonitoring Servers/Devices: - We need to monitor all Servers and Devices present from headend toSTB. E.g. Servers like Content acquisition server, Content delivery servers and Devices like Routers,DSLAM, ONT, Edge routers etc. Some of the parameters that need to be monitored here are:- CPU & Memory Utilization of Servers Routers Utilization and their Traffic Metrics Throughput & Availability Behavior under heavy load condition Response delays of Servers, Request Error, and Blocked RequestIP Network performance parameters: - Video is transported from the core network through the accessnetwork to customer. Once video has left the headend major factors that may impair video areLoss/Latency/Jitter of packets and impairment in Transport stream structure. If left unattended, theseissues will cause perceivable impairment of video. Major parameters that are suggested by TR-126 andITU-T G.1080 that need to be monitored here are:- a) RTP packet Received, Lost, Repaired and Discarded b) Proportion of I/P/B/SI/SP frame Received, Lost, Repaired and Discarded. Data loss from I and P frames produce different impairments than B frame packet losses c) Burst Loss Rate, Burst Loss Length d) Gap Length, Gap Loss, Gap count e) Loss Period, Loss Distance8 © Tech Mahindra Limited 2010
  10. 10. f) Jitter should be monitored as suggested by RFC 3350. De-jitter buffer at STB can mitigate some effect of end-to-end delay and jitter. g) Decoder concealment algorithm used. It can mitigate some perceptual impact of losses h) Bandwidth UtilizationAs suggested by TR-126 and ITU-T–1540 below mentioned threshold limit for these parameters shouldnot be breached. Parameter Threshold Value Latency Less than 200ms Loss distance 1 error event per 4 hours Jitter Less than 50 ms Max duration of a single error Less than 16ms IP video stream Packet loss rate less than 1.22E-06 Jitter buffer fill 150-200 ms I-Frame delay 500 msMPEG Transport parameters: - Video is often carried in MPEG Transport streams. MPEG TS containtime stamps, sequence numbers, and program associations for packetized video streams. It is suggestedthat ETSI TR 101-290 - Level 1, 2 and 3 parameters should be monitored by service providers. Itrecommends various checks including Synchronization Errors (TS Sync, Sync byte), Table errors (PAT,PSI), PMT, Missing PID, CRC, PTS, and PCR etc. This metrics provide information on key error typesthat occur with MPEG transport protocols, and are useful for identifying and resolving error conditions.Service Availability & Response Time: - Channel change Time, VOD Request, Response of Trick plays(Pause, FW, and RW), EPG Navigation, Authorization and Authentication, Connection success Rate,Connection Time and Availability of service.Channel Change time is one of major factor affecting user’s experience. It is an area of concern with IPTVsince it uses IP Multicasting and IGMP for channel change. The IGMP join-and-leave delays in thenetwork effect customer experience. Delay in response of trick plays too effect customer experience.Authorization and Authentication is done in order to check validity of user each time the set-top-box bootsup or when request for a media is made. Delay in these authentication too effect user experience.As recommended by TR-126 thresholds values of below mentioned parameters should not be breached tohave a good end-user experience. Parameter Threshold Value User Interface Actions like EPG 200 ms Channel Change 2 sec Service Start-up Time 10 sec Conditional access delay 0 msec-2 sec Multicast leave for old channel 50 ms Delay for multicast stream to stop 150 ms Multicast join for new channel 50 ms 9
  11. 11. STB Related parameters like: -The video quality delivered to customer depends on decoding processand error concealment algorithm implemented in STB. Jitter that can have significant impact on videoquality can be neutralized by decoder buffer.STB boot time also plays a significant role in terms of userexperience.Other Parameters a) Synchronization of Audio and Video, Lip synchronization: - Audio-Video should be synchronized in order to have good viewing experience. Max threshold recommended by TR-126 is Audio Lead Video by 15ms max and Audio Lag Video by 45ms. 6. QoE in IPTVFigure-7: QoE MethodsFor service like IPTV, where user satisfaction is the ultimate metric of performance. So a method toaccurately measure the QoE is required. QoE is a subjective term and using subjective measurements onlarge scale is not practical as this method relies on input from actual users watching a video. Though thismethod is accurate but is expensive and too time consuming therefore objective methods are used forestimating QoE. Objective measurements infer video quality based on the video stream without directinput from users. Objective measurements that can incorporate human perception is a very challengingtask. Objective measurement can be done by three methods. Payload based - J.144(Full reference Model) and PSNR Codec aware Packet based – MPQM Codec Independent packet based – MDI10 © Tech Mahindra Limited 2010
  12. 12. MDI Other Complementary Techniques MDI relies on packet-level information. Its There exists some techniques that looks at packet loss, components can directly translate into network jitter and also incorporate it with codec information terms like delay and loss. and video header information. But this makes them No codec information is taken into account. computationally intensive and thus they require lots of It is a very good diagnostic method that can assess hardware support. network performance for real-time delivery of Some of them correlate to human perception. video. Some of techniques return single number between 1-5 It does not require lots of hardware support. that gives little indication of reason of video quality. It is highly scalable and thus can monitor thousand’s In most of complementary techniques impairments due of video streams simultaneously. to encoding, network are indistinguishable. It poorly correlates to human perception Limited scalability cast doubts in its application for Here it is easier to isolate the problems in video real time video monitoring for services like IPTV that quality. requires continuous monitoring of thousands of It is suitable for services like IPTV streams.Table-1 Comparison of Objective Measurements MethodsBased on above comparison MDI seems to be most suitable choice for applications like IPTV.Media Delivery Index: - As described in RFC 4445 it is a diagnostic tool or a quality indicator of videoquality for monitoring network intended to deliver a video. The MDI is expressed as delay factor (DF) andthe media loss rate (MLR).Delay Factor: - This component indicates how many milliseconds of data buffers must contain in order toeliminate jitter.Media Loss Rate (MLR):- It is simply defined as the number of lost or out-of-order media packets persecond.QoE EstimationQoE is dynamic and depends on many factors. QoE should be measured continuously. It is a function ofmany factors having different weights.Quality of video is affected by impairments introduced during encoding, decoding process and inplayback of reconstructed video signals. It is inevitably introduced due to measures taken to conservebandwidth like codec quantization level, longer GoP structure, lower frame rate etc. Various humanfactors that affect user experience are there emotional state, previous experience, service billing. For.egCustomers who have been watching TV on satellite or cable may be annoyed by channel change delay inIPTV. Environmental factors that may affect user experience are weather you are viewing it on Mobile,HDTV, SDTV. A particular video will be rated differently for HDTV and SDTV. QoE for IPTV = f∫ (w1*MDI + w2*Transport Layer parameters + w3*Availability+ w4*Environment Factors + w5*Encoding and Decoding efficiency+ w6*Human factors + w7*Service Response Time). w1 to w7 are weights of that parameter 11
  13. 13. 7. SummaryIn this competitive IPTV market, successful service providers have to fulfill subscriber’s expectation ofalmost zero tolerance for poor or spotty video and unavailability of service. Delivering this kind of qualityservices on IP network requires monitoring service at all time on all locations. The quality of IP video canbe affected by impairments introduced during encoding, transmission of packets, decoding etc. Video isso sensitive that a loss of few packets may lead to freeze frames, blank screen etc. Any such impairmentmay bring dissatisfaction in customer leading to customer churn and thus loss of revenue. In this scenariotools for end-to-end monitoring of IPTV becomes extremely critical. Service provider needs to monitorwhole stack of IPTV at various interfaces, servers, network elements for various performance levelparameters that impact QoE of customers. Monitoring those parameters will give better visibility of whatis happening in the network. Following a proactive approach for monitoring will help service provider indetecting problems even before customer reports for it. Delivering good IPTV services will improvecustomer loyalty and service provider revenue.8. References 1. Recommendation ITU-T G.1080 (2008), Quality of experience requirements for IPTV services. 2. Recommendation ITU-T G.1081 (2008), Performance monitoring points for IPTV. 3. Recommendation ITU-T Y.1540 (2007), Internet protocol data communication service – IP packet transfer and availability performance parameters. 4. TR-126 “Triple-Play Services Quality of Experience (QoE) Requirements”, Broadband Forum Technical Report 13 December 2006 5. TR-135 "Data Model for a TR-069 Enabled STB" December 2007 6. ETSI TR 101 290 V1.2.1 (2001-05) Technical Report Digital Video Broadcasting (DVB); Measurement guidelines for DVB systems 7. RFC 4445 proposed “Media Delivery Index” 8. RFC 3550 “ RTP: A Transport Protocol for Real-Time Applications”AcknowledgementI will like to thank Priyadarshini, Sandeep Rajhans and Neelesh Kumbhojkar for sparing precious timeand providing me with valuable feedback. I will also thank them for their encouragement and support.9. Abbreviations ADSL Asymmetric Digital Subscriber Line CA Conditional Access CBR Constant Bit Rate CPE customer Premises Equipment DF Delay factor12 © Tech Mahindra Limited 2010
  14. 14. DHCP Dynamic Host Configuration ProtocolDNS Domain Naming serverDRM Digital rights ManagementDSLAM Digital Subscriber Line access MultiplexerEPG Electronic Program GuideFTTC Fiber to the curbFTTH Fiber to the HomeFTTN Fiber to the NodeGOP Group of PictureHDTV High Definition TelevisionIGMP Internet Group Management ProtocolIP Internet ProtocolIPG Interactive Program guideIPTV Internet Protocol televisionIRD Integrated Receiver DecoderMDI Media delivery IndexMoCA Multimedia over Coax AllianceMPEG Motion Picture Expert GroupMRG Multimedia Research GroupONT Optical Network TerminationONU Optical Network UnitPAT Program Association TablePCR Program check referencePID Program IDPIP Picture in PicturePMT Program Map TablesPVR Personal Video RecordingQoE Quality of ExperienceQoS Quality of ServiceRTP Real Time ProtocolDI Serial digital InterfaceSDTV Standard Definition TelevisionSHE Super Head EndSMPTE - VC1 Society of Motion Picture and Television Engineers - Video codecSTB Set Top BoxTS Transport streamUDP User Datagram ProtocolVBR Variable Bit RateVDSL Very High Bit Rate Digital Subscriber LineVHO Video Hub officesVoD Video on DemandVOIP Voice over Internet Protocol 13