Active Networking provides a programmable network environment. To realize this idea, IEEE forms a working group to define a router programming interface, called P1520. This thesis implements P1520 L- interface based on Linux OS. We use Linux CBQ queuing system as the core of P1520 and extend it to allow dynamic module loading. Based on our developed P1520 L- interface, we designed a DiffServ module for both Diffserv border node and interior node. Experiment results show that our implementation performs well and can provide excellent active networking functions.