I implemented a new algorithm in ns, (like RED, for flow control) but when execute double m=link_->bandwidth(); it gives the error message of Segmentation fault (core dumped). I am sure everything defined well(:TclClass, ***:Queue, etc.) How to solve it? Thanks, Huike (Victor) Li Department of EEE University of Melbourne Victoria 3051 Australia Tel: +61 3 9344 9201 Fax: +61 3 9344 9188