@ARTICLE{SalahTNSM12, 
author={Salah, K. and Elbadawi, K. and Boutaba, R.}, 
journal={Network and Service Management, IEEE Transactions on}, 
title={Performance Modeling and Analysis of Network Firewalls}, 
year={2012}, 
month={march }, 
volume={9}, 
number={1}, 
pages={12 -21}, 
}