Recently, IP - VPN is proposed as a way satisfying large company´s inter-connect requirement because of the prevalence of Internet. But there are some problems to be solved, especially security and QoS. In this paper, one way of network-based VPN QoS is proposed based on analysis of some available QoS algorithms. For IP - VPN, now there are several mechanisms： VLL, VPRN, VPLS and VPDN. This paper places emphasis on VPRN and VPLS. Two kinds of VPRN: BGP/MPLS and VR are discussed and compared with each other. And besides, VLAN, one way of VPLS, is introduced.