Tang Ke Wang Min

（Network Division of ZTE Corporation， Nanjing 210012， China）

AbstractThe complexity of terminal equipment and diversity of services in a home network have more requirements for terminal management.The Digital Subscriber Line（DSL）forum has defined a special protocol for terminal management.This is the TRO69.The TRO69 uses the client/server model of Hypertext Transfer Protocol（HTTP）for architecture design and fully use the mature Web technologies for reference.Therefore，it supports simple protocol fulfillment and has good scalability.Moreover，the management parameters the TRO69 defines are totally aimed at the characteristics of terminal services.A TRO69-based network management system helps greatly simplify the configuration and management work at the user side，and makes the equipment easier to use and manage.Accordingly，the TRO69 may help a home network deploy equipment and launch services quickly.

B roadband access for home is more popular，and Voice over IP（VoIP）and IPTVservices are growing quickly.For this reason increasing number of IPterminal devices are being introduced to the home network，and the traditional Simple Network Management Protocol（SNMP）manages the numerous terminal devices more difficultly.

Operators have to consider how to implement the effective management of home network equipment.

The Customer Premises Equipment Wide Area Network Management Protocol（CWMP）is a terminal-oriented network management protocol defined by the Digital Subscriber Line（DSL）forum with the file number of TRO69.It defines brand new network management architecture，including the management model，interactive interfaces，and basic management parameters.

1 Introduction of TR069

1.1 The Characteristics of TR069

In the network model defined by TRO69，the management server is called Auto Configuration Server（ACS），which is responsible for the management of Customer Premise Equipment（CPE）.The interface between ACSand CPEis called the south interface.The interface between ACSand other network management systems，service management systems and billing systems is called the north interface.The TRO69 defines the standards for the south interface[1].

The TRO69 is an application-layer protocol above IP.Therefore，it has wide application with no restrictions on access modes.All the CPEbased on Asymmetric Digital Subscriber Line（ADSL），Ethernet，and Passive Optical Network（PON）can use this protocol.The TRO69-based network management architecture is shown in Figure 1.

The TRO69 fully absorbs the strengths of Web technologies.Transmission is based on the Transport Control Protocol（TCP）.The interaction between ACSand CPEis based on Hypertext TransferProtocol（HTTP）with ACSas the HTTP server and CPEas the client.Remote Procedure Call（RPC）based on the Extensible Markup Language（XML）fulfills the practical management operation.The current version of TRO69 defines nine basic and six optional RPCs for CPE，and two basic and two optional RPCs for ACS.Figure 2 shows the layered structure of TRO69.Using a number of mature Web technologies，TRO69 is easy to be fulfilled.This reduces the difficulty in development and deployment of terminal products.

▲Figure 1. TR069-based network management architecture.

▲Figure 2. The TR069 layers.

▲Figure 3. Protocol interaction of TR069.

In the interaction process defined by TRO69，all the management interactions are initiated by CPE，that is，CPE"requests"ACSto conduct management，in order to adapt to numerous terminals and unfixed addresses（as shown in Figure 3）.When ACSwants to initiate the CPEmanagement，TRO69 defines a reverse trigger mechanism as the following.

·CPEfirst establishes and maintains an HTTPport for detection，and the message about this port is sent to the ACSat the time of initial connection of CPE；

·ACSwill establish a TCP connection to this port and send an empty POSTmessage if it wants to manage the CPE；

·CPEwill initiate a forward HTTP/HTTPSconnection to request the management of ACSonce it receives the message.

1.2 Network Management Functions Based on TR069

The network management functions based on TRO69 include:

（1）Configuration Management ACSinitiates the configuration management defined by TRO69，and Get/SetParamerterValue RPC implements the comparison and configuration of CPE parameters.The ACSthat implements configuration management strategy and the CPEthat actively requests management simplify equipment configuration.

（2）Version Management

The TRO69 allows CPEto take the initiative in requesting version/firmware upgrade，and ACSto conduct version upgrade coercively as well.The ACS makes decision of version upgrade for both upgrade models.This function may not only fulfill the traditional version upgrade，but also works with the configuration function.Together these functions implement the control of dynamic download of services，which offers deployment means of value-added services for operators.

（3）Performance Monitoring and Control

The ACSmay use GetPramerterVal RPC to inquiry real-time equipment state.Moreover，it uses log files obtained by upload to analyze the history states of CPE.

（4）Diagnosis

The TRO69 doesn't define special RPC for diagnosis.It uses Set/GetParamterVal RPC to fulfillthe diagnosis function.Using SETto setting diagnosis parameters triggers a diagnosis process，and the diagnosis results are read by operating GET.

（5）Warning

The CPEtakes the initiative in sending event reports to implement real-time warning.

1.3 Other Standards of TR069 Protocol Family

With TR-O69 and other protocols，the TRO69 is a complete protocol family of network management.Its matching protocols TR-O98 and TR-1O4 define management parameters of data services for CPEand management parameters of VoIPservices respectively.The WT-135 protocol defines management parameters of the set-top box and TR-111 defines mechanism of deploying TRO69 network management to internal home devices.The WT-121 collects protocolmodifications various vendors have made during fulfillment and deployment of TRO69.

2 Applications of TR069 in Home Networks

Atriple-play home network includes the home gateway，VoIPterminals，and the Set-top Box（STB），as shown in Figure 4.

The home gateway allows ADSL access and uses four Permanent Virtual Connections（PVCs）to offer voice，data，and IPTVservices respectively.In a home network，the analog phone line，Ethernet and Wireless Local Area Network（WLAN）are used to connect POTSes，IPtelephones，PCs，and IP STBs respectively.As the core of a home network，the gateway is responsible for providing addresses management，Network Address Translation（NAT），data forwarding，QoS，security，and other services.

Numerous devices are involved in thenetworking，therefore，the equipment configuration and management is troublesome for the operators as well as for the users.Fortunately，the TRO69 network management system greatly simplifies the maintenance/management work.

▲Figure 4. Structure of a home network.

The TRO69 is IP-based network management protocol.Therefore，the IP-layer authentication and access of users is a must at first if a home network should be a manageable element of the network management system，based on which registration of the network elements on the network management system willbe then fulfilled.There are three significant steps in the available terminal deployment process.

（1）Initial Equipment Configuration

Before a home device is given to a user，the operator needs to pretreat it and configure some basic parameters for access the home network.Since the home gateway is a key device，it requires preparations and parameter configuration.The parameters include access information at the WAN side and access information of ACS.However，it is unnecessary to pre-configure devices at the LAN side such as STB.

（2）Initialization of Home Network

The home gateway is the port of a home network for connection with Internet，and the initialization of a home network begins at the gateway.The gateway，by pre-configuring its internal basic parameters（such as PVC，user name，and password），first establishes an Internet connection and gets the basic network parameters（such as IP addresses and domain name）.With regard to networking，this is to establish an Internet connection on the PVC used for data services.Then the gateway uses the pre-stored URL message to access ACS.The ACSuses TRO69 to get user information from the gateway，the north interface to get service parameters of a user from service system，and the TRO69 to fulfill configuration of the gateway（setting parameters for IPTVand VoIP connection，routing messages，VoIP parameters，QoSstrategy，and security strategy）.Based on gateway initialization，devices in a home network begin to be initialized.In order for ACSto make unified management of home devices，it is necessary for the gateway and home devices to use the interaction mechanism defined by TR-111.The gateway uses Dynamic Host Configure Protocol（DHCP）to notify home devices of the ACSaddress，and the home devices use the datagram protocol and Simple Traversal of UDPover NAT（STUN）mechanism to establish a port mapping that interactive with ACS.In this way，ACSmakes the configuration of home devices through the gateway（setting encoding/decoding features of the STBand EPG address[2]）.With the process mentioned，the initialization of a home network is completed and various services the user applied can be used.

（3）Routine Management

In the network shown in Figure 4，ACS may directly manage the home gateway and the devices below the gateway.The parameter configuration，equipment diagnosis，warning，and version upgrade can all be handled by TRO69.This realizes the unified management of a home network.

3 Conclusions

The management of home network devices is becoming increasingly complex with the large-scale launching of triple-play services.It is a popular problem for operators to meet users'demand of"zero configuration"and simplify equipment maintenance and management.The deployment of TRO69 helps reduce network maintenance cost greatly.Therefore，operators have deployed the TRO69 based terminal management system one by one since the DSLforum released the protocol in May 2OO4.As the case stands，TR-O69 is still in improvement.The service parameter model needs to support more terminal services and features，and the modification and detailing of several processes are necessary for protocol inter-working.