Multipath TCP (MPTCP) has gained great attention by the researchers and network application developers due to its features providing better bandwidth utilization and higher reliability recently. Utilizing MPTCP in the datacenters provides performance gain to the applications. If the underlying network has Software Defined Networking (SDN) architecture, the routing of the MPTCP subflows can be specialized. In this paper, we propose an architecture utilizing MPTCP in an SDN-based ISP in order to serve guaranteed services to the video streaming clients. The number of MPTCP subflows and routes of the subflows are determined based on a mixed integer linear programming model. The simulation results show that the proposed architecture provides increase in received throughput and decrease in duration of outages when it is compared to a general-purposed throughput maximization approach.