Performance analysis of Routing Protocol for Low power and Lossy Networks (RPL) in large scale networks Article (Accepted Version) Liu, Xiyuan, Sheng, Zhengguo, Yin, Changchuan, Ali, Falah and Roggen, Daniel (2017) Performance analysis of Routing Protocol for Low power and Lossy Networks (RPL) in large scale networks. IEEE Internet-of-Things Journal, PP (99). ISSN 2327-4662 This version is available from Sussex Research Online: http://sro.sussex.ac.uk/id/eprint/70224/ This document is made available in accordance with publisher policies and may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher’s version. Please see the URL above for details on accessing the published version. Copyright and reuse: Sussex Research Online is a digital repository of the research output of the University. 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Copies of full text items generally can be reproduced, displayed or performed and given to third parties in any format or medium for personal research or study, educational, or not-for-profit purposes without prior permission or charge, provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. http://sro.sussex.ac.uk 1 Performance Analysis of Routing Protocol for Low Power and Lossy Networks (RPL) in Large Scale Networks Xiyuan Liu, Zhengguo Sheng, Changchuan Yin, Senior Member, IEEE, Falah Ali, Senior Member, IEEE, and Daniel Roggen Abstract—With growing needs to better understand our en- (battery power), processing and storage capability, radio com- vironments, the Internet-of-Things (IoT) is gaining importance munication range and reliability, etc., and yet their deployment among information and communication technologies. IoT will en- must cover a wide range of areas. In order to cope with able billions of intelligent devices and networks, such as wireless sensor networks (WSNs), to be connected and integrated with those challenges, a number of breakthrough solutions have computer networks. In order to support large scale networks, been developed, for example, efficient channel hopping in IETF has defined the Routing Protocol for Low power and IEEE 802.15.4e TSCH [3], emerging IPv6 protocol stack for Lossy Networks (RPL) to facilitate the multi-hop connectivity. connected devices [4] and improved bandwidth of mobile In this paper, we provide an in-depth review of current research transmission. activities. Specifically, the large scale simulation development and performance evaluation under various objective functions Routing, particular in large scale networks, is always chal- and routing metrics are pioneering works in RPL study. The lenging for resource constrained sensor devices. The IETF results are expected to serve as a reference for evaluating the Routing Over Low-power and Lossy networks (ROLL) work- effectiveness of routing solutions in large scale IoT use cases. ing group has been focusing on routing protocol design and Index Terms—RPL, WSN, Large Scale Network, Performance is committed to standardize the IPv6 routing protocol for Analysis Low-power and Lossy Networks (LLN). RFC6550 [5], first proposed by ROLL group of IETF in the form of draft to define Routing Protocol over Low Power and Lossy Networks I. INTRODUCTION (RPL), serves as a milestone in solving routing problems in LLNs. Due to the limitation of short-range radio in personal HE Internet-of-Things (IoT) has become a new focus for area network (PAN) and local area network (LAN), multi- both industry and academia involving information and T hop transmission is necessary in large scale networks. RPL communication technologies (ICTs), and it is predicted that is designated to provide such a viable solution to maintain there would be almost 50 billion devices connected with each connectivity and efficiency in a cost effective way. However, other through IoT by 2020 [1]. The concept of IoT can be there is a lack of existing literature in evaluating the RPL traced back to the pioneering work done by Kevin Ashton performance in large scale networks. in 1999 and it is initially linked to the new idea of using In this paper, we focus on the comprehensive review of radio frequency identification in supply chains. Soon after, this RPL protocol and its performance in large scale networks. term became popular and is well known as a new ICT where Our contribution can be summarized as follows: the Internet is connected to the physical world via ubiquitous • We make a deep analysis of objective functions and wireless sensor networks (WSNs) [2]. metrics in RPL under varied scenarios, with references to With the development of WSN technologies, a wide range of the latest literature and studies, which can fundamentally intelligent and tiny wireless sensing devices will be deployed contribute to the understanding of RPL performance in a variety of application environments. Generally, these and provide inspiration to raise more viable methods to sensing devices are constrained by limited energy resources further improve the network performance. An extended discussion of security issue and future challenges are also This work was supported in part by National Natural Science Foundation of China under Grants 61629101 and 61671086, Director Funds of Beijing included. Key Laboratory of Network System Architecture and Convergence (2017BKL- • We make the first attempt to build a large scale network NSAC-ZJ-04), the 111 project (No.B17007), and Asa Briggs Visiting Fellow- using RPL and provide analytical results under different ship from University of Sussex. Copyright (c) 2012 IEEE. Personal use of this material is permitted. objective functions. A more practical scenario incorporat- However, permission to use this material for any other purposes must be ing UDP, IPv6 and 6LowPAN has also be considered in obtained from the IEEE by sending a request to [email protected]. the analysis. X. Liu and C. Yin are with Beijing Laboratory of Advanced Information Networks and Beijing Key Laboratory of Network System Architecture and • We make an investigation on network simulation tools Convergence, Beijing University of Posts and Telecommunications, Beijing, and select OMNeT++ as the ideal one for a large scale (Email: {lxy, ccyin}@bupt.edu.cn). RPL simulation. We have fully implemented the RPL Z. Sheng, F. Ali and D. Roggen are with Department of Engineer- ing and Design, University of Sussex, UK (Email: {z.sheng, F.H.Ali, protocol according to IETF specifications in OMNeT++ D.Roggen}@sussex.ac.uk.) and discussed its performance. The source code is also 2 supplemented online to support further study by the Sink Node research community. a Preferred Path The rest of the paper is organized as follows. Section II Alternative Path DIO gives an overview of RPL definition. Section III discusses DIO the current Objective Functions and routing metrics in RPL. b Section IV introduces simulation platforms and our practice in c developing RPL as well as its performance analysis. Section Preferred Parent Set V provides further discussions on the applications of RPL in e d reality. Based on the research findings in previous sections, a DAO Parent Node Set future prospect and challenges are raised in Section VI. The f g conclusion is then given in Section VII. h Neighbor Node Set i II. INTRODUCTION OF RPL LLNs are resource constrained networks in terms of mem- ory, energy and processing power. IETF ROLL Working Group Fig. 1. An example of DODAG and node set relationships. mainly focuses on the routing in LLNs and has proposed RPL in RFC6550 [5]. RFC6550 was firstly released in March 2012 and then a number of supplementary and supportive RFCs and those neighbour nodes will re-broadcast DIOs to further nodes. Internet drafts have been progressed. For instance, RFC6997 The similar step will repeat in such way that the DODAG [6] is aimed at clarifying the specified route discovery mecha- topology is constructed through handling DIOs and building nism, while RFC7416 [7] is with the purpose of strengthening parent sets. DIS message is used for soliciting the sending the security issues in RPL. of DIO in order to make immediate response to network With the development of IoT, RPL is entitled to new chance inconsistency. The structure of DIO message is presented in for the development of wireless sensor networks in a large the following subsection. scale. It is able to meet the specific routing requirements of DAO message is used for downward routing construction application areas including urban networks (RFC 5548) [8], (Point-to-Point and Point-to-multipoint). There are two modes building automation (RFC 5867) [9], industrial automation of downward routing - storing and non-storing modes, which (RFC 5673) [10], and home automation (RFC 5826) [11]. indicate that the routing table information is stored in inter- Among those mechanisms standardized in RPL, routing and mediate nodes (non-root and non-leaf nodes) and root node, message control are two important mechanisms in establishing respectively. and maintaining an effective and reliable network, which will An Objective Function (OF) defines the rule of selecting be highlighted in details as follows. neighbours and parent nodes by rank computation. Routing metrics related to link or node characteristics (RFC6551 [12]) A. Routing Mechanism of RPL can be used by OF to make routing determination. One of the widely used OF0 is defined in RFC6552 with hop count as RPL is a distance vector routing protocol. It does not the routing metrics. OF determines Neighbour Set, Parent Set have predefined topology but will be generated through the and Preferred Parents according to specified routing metrics construction of Destination-Oriented Directed Acyclic Graphs and constraints.