0　引言水电厂计算机监控系统(CCS)往往采用局域网,如能将局域网延伸到数百千米以外的城区,则电厂运行人员可通过网络对数百千米之外的机组进行监视与控制,从而使大部分员工生活、工作在城区,这对于水电厂减人增效具有重要意义。局域网网络延伸实质上是实现同构网络互联[1,2]。 0 Introduction Computer monitoring systems (CCSs) in hydropower plants often use local area networks. If they can extend LANs to urban areas hundreds of kilometers away, plant operators can monitor and control hundreds of kilometers of units over the network. So that most employees live and work in urban areas, which is of great significance for reducing the efficiency of hydropower plants. LAN extension is essentially the realization of homogeneous network interconnection [1,2].