The advantages of "VPN over Internet" are cost-effectiveness and flexibility However, the disadvantages are the lack of sufficient QoS mechanism and transmission capacity for high bandwidth service. Given this increasing demand for high bandwidth Internet and QoS assurances in "PN over Internet", IP/GMPLS based control plane combined with a high bandwidth capacity of DWDM optical network is seen as a very favorable approach for the realization of future "OVPN over IP/GMPLS over DWDM" Within OVPN for providing QoS guaranteed multimedia service over the NGOI(Next Generation Optical Internet) based on the "IP/GMPLS over DWDM" concept, differentiated QoS framework is one of the key issues to implement OVPN over DWDM-based NGOI. Keeping in mind that IETF(Internet Engineering Task Force) and ITU-T(International Telecommunication Union) are standardizing IP/GMPLS over DWDM protocol framework as a solution for the NGOI, in this paper, we suggest Optical-LSP establishment and QoS maintenance scheme based on DOQS(Differentiated Optical QoS Service) classes, which are the key issue of DOQS protocol framework for assuring end-to-end QoS in "OVPN over IP/GMPLS over DWDM".