Changchun University of Science and Technology Changchun University of Science and Technology Changchun University of Science and Technology This document aims to study and implement Multipath Transmission Control Protocol (MPTCP) and Multipath QUIC (MPQUIC) using application layer traffic optimization (ALTO) in software defined network (SDN). In a software-defined network, ALTO server collects network cost indicators (including link delay, number of paths, availability, network traffic, bandwidth and packet loss rate etc.), and the controller extracts MPTCP or MPQUIC packet header to allocate MPTCP or MPQUIC packet to suitable transmission path according to the network cost indicators by ALTO, which can reduce the probability of transmission path congestion and improving path utilization in a multipath transmission network.