Conference Paper

ERPL: An Enhanced Peer-to-Peer Routing Mechanism for Low-Power and Lossy Networks

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Abstract

The Routing Protocol for low-power and Lossy networks (RPL) is the most popular routing protocol for low-power and lossy networks (LLNs). Recent studies demonstrate that RPL performs poorly in peer-to-peer (P2P) communication. However, P2P communication is of immense importance in many LLNs that require actuation and control operations, such as cyber-physical systems. In order to alleviate the performance problem of RPL, we present a mechanism to enhance P2P route construction and data packet forwarding in RPL's storing and non-storing mode of operations (MoPs), which we call Enhanced RPL (ERPL). The salient features of ERPL include the following: (i) optimized P2P routing and data forwarding, (ii) no additional control messages, and (iii) ERPL can coexist with standard RPL implementations. We have implemented ERPL in the Contiki operating system and extensively evaluated it against a RPL implementation using Cooja-based emulation and physical testbed based experiments. Our results demonstrate that ERPL outperforms standard RPL in P2P communication and its optimized P2P route construction and data forwarding algorithms also positively impact the protocol's performance in multipoint to point (MP2P) and point to multipoint (P2MP) communications. Moreover, ERPL is more energy-efficient. Our results also shed light on the performance of MP2P, P2MP, and P2P communications relative to RPL's destination-oriented directed acyclic graph (DODAG) depth, i.e., a deeper DODAG negatively impacts the performance of MP2P and P2MP communications, however it positively impacts P2P communication, while the reverse holds true for a relatively shallow DODAG.

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... There are few works which go down the broadcast and multicast methods for improving the downward routing. A DIO overhearing based mechanism proposed by ERPL [31] which improves both the storing and non-storing mode by adding a route to the direct neighbours. Though this reduces the length of P2P routes for a subset of nodes, other nodes follow the original longer paths. ...
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Internet of Things is evolving from information gathering platforms into collaborative systems where smart devices actively interact with each other in a seamless manner. For instance, Internet of Robotic Things is envisioned to provide augmented solutions through collaboration of varied smart devices and robots. These visions revolve around the ability of smart devices to directly communicate and cooperate with each other in real time. In this context, this paper is an attempt to study RPL’s point to point routing that creates multi-hop paths between peer nodes. This standard routing protocol is known for robust and failsafe upward paths but its peer to peer (P2P) routes are reported to be sub optimal. This work assesses P2P performance of RPL’s storing mode in a network of new generation devices having higher memory. Further, a Collaborative and Proactive Peer to Peer (C3P) path selection and sustenance approach is proposed where root node collates incremental topology from collaborative nodes and disseminates optimal single source shortest path trees SPT(n). A progressive node betweenness centrality score ensures spread out paths. Minor topology changes are accommodated through incremental node and edge updates to targeted SPT(n) locally. Storing SPTs in intermediate nodes reduces storage and packet size. Through simulations and testbed experiments, it is proven that C3P-RPL improves simultaneous peer to peer communication between all the nodes. Specifically, the path length is reduced by 30% and subsequently the network latency drops by 65% in an experimental testbed of 47 nodes, making it suitable for collaborations.
... Farooq et al. proposed ERPL [37] which has a mechanism to forward packet directly without upward routing if the destination node is a direct neighbor to the source node or a direct neighbor to the parent nodes of the source node. ERPL achieves an effect similar to multicast DAO (MDAO) messages through DIO, without the need to transmit additional MDAO messages. ...
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RPL, the standard IPv6 routing protocol for low-power and lossy networks in the emerging Internet of things (IoT), is designed mainly for efficient many-to-one data collection scenarios where the majority of the traffic flows from embedded devices to a gateway. Although RPL does support root-to-node downwards routing and peer-to-peer (P2P) communication, its P2P performance is inefficient and unsatisfactory due to excessively high churn and bottlenecks in the P2P path. However, P2P routing is important for machine-to-machine communication where nodes in IoT applications communicate with one another and control devices beyond simply collecting data. In this work, we propose a neighbor-graph-based RPL (NG-RPL) that significantly improves P2P routing performance. By including additional routing information when a packet passes through the root node for the first time in a P2P communication, NG-RPL finds efficient P2P routes opportunistically, when available, without significant overhead. We implement NG-RPL in Contiki-NG and evaluate its performance through extensive Cooja simulations. Results show that NG-RPL reduces routing churn, which improves packet reception ratio, round-trip time, and energy usage of P2P communication compared to standard RPL.
... The discovered path to the destination, therefore, might not be the optimal one especially under asymmetric links, 3) it adds an extra overhead due to maintaining an additional temporary DODAG by all participating nodes, and 4) it defines new control messages requiring changes to the specifications of the standard protocol which lead to possible compatibility issues. Finally, [57] and [58] propose enhancements to RPL, named ERPL, that are limited to work only when the destination node is either a direct neighbor of the source node or a direct neighbor of a node relaying the data packet. However, multihop N2N communications are not supported in ERPL, where ERPL falls back to using the original RPL protocol. ...
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Routing discovery is a pivotal component of the communication stack in Low-power and Lossy Networks (LLNs). The IPv6 routing protocol for LLNs, termed RPL, has been recently standardized to provide routing discovery in a wide range of LLN-based deployments realizing the Internet of Things (IoT) vision. RPL was mainly designed with the assumption that the predominant traffic flow would be gathering data towards a single destination, typically the root node. However, node-to-node (N2N) communication, where the root is neither source nor destination, is a prime requirement in most of the LLN-based applications such as actuating, decision making, and controlling applications. RPL in its current form does not cater well to such applications where there is a good number of inward N2N traffic flows. In this paper, we propose a hybrid routing mechanism based on RPL for high N2N communications in LLNs referred to by HRPL. HRPL is implemented on Contiki and evaluated through extensive simulations on Cooja. HRPL is fully backward compatible with RPL where HRPL and RPL nodes can work together seamlessly in a hybrid network. Results show that HRPL provides a considerable improvement in packet delivery ratio relative to the standardized RPL-based modes and to the RPL-based opportunistic routing approach. While HRPL requires a slightly larger memory footprint more than that for RPL, HRPL manages to significantly reduce the control plane packets, number of hops, and MAC transmissions needed to successfully deliver N2N data packets. Accordingly, this is translated to lower packet delay and less energy consumption.
... Finally, an extension for RPL is proposed in [25] and [26] named ERPL. The proposed ERPL enhancements are limited to work only when a destination node is a direct neighbor of a source node or the destination node is a direct neighbor of a node relaying a data packet. ...
... These aspects are largely missing in the existing literature. Furthermore, this paper extends the work presented in [19]. ...
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In this paper we present enhanced routing protocol for low-lower and lossy networks (ERPL), a reduced overhead routing protocol for short-range low-power and lossy wireless networks, based on RPL. ERPL enhances peer-to-peer (P2P) route construction and data packet forwarding in RPL's storing and non-storing modes of operation (MoPs). In order to minimize source routing overhead, it encodes routing paths in Bloom Filters (BF). The salient features of ERPL include the following: (i) optimized P2P routing and data forwarding; (ii) no additional control messages; and (iii) minimized source routing overhead. We extensively evaluated ERPL against RPL using emulation, simulation, and physical test-bed based experiments. Our results demonstrate that ERPL outperforms standard RPL in P2P communication and its optimized P2P route construction and data forwarding algorithms also positively impact the protocol's performance in multi-point to point (MP2P) and point to multi-point (P2MP) communications. Our results demonstrate that the BF-based approach towards compressed source routing information is feasible for the kinds of networks considered in this paper. The BF-based approach results in 65% lower source routing control overhead compared to RPL. Our results also provide new insights into the performance of MP2P, P2MP, and P2P communications relative to RPL's destination-oriented directed a-cyclic graph (DODAG) depth, i.e., a deeper DODAG negatively impacts the performance of MP2P and P2MP communications, however it positively impacts P2P communication, while the reverse holds true for a relatively shallow DODAG.
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Reactive Discovery of Point-to-Point Routes in Low-Power and Lossy Networks
  • M Goyal
  • E Baccelli
  • M Philipp
  • A Brandt
  • J Martocci
M. Goyal, E. Baccelli, M. Philipp, A. Brandt, and J. Martocci, "Reactive Discovery of Point-to-Point Routes in Low-Power and Lossy Networks," August 2013, RFC 6997.