Ring system enables flexible expandability with excellent fault recovery functionality

NEC Corporation has succeeded in the development of packet transport network technologies for next generation networks (NGN)), which enable construction of 10Gbps-class broadband metropolitan area networks* that deliver carrier-grade reliability, fast recovery, and flexible network expandability.

The newly developed technologies consist of resilient packet ring2 (RPR) card redundancy technology that enables swift fault recovery and highly reliable network systems, and inter-link redundancy technology that enables expansion of highly reliable networks by connecting two ring-topology networks with multiple links.

Although metropolitan area networks are constructed with fault-tolerant multiple-ring topology, they have been designed for legacy telephone services. NEC’s new technologies, which enable highly reliable network systems and construction of flexible and scalable regional packet-optimized ring network infrastructure, are a significant step toward the realization of NGNs that provide various IP-based services, including broadband VoD, HDTV, and FMC3. Once installed, the technologies facilitate easy expansion of networks by operators, in accordance with their needs, thereby enabling optimization of hardware and operational resource allocation and a reduction in initial network construction costs.

Features of the new technologies include:
1. RPR card redundancy technology and optimization of the packet forwarding mechanism between cards allow two cards to operate simultaneously, so that when one card fails, the other card takes over RPR card control, achieving network service continuity. In addition to guaranteeing highly reliable network equipment, the RPR card redundancy technology realizes a maximum client add/drop rate of up to 20Gbps during normal operation.

2. Inter-link redundancy technology, which allows multiple links between two ring-topology networks, provides rapid fault recovery in less than 50ms, protecting networks from fatal service interruption caused by trouble on inter-link connections. This new technology ensures highly reliable expansion of multi-ring networks.

Network carriers have started to introduce multi-service transport systems employing RPR technology for packet ring networks. The RPR technology realizes a high level of reliability in single ring-topology applications by employing a simple failure recovery procedure. This procedure consists of packets being switched to either one of the two rings for transmission, where they are directed clockwise or anticlockwise to prevent failure. Such a system achieves fault recovery performance superior to Ethernet technology. However, as the protocols for reliable inter-link connection are not defined in the RPR, or other packet layer standards, it has been difficult to realize carrier-class reliability on networks consisting of multiple-packet RPR rings.

The two new technologies developed by NEC respond to strong market demand to enable network expansion that offers reliability equivalent to that of single ring-topology networks, and to enhance reliability of redundant duplicated cards for increased service capacity. In the future, the technologies are expected to achieve highly reliable packet transport networks, and strengthen NEC’s existing product portfolio of multi-service transport platforms (transport systems), which already accommodate a variety of packet-based broadband services in metropolitan networks.

NEC will continue to develop the technologies toward their early commercialization on a wide variety of system platforms. This project has partly been supported by the Ministry of Internal Affairs and Communications (MIC).

Notes
1.A metropolitan network is a network that provides connections among backbone networks and various access networks, which aggregate access lines from the end user.
2.Resilient packet ring (RPR) is a technology standardized in IEEE802.17. The RPR provides prioritized grades of service, from 3-5 classes, fast protection, restoration, efficient bandwidth usage by statistical packet multiplexing, and fair use of packet transmission rates among RPR nodes.
3.Abbreviation of fixed mobile convergence. FMC refers to a technology that closely links fixed phone lines and mobile communications, or a service that uses the technology.