Deutsche Telekom Karlstad University Karlstad University City, University of London BT DCCP communications as defined in RFC 4340 are restricted to a single path per connection, yet multiple paths often exist between peers. The simultaneous use of available multiple paths for a DCCP session could improve resource usage within the network and, thus, improve user experience through higher throughput and improved resilience to network failures. Use cases for Multipath DCCP (MP-DCCP) are mobile devices (e.g., handsets, vehicles) and residential home gateways simultaneously connected to distinct networks as, e.g., a cellular and a Wireless Local Area (WLAN) network or a cellular and a fixed access network. Compared to existing multipath protocols such as MPTCP, MP-DCCP offers special support for latency-sensitive services with different requirements for reliability and in-order delivery. This document specifies a set of extensions to DCCP to support multipath operations. The protocol offers the same type of service to applications as DCCP and provides the components necessary to establish and use multiple DCCP flows across different paths simultaneously.