Today?s traffic accounting systems are based on the assumption that one IP address is associated with one user. But this assumption cannot be applied to multiuser systems, where an IP address can be shared by multiple users at the same time. In this case an IP address can not be uniquely mapped to a single user. In order to provide finer granularity traffic accounting information we suggest a user based traffic accounting concept which can collect and analyze network resource usage metrics on the basis of users. This is an extension to current traffic accounting methods. With this not only IP address attribute but also user attribute are used as aggregating index in collecting the network resource usage information. This paper introduces user based traffic accounting technology and discusses several different mechanisms for user based traffic accounting. The implementation of a user based traffic accounting prototype system with Agent mechanism is introduced. Performance test results indicate that, if carefully designed the user based traffic accounting system affects performance of the system in which it resides only slightly.