manageable IP networks that support multicast mainly involve services such as direct broadcasting TV (relay TV broadcasting), Time - shift TV and VOD.
As for network infrastructure, IPTV systems in China adopt a Client/server model and provide unicast and on demand (including VOD and Time - shift TV) services. To let hundreds of thousand and even millions of users to concurrently receive and view broadcasting programs, existing networks will have to be reconstructed or upgraded to support multicast. This involves heavy infrastructure cost. Moreover, IPTV can only provide broadcasting services within reconstructed local networks. For network coverage in wider areas, the Client/server model cannot provide adequate support.
In addition, due to its inherent architectural shortcomings, CDN can hardly meet the program requirements of IPTV services. It cannot carry all the functions of IPTV, and may lead to traffic bottlenecks. Currently, CDN technology is adopted for VOD services to place servers close to customers to reduce network load. However, as the existing CDN networks were evolved from PC-based streaming media services, technical issues such as reduced efficiency and complicated reorientation mechanisms are likely to happen when large numbers of subscribers select the same content.
The media delivery system only offers relatively limited support for direct broadcasting TV, Time - shift TV and various value-added services. P2P technology which has been widely used in the Internet provides a rather good roadmap for solving the above problems. During broadcast, VOD and Push VOD video programs, P2P can transmit video contents through active or automatic mutual transfer between user ends, thus avoiding network congestion when all contents are transmitted from one or a few servers.
Under such distribution network, participants that share hardware and network resources are both resources providers and resources recipients. This not only solves the problem of low utilization efficiency resulting from the Client/server network infrastructure's over reliance on servers but also enriches program sources and offers users with more choices.
P2P makes streaming services evenly distributed in the whole network, thus avoiding congestions in edge servers. Using P2P technology to establish new media payment and distribution systems is essentially to stream program contents in advance and store them in several edge servers in blocks. The scheduling server will perform centralized control in line with the principles of proximity and load balancing. It is possible to real time select and rotate edge servers which provide streaming services to users based on the network situation.
At the technical level, P2P can indeed overcome the deficiencies of the existing IPTV technologies. But compared with manageable IPTV carrying networks that support multicast, it still has certain fatal defects. For example, many informal, private and non-copyright programs may appear on the network; as PC terminals become more transparent, network security expenditures will rise; and Internet-based technology gives no consideration to control or management problems.
P2P IPTV mainly faces a management short board. To successfully apply P2P technology in telecom-level IPTV networks, operators must also address issues of service delay, bandwidth asymmetry and network controllability and manageability, and build truly reliable and secure telecom-level IPTV networks. Also, IPTV is now still restricted by the development of DTV in the radio and TV industry. IPTV has yet to greet its period of fast expansion. Cross-regional IPTV networks are unlikely to emerge at present. It follows that P2P IPTV is unlikely to replace the existing IPTV technology framework in the next two or three years.
