iptv testing - ensuring quality of experience through intelligent
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How is IPTV Delivered?
Delivery of video to the consumer has undergone rapid change in recent years and is guaranteed to continue to do so in the foreseeable future.
Cable TV networks deliver a large range of content, and the ability to provide user interactive features including VoD.
Carrying the most promise for the future is delivery of video over multi-service IP networks. This is commonly referred to as IPTV. It is delivered as a Triple-Play service to consumers that includes high speed Internet (HSI) and Voice over IP (VoIP).
Video over IP Information Flow
The major components and data flow in IPTV networks consists of media and control flowing between content servers and home networks.
The two types of video services delivered are linear broadcast and VoD. Both have dramatically different characteristics that affect the networks that handle them. Broadcasts are regularly scheduled programs sent to large numbers of subscribers. It is sent efficiently over multicast IP routes.
VoD service delivery exhibits an entirely different behavior. Stored videos are sent to the subscriber
on demand. Each subscriber receives their own video flow, which they can control with VCR-like controls.
The differences are responsible for the complexity of the delivery network. Broadcast TV over IP is primarily a one-way channel, using well understood multicast protocols. The home network is responsibe for multicast messages and image display. VoD adds another level of complexity. Requests for and control of video content are transmitted upstream from the subscriber to the service provider using the Real-Time Streaming Protocol (RTSP). Video content is returned to the subscriber via the Real-time Transport Protocol (RTP).
IPTV Delivery Challenges
Until differentiating services are developed for IP-based video-voice-data networks, IPTV services will continue to be compared with traditional TV, cable and satellite service. As such, the IP delivery network must remain transparent to customers. Customers expect video quality and service availability to be on par or better to make the switch.
With multiple choices available to consumers, there is little tolerance for poor quality and operational problems. A poorly engineered network can lead to substantial customer churn.
To successfully deploy IPTV, the following end-user requirements must be addressed:Video quality – subscribers’ perception of quality must be the same or better than other alternativesMinimal channel change delay – since instant response is expectedAssured service delivery and availability for an always-on service.
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Data
VideoVoice
Data
Voice
Video(Broadband TV,
Video-on-Demand)
Metro Metro
Core
UDP/RTP
UDP/RTP
UDP/RTP UDP/RTP
UDP/RTP
Video-on-Demand Media Stream
Video and voice quality perception is highly sensitive to loss, jitter and delay. These and other network impairments appear on a TV as choppy or blocky video, frozen frames and garbled voices as shown on the cover.
Quality of service for IPTV delivery networks must be optimized to minimize jitter and packet loss for video over IP streams.
Bandwidth management is closely related to the video compression algorithm in use. The standard video CODEC is MPEG-2, which is showing its age; an MPEG-2 stream for an HDTV channel requires more than 15 Mbps of bandwidth. New video encoders are ready to facilitate IPTV deployments, including MPEG-4, which halves the data rates required to match MPEG-2 quality.
Channel change performance (CCP) relates to how effectively channel change requests are handled. A number of factors affect CCP:
Network multicast – IGMP messages must make their way upstream from the customer, through multiple levels of routersThe set-top box improves the subscriber’s perception by buffering media packetsThe frequency of I-frames sent by the content server. I-frames define an entire picture frame and dictate when the new channel can first be displayed.
Device interoperation must be carefully engineered for tight signal integrity. Multi-service networks are busy delivering Voice over IP (VoIP) along with mundane Web traffic. In such networks, strict QoS mechanisms must exist to deliver differentiated classes of service.
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IPTV Testing Requirements
Service providers must systematically test and verify network devices in each of the video transport architectures, including video content servers, core and edge routers, access devices, and customer premises equipment. Such testing provides an understanding of individual device performance and may determine how much impact each has on the overall system.
System-level tests that incorporate more than one demarcation point in the transport architecture are required. In this way, a clear understanding of how well the individual systems play with each other is determined.
Finally, the network must be tested end-to-end. Most standard routing and forwarding performance tests should be performed, looking at packet loss or latency under different load conditions.
The modern IPTV delivery system is a complex
JoinChannel1
Multicast Channel 1JoinLatency
Leave
Join Channel 3
ChannelSwitch Delay
Multicast Channel 3Channel ChangeLatency
Leave LatencyOverlap
Local Ring& Servers
GE QAMGW
Access NetworkCable Co/HFC
QAM/HFC
Local Ring& Servers
GE Switch
Access NetworkTelco/ETTH
Etn/PON
Local Ring& Servers
RT/DSLAM/OLT/DLC/UBLC
Access Network Telco/ADSL Home
Home
Home
MulticastTransport Network
ContentServers
xDSL
GE/10 GEOC12-48ATM x N
VODContent
DistributionServer Farm
Customer Premises with Residential Gateways/
Set Top Box/VoIP Phone/PC
Access Networkwith access equipment
Broadcast Programsand Advertisement; live or pre-recorded;sent with multicast
Digital HeadEnd – LiveProgram
Feed ServerFarm
Back OfficeServers and
Service
.mpglib
BroadcastFeed
Ads
Media FlowSubscriberService Provider
Video Transport and Distribution using
IP/UDP/(RTP)
Video Servers with moviesfor Video-on-Demand;
sent with multicast
Local Ring& Servers
GE QAMGW
Access NetworkCable Co/HFC
QAM/HFC
Local Ring& Servers
GE Switch
Access NetworkTelco/ETTH
Etn/PON
Local Ring& Servers
RT/DSLAM/OLT/DLC/UBLC
Access Network Telco/ADSL Home
Home
Home
MulticastTransport Network
ContentServers
xDSL
GE/10 GEOC12-48ATM x N
VODContent
DistributionServer Farm
Customer Premises with Residential Gateways/
Set Top Box/VoIP Phone/PC
Access Networkwith access equipment
Broadcast Programsand Advertisement; live or pre-recorded;sent with multicast
Digital HeadEnd – LiveProgram
Feed ServerFarm
Back OfficeServers and
Service
.mpglib
BroadcastFeed
Ads
Media FlowSubscriberService Provider
Video Transport and Distribution using
IP/UDP/(RTP)
Video Servers with moviesfor Video-on-Demand;
sent with multicast
beast. The sub-systems that we’ll look at are:Super Video Head-EndVideo Transport NetworkAccess / Broadband NetworkInfrastructure Components
Common testing requirements for all subsystems and especially the SVHE include:
Jitter, latency and loss distribution as video traffic increases.
Quality of Experience (QoE) is measured both at the network level and at the perceptual video level.
The Super Video Head-End (SVHE) system’s takes the video content from multiple sources and processes it for delivery to the IP network. It consists of components that convert digital video and analog content into IP packets, components that encode the video into MPEG and other encoding formats, VoD servers that hold and deliver content and middleware components that service set-top box requests and billing.
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SVHE-specific testing requirements include:Characterizing the encoders and IP converters to ensure video stream qualityMeasurement of the performance of aggregation switches within the SVHE and at the edge of the metro network
The Video Transport Network includes national and regional networks that serve to connect the SVHE to the Access Networks.
Testing requirements include:Measurement of raw throughput in the delivery of VoD UDP trafficMeasurement of multicast capacity for broadcast TVDetermining QoS enforcement effectiveness in forwarding broadcast TV, VoD, VoIP and data trafficMeasurement of switch-over and routing convergence time under network failure
The Access/Broadband Network consists of geographically distributed multi-purpose devices. The specific device is directly related to the type of last-mile network used and include MSANs, DSLAMs, B-RASs, and PON/OLTs.
Testing requirements include:Ensuring support for maximum subscribersMeasure VoD performance at various load levelsMeasure channel change performanceMeasure the performance of AAA servers in response to user sign-on requests.Gauge QoS assurance for triple-play trafficDetermine admission control mechanisms effectivenessAnalyze the subjective quality of video
Infrastructure Components should not be overlooked. Special TV events and network re-starts can result in huge numbers of subscribers activities. Each event must be quickly recorded and serviced.
Infrastructure components include:DHCP and AAA servicesDNS servers for name resolutionCPE management systems
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How Can Ixia Help?
Ixia’s IxLoad is a highly scalable, integrated test solution that assesses the performance of triple-play networks and devices. IxLoad emulates IPTV and triple-play subscribers and associated protocols to ensure subscriber Quality of Experience.
IxLoad supports the full range of protocols used in IPTV and triple-play testing:
Video – MPEG, IGMP, RTSPVoice – SIP, MGCPData – HTTP, FTP, SMTP and others.
IxLoad has a number of powerful features designed specifically for video testing:
Video subscriber emulation Video server emulation Quality of Experience (QoE) measurement Single and Multi-Program Transport Streams Substantial CODEC supportExtensive statisticsReal-time Video Capture and PlaybackFull packet capture and analysis
Ixia’s customers enjoy the simplicity of a single platform to emulate true subscriber group modeling with concurrent IPTV, VoIP and high speed Internet traffic. All your Layer 4-7 testing needs are satisfied in a single box – a feature not offered by any other test equipment vendor. All other Ixia applications run on the very same platform, maximizing your investment.
Ixia’s platform and interfaces offer the highest line-rate stateful traffic at 10G, the highest number of concurrent connections, and the
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industry’s leading protocol coverage – all necessary to reveal accurate performance benchmarks. Stateful traffic is essential to validate the performance of next generation Deep Packet Inspection (DPI) devices. DPI devices are required to optimize QoS at the granular level as QoE intensive video applications network push bandwidth limits.
Ixia’s legendary ease of use continues with features like One-Touch Automation, extensive analysis tools, and statistical viewers. All this means test engineers can ramp up with
less training, less time is required to develop automation scripts, and more productivity.
IxLoad is the complete solution for IPTV network testing, addressing all aspects of video delivery, along with the voice, user data and
915-1729-01 Rev A September 2007
Ixia’s product line includes:
HardwareOptixia Chassis – a family of ultra-high density, flexible testing platform used to hold Ixia Load Modules. All chassis contain a high-performance Windows computer system. All Ixia chassis, old and new, are compatible and may be daisy-chained together in a large scale test.
Optixia Load Modules – a wide array of interface modules available for use in Optixia chassis. Load Modules are available for 10/100/1G/10G Ethernet, SONET/POS, ATM, and PoE.
SoftwareIxNetwork – tests complex routing topologies by emulating a wide range of routing protocols, along with authentication and broadband encapsulations. Powerful traffic generation tools for any type of Layer 2/3 testing.
IxLoad – tests Layer 4-7 Triple-Play networks and devices through emulation of Internet protocols. Data protocols include HTTP, FTP, SMTP, DHCP, DNS, and AAA services; voice protocols include SIP and MGCP; video protocols include IGMP, MLD, RTSP and MPEG.
IxExplorer – provides access to all Ixia hardware functionality. Direct control over Ixia’s powerful stream engines is available to generate and capture any data.
IxAutomate – an automation engine for Ixia tests that includes a wide range of pre-built tests for Layer 2 through 7 testing, including many industry-standard RFC tests. IxAutomate is the perfect tool for regression suite development.
Test Conductor - a comprehensive regression harness compatible with key Ixia test tools.
IxANVL - the industry standard for automated network protocol validation. Test suites are available for most popular Internet protocols.
IxChariot - simulates real-world applications to predict device and system performance under realistic load conditions. IxChariot offers thorough network performance assessment and device testing by simulating hundreds of protocols across thousands of network endpoints.
IxVPN - an extremely scalable performance analysis solution for validating the performance of IPSec VPN gateways. IxVPN utilizes Ixia’s purpose-build Load Modules including the Encryption Load Module (ELM) with dedicated security processors.
IxVoice - a comprehensive hardware and software test framework that provides unified VoIP and PSTN test solutions. With its cost-effective and scalable test libraries it addresses all major VoIP protocols: SIP, SCCP (Skinny), H.323, MGCP, H.248 (MEGACO) as well as TDM and analog telephony services.
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Who is Ixia?Ixia is a leading provider of performance test systems for IP-based infrastructure and services. Ixia is a public company (NASDAQ: XXIA) operating in over 30 countries worldwide. Communications and entertainment delivery is rapidly moving to an IP infrastructure. To achieve “utility grade” quality, this infrastructure must be thoroughly tested. It is Ixia’s vision to accelerate the migration of communications and entertainment to IP by providing the best performance Test Systems in the industry. Network Equipment
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