Abstract: Based on testbed network experimental research， investigated five congestion control protocols in Linux kernel， such as Cubic， Htcp， Hybla， Westwood and Veno in different network environments. The link utilization， RTT fairness and TCP friendliness were compared. Then analyzed the experiment results， and evaluated the advantage and disadvantage of these algorithms. On this base， considering Cubic and Veno， a new environmental adaptive congestion control protocol， named CVTCP has been designed and tested. The experimental results showed， the link utilization rate was fairly high without obvious reducing RTT fairness and TCP friendliness， the CVTCP has good environmental adaptability.

Key words: network testbed, congestion control protocol, performance evaluation, link utilization rate, RTT fairness, TCP friendliness