IPTV End-to-End Performance MonitoringNTSS CSU

Abstract:Service Providers are spending millions of dollars inrolling out IPTV services. In order to deliver profitable services in this competitive market, a service provider should focus on reliability and service quality. To gauge end-user experience they should deploy an 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- Top-Box. Trouble alarms raised need to be addressed before they accumulate and impact end-user experience. Following a proactive approach for monitoring will help service provider in early detection and resolution of faults. The ability to do so will help in improving end-user experience and in turn increase service provider revenue.

Author

Priya Gupta, Senior Technical AssociateChitresh Markanda- Principal Consultant-TechArvind Bhosale- Senior Consultant-TechNaveen Sharma - Senior Solution Architect

August 2013

Contents 1. Introduction .............................................................................................................................. 2 2. Components of IPTV Architecture ................................................................................................ 2 2.1 Super Headend & Video Hub office............................................................................................ 3 2.2Core Network......................................................................................................................... 4 2.3Access Network ..................................................................................................................... 4 2.4 Home Network ...................................................................................................................... 4 3. Need for performance monitoring and its benefits .......................................................................... 5 4. Approach for performance monitoring .......................................................................................... 5 5. Performance Metrics in IPTV........................................................................................................ 6 6. QoE in IPTV ................................................................................................................................8 7. Summary ................................................................................................................................. 10 8. References .............................................................................................................................. 10 9. Abbreviations ........................................................................................................................... 10

1. IntroductionIPTV is the use of a broadband network for delivery of broadcast television, VoD and rich media content over an IP 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 technology areamany 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, the 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 the 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 perceived subjectively by the end user. ”QoE is a measure of end-to-end performance levels from the user perspective 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 their 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

Figure-1: IPTV Architecture Stack

2.1 Super Headend & Video Hub office closest to the clients.SHO component is responsible for acquiring television signals and videos, processing and distributing it to customer through VHO. IPTV network generally contains one SHO and multiple VHOs, where national services are acquired at the SHO and regional, local services and video on demand services are acquired and integrated at each of the VHOs. The contentdistribution systems are located in the VHOs 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 for distribution.

This system is also responsible for streaming of RTP packets, storing video content and supporting personalized and interactive services like nPVR, TV time shifting. Figure-3 also shows various protocols that are used for delivering IPTV.

SHO consists of various elements like:-Servers: - Content Acquisition Server (EPG listing, •VOD Assets, VOD Metadata), ContentDistribution 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 toDigital Receiver, Satellite Receivers and Off Air •receive system etcOthers: - 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 the bandwidth 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 loop is 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 involve redesign of existing infrastructure. Thus, current broadband technology (ADSL2+ and VDSL) seems to be the most economical means of deployment of real time

video services. Figure-4 shows access technology infrastructure for IPTV. Various Access Network elements are:-

Access Network elements:- DSLAM ports, ONT, •ONU or DSL modems and Residential Gateways etc

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 a critical factor to assure good delivery of IPTV service to the subscribers. Service providers need to provide IPTV service by utilizing existing wiring (power lines, phone lines, coaxial cables and wireless technologies) that are available at the subscriber premises. This area needs more attention since nearly 40% of video issues occur in the 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 TV

Figure -2: IPTV Headend Figure-3: IPTV Protocol Stack

3. Need for performance monitoring and its benefitsWhile service providers are spending millions of dollars in rolling out IPTV service, spend on proactive end-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 the growth and long term survival of the service provider.Since service quality is a primary reason for •customer churn and dissatisfaction. Therefore

the servic provider should meet the 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 the service •provider complete knowledge of outage, its scope and magnitude. This knowledge will allow them to act proactively rather than reactively to any outage.

Figure-4: Access and Network Infrastructure

Benefits of monitoringServices can be made available with required QoS •performanceReacting to outage before customer complaints •and thus improve QoEReduce 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. Many factors can degrade video quality that may lead to user impacting impairments. Achieving the desired high service availability with required QoS performance in such a complex and dynamic system requires continuous monitoring and performance analysis. Following a proactive approach for monitoring will helpthe service provider in detecting and responding to problems before an end user is even aware that a problem has occurred. For performing end-to-end monitoring, the following approach is recommended. The flow of approach is also shown in Figure-5.

Monitoring PointsIn order to have a complete unified view, IPTV stack should be monitored at all interfaces with all devices, servers and network elements that are present between Super-headend to subscriber. Some of the interfaces 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 these are listed in section 2Devices: - Routers, DSLAM and Encoders etcNetwork: - Access Network and Home Network etc

Performance MetricsListed in the Section-5 are some of major monitoring performance parameters that need to be monitoredby the service provider for delivering good quality video to customers.

How to MonitorMonitoring can be done by putting probes or agents on all servers, devices and network elements from SHO through the distribution network to the customer premises equipment. Probes located in the servers willmonitor the performance parameters of servers. Probes on the network will monitor video stream quality for various impairments. Probes should be able to analyze transactions, signals and video flows and raise alarms when thresholds of various performance parameters are breached.

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 tothe dashboard. 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 the 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 the regional networklevel to the subscriber level. This visibility will enable them to react to any outage even before the customercomplains.

Figure-5: Performance Monitoring Flow

Figure-6 Performance Metric in IPTV

5. Performance Metrics in IPTV

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 external sources are aggregated. It is absolutely necessary to monitor source quality of Audio/Video streams received at SHO/VHO. If Source quality is not good the service provider will not be able to deliver good quality video to the customer.

Coding Parameters for Audio/Video: - Media streams received at SHO/VHO are processed i.e. encoded, translated etc. Encoding has a significant impact on video quality. Efficiency of encoding aids in

bandwidth efficiency while preserving the video quality. Due to measures taken to conserve bandwidth certain 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, Motion vector 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 video application layer performance objectives for broadcast SDTV & HDTV are:

Monitoring Servers/Devices: - We need to monitor all Servers and Devices present from headend to STB. 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 Request

IP Network performance parameters: - Video is transported from the core network through the access network to the customer. Once the video leaves the headend the major factors that may impair video are Loss/Latency/Jitter of packets and impairment in the Transport stream structure. If left unattended, these issues will cause perceivable impairment of video.

Major parameters that are suggested by TR-126 and ITU-T G.1080 that need to be monitored here are:-a) RTP packet Received, Lost, Repaired and Discardedb) 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 lossesc) Burst Loss Rate, Burst Loss Lengthd) Gap Length, Gap Loss, Gap counte) Loss Period, Loss Distancef) Jitter should be monitored as suggested by RFC 3350. De-jitter buffer at STB can mitigate some effect of end-to-end delay and jitterg) Decoder concealment algorithm used. It can mitigate some perceptual impact of lossesh) Bandwidth Utilization

As suggested by TR-126 and ITU-T–1540, below mentioned threshold limit for these parameters shouldnot be breached.

Bit rateSDTV broadcast Video

HDTV Broadcast Video

VOD SDTV

Threshold values 1.75 Mbps CBR

10 Mbps CBR

2.1 Mbps CBR

ParameterLatency

Loss distance

Jitter

Max duration of a single error

IP video stream Packet loss rate

Jitter buffer fill

I-Frame delay

Threshold ValueLess than 200ms

1 error event per 4 hours

Less than 50 ms

Less than 16ms

Less than 1.22E-06

150-200 ms

500 ms

MPEG Transport parameters: - Video is often carried in MPEG Transport streams. MPEG TS contain time stamps, sequence numbers, and program associations for packetized video streams. It is suggested that ETSI TR 101-290 - Level 1, 2 and 3 parameters should be monitored by service providers. It recommends 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 types that 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 IPTV since it uses IP Multicasting and IGMP for channel change. The IGMP join-and-leave delays in the network effect customer experience. Delay in response of trick plays too affect customer experience. Authorization and Authentication is done in order to check validity of user each time the set-top-box boots up or when request for a media is made. Delay in this authentication too affects user experience. As recommended by TR-126 threshold values of below mentioned parameters should not be breached, to enable a good end-user experience.

STB Related parameters like the following:- The video quality delivered to customer depends on the decoding process and an error concealment algorithm implemented in STB. Jitter that can have significant impact on video quality can be neutralized by decoder buffer.STB boot time also plays a significant role in terms of user experience.

Other Parametersa) 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 IPTVFor service like IPTV, where user satisfaction is the ultimate metric of performance, a method to accurately measure the QoE is much required. QoE is a subjective term and using subjective measurements on a large scale is not practical as this method relies on inputs from actual users watching a video. Though this method is accurate, it is expensive and too time consuming, and therefore, objective methods are used for estimating QoE. Objective measurements infer video quality based on the video stream without directinput from users. Objective measurements that can incorporate human perception are a very challengingtask. Objective measurement can be done by three methods:

Payload based - J.144(Full reference Model) and •PSNRCodec Aware Packet based – MPQM•Codec Independent packet based – MDI•

ParameterUser Interface Actions like EPG

Channel Change

Service Start-up Time

Conditional access delay

Multicast leave for old channel

Delay for multicast stream to stop

Multicast join for new channel

Threshold Value200 ms

2 sec

10 sec

0 msec-2 sec

50 ms

150 ms

50 ms

Figure-7: QoE Methods

Based on the above comparison, MDI seems to be the 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.

MDIMDI relies on packet-level information. Its •components can directly translate into network terms like delay and loss.No codec information is taken into account.•It is a very good diagnostic method that can •assess network performance for real-time delivery of video.It does not require lots of hardware support.•It is highly scalable and thus can monitor •thousands of video streams simultaneously.It poorly correlates to human perception.•Here it is easier to isolate the problems in video •quality.It is suitable for services like IPTV•

Other Complementary TechniquesThere exists some techniques that look at packet •loss, jitter and also incorporate it with codec information and video header information. But this makes the computationally intensive and thus they require lots of hardware support.Some of them correlate to human perception.•Some of these techniques return single number •between 1-5 which gives little indication of the reason for video quality. In most of the complementary techniques, •impairments due to encoding and network are indistinguishable.Limited scalability cast doubts in its application for •real time video monitoring for services like IPTV that requires continuous monitoring of thousands of streams.

Table-1 Comparison of Objective Measurements Methods

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 in playback of reconstructed video signals. It is inevitably introduced due to measures taken to conserve bandwidth like codec quantization level, longer GoP structure, lower frame rate etc. Various human factors that affect user experience are their emotional state, previous

experience, service billing. For.eg

Customers who have been watching TV on satellite or cable may be annoyed by channel change delay in IPTV. Environmental factors that may affect user experience are whether you are viewing it on Mobile, HDTV, or SDTV. A particular video will be rated differently for HDTV and SDTV.

7. SummaryIn this competitive IPTV market, successful service providers have to fulfill the subscriber’s expectation ofalmost zero tolerance for poor or spotty video and unavailability of service. Delivering this kind of qualityservices on an IP network requires monitoring of service at all time in all locations. The quality of IP video can be affected by impairments introduced during encoding, transmission of packets, decoding etc. Video is so sensitive that a loss of a few packets may lead to freeze frames, blank screen etc. Any such impairment may bring dissatisfaction to the customer leading to customer churn and thus loss of revenue. In this scenario tools for end-to-end monitoring of IPTV becomes extremely critical. Service provider needs to monitor the whole stack of IPTV at various interfaces, servers, and network elements for various performance level parameters that impact QoE of customers. Monitoring those parameters will give better visibility of what is happening in the network. Following a proactive approach for monitoring will help the service provider in detecting problems even before the customer reports them. Delivering good IPTV services will improve customer loyalty and service provider revenue.

8. References1. 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 20065. TR-135 “Data Model for a TR-069 Enabled STB” December 20076. ETSI TR 101 290 V1.2.1 (2001-05) Technical Report Digital Video Broadcasting (DVB); Measurement guidelines for DVB systems7. RFC 4445 proposed “Media Delivery Index”8. RFC 3550 “ RTP: A Transport Protocol for Real- Time Applications”

AcknowledgementI would like to thank Priyadarshini, Sandeep Rajhans and Neelesh Kumbhojkar for sparing precious time and providing me with valuable feedback. I will also thank them for their encouragement and support.

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

9. AbbreviationsADSL

CA

CBR

CPE

DF

Asymmetric Digital Subscriber Line

Conditional Access

Constant Bit Rate

Customer Premises Equipment

Delay Factor

DHCPDNSDRMDSLAMEPGFTTCFTTHFTTNGOPHDTVIGMPIPIPGIPTVIRDMDIMoCAMPEGMRGONTONUPATPCRPIDPIPPMTPVRQoEQoSRTPDISDTVSHESMPTE - VC1

STBTSUDPVBRVDSLVHOVoDVOIP

Dynamic Host Configuration ProtocolDomain Naming ServerDigital Rights ManagementDigital Subscriber Line access MultiplexerElectronic Program GuideFiber to the CurbFiber to the HomeFiber to the NodeGroup of PictureHigh Definition TelevisionInternet Group Management ProtocolInternet ProtocolInteractive Program GuideInternet Protocol TelevisionIntegrated Receiver DecoderMedia Delivery IndexMultimedia over Coax AllianceMotion Picture Expert GroupMultimedia Research GroupOptical Network TerminationOptical Network UnitProgram Association TableProgram Check ReferenceProgram IDPicture in PictureProgram Map TablesPersonal Video RecordingQuality of ExperienceQuality of ServiceReal Time ProtocolSerial Digital InterfaceStandard Definition TelevisionSuper Head EndSociety of Motion Picture and Television Engineers - Video codecSet Top BoxTransport streamUser Datagram ProtocolVariable Bit RateVery High Bit Rate Digital Subscriber LineVideo Hub officesVideo on DemandVoice over Internet Protocol

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