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IPTV End-to-End Performance Monitoring NTSS CSU Author Priya Gupta, Senior Technical Associate Chitresh Markanda- Principal Consultant-Tech Arvind Bhosale- Senior Consultant-Tech Naveen Sharma - Senior Solution Architect

Abstract: Service Providers are spending millions of dollars inrolling out IPTV services. In order to deliver profitableservices in this competitive market service providershould focus on reliability and service quality. Togauge end-user experience they should deploy end-to-end proactive performance monitoring solution forIPTV. Monitoring should be done at various identifiedinterfaces, servers, network elements for userimpacting impairments from Super-headend to Set-Top-Box. Trouble alarms raised need to be addressedbefore they accumulate and impact end-userexperience. Following a proactive approach formonitoring will help service provider in earlydetection and resolution of faults. The ability to do sowill help in improving end-user experience and in turnincrease service provider revenue.

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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 

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1. Introduction

IPTV is use of broadband network for delivery of broadcast television, VoD and rich media content over IP network. IPTV is one facet of Triple Play (VoIP, IPTV and Data services) and Quadplay (also includes mobile services) services. It is a game changing technology as it provides end-users a two-way communication 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 many telecom service providers are now offering services like Triple/Quadplay in an attempt to gain greater market share. According to 2010 IPTV Global Forecast by MRG, Inc number of global IPTV subscribers will grow from 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 at a compound annual growth rate of 27% by 2014. In general, Quality of Service(QoS) metric measures the performance of the system from network perspective. 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 end user. ”QoE is a measure of an 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 there counterparts offering IPTV services and Cable & Satellite TV providers. To be successful, they have to meet and exceed today’s high standards of a reliability and service quality. Service Quality is a primary reason for customer churn and dissatisfaction. Hence end-to-end performance monitoring plays a very crucial role in any successful rollout and management of IPTV offerings.

2. Components of IPTV Architecture

Major Components of Architecture of IPTV includes 1. Super Headend 2. Video Hub Office 3. Core Network 4. Access Network 5. Home Network 

 

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 Figure-1: IPTV Architecture Stack

2.1 Super Headend & Video Hub office

Figure -2: IPTV Headend SHE 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 content distribution 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 contents and supporting personalized and interactive services like nPVR, TV time shifting. Figure-3 also shows various protocols that are used for delivering IPTV.

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Figure-3: IPTV Protocol Stack SHO 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 Network Core Network of IPTV needs to be re-engineered to support carriage of large volumes of video content from SHO to Access network. Major technologies that can be used in IPTV core network are ATM over SONET/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 Network In 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 involves redesign of existing infrastructure. Thus currently 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

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2.4 Home Network Home Network becomes increasingly important as IPTV Service Providers are looking to offer IPTV services to their subscribers. The bandwidth of network within the home will be 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, coax cables and wireless technologies) that are available at 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 networking technologies 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-4: Access and Network Infrastructure IPTV

3. Need for performance monitoring and its benefits

While 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 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.

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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 monitoring

Monitoring 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 help service provider to detect and respond to problems before an end user is even aware that problem has occurred. For performing end-to-end monitoring following approach is recommended. The flow of approach is also shown in Figure-5. Monitoring Points In 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 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-Headend M2:- Domain Border between SHO and Core Network M3:- Domain Border between Core Network and Access Network M4:- Domain Border between Access Network and Home Network M5:- Between STB and TV Servers: - Content acquisition server, Content distribution server, Advertisement Server etc. Few of these are listed in section 2 Devices: - Routers, DSLAM and Encoders etc Network: - Access Network and Home Network etc Performance Metrics Listed in the section-5 are some of major monitoring performance parameters that need to be monitored by service provider for delivering good quality video to customers. How to do Monitoring Monitoring can be done by putting probes or agents on all servers, devices and network elements from SHO through distribution network to customer premises equipments. Probes located in servers will monitor performance parameters of servers. Probes on network will monitor video stream quality for various impairments. Probes should be able to analyze transactions, signals and video flows and raise alarm when thresholds of various performance parameters are breached.

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Correlation engine This system should be able to correlate the alarms as far as possible that are coming from different monitoring points. It should also be able to generalize the problem and then send those global alarms to dashboard. Correlation of different alarms will not only help in problem location but will also help in earlier fault diagnosis and its resolution. Unified dashboard Service providers should have a unified dashboard that is going to pull all performance metrics from different demarcated points suggested above in IPTV. This dashboard will enable service provider to have end-to-end visibility of what is happening in their IPTV stack from headend to STB. This dashboard will also enable to view alarms and to drill down at various levels of granularity from regional network level to subscriber level. This visibility will enable them to react to any outage even before customer complains.

Figure-5: Performance Monitoring Flow

5. Performance Metrics in IPTV

Figure-6 Performance Metric in IPTV

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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 very necessary to monitor source quality of Audio/Video streams received at SHO/VHO. If Source quality is not good service provider will not be able to deliver good quality video to customer. 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 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 and compression 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 customer. Once video has left the headend major factors that may impair video are Loss/Latency/Jitter of packets and impairment in 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 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 Distance

Bit rate Threshold valuesSDTV broadcast Video 1.75 Mbps CBRHDTV Broadcast Video 10 Mbps CBRVOD SDTV 2.1 Mbps CBR

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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 Utilization

As suggested by TR-126 and ITU-T–1540 below mentioned threshold limit for these parameters should not be breached.

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 effect 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 these authentication too effect user experience. As recommended by TR-126 thresholds values of below mentioned parameters should not be breached to have a good end-user experience.

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 ms

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

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STB Related parameters like: -The video quality delivered to customer depends on decoding process and 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 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 IPTV

Figure-7: QoE Methods For service like IPTV, where user satisfaction is the ultimate metric of performance. So a method to accurately measure the QoE is required. QoE is a subjective term and using subjective measurements on large scale is not practical as this method relies on input from actual users watching a video. Though this method is accurate but is expensive and too time consuming therefore objective methods are used for estimating QoE. Objective measurements infer video quality based on the video stream without direct input from users. Objective measurements that can incorporate human perception is a very challenging task. 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 – MDI

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MDI MDI 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 thousand’s

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 Techniques There exists some techniques that looks at packet loss,

jitter and also incorporate it with codec information and video header information. But this makes them computationally intensive and thus they require lots of hardware support.

Some of them correlate to human perception. Some of techniques return single number between 1-5

that gives little indication of reason of video quality. In most of complementary techniques impairments due

to encoding, 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 Based 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 video quality for monitoring network intended to deliver a video. The MDI is expressed as delay factor (DF) and the media loss rate (MLR). Delay Factor: - This component indicates how many milliseconds of data buffers must contain in order to eliminate jitter. Media Loss Rate (MLR):- It is simply defined as the number of lost or out-of-order media packets per second.

QoE Estimation QoE is dynamic and depends on many factors. QoE should be measured continuously. It is a function of many 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 there 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 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

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7. Summary

In this competitive IPTV market, successful service providers have to fulfill subscriber’s expectation of almost zero tolerance for poor or spotty video and unavailability of service. Delivering this kind of quality services on IP network requires monitoring service at all time on 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 few packets may lead to freeze frames, blank screen etc. Any such impairment may bring dissatisfaction in 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 whole stack of IPTV at various interfaces, servers, 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 service provider in detecting problems even before customer reports for it. Delivering good IPTV services will improve customer 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”

Acknowledgement I will 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.

9. Abbreviations

ADSL Asymmetric Digital Subscriber Line CA Conditional Access CBR Constant Bit Rate CPE customer Premises Equipment DF Delay factor

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DHCP Dynamic Host Configuration Protocol DNS Domain Naming serverDRM Digital rights Management DSLAM Digital Subscriber Line access Multiplexer EPG Electronic Program GuideFTTC Fiber to the curb FTTH Fiber to the Home FTTN Fiber to the Node GOP Group of Picture HDTV High Definition Television IGMP Internet Group Management Protocol IP Internet Protocol IPG Interactive Program guide IPTV Internet Protocol televisionIRD Integrated Receiver Decoder MDI Media delivery Index MoCA Multimedia over Coax Alliance MPEG Motion Picture Expert Group MRG Multimedia Research Group ONT Optical Network TerminationONU Optical Network Unit PAT Program Association Table PCR Program check referencePID Program ID PIP Picture in Picture PMT Program Map Tables PVR Personal Video Recording QoE Quality of Experience QoS Quality of Service RTP Real Time Protocol DI Serial digital Interface SDTV Standard Definition TelevisionSHE Super Head End SMPTE - VC1 Society of Motion Picture and Television Engineers - Video codec STB Set Top Box TS Transport stream UDP User Datagram Protocol VBR Variable Bit Rate VDSL Very High Bit Rate Digital Subscriber Line VHO Video Hub offices VoD Video on DemandVOIP Voice over Internet Protocol