Network infrastructure for IPTV

Transcription

1 Network infrastructure for IPTV Peter Arberg, Torbjörn Cagenius, Olle V. Tidblad, Mats Ullerstig and Phil Winterbottom Millions of people around the world already subscribe to IPTV over broadband networks, and looking ahead, the anticipated uptake in subscribers is substantial. Two factors an operator should take into account when designing an IPTV-capable broadband network are the expected mix of unicast and multicast content and the range of combinational services, including communication services. The authors describe Ericsson s IPTV solution, calling special attention to the network infrastructure, which emphasizes recent additions of GPON fiber access and Multi Service Edge Routers (MSER) to the product portfolio. They also highlight experiences garnered from several years of deploying broadband networks for IPTV delivery. Introduction to IPTV IPTV, as an operator service over broadband networks, has been available for some time. Until recently, however, it has mainly been offered in small networks or in parts of networks. Figure 1 shows the anticipated increase in traffic over broadband access networks. This increase will largely be driven by IPTV service. Even though today s networks have been built to support triple-play service, upgrading them to support mass deployment of IPTV service will be a major challenge. This is because the new media experience this service provides is not restricted to passively viewing broadcasted content but rather presents end users with interactive and personalized media, including on-demand content and combinational communication services. 1 To meet these challenges, operators are investing in deep-fiber access 2 and upgrading their IP edge capabilities. Ultimately, the network must support an increasing portion of unicast traffic (that is, dedicated media streams to individual users). Notwithstanding, multicast traffic will continue to be an important feature for efficiently distributing content to many users. Another challenging issue relates to the efficient distribution of content while guaranteeing the quality of the IPTV media experience. In summary, to successfully deliver this service, the network must scale well and be flexible in order to account for user uptake and future services. This article describes the IPTV network infrastructure as currently deployed by Ericsson and how it can evolve into the Full Service Broadband architecture, thereby supporting the new media experience of IPTV. The broadband access network The broadband access network must support quality of service (QoS), multicast, the separation of end-user traffic, and differentiate between services; it must be secure and robust (with high in-service performance); and it must have a telecommunications management solution that supports network operation and maintenance (O&M). Many of these features have been standardized in DSL Forum specification TR-101, which calls for an Ethernetbased aggregation network. 3 Figure 2 shows a simplified view of the network architecture. The key network elements in Ericsson s broadband portfolio are access nodes the network must support a large range of access technologies, including a variety of DSL technologies, point-topoint Ethernet over fiber or CAT5/6, and TERMS AND ABBREVIATIONS ASP BFD DLNA DSL DVB ETSI FRR GPON HDTV IGMP IMS IPTV ISP ITU-T Application service provider Bidirectional forward detection Digital Living Network Alliance Digital subscriber line Digital video broadcasting European Telecommunications Standards Institute Fast reroute Gigabit passive optical network High-definition television Internet group multicast protocol IP Multimedia Subsystem IP television Internet service provider International Telecommunications Union Telecommunication gigabit passive optical network (GPON) technology; metro aggregation nodes metro networks transport traffic between access and IP edge nodes and provide transport-based connectivity services in their own right; and IP edge nodes a versatile IP edge platform for enhanced network efficiency and simplified operations in a single MSER platform. There is also a policy-control function that manages per-user policy profi les and QoS settings (Figure 2). The addition of Entrisphere (GPON) and Redback (MSER) products to an already comprehensive broadband access portfolio (which includes the former Marconi access and transport products as well as Ericsson s own access products) enables Ericsson to offer a highly competitive portfolio that supports the requirements of IPTV service and the evolution toward Full Service Broadband. Supporting features The IPTV service puts unique demands on every node in the broadband network. For instance, to deliver unicast and multicast video services, the network must provide continuous bandwidth, IP control features, and scalability. In addition, it must provide the same level of flexibility and reliability as are associated with telecom carriers services. Efficient and reliable multicast To enable cost-effective distribution of linear TV over the broadband network (by reduc- Standardization Sector MPLS Multiprotocol label switching MSER Multi Service Edge Router npvr Network PVR OS Operating system PIM-SM Protocol-independent multicast sparse mode PIM-SSM Protocol-independent multicast source-specific multicast PVR Personal video recorder QoS Quality of service TISPAN Telecommunications and Internet converged Services and Protocols for Advanced Networking (a technical committee of ETSI) VDSL2 Very-high bit rate DSL Ericsson Review No. 3,

2 Figure 1 Traffic increase in broadband networks. ing network load), the service makes use of IP and Ethernet multicast throughout the network. Multicast begins as a single stream that is transported through the network to a point as close to the intended recipients (end users) as possible. The stream is then duplicated for hundreds or even thousands Figure 2 Architecture of the broadband access network. 80 of end-users who receive the same data at the same time without overloading the network or video server. The switched nodes in the IPTV network must support the internet group multicast protocol (IGMP), which hosts (for example, set-top boxes) use to join or leave multicast streams (a multicast stream is equivalent to a TV channel). For efficient multicasting, IGMP needs to be implemented throughout the access network and as close as possible to the intended end users. Moreover, to support a variety of carrier network modes, every node in the IPTV network must have a flexible and scalable multicast implementation. To limit the number of IGMP reports processed in the network, some carriers choose a model which suppresses IGMP reports or which uses an IGMP proxy in the access node. Other carriers choose a transparent IGMP snooping model which enables the IP edge router to see every IGMP request and implements full subscriber awareness at the IP edge. The service must also support highavailability multicast at the IP layer, primarily from the IP backbone network to the IP edge routers. To manage layer-3 multicast traffic, the IP edge router employs the PIM-SM or PIM-SSM-with-graceful-restart multicast protocols. This feature makes certain the multicast streams are delivered to the IP edge router in a timely and reliable fashion. Different functionalities, such as bidirectional forward detection (BFD) in combination with PIM dual-join or multiprotocol label switching (MPLS) fast reroute (FRR), can be used to detect network failure and reroute traffic without disrupting the end-user experience. Apart from the multicast features mentioned here, Ericsson s IPTV multicast solution supports GPON-specific multicast, Ericsson Review No. 3, 2007

3 according to ITU-T standard G In this case, the passive splitting of the optical network is used to deliver a single video stream (TV channel) to every viewer served by the passive optical network in question. This feature can be used in combination with the IP and Ethernet multicast techniques to further enhance the efficiency of bandwidth usage over the passive optical network. Unicast services A unicast delivery model is required to deliver unique content to a single user. Unicast service establishes a point-to-point connection between a user s set-top box and the media in the network. The service request establishes several parameters, including bandwidth, quality of service, and latency. In many instances, unicast services, such as video on demand (VoD) and network personal video recorder (npvr), are delivered from a central media server in the service layer network. And it is anticipated that a greater share of services, driven by interactivity and personalization of the IPTV service, will be delivered as unicast traffic that is, as an individual media stream to each end user. As a consequence, it will become necessary to distribute content closer to end users, in order to minimize the number of unicast streams and thereby traffic load on the backbone network. For simple use cases, the solution might be to add a PVR in the home. To cover a broader range of services, however, a network-based media cache is required. Media cache servers are already being distributed to some extent, but to attain scalability, more efficient solutions are being investigated. One solution is to integrate the distributed media cache with nodes in the broadband network for example, the IP edge node, which has been optimized to transport user data, including video streams. Figure 3 shows the difference between unicast and multicast video delivery in the broadband access network. Scalability and flexibility for increasing traffic demand To support the evolving IPTV service, the broadband network must be scalable in several dimensions, the most important of which are service penetration (for support of up to 100% service uptake), network capacity (driven by high definition TV, HDTV, and unicast services), and service mix (scalable and flexible support for the introduction of new services). Figure 3 Broadband access networks must support the delivery of unicast and multicast services. Although the initial service penetration rates may be moderate, on average, the network architecture must, from the outset, be flexible enough to handle substantially higher penetration rates in smaller sections of the service area, driven, for example, by local word-of-mouth reports of the service. Obviously, network capacity is directly related to service penetration, but it is also a matter of network architecture (degree of flexibility). To support high levels of penetration, heavy simultaneous usage, multiple channels per home, and high-bandwidth services (driven to a large extent by unicast and HDTV traffic) the broadband network must provide sufficient bandwidth both for switching capacity and transport connections. One must also be able to police viewers bandwidth requests. Indeed, a network with sufficient capacity for multicast video might not scale well as the service mix transitions from multicast to unicast combined with an increasing ratio of high-definition content. To meet the anticipated demand in traffic, the broadband network architecture must flexibly and efficiently be able to move capacity where it is needed most, for example, by means of flexible VDSL2 drops in compact outdoor cabinets. The scalability dimension pertains to the evolution of the service mix. Over time, IPTV will give end users an interactive and personalized media experience that includes on-demand content and combinational communication services. At present, however, it is difficult to say what the rate of service uptake will be or what requirements a future service mix will put on the network. The network design must facilitate moving services further out in the network for example, by moving video-on-demand servers closer to end users to free up bandwidth in metro and backbone networks. In many instances, this will mean placing the IP edge routers further out in the network. IPTV network infrastructure deployments Ericsson s IPTV network infrastructure portfolio plays a key role in many major commercial IPTV deployments. Customers who have leveraged Ericsson broadband infrastructure for IPTV include Belgacom, China Netcom, China Telecom, Chunghwa Telecom, KPN, and TeliaSonera. The top reasons given for selecting Ericsson s solution include flexibility, reliability, scalability, and a migration path from existing infrastructure. Ericsson Review No. 3,

4 Figure 4 Functional blocks of the IPTV architecture. BOX A, SMARTEDGE MSER 82 Customer reference case Some of the largest and most challenging IPTV deployments to date comprise the TV service offered by incumbent telephone operators. Although the first commercial IPTV services were launched only a few years ago, they have already gained tremendous subscriber acceptance. TeliaSonera, for example, has more than 200,000 IPTV subscribers. Likewise, Chunghwa Telecom intends to increase its IPTV subscriber base to around 600,000 by the end of The requirement for rapid scalability and the need to limit financial expenditures motivate carriers to focus on a shared Ethernet network infrastructure 5 for all their services, including IPTV. A consistent service offering across existing access technologies, such as various DSL technologies, and new and emerging access technologies, such as GPON and point-to-point fiber, will have a decisive role in any IPTV rollout plan. To compete with existing cable, satellite, and terrestrial TV providers, one must secure reliable delivery of video and the flexibility needed to introduce complex new services over different access technologies while still fulfilling the demand for personalization, service bundling and interactivity. Besides functionality to ensure carrierclass reliability through a modular operating system and advanced QoS feature sets, key network components to secure a successful IPTV deployment include SmartEdge The SmartEdge Multi Service Edge Router (MSER) family integrates three key functions into a single, multi-functional platform that includes edge routing, Ethernet aggregation, and subscriber management. Designed from the ground-up with availability, scalability, programmability, and high performance in mind, the product supports % availability, and scales both physically and logically to thousands of sessions. It is flexible enough to be upgraded to support new services and can forward packets at line rate even with features enabled. All common equipment and line cards are hot-swappable, and critical components, such as the Route Processor, can be put in service in redundant configuration. To improve system reliability, the SmartEdge OS is highly modular. Every protocol is implemented as a separate process. Innovative software enables fast failover to a hot standby Route Processor with no interruption to forwarding and near-hitless software upgrades. The packet-switching mesh, which employs high-performance ASICs developed by Redback, is distributed to every line card in other words, there is no single point of failure. A dedicated processor handles time-critical input/output (I/O) functions, such as fault and performance monitoring, and alarms. Power and return lines are diversely routed across the backplane to every slot in the chassis. Optimization for video service delivery on the SmartEdge MSER is showcased with highly scalable multicast for traditional broadcast video services, as well as support for advanced video-ondemand services via application-level traffi c control on a per-user basis. A single platform for delivery of multiple services minimizes capital expenditures (CAPEX) and operating expenses (OPEX). MSER subscriber functionality coupled with the EDA 1200 broadband access nodes and EDA 1500 GPON systems, which support per-subscriber multicast replication and persubscriber service utilization visibility. This combination provides optimal bandwidth and a very secure network infrastructure, giving operators control through an individual subscriber view of voice, video and data delivery, and making certain the correct data rate and priority are assigned to each service. Evolution toward Full Service Broadband The broadband network infrastructure described above will be the basis of, and a prerequisite for, the new IPTV media experience, taking it beyond linear TV and sporadic video-on-demand services. The IP Multimedia Subsystem (IMS) is a standard for establishing and controlling communication sessions. By adding an IMS control layer, IPTV operators can accelerate the introduction of new services, efficiently combine TV service with communication services, offer the service over multiple access networks, and deliver IPTV to any end-user screen. In essence, the broadband network infrastructure becomes part of the Full Service Broadband architecture. 6 The target IPTV architecture gives users a mix of broadcast TV, interactivity with TV programs, video on demand, and networkbased recording. It also supports the integration of TV service with personalized information (including emergency messages) and communication services. The architecture uses session initiation Ericsson Review No. 3, 2007

5 protocol (SIP) for session control signaling, and IMS for authenticating and authorizing subscribers, controlling admission, and reserving resources. The benefits of using IMS as a control mechanism are integration with communication services, such as multimedia telephony, and messaging, which greatly enhances the user experience; security thanks to built-in identity management, authentication, authorization and service-access-protection functions; mechanisms for supporting the delivery of multiple services with controllable QoS over the common managed transport; mechanisms for supporting interactivity and the personalization of IPTV services; and ability to deliver the service over multiple types of access networks. In summary, the IMS-based IPTV solution brings interactivity, personalization, and mobile convergence to the TV service. Figure 4 gives an overview of the functional blocks of the IPTV architecture, including the IMS control layer as an enabler of the Full Service Broadband architecture. The interfaces between the IMS layer and the broadband network are primarily for controlling session QoS and policies. Standardization The DSL Forum TR-101 and ETSI TISPAN Release 1 specifications define interfaces for QoS and resource control, ensuring adequate QoS, traffic separation, and resource allocation. The Full Service Broadband IPTV architecture is based on standard IPTV protocols, as specified by DVB (Digital Video Broadcasting Project), and complemented with standards, such as IMS and DLNA (Digital Living Network Alliance), to achieve an endto-end IPTV architecture. The Open IPTV Forum was launched in March 2007 to harmonize the IPTV standard by defining an interoperable, end-to-end specification for the delivery of IPTV services. The forum, will emphasize the development of open standards that help to streamline and accelerate the deployment of IPTV technologies. 7 Conclusion As an operator-provided service over broadband access networks, IPTV has been available for some time but only in small networks or parts of networks. Today s broadband networks can support the introduction of triple-play services, but upgrading them to support mass deployment of IPTV service will be a major challenge because the new media experience that IPTV service provides is not restricted to passively viewing broadcasted content. On the contrary, it presents end users with interactive and personalized media. IPTV service thus puts unique demands on every node in the broadband network. For instance, to deliver unicast and multicast video services, the network must provide high bandwidth, IP control features, and scalability. It must also provide the same level of flexibility and reliability that are associated with telecom carriers services. To optimize the customer experience and enable cost-effective delivery of linear broadcast TV, the service makes use of IP and Ethernet multicast throughout the network. To support the evolving IPTV service, the broadband network must be able to scale in several dimensions, the most important of which are service penetration, network capacity, and service mix. By adding an IMS control layer to the broadband network infrastructure, operators can accelerate the introduction of new services, efficiently combine the TV service with communication services, and offer the service over multiple access networks. In essence, the IPTV network infrastructure becomes part of the Full Service Broadband architecture. REFERENCES 1. Cagenius, T., Fasbender, A., Hjelm, J., Ivars, I. and Selberg, N.: Evolving the TV experience: Anytime, anywhere, any device. Ericsson Review, Vol. 83(2006)3, pp Baker, J., Cagenius, T., Goodwin, C., Hansson, M. and Hatas, M.: Deep-fiber broadband access networks. Ericsson Review, Vol. 84(2007)1, pp DSL Forum TR Migration to Ethernet-based DSL Aggregation, April ITU-T Gigabit-capable Passive Optical Network standards G Green, H., Monette, S., Olsson, J., Saltsidis, P. and Takács, A.: Carrier Ethernet: The native approach. Ericsson Review, Vol. 84(2007)3, pp White paper on Full Service Broadband: _Full_Service_Broadband_Arch_A.pdf 7. Cedervall, M., Horn, U., Hu, Y., Ivars, I. and Näsström, T.: Open IPTV Forum Toward an open IPTV standard. Ericsson Review, Vol. 84(2007)3, pp Ericsson Review No. 3,