Research Of MPTCP Scheduling Policy With RTT Asymmetric Subpaths

MPTCP(MultiPath TCP)effectively utilizes multiple paths between terminal devices for data transmission,thereby improving transmission efficiency.However,for terminal devices,opening multiple communication interfaces undoubtedly increases energy consumption,especially mobile terminal devices and laptops are often limited by the available battery power.Therefore,to balance the transmission revenue and interface energy consumption,it is very important to adopt an effective scheduling policy to packet scheduling.Currently,Lowest-RTT-First-RP(Lowest-Round Trip Time-First with Retransmission Penalization)scheduling policy is used for packet scheduling by default in the MPTCP Linux kernel.In this paper,it is found that according to Lowest-RTT-First-RP scheduling policy,data can not be transmitted firstly through faster subflow when sub:flow RTT(Round Trip Time)difference is smaller than subflow congestion degree difference,and MPTCP slower subflow delays task which will become more prominent as the RTT difference increases.In order to solve the above two problems,this paper proposes an MPTCP scheduling policy EMS(Enhance MPTCP Scheduler)to improve the MPTCP default scheduling policy Lowest-RTT-First-RP.The main contributions are:(1)Add congestion measurement on path selection mechanism.ECN(Explicit Congestion Notification)is used to sense subflow congestion event,and calculates subflow congestion factor y.Combine it with the RTT value as the basis for path selection to select the faster subflow for the priority transmission of data.(2)Propose a new data allocation mechanism.SSCD(Shortened Subflow Completion Difference)mechanism is used to allocate the amount of transmitted data,according to the speed of the transmission on path.That reduce the difference of completion time caused by the RTT difference of path,thereby reducing the overall completion time of task.The evaluation experiment results show that compared with Lowest-RTT-First-RP,EMS can effectively select the faster subflow to data transmission and effectively reduce the difference of subflow completion time.Thus,in RTT asymmetric subpaths network scenario,the task completion time is effectively reduced(e.g.,average download time reduction of 36.5%for 10MB files and average download time reduction of 49.3%for 200MB files).