This paper presents the design of a next generation network traffic monitoring and analysis system, called NG-MON (Next Generation MONitoring), for high-speed networks such as 10 Gbps and above. Packet capturing and analysis on such high-speed networks is very difficult using traditional approaches. Using distributed, pipelining and parallel processing techniques, we have designed a flexible and scalable monitoring and analysis system, which can run on off-the-shelf, cost-effective computers. The monitoring and analysis task in NG-MON is divided into five phases; packet capture, flow generation, flow store, traffic analysis, and presentation. Each phase can be executed on separate computer systems and cooperates with adjacent phases using pipeline processing. Each phase can be composed of a cluster of computers wherever the system load of the phase is higher than the performance of a single computer system. We have defined efficient communication methods and message formats between phases. Numerical analysis results of our design for 10 Gbps networks are also provided.