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城域网络是介于接入网络和骨干网络之间的技术,DWDM技术和OXC/OADM在骨干网的应用极大的提高了骨干网络的信息容量,而接入网络经过这几年的改造,大量的宽带接入技术如:xDSL、100/1000M以太网、HFC、LMDS的使用能够提供足够的带宽,满足用户不断发展的多业务接入需要。但是在城域网络一直没有一种合适的技术能够有效的融合接入网络和骨干网络。目前城域网络的主要技术有SDH/ATM 和以太网技术。它们各有优缺点:SDH和ATM技术复杂、价格昂贵、在传输分组业务时对线路资源利用效率不高;以太网技术在局域网中得到了广泛应用,走的是低价、简单的技术路线,但是缺乏有效的QoS、网络恢复与保护及网管机制,不能满足城域网的可靠性和扩展性方面的要求。人们于是很自然地想到了在城域范围内构建新的环形拓扑结构,通过传输类似以太网结构的分组来提供各种增强型业务,在不降低网络性能和可靠性的前提下提供更加经济的MAN/WAN解决方案。弹性分组环(Resilient Packet Ring,RPR)技术即是在这样的背景下提出的。
Metropolitan area network is between the access network and the backbone network technology, DWDM technology and OXC / OADM in the backbone network greatly improves the information capacity of the backbone network, and access network after several years of transformation, The use of a large number of broadband access technologies such as xDSL, 100 / 1000M Ethernet, HFC and LMDS can provide enough bandwidth to meet the evolving needs of users for multi-service access. However, there is no suitable technology in metropolitan area network to effectively integrate access network and backbone network. At present the main metropolitan area network technology has SDH / ATM and Ethernet technology. Each of them has its own advantages and disadvantages: SDH and ATM are complicated and expensive, and their utilization of line resources is not efficient when transmitting packet services. Ethernet technology has been widely used in local area networks, taking the low-cost and simple technical route, But the lack of effective QoS, network recovery and protection and network management mechanisms can not meet the requirements of MAN reliability and scalability. It is then natural for people to think of building a new ring topology within the metropolitan area, providing a variety of enhanced services by transporting packets like Ethernet fabrics, and providing a more cost-effective solution without degrading network performance and reliability MAN / WAN solution. Resilient Packet Ring (RPR) technology is proposed in this context.