Wa Runbin

（Network Division of ZTE Corporation， Shanghai 201203， China）

AbstractThe rapidly developing multi-play services，with new features as multimedia and interaction，create a difficult task for the present broadband networks to carry them effectively.Complete new technologies must be adopted，as the bearer became a constriction factor of the further development of multi-play services.These new technologies will make the bearer effective to be able to operate，manage and add value to multi-play services over the broadband networks.Among all new technologies，the high-bandwidth network technologies enrich network resources；QoS technologies guarantee QoS by implementing differentiated services；powerful multicast technologies effectively control and guarantee the deployment of multimedia services；security guarantee technologies provide a high-quality and perfect security operation system for multi-play services，and high-reliability technologies provide a reliable and uninterrupted operation system for the broadband network to carry multi-play services.

T he Internet is designed to provide a computer communication network for simple and effective data transfer via universal and simple IPpacket protocols to maximally meet people's requirement for information exchange.The widespread usage of Internet gives rise to the emergence of a great variety of new applications and services.Each application and service runs separately and competes for transfer resources of the IPnetwork.Through decades of development and evolution，it is a new development chance for the Internet to carry voice，video and media services other than data.However，these services occupy relatively high network bandwidth.Consequently，a broadband network must be adopted to carry them.Therefore，telecom operators，especially fixed network operators，invest huge amounts of capital to construct data networks and broadband access networks to drive the rapid growth of Internet-based new services such as E-business，Instant Messaging（IM）and search engine.

The numerous Internet services are not controlled by telecom operators.What the telecom operators offer to users are merely the Internet access services（also called broadband access services），by that reason they can only charge users for network access.As many parts of the service transfer are not managed and controlled，the problems of service bandwidth，Quality of Service（QoS）and security have not yet solved.Consequently，these services are not successfully deployed and operators fail to get satisfactory returns on their investments.

Moreover，as the current traditional voice service is affected by its substitute services such as mobile phone，Voice over IP（VoIP），and Short Message Service（SMS），the voice traffic and its provided income tends to decrease year after year.Therefore，all telecom operators are facing with the pressure of transition from conventional infrastructure network operators to modern integrated information service providers.

As mature and diversified technologies and devices such as Ethernet，Wireless Local Area Network（WLAN）and Power Line Communications（PLC）are adopted in a home network，the home network has been completely turned into a local area broadband network that can better carry multi-play services[1].The emphasis of how to deploy multi-play services in the entire network has shifted how to effectively carry multi-play services over the broadband network based on the construction of the home network.Therefore，major concerns for telecom operators are how to make the bearer effective to be able to operate，manage and value add multi-play services over the broadband network based on the construction of the home network.In addition，to provide users with new，diversified，intelligent，cooperative，mobile，and multi-media services，and drive the network transition through theservice transition.

1 Development Trends and Basic Features of Multi-play Services

Multi-play services in China undergo different phases of development.Through several years of development，the early broadband multi-play services based on PC terminals began to take shape such as China VNET，network TV，online games，IM，new vision，and global E-eye.These broadband services effectively boost the rapid development of broadband networks in China.

However，these services have the problems as the technical barriers based on PC services and a limited user group.That means，users who access these services must have computers and basic computer knowledge.This keeps users always confined to a computer user group and consequently leads to a limited user development potential.

In recent two years，the multi-play services based on non-PC terminals have been introduced such as IPTV，network interactive games，Personal Video Recorder（PVR），Time Shift TV（TSTV），music，and interactive advertising[2].These new services avoid the previous problems such as the technical barriers based on PCservices and a limited user group，and are oriented to a more widely potential user group，that is，an enormous TVuser group.Therefore，it is an inevitable trend for broadband multi-play services to evolve into the services based on non-PC terminals.

The following development trends are observed with the continuous growth of broadband multi-play services.

·Dominated by multimedia and interactive services.

·Diversified service combinations and packages for binding sale.

·IP-based services（convergence of video，voice，and data）.

·Personalized Point-to-point（P2P）communication applications.

·Sufficient dynamic bandwidth resource on demand.

Therefore，broadband multi-play services will ultimately feature multimedia，interactive，P2Pand IP-based full services able to achieve a complete convergence of voice，video and，data services.The development trends and features of broadband multi-play services will make the current networks transit from the extensive operation mode to the service-centered operation mode，and gradually evolve into the next-generation networks to continually meet the requirement of new services.

2 Technologies Necessary for Carrying Multi-play Services

In view of the development trends and features of broadband multi-play services，the broadband network must be constructed to support a variety of the existing broadband multi-play services and the future constantly-emerged new ones to achieve integrated full-services bearing capability.Hence，in order to carry multi-play services or to carry video，data and voice services on a uniform basis，the broadband network must provide open architecture that oriented to full services.In addition，it must provide various technologies involving high-bandwidth broadband access，powerful multicast control，service management，high QoS guarantee，high security guarantee，and high reliability.These technologies aim to effectively guarantee the transfer of multi-play services from the service network to the home network via broadband network，and provide users with multi-play services.As many technologies such as QoSand multicast are also implemented in the home network，the home network can well coordinate with the broadband network to enable the end-to-end QoS guarantee.

2.1 High Bandwidth Network Technologies

Based on the analysis of broadband multi-play services as well as the knowledge about development trends of the next-generation network，the following development trends of the next-generation broadband bearer network are observed.

（1）Flat Network Structure with Wide Area Coverage

The next-generation broadband bearer network can provide a flat network structure，keep the access modules as close as possible to users，guarantee the bandwidth，and adopt multiple modes for extensive access to every users.

（2）Great Increase in Bandwidth Requirement

From the perspective of the current service development，the gradually emerged high-bandwidth services have raised an urgent requirement for increase in bit rate.In the near future，the bandwidth required per user willrange from 1OMbps to 3OMbps.

（3）Diversified Access Modes To meet the requirement for high bandwidth per user diversified access modes are adopted.For example，the Digital Subscriber Line（DSL）has evolved from the original access modes such as Symmetric High-speed Digital Subscriber Line（SHDSL）.The Asynchronous Digital Subscriber Line（ADSL）has evolved to the current access modes that provide higher bandwidth such as Very-high-data-rate Digital Subscriber Line（VDSL）and ADSL2/2+.

（4）Scale Use of Fiber

As a very high bandwidth can be provided，the scale use of fiber on the access layer is an inevitable trend.This will be a gradual process，and the Ethernet Passive Optical Network/Gigabit Passive Optical Network（EPON/GPON）will be a hot technology to achieve the optical access layer.

（5）Fixed-and-wireless Convergence

The wireless access as an easy one can be applied in various scenarios and offer fast broadband services to users.The WiMAXwill become a hot technology for wireless access.

（6）Gradual Implementation of Full Services Access

The convergence of access to the services based on all network technologies is gradually implemented.The dedicated line，Virtual Private Network（VPN），video streams，VoIP，data and other services are required to be accessed via a unified platform.Therefore，the next-generation broadband bearer network can better carry all services and guarantee the QoS.

（7）Improvement of Management and Control Capability

The next-generation broadband bearer network can provide the QoSguarantee and security for various applications including VoIP，3G，and VPN.It supports accurate management of bandwidth resources，provides the multicast and switching capability necessary for IPTVservices，delivers a series of security guarantee functions including broadband user port location.In addition，it coordinates with the backbone network to implement the admission control mechanism for user service application based on the usage of network resources.

（8）Convergence with the Next-generation Network

The service，control，and bearer planes can meet the requirement of the next-generation network.

Therefore，driven by broadband multi-play services，the broadband network will adopt various technologies.These technologies for gradualmigration to the next-generation network，such as advanced DSL access technology，higher bandwidth EPON/GPONoptical access technology，and the WiMAX wireless access technology that is more flexible.

2.2 QoS Guarantee Technologies

The technologies to guarantee QoSare designed to differentiate services and aiming at offering different QoSto suit to the specific requirements of the application.

The International Telecommunication Union-Telecommunication Standardization Sector（ITU-T）specifies three planes in the Y.1291 standard for the IPQoSnetwork framework.

These planes，control plane，data plane and management plane are for the end-to-end QoSto have effective capability in an IPnetwork.

The control plane contains the mechanisms related to the transfer path of service flows.These mechanisms involve access control，QoSrouting and resource reservation.The data plane contains the mechanisms related to the processing of user data flows.These mechanisms include buffer management，congestion avoidance，message labelling，queuing and scheduling，flow classification，flow policies，and traffic shaping.The management plane contains the mechanisms related to the operation and management.These mechanisms include Service Level Agreement（SLA），service recovery，as well as metering and policy management.

Based on the IPQoSnetwork framework，the Internet Engineering Task Force（IETF）recommends numerous service models and mechanisms to meet the QoSrequirement.The most commonly used models are best effort service model，Integrated Services（IntServ），Differentiated Services（DiffServ），Multi Protocol Label Switching（MPLS），and Traffic Engineering（TE）.

Implementing the QoSmechanisms in the current operable telecom-class IP broadband network，two methods are available to provide QoSfor the core or backbone network:adopting TEor deploying DiffServ.In order to deploy and enable the QoSin a simple，fast and effective manner on the convergence/access layer，the idea of DiffServ is usually adopted，that is，flow classification and priority-based queuing are performed.

As the devices at the convergence/access layer are characterized by diversity and complexity，the deployment of DiffServ should be simple，effective and practical[3].Hence，with reference to the IPQoSnetwork framework，the devices on the convergence/access layer should above all consider implementing the following QoS functions:buffer management；congestion avoidance；message labelling；queuing and scheduling；flow classification；flow policies and traffic shaping for the data plane；as well as metering and policy management for the management plane.

The ultimate aim of implementing QoS in the broadband network is to have effective end-to-end QoSguarantee.

2.3 Multicast Technologies

Compared with broadcast and unicast，multicast is a point-to-multipoint or multipoint-to-multipoint transmission.Its basic idea is that multiple receivers can simultaneously receive a copy of the same data sent by the same source or group of sources.

The current multicast technologies involve:

（1）Multicast Management Protocols The Internet Group Management Protocol（IGMP）has 3 protocol standards:IGMPv1，IGMPv2[4]and IGMPv3.

（2）Multicast Routing Protocols Multicast routing protocols gall into three categories:dense-mode protocols such as Distance Vector Multicast Routing Protocol（DVMRP）and Protocol Independent Multicast-dense Mode（PIM-DM）；sparse-mode protocols such as Protocol Independent Multicast-sparse Mode（PIM-SM）and Core Based Tree（CBT）；and link status protocols such as Multicast Extension to Open Shortest Path First（MOSPF）.

（3）IGMPProxy

Under certain specified network topologies，multicast distribution can be made simply by learning the multicast member to forward the multicast messages based on the register information without running the IGMP protocol.This technology is called IGMP proxy.

（4）IGMPSnooping

The IGMPprotocol operates on the network layer while the IGMPsnooping runs on the link layer.When a device receives IGMPpackets transmitted between the host and the router，the IGMPsnooping analyzes the information carried by the IGMPpackets，creates and maintains a Media Access Control（MAC）multicast address list.After this，the multicast packets sent by routers will be forwarded in accordance with the MAC multicast address list.

The extensively deployed broadband IPTVservices generally fall into two types:live broadcasting service and on demand service.The live broadcasting service needs to use multicast technologies.Compared with the video service network where transmission is not controlled，the broadband access network should be more operable while implementing the transport function.

To support IPTVand other value-added services，it is necessary for the network devices to provide powerful multicast control and switching capabilities.They must support basic functions such as IGMPsnooping，IGMPv1/v2，IGMPproxy and Multicast Virtual Local Area Network（MVLAN）.Besides，also support functions for carrying IPTVservice in an operable manner as Channel Access Control（CAC），Preview（PRV），Call Detail Record（CDR），and service management[5].

▲Figure 1. Broadband network carrying the triple-play service.

2.4 Security Guarantee Technologies

To securely carry high-quality multi-play services，the broadband network and devices must provide the following security technologies.

·Limit on the number learned on the port:limiting the number of MAC addresses learned on the port；

·Port separation:ensuring the separation between different ports in the same Layer 2 Virtual Local Area Network（VLAN）；

·Address binding:preventing unauthorized use of account number and falsification of network ID；

·Broadcast packet suppression:preventing from being attacked by the broadcast virus as Blast；

·Layer 2 frame filtering:filtering source and destination-based MAC addresses，loop packets，extra-long packets，and illegal Layer 2 frames；

·Port mirroring:setting the mirroring to allow the operator to monitor data flows on other ports；

·Controllable multicast:preventing illegal multicast channels，multicast groups，and multicast users.

·Access Control List（ACL）:filtering the information above the protocol layer to guarantee network security；

·Security log:recording the changes to the configuration made by the operator and providing a log file；

·Network management security:limiting the authority of each operator to prevent illegal or rule-breaking operation.

Therefore，with the aforesaid series of security measures，the broadband network and devices can act as a whole to effectively implement the high-quality and complete security guarantee mechanisms and ensure the secure and smooth deployment of a variety of services.

2.5 High-reliability Technologies

To enable a reliable and uninterrupted operation of multi-play services，the broadband network and devices must provide the following reliability related technologies.（1）Ring Network Protection

In networking applications，different technologies are used to provide reliability and high bandwidth for the broadband network to smoothly carry and deploy multi-play services.

These technologies are:the Ethernet ring protection technology；the Resilient Packet Ring（RPR）technology；the Multiple Service Transport Platform（MSTP）technology；and the Synchronous Digital Hierarchy（SDH）technology.

（2）Automatic Fault Recovery In the event of failure，the broadband network must be able to recover automatically within several ten milliseconds to maintain a reliable and uninterrupted running of alldifferent services.

3 Carrying Triple-play Service

The triple-play service is a sort of bundled service mode integrating voice，data and video services.It has two meanings:service bundle and service convergence.Most of telecom operators deliver the triple-play service in the service convergence mode，that is，providing the convergence of VoIP，broadband and IPTVservices over the IP network.The triple-play service has three important characteristics.Firstly，it brings a great number of IPdata flows into the broadband access network，with the peak bandwidth in each home network reaching 2OMbps to 3OMbps.Secondly，its data flows contain various service data that have different requirements for delay，jitter，packet loss rate，and redundancy.Finally，it has a nature of burst.Therefore，the triple-play service poses strict technical requirements for the broadband access network.To better support the triple-play service，the broadband network and devices must provide the following capabilities.

（1）Multi-services Access Capability

They must form a unified platform to carry multi-services providing the capability to simultaneously access the voice，data，and video services.

（2）High-bandwidth Capability They gradually adopt optical technologies such as EPON/GPON tooffer higher bandwidth.

（3）Powerful QoSGuarantee Capability

They must support flow classification and flow policies to enable triple-play service awareness and identification，and to ensure normalservice operation.

（4）Powerfuland Manageable Multicast Capability

They must provide powerfuland manageable multicast capability as well as multicast reproduction and distribution capabilities.

The broadband network carrying the triple-play service is shown in Figure 1.

As shown in Figure 1，the broadband network can simultaneously carry data，video，and voice flows.The video flow falls into Video on Demand（VOD）and BTVflow.The three service flows are connected to the Digital Subscriber Line Access Multiplexer（DSLAM）in the broadband access network via the modem in the home network.A different Permanent Virtual Circuit（PVC）or VLAN is used to separate the services and the Layer 2 Class of Service（CoS）priority is adopted to guarantee the QoSfor each service.Through multiple Fast Ethernet/Gigabit Ethernet（FE/GE）uplink interfaces，the three service flows are connected to the corresponding BRAS and SR.If the IPTVBTVservices are widely deployed，a special service transport network can be constructed to carry them.On the edge of the IP backbone network，devices such as Broadband Remote Access Server（BRAS）and Service Router（SR）label the three service flows with the corresponding Layer 3 priority.In addition，they use the VPN path technology to transmit them to the corresponding upper-layer service network.

4 Conclusions

The key to improving competitive edge and generating more profits for current telecom operators is to make the bearer effective to be able to operate，manage and value add multi-play services over the broadband network based on the construction of the home network.In addition，to provide users with new，diversified，intelligent，cooperative，mobile，and multi-media services，and drive the network transition through the service transition.