ZTE's High-Reliability IPTV System Solution

Since 2008, the IPTV business has grown rapidly both at home and abroad. In China, Shanghai Telecom and Jiangsu Telecom have deployed large-scale IPTV systems, and have both grown subscriber bases of over one million viewers. With the expansion of IPTV networks, the key to attracting subscribers and increasing operating revenue is to provide reliable and efficient IPTV services. In order to satisfy the high reliability needs of operators running IPTV, ZTE has developed a high-reliability solution, drawing on a wealth of experience in large-scale IPTV network commercialization for Shanghai Telecom and Jiangsu Telecom. This solution guarantees access to IPTV services, and quick recovery of normal IPTV services under all circumstances.

ZTE’s IPTV system employs a 3-layered network structure including a provincial center node, regional center nodes, and edge nodes. The provincial center node is responsible for operation, management, and dispatch of the whole IPTV system; the regional center nodes dispatch IPTV services within the regions and manage edge nodes; and the edge nodes provide IPTV services to subscribers according to the system dispatch.

Considering all abnormal cases that may occur during system operation, ZTE has rolled out a high-reliability IPTV system solution. First, the IPTV system provides backup for key parts and enables automatic switching in the event of failure. Second, the system adopts a distributed node architecture and dynamic dispatch mechanism to ensure service reliability at each node. Third, the system supports a remote disaster recovery mechanism using double provincial centers, so that when one provincial center fails, the remote can quickly take over. The system can be recovered without any loss of service.

Hot Backup for Key Parts

As the provincial center node is responsible for operation, management, and service dispatch for the whole IPTV system, its normal operation is important for ensuring reliable services. Key parts of the provincial center node include Call Detail Record (CDR), Database (DB), Portal, Content Distribution Network Manager (CDN-Manager), Control Processor (CP), and Master Electronic Program Guide (Master EPG). All these parts are hot backup-ed to ensure smooth service provision in the event of failure. In particular, the Master CP for user service handling is configured in hot backup mode; it monitors the status of other CPs and assigns tasks to them based on load conditions (see Figure 1). In this way, the system can handle a large number of concurrent user requests during large scale commercialization.

Furthermore, Livecast Server—as a key part of the IPTV system—also provides complete backup protection, with all functional boards configured in hot backup mode. Normally, key data is automatically synchronized between the master and salve boards.

Distributed Node Architecture and Dynamic Dispatch Mechanism

ZTE’s IPTV system adopts a distributed node architecture, in which a hierarchical relationship among all serving nodes (the provincial center node, regional center nodes, and edge nodes) is established. The provincial center node monitors other serving nodes in the system. Based on the observed data for equipment status and traffic load, the provincial center node can dispatch resources dynamically to meet user requests. This can avoid service interruption caused by equipment failure or a highly-unbalanced traffic load, and can effectively enhance system stability and reliability.

Remote Disaster Recovery Mechanism Based on Double Provincial Centers

Under the dynamic dispatch of the provincial center node, both regional center nodes and edge nodes work with and depend on each other to deliver reliable IPTV services. Although the provincial center node—the core of the IPTV system—provides hot backup for its key parts in order to ensure service reliability, its stand-alone operation (independent of other layers) could eventually lead to system collapse in the event of disasters such as earthquake, fire, or flood.

To eliminate the risks associated with independent operation at the provincial center, ZTE’s IPTV system supports double-center networking, and provides hot backup for system operation data and management links connected to subordinate nodes. In general, a backup provincial center is built at a remote location. If the serving provincial center is rendered inoperable by disaster, the backup provincial center will rapidly assume responsibility for operation, management, and node resources of the fault center. Normal IPTV services will continue to be delivered.

Typical Self-Healing Process

In case of disaster or equipment failure, ZTE’s IPTV system can implement self-healing through a reliability mechanism. Described below are some typical cases.

In the case of media server failure

Live broadcast is a basic IPTV service, and live streams are generally introduced by a live broadcast server. After the conversion, the live broadcast server sends or multicasts the coded streams to subscribers. A live broadcast is completed in this way. In ZTE’s IPTV system, all functional boards of the live broadcast server are configured in hot backup mode. If any blade of the server fails, the backup blade will automatically take over, and quickly resume multicasting while alarms are sent to the network management center.

In the case of EPG server failure

When a user logs in, an EPG server based on the user’s IP address is generally chosen by the IPTV system in order to offer services. In practical operation, however, the user might not access IPTV services after the login because of EPG server failure. Because ZTE’s IPTV system adopts a distributed node architecture and dynamic dispatch mechanism, it can monitor the status of all servers and judge whether the selected EPG server is operating normally when a user logs in. When the EPG server is found faulty, the system dispatches another EPG that runs smoothly and has a dependent relationship with the faulty EPG to offer IPTV services.

In the case of provincial center failure

With the double-center structure, the system administrator can initiate the takeover process through the backup provincial center in order to enable system self-healing when the serving provincial center fails or is destroyed by disaster. The switching operations performed by the system administrator involve:

■    Switching operation data: the backup provincial center takes over operation and management of the faulty provincial center.

■    Switching functional nodes: all regional center nodes and edge nodes connected to the faulty provincial center are switched to and managed by the CDN-Manager of the backup provincial center.

Through the above operations, all users, regional center nodes, and edge nodes are switched into the backup provincial center, and the system can recover normal operation.

Conclusion

Responding to the trend of large-scale IPTV commercialization, ZTE has drawn on its rich experience in IPTV technology research and network commercialization to launch a high-reliability IPTV system solution. This solution adopts an advanced design concept and takes into full consideration equipment, node, and system reliability. It not only paves the way for large-scale deployment of IPTV business, but also helps ZTE maintain a leading poison in the industry.