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  1. 1. For discussion only TSAC Paper No. 4/2008 TELECOMMUNICATIONS STANDARDS ADVISORY COMMITTEE Brief Introduction to Internet Protocol Television (IPTV) IPTV 的 簡 介 Introduction This paper gives a brief introduction to Internet Protocol Television (IPTV) which is a system where a digital TV service is delivered using Internet Protocol (IP) over a network infrastructure to the subscribers for viewing on TV sets, usually via set-top boxes (STBs). 2. Traditionally, television services have been provided to the viewers using terrestrial broadcast networks, and later over cable networks and via satellites. With the extensive reach of IP networks and the widespread adoption of broadband access technologies, service providers can now use the IP networks to launch the services. IPTV1 often refers to the service with back-to-back service management along with tight quality of service (QoS) and security considerations. For residential users, IPTV is very often bundled with other services such as Voice over IP (VoIP) and Internet access. System Overview IPTV architecture 3. An IPTV system typically consists of major functional elements as depicted in the figure below. In the video headend, the video content from the content providers are captured and formatted for distribution over the IP network. The video headend also provides operations support and subscriber management functions. Video signals from the headend are delivered across the core network using unicast or multicast technology to the network edge. The access network provides connectivity from the customer premises to the core network. Various access technologies are being used, including digital subscriber lines (e.g. ADSL, VDSL), Ethernet, fibre. The core and access networks are usually private IP networks for which the network provider can manage to provide the required QoS. The home network is responsible for distributing IPTV services throughout the home. The end-points of the home network include telephones, personal computers, STBs. 1 At present, IPTV is usually provided over private IP network where the provider can manage to guarantee the QoS. In contrast, “Internet TV” commonly refers to the provision of video services to viewers (usually view on computer screen with media player software) using the best-effort delivery service of the public Internet. TSAC Paper No. 4/2008 Page 1 May 2008
  2. 2. For discussion only TSAC Paper No. 4/2008 Category of services 4. In an IPTV environment, the service provider can use the access network to provide a single high bandwidth connection to the customer’s premises. That connection enables multiple TV channels, VoIP and broadband Internet access. The IPTV provider will provide an electronic program guide (EPG) to the subscribers to let them know the available TV content they can access. 5. By resolution, digital TV can be categorized as Standard-Definition TV (SDTV) and High-Definition TV (HDTV). Typically, SDTV supports a resolution (V×H) of 480×640 with interlaced scan whereas HDTV supports the resolutions 720×1280 (progressive scan, i.e. 720p) and 1080×1920 (both progressive scan, i.e. 1080p, and interlaced scan, i.e. 1080i). 6. IPTV also supports a variety of service types, including broadcast TV, VOD, interactive TV and personal video recording (PVR). Both live broadcast and stored content can be provided. With VOD or interactive TV, the subscribers are given certain degree of selectivity and interactivity. For example, in addition to subtitle and dialect, a subscriber can also select the angle of view of a movie, or pause, rewind or forward the video content. The IPTV services can be bought as a pre-paid package or by pay-per-view (PPV). Video compression technology 7. Raw video signals occupy huge bandwidth. Delivery of them without compression over IP networks would not be feasible. The Moving Pictures Experts Group (MPEG) has developed a number of compression systems which are widely used in many IPTV implementations today. Among these systems, the most common ones are MPEG-2, MPEG-4 Part 2, and MPEG-4 Part 102 (also referred to as H.264). Another popular format is VC-1 (generic name “Windows Media Video 9 (WMV9)”) developed by Microsoft. China is also developing its own compression standard, the Audio Video coding Standard (AVS), for use in its IPTV implementations with a view to avoiding payment of the patent fees incurred in using the MPEG or VC-1 standards. 8. Typically, MPEG-2 requires 2-3 Mbit/s for a SDTV channel and 12-19 Mbit/s for an HDTV channel. H.264 incorporates new technologies for video compression developed in the past decade, and is possible to provide good video quality at half the bit rate of MPEG-2, typically 6-9 Mbit/s for HDTV. But this comes at the cost of more complex and costly codec. Yet, H.264 is becoming increasingly popular. VC-1 is similar in performance to H.264. There is no compelling evidence that one is better than the other. Many vendors have designed codec supporting both H.264 and VC-1. 9. Among the compression formats described above, IPTV providers normally choose one format for all video content. This helps simplify overall management of the IPTV system. Moreover, IPTV providers normally compress the video content into a common bit rate, usually one bit rate for SDTV and another for HDTV. This simplifies bandwidth management and the process of channel switching. 2 MPEG-4 Part 10 is jointly developed by ITU-T and MPEG, and is commonly referred to as H.264 or AVC (Advanced Video Coding). MPEG-4 Part 10 defines a different format than MPEG-4 Part 2, and is not to be confused with it. TSAC Paper No. 4/2008 Page 2 May 2008
  3. 3. For discussion only TSAC Paper No. 4/2008 Content distribution 10. There are two methods commonly used in IPTV systems for content delivery - multicast for broadcast TV, and content distribution network (CDN) for VOD. For broadcast TV, each subscriber will receive the same content. All subscribers who select the same video content will participate in a multicast group. Instead of delivering to each subscriber an individual copy, one single copy of the video content is delivered from the headend to the network for distribution to each subscriber in the multicast group. The content is sent across each link of the network only once, and copy is created only when the links to the destinations split. This can help reduce traffic in the network. 11. VOD responds to a request generated by a subscriber through the STB, and the response flows as a unicast stream to the subscriber. For such service, the CDN may be used to deliver the video contents requested by individual subscribers. CDN consists of a group of interconnected cache servers distributed across the IP network that cooperate to deliver content to the subscribers. Video contents are dynamically distributed from the video headend to the cache servers using some server load balancing techniques. Under the control of a content distribution controller, a request for content is intelligently directed to the cache server which can optimally serve the request, e.g. the server that can provide the content to reach the subscriber most quickly such as via fewest hops. CDN can help reduce bandwidth costs and shorten the response time to subscribers’ requests. Protocol 12. In addition to IP itself, and the well-known transport protocols Transmission Control Protocol (TCP) and User Datagram Protocol (UDP), the following protocols developed by the Internet Engineering Task Force (IETF) are also commonly used in IPTV systems: For content transport (a) Real-time Transport Protocol (RTP) - RTP is a transport layer protocol intended for carrying real-time multimedia contents. RTP operates on top of UDP. It adds functions of time stamping, packet sequencing, etc. to ensure packets carrying audio and video content are delivered to the end-users in proper temporal order and in synchronization. For control purposes (b) Real-time Transport Control Protocol (RTCP) - The primary function of RTCP is to provide feedback on the quality of RTP distribution for the network provider to diagnose network problems. RTCP uses a UDP connection for communication, which is separate from the UDP connection used by RTP. (c) Internet Group Management Protocol (IGMP) - IGMP is used to report multicast group memberships to multicast routers in the core networks to allow multicasting of broadcast TV content to the multicast group participants as described in para. 10 above. IGMP uses IP to carry messages. (d) Real Time Streaming Protocol (RTSP) - RTSP is used in VOD services for control purposes. It allows a client to remotely control a VOD server, issuing VCR-like commands like play, pause, forward, rewind, record, etc. (e) Internet Content Adaptation Protocol (ICAP) - ICAP is designed to off-load the video content from the video headend to the cache servers in the content distribution networks (CDNs) as described in para. 11 above. TSAC Paper No. 4/2008 Page 3 May 2008
  4. 4. For discussion only TSAC Paper No. 4/2008 Security 13. There are usually two security functions involved in an IPTV system: Conditional Access (CA) and Digital Rights Management (DRM). CA is a group of techniques used to ensure that only authorized viewers are given access to the content. The basic technique is to encrypt the content so that unauthorized viewers receiving the signals are unable to view it. Authorized viewers are given numeric keys which permit their STBs to decrypt the signals. One common form of key distribution is the smart card which store the private part of a public/private key pair and uses that private key for decrypting the video content. 14. DRM is a set of functions for protecting the ownership rights of the content owners. While CA controls whether a viewer is allowed to view content, the purpose of DRM is to control the way a viewer can use the content. Typical examples of DRM control include whether the viewer can copy or record the content to other devices or media, time window the content can be viewed. Set-top box (STB) and Middleware 15. One key component in an IPTV system is the STB, which can be considered as an interface between the service provider and the subscriber’s TV set. Through the STB, the subscribers can have access to an EPG, and can perform control functions like channel/ content selection, play, pause, rewind, forward, etc. 16. The main job of the STB is to receive incoming IPTV signal and convert it to a video signal that can be displayed on the subscriber’s TV set. Many STBs support both SDTV and HDTV, and provide a multiplicity of video outputs, e.g. analogue PAL, NTSC, and digital DVI (Digital Visual Interface) and HDMI (High Definition Multimedia Interface). CA and DRM functions are built in to allow legitimate access to contents and to protect the rights of content owners respectively. Some STBs also include a hard disk drive, enabling subscribers to record programs for later viewing. In addition, some STBs may also have functionalities to support VoIP and Internet access, allowing the subscribers to make video phones call, surf the Web, or play online games, all on the TV sets. 17. The IPTV middleware refers to the software packages associated with the delivery of IPTV services. It typically has a client-server architecture with the client part residing on the STB, and the server part residing on the headend or video server side. There are a variety of vendors providing IPTV middleware, each with its own unique approach to IPTV. The middleware controls the user experience, and defines how the subscriber interacts with the service. For example, the user interface and services available (e.g. EPG, broadcast TV or VOD) are all made available and controlled through the middleware. Middleware also links client and server systems used for CA and DRM purposes. Standardization Work 18. The common compression standards and communications protocols as described above are already in place and are being used in many IPTV implementations. However, architectural standards which specify the complete IPTV framework for end-to-end service delivery, and to ensure interoperability of different network elements and interworking of different administrative domains remain to be worked out. Following is the work of some standards development organizations (SDOs) in this respect. TSAC Paper No. 4/2008 Page 4 May 2008
  5. 5. For discussion only TSAC Paper No. 4/2008 ATIS (Alliance for Telecommunications Industry Solutions) 19. The IPTV Interoperability Forum (IIF) of the ATIS3 is responsible for developing standards which enable interoperability, interconnection and implementation of IPTV systems and services. Since its creation in June 2005, the IIF has published several standards on IPTV, covering the following areas: (a) IPTV high level architecture requirements; (b) high level Operating Support System/Business Support System (OSS/BSS) functional requirements and reference architecture for IPTV; (c) QoS metrics and measurements; and (d) interoperability requirements on scrambling algorithms and digital right management. The list of IPTV standards released by the IIF can be found in the ATIS website at At present, work in the IIF is underway in five other key areas, including linear/broadcast TV service; consumer-domain initialization and attachment; media protocols; remote management of devices in the consumer domain; and an emergency alert system for IPTV. ETSI (European Telecommunications Standards Institute) 20. The Telecommunications and Internet converged Services and Protocols for Advanced Networking (TISPAN) Technical Committee of ETSI is responsible for the Next Generation Network (NGN) standardization work. At the end of 2005 TISPAN published the NGN release 1 specifications, and it is now working on the release 2 specifications. The release 2 specifications focus on enhanced mobility, new services and content delivery with improved security and network management. IPTV is one of the new services covered in the release 2 specifications, and TISPAN has taken initial steps in defining network support for IPTV. TISPAN has recently published some technical specifications on IPTV, as follows: (a) TS 181 014 Requirements for network transport capabilities to support IPTV services, covering high level requirements on admission control, multicast/unicast support, security, accounting, etc. (b) TS 181 016 Service Layer Requirements to integrate NGN services and IPTV, covering high level requirements on service discovery, service delivery, user profile, parental control, terminal provisioning, quality of experience (QoE), interaction of IPTV with other services such as presence, video telephony, etc. (c) TS 182 027 IPTV architecture; IPTV functions supported by the IMS subsystem, specifying the functional architecture of an IPTV system which makes use of the IP multimedia subsystem (IMS) architecture and its features. (d) TS 182 028 IPTV architecture; Dedicated subsystem for IPTV functions, describing the IPTV functions within the NGN architecture, including areas like authentication and authorization, content protection, capability exchange, resource management, charging, and user profiles. 3 ATIS is a US-based industry body committed to developing technical and operations standards for the communications and related information technologies industry. ATIS is accredited by the American National Standards Institute (ANSI). TSAC Paper No. 4/2008 Page 5 May 2008
  6. 6. For discussion only TSAC Paper No. 4/2008 ITU (International Telecommunication Union) 21. Given that IPTV is becoming an increasingly important service, ITU-T established the IPTV Focus Group (FG IPTV) in April 2006 to coordinate and promote the development of global IPTV standards, taking into account existing work of the ITU study groups and other SDOs such as ATIS and ETSI as mentioned above. The Focus Group is under the lead of ITU-T Study Group 13 which is the NGN lead group. The goals of FG IPTV include the identification of IPTV architecture and service requirements, coordination of existing standardization activities, harmonization of the development of new standards, and encouraging interoperability with existing systems. FG IPTV consists of six working groups responsible for different areas as follows: WG1 : Architecture and Requirements WG2 : QoS and Performance Aspects WG3 : Service Security and Contents Protection WG4 : IPTV Network Control WG5 : End Systems and Interoperability Aspects WG6 : Middleware, Application and Content Platforms 22. Since its establishment, FG IPTV has held a total of seven meetings. The work of the Focus Group ended after its final meeting of December 2007, and the reports and other deliverables have been transferred to the appropriate ITU-T study groups via SG 13 for development of draft recommendations on IPTV. These reports and deliverables cover various aspects of IPTV, and are available for free download from the ITU website at The continuation of the work on IPTV by the relevant study groups will be carried out under the umbrella of a Global Standards Initiative, i.e. the IPTV-GSI. IPTV-GSI will coordinate activities planning and organize co-located meetings for the relevant study groups to progress the IPTV work. The first IPTV-GSI event took place in January 2008 in Korea. There were some discussions on the study questions related to IPTV from the following study groups: (a) SG 9 (Integrated broadband cable networks and television and sound transmission) (b) SG 11 (Signalling requirements and protocols) (c) SG 12 (Performance and quality of service) (d) SG 13 (Next generation networks) (e) SG 16 (Multimedia terminals, systems and applications) (f) SG 17 (Security, language and telecommunication software) 23. In addition, SG 9 in November 2007 also gave consent to a new recommendation J.700 titled “IPTV Service Requirements and Framework for Secondary Distribution”, which describes the high level service requirements and functional framework architecture for the support of IPTV services delivered over IP-based core networks, and cable, fibre or wireless access networks to the end-users. Moreover, SG 16 (Multimedia Terminals, Systems and Applications) has adopted a new study question on Multimedia application platforms and end systems for IPTV, with the intention to producing deliverables related to the study of IPTV platforms. TSAC Paper No. 4/2008 Page 6 May 2008
  7. 7. For discussion only TSAC Paper No. 4/2008 Development 24. According to the research of a broadband analyst company in October 2007, there are over 8 million IPTV subscribers worldwide in 2007. Analysis from another researcher forecasts that from 2007 to 2011 there will be a five-fold increase in the number of IPTV subscribers globally. Europe still leads the world IPTV market. But many Asian countries are seeing emerging markets and are taking large steps to growth. The number of IPTV subscribers in Asia is forecasted to equalize that in Europe in the coming few years. The growth in North America will also be steady. Currently, over 80% of the global IPTV subscribers are in Europe and Asia whereas the remaining are in North America and the rest of the world. 25. Technically, DSL continues to be the dominant access technology, but fibre-to-the-home (FTTH) is beginning to show more attraction in both developed and developing markets. MPEG-4 (or H.264) is consistently replacing MPEG-2 in new installations while MPEG-2 ceases to be sold even in cost-sensitive markets like China or Eastern Europe. Europe 26. Europe currently has the biggest and fastest growing IPTV market in the world, with France, the Netherlands, Spain and Italy taking the lead. As at end of June 2007, the number of IPTV subscribers in Europe reportedly amounted to about 5 million. The largest IPTV market is in France which has over 2.5 million IPTV subscribers. The French providers provide both SDTV and HDTV, using DSL now as the major access technology. The success of IPTV in France occurs for a number of reasons: (a) Broadband customer base - According to a consultancy, France had about 11.7 million broadband subscribers as at June 2007. So there would be a significant number of potential IPTV subscribers. (b) Pricing - Currently there are several IPTV providers in France, with France Telecom, Neuf Cegetel and Free (a subsidiary of the Iliad Group) being the major players. Due to a very competitive market, the prices for IPTV services are very low. France Telecom offers basic IPTV services with over 40 channels at about 15 Euros/month. (c) Weak competition from other services - The main alternatives to IPTV are cable TV and satellite TV, both of which achieve penetration in France far below levels in other European countries. For many potential viewers, IPTV becomes the only way to get digital TV services with wide range of content. The other major IPTV markets in Europe are in the Netherlands, Spain and Italy, with each of them reportedly having about 500,000 IPTV subscribers as at end of June 2007. 27. The major IPTV providers in the UK are BT Vision, Tiscali TV and Inuk Networks. Although the service providers have plans to expand their service coverage, the number of IPTV subscribers in the UK is reportedly low. According to some analyses, the low IPTV penetration in the UK could be due to competition from other services like cable and satellite. UK has roughly the same TV households as France, but there were twice as many satellite subscribers as in France. Overall, the penetration of digital TV services was almost 70% of viewers. This is a much higher ratio than those in France and many other European countries. So there may not be strong incentive for the UK viewers to subscribe for IPTV services. TSAC Paper No. 4/2008 Page 7 May 2008
  8. 8. For discussion only TSAC Paper No. 4/2008 Asia Pacific 28. Asia Pacific is next to Europe in IPTV development and has reportedly over 2 million IPTV subscribers as at end of June 2007. Hong Kong is the pioneer in the rollout of IPTV services and now has very high service penetration. The number of IPTV subscribers in Hong Kong is about 50% of the total number of broadband subscribers, which ranks very high at the worldwide level. There are currently three IPTV providers in Hong Kong and some of them are also network operators. In addition to SDTV, HDTV is also available from one service provider. According to a research, the number of IPTV subscribers in Hong Kong as at the end of June 2007 is close to one million, which is comparable to the total number of IPTV subscriber in US at the same time. 29. The major IPTV service providers in Japan are NTT, KDDI and Softbank. The number of IPTV subscribers in Japan reportedly amounted to about 350,000 as at end of June 2007. In Korea, regulatory problems have ever impacted the IPTV market. While the Korean operators like Korea Telecom and Hanaro Telecom could provide VOD services via IPTV, they were not allowed to offer broadcast TV over their networks. In December 2007, Korea passed a bill clearing the regulatory obstacles for the full launch of IPTV. This is expected to greatly boost the subscriber number for the three existing IPTV players, i.e. Korea Telecom, Hanaro Telecom and LG Dacom. 30. In Mainland China, China Telecom and China Netcom are the major network providers (or carriers) for IPTV. But the network providers are prohibited from producing their own TV content by the broadcast regulator, i.e. the State Administration of Radio Film and Television (SARFT) ( 局總視電影電播廣家國 ). As such, over the last few years they have partnered with IPTV providers4 like China Central Television (CCTV) and Shanghai Media Group (SMG) ( 團集媒傳聞新廣文海上 ) to launch IPTV trials in many Chinese cities. Following the trials, commercial IPTV services are being provided in some cities, including Shanghai, Harbin, Fuzhou, Xiamen. The number of cities with IPTV trials or commercial launch keeps increasing. DSL is the major access technology used for the time being. Over time, the network operators will deploy fibre access to support HDTV programming. The Chinese market is now starting to move from trials to full deployments. According to a Chinese information source, the number of IPTV subscribers in the Mainland was about 450,000 in 2006, and the figure is very optimistically projected to over 17 million in 2010. US 31. There are two major IPTV providers in the US - Verizon and AT&T, each providing the services in several states. In addition, a plentiful of local IPTV providers are also providing the services in individual states. Both Verizon and AT&T have deployed fibre close to the customer locations, either fibre-to-the-neigbourhood (FTTN) or fibre-to-the- premises (FTTP), to enable the provision of IPTV service in a triple-play package. The fibre connections can provide over 30 Mbit/s capacity to each customer, allowing simultaneous viewing of three to four different programs. The services provided by Verizon and AT&T are also very similar, including broadcast TV and VOD on a pre-paid or pay-per-view basis. Personal video recording is also available. As at end of June 2007, there were reportedly about 1 million IPTV subscribers in the US. 4 The IPTV providers in the Mainland are all affiliates of SARFT. TSAC Paper No. 4/2008 Page 8 May 2008
  9. 9. For discussion only TSAC Paper No. 4/2008 Considerations Access bandwidth 32. Video is a bandwidth-intensive application, and access bandwidth is one thing the operators are striving to boost up to augment the attractiveness of IPTV. The home appliances are becoming increasingly versatile and are evolving to a home network where several appliances, e.g. STBs, TV sets, personal computers, smart phones, are all linked up together. The subscribers may gradually demand delivery of several TV program channels for simultaneous viewing on different TV sets, and this calls for increased access bandwidth. 33. While ADSL may not provide sufficient bandwidth for carrying HDTV or more than one SDTV channel, with a combination of fibre-to-the-neighbourhood (FTTN) or fibre-to-the-curb (FTTC) and advanced DSL technologies like VDSL, a data rate of tens of Mbit/s can be provided for carrying several SDTV and HDTV channels. The penetration of fibre-to-the-home (FTTH) is also expected to grow with time. It is considered that access bandwidth would not be a hurdle to the development of IPTV. Interconnection issues 34. In all known commercial IPTV implementations today, the service is provided within a private IP network managed by the network provider (which may also be the IPTV provider). The IPTV traffic does not traverse across other operators’ networks. It is expected this situation will persist for some time, and apparently there are no major concerns on interconnection for the time being. However, as stipulated in ITU’s NGN definition, one requirement of NGN is to allow users to have unfettered access to services. While IPTV is one of the NGN services, limiting the subscribers to access certain service packages through a particular network provider appears to violate this requirement. As such, interconnection of different administrative IPTV networks is among the study topics of ITU. There are interconnection or interoperability requirements on the service level and the network level. Service interoperability 35. In principle, IPTV service provisioning now is based on the client-server model with interactions between the STB and the server platform. Very often, the service provider procures a turnkey solution from a vendor which provides everything necessary to be installed at the server side and the subscriber side. And the service provider will provide the STBs to the subscribers so that interoperability with its server platform is ensured. Yet, the STB and the associated middleware of every IPTV implementation may have some distinct features from other implementations. When the subscriber changes service provider, the original STB may no longer be usable. 36. There seems not yet any established and widely adopted standards to allow interoperability of IPTV equipment from different vendors. Yet in ITU and other SDOs, study about this is underway. In the long term when there are sufficiently mature and widely adopted standards, IPTV providers may acquire system components (including STBs) from different vendors. This may bring economy of scale, and help reduce IPTV implementation costs. Moreover, maybe at some time the functions of the STB can be built into the TV set. This may help reduce costs and save subscriber accommodation space for the home equipment. Thus, the international IPTV standardization work to facilitate equipment interoperability is to be monitored. TSAC Paper No. 4/2008 Page 9 May 2008
  10. 10. For discussion only TSAC Paper No. 4/2008 Network interconnection 37. QoS is one major technical concern when considering interconnection of IPTV networks. IPTV, either live broadcast or stored content, is sensitive to transmission defects such as packet loss, jitter and delay. When provided within a single administrative domain, the responsible network operator will ensure that the network performance objectives are met so that the required QoS can be maintained. However, different network operators may have different QoS and resource control policies. When there is a need for the IPTV traffic to traverse across different administrative domains, either due to market demand or required by regulators, the concerned network operators would need to harmonize their QoS and resource control policies in order to deliver the required end-to-end QoS. 38. For broadcast TV services, the routers of the interconnecting networks may need to collaborate for management of multicast group membership and for effective routing of video content through the multicast mechanism. For VOD, coordination between network operators may also be required to harmonize their respective content distribution and caching mechanisms. Even the operators may employ similar techniques in their implementations, each implementation inevitably differ from the others in certain details. Thus, harmonization is required to ensure interworking among the protocols, signalling, addressing and naming schemes, etc. used in different implementations, and to ensure effective delivery of IPTV services across different administrative domains. 39. Work is in progress in ITU and other SDOs to study the aforesaid interconnection requirements with a view to producing some technical standards. We may need to keep in view international standards development in these areas to prepare for our future standardization needs. Consultation in the CCS-WG 40. The brief introduction to IPTV had been given to the CCS-WG members at the last CCS-WG meeting of 11 March 2008. Members have noted the content of the paper and also exchanged views on IPTV interconnection. There were views that IPTV interconnection might concern harmonization of QoS polices and network resource utilization between the interconnecting networks. So the network operators might be more concerned than the service providers. But the need for IPTV interconnection might still be remote. Advice Sought 41. Members are invited to provide information on their IPTV implementations as appropriate, and comment on any specific aspects of IPTV for which standardization would be necessary. Office of the Telecommunications Authority May 2008 TSAC Paper No. 4/2008 Page 10 May 2008