Network Working Group Changqiao Xu Internet Draft BUPT Intended status: Experimental Kai Gao Expires: October 2019 BUPT Jiuren Qin BUPT May 6, 2019 A Stochastic Optimal Scheduler for Multipath Transmission Control Protocol (MPTCP) draft-xu-mptcp-sosmp-01.txt Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. 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Abstract This memo presents a new stochastic optimal scheduler for the Multipath Transmission Control Protocol (MPTCP). The new scheduler is based on the Lyapunov optimatization technique, which can make online control decision for data scheduling. Considering the payment of users for different paths, this memo makes a trade off between the throughput utility and the cost. The new scheduler can not only satisfy the demand of service, but also minimize the cost as much as possible. Table of Contents 1. Introduction ................................................ 3 1.1. Motivation ............................................. 3 1.2. Overview of SOS-MPTCP .................. 3 2. Conventions ................................................. 3 3. A New Stochastic Optimal Scheduler ... 3 3.1. Admission Control ............................. 4 3.2. Packets Allocation ........................... 4 3.3. Purchasing Data Traffic ................. 4 4. Building Queue ...................................... 4 5. Transmission Performance and Problem Optimization ............ 5 6. Stochastic Optimal Scheduler ................................. 5 7. Security Considerations ...................................... 5 8. Implementation Considerations ................................ 5 9. References .................................................. 5 9.1. Normative References .................................... 5 9.2. Informative References .................................. 6 10. Acknowledgments ............................................ 6 Xu, et al Expires October 6, 2019 [Page 2] Internet-Draft SOSMPTCP May 2019 1. Introduction SOS-MPTCP is a new scheduler of MPTCP which can make online control decisions for data distribution. By taking advantage of queue stability, the new stochastic optimal scheduler can make a trade off between the throughput utility and the cost. 1.1. Motivation The scheduler plays an important role in the data distribution. In the heterogeneous wireless network, the cost of each path is quite diverse and depends on the amount of packets assigned by the scheduler. Traditional scheduler just focuses on the transmission performance without considering the payment cost of users. This memo intends to fill the gap with the Lyapunov optimatization technique. 1.2. Overview of SOS-MPTCP This demo mainly describes the new scheduler of MPTCP. The objection of this scheduler is to maximize the throughput and minimize the corresponding cost to different communication operators. To achieve this goal, the following three important control decisions are to be made: o How many packets of different connections can be admitted into transmission layer. o How to distribute the admitted packets to all paths. o How to purchase data traffic for different paths in advance. 2. Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC-2119 [RFC2119]. 3. A New Stochastic Optimal Scheduler A number of paths which are available are denoted by J={1,2,?j}. And there are different connections I={1,2,?i} of packets with diverse arrival rates from the application layer. In order to facilitate the analysis, we consider the system as a discrete time-slotted model divided by t={1,2,?T}. In each time slot t, a number of the ith connection of packets arrive at the system randomly. Let A i(t) Xu, et al Expires October 6, 2019 [Page 3] Internet-Draft SOSMPTCP May 2019 denote the number of data packets of connection i in time slot t. The unit price of path j is denoted by p_j. 3.1. Admission Control In each time slot, a lot of packets arrive at the transmission layer. To prevent the system from congestion, the admission control module decides that the total number of packets noticed by A_i(t). can be admitted into transmission layer. Therefore, A_i(t) SHOULD less than the number of arriving packets R_i(t). 3.2. Packets Allocation After the packets of connection i are admitted into the transmission layer, the packets allocation module assigns packets to each path. The number of packets of type i distributed to path j in time slot t is denoted as A_ij(t). And this assignment should satisfy the constraint: A_i(t)=SUM_i(A_ij(t)). Each path maintains a queue for each connection of packets which can be transmitted later. We define the queue backlog Q_ij(t) of ith connection of packets assigned on the jth path as the number of pending packets waiting in the queue. We also define S_ij(t) as the number of packets which have been sent successfully and acknowledged. 3.3. Purchasing Data Traffic In order to satisfy the service demand of users, they will purchase data traffic in advance from the communication operator. We use W_j(t) to denote the cost of paying for the path j belonging to respective operator in the time slot t. The total cost of the multipath transmission control system can be denoted by H_j(t) to maintain the consumption for the users. 4. Building Queue According to the control framework described above, the dynamic updating of queue backlog can be defined as the equation: Q_ij(t+1)=max[Q_ij(t)- S_ij(t),0]+ A_ij(t) Similarly, H_j(t) denotes the cost queue size of path j in the time slot t. Under the control decision of purchasing data traffic, the queue H_j(t) can be expressed as follows, H_j(t+1)= H_j(t)- SUM_j (S_ij(t)*p_j)+ W_j(t) Xu, et al Expires October 6, 2019 [Page 4] Internet-Draft SOSMPTCP May 2019 5. Transmission Performance and Problem Optimization We define the time averaged throughput SUM_i (Thr_i(t))=lim_t (1/T) SUM_t E{S_i(t)}. We also define a cost utility function SUM_j(W_j(t))=lim_t(1/T)SUM j(E{W_j(t))}. It is challenging to tradeoff the transmission throughput and cost utility function. The transmission performance depends on the throughput and cost utility. Therefore, we NEED to construct an objective to take both sides into consideration. The problem of maximizing transmission performance is defined as Max { SUM_i (Thr_i(t)) - SUM_j (W_j(t))} s.t. Q_ij is stable 6. Stochastic Optimal Scheduler In order to solve the problem mentioned above, we design a distribution approach by using Lyapunov optimization [SNO2010] which contains Lyapunov draft and queue stability. The value of A_i(t), A_ij(t) are calculated by the queue H(t) and Q(t). And H(t) and Q(t) are updated by the calculation results. 7. Security Considerations This memo develops no new security scheme for MPTCP. SOS-MPTCP share the same security issues discussed in [RFC6824] with MPTCP. 8. Implementation Considerations This approach is a new scheduler for MPTCP, which is named as "stochastic". We can select the scheduler through the socket-option MPTCP_SCHEDULER from the following four schedulers: "default", "roundrobin", "redundant", "stochastic". 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Xu, et al Expires October 6, 2019 [Page 5] Internet-Draft SOSMPTCP May 2019 9.2. Informative References [RFC6824] Ford, A., Raiciu, C., Handley, M., and O. Bonaventure, "TCP Extensions for Multipath Operation with Multiple Addresses", RFC 6824, January 2013. [SNO2010] M. J. Neely, Stochastic Network Optimization with Application to Communication and Queueing Systems, J. Walrand, Ed. San Rafael, CA,USA: Morgan & Claypool, 2010. 10. Acknowledgments This Internet Draft is the result of a great deal of constructive discussion with several people, notably Tengfei Cao and Jiangzhong Bai. This document was prepared using 2-Word-v2.0.template.dot. Xu, et al Expires October 6, 2019 [Page 6] Internet-Draft SOSMPTCP May 2019 Authors' Addresses Changqiao Xu Beijing University of Posts and Telecommunications Institute of Network Technology, No. 10, Xitucheng Road, Haidian District, Beijing P.R. China Email: cqxu@bupt.edu.cn Kai Gao Beijing University of Posts and Telecommunications Institute of Network Technology, No. 10, Xitucheng Road, Haidian District, Beijing P.R. China Email: gaokai@bupt.edu.cn Jiuren Qin Beijing University of Posts and Telecommunications Institute of Network Technology, No. 10, Xitucheng Road, Haidian District, Beijing P.R. China Email: jrqin@bupt.edu.cn Xu, et al Expires April 5, 2019 [Page 7]