Ulrich Herberg

A critical evaluation of the IPv6 Routing Protocol for Low Power and Lossy Networks (RPL)

With RPL - the “IPv6 Routing Protocol for Low-power Lossy Networks” - emerging as a Proposed Standard “Request For Comment” (RFC) in the Internet Engineering Task Force (IETF) after a ∼2-year development cycle, this paper presents a critical evaluation of the resulting protocol and its applicability and limits. The paper presents a selection of observations of the protocol characteristics, exposes experiences acquired when producing a prototype implementation of RPL, and presents results obtained from testing this protocol - both in a network simulator, and in real-world experiments on a wireless sensor network testbed. The paper aims at providing a better understanding of possible weaknesses and limits of RPL, notably the possible directions that further protocol developments should explore, in order to address these.

A comparative performance study of the routing protocols LOAD and RPL with bi-directional traffic in low-power and lossy networks (LLN)

Routing protocols for sensor networks are often designed with explicit assumptions, serving to simplify design and reduce the necessary energy, processing and communications requirements. Different protocols make different assumptions - and this paper considers those made by the designers of RPL - an IPv6 routing protocol for such networks, developed within the IETF. Specific attention is given to the predominance of bi-directional traffic flows in a large class of sensor networks, and this paper therefore studies the performance of RPL for such flows. As a point of comparison, a different protocol, called LOAD, is also studied. LOAD is derived from AODV and supports more general kinds of traffic flows. The results of this investigation reveal that for scenarios where bi-directional traffic flows are predominant, LOAD provides similar data delivery ratios as RPL, while incurring less overhead and being simultaneously less constrained in the types of topologies supported.

Comparative study of RPL-enabled optimized broadcast in Wireless Sensor Networks

Recent trends have suggested convergence to Wireless Sensor Networks (WSNs) becoming IPv6-based. To this effect, the Internet Engineering Task Force has chartered a Working Group to develop a routing protocol specification, enabling IPv6-based multi-hop WSNs. The current effort of this working group is development of a unicast routing protocol denoted RPL. RPL constructs a “DAG-like” logical structure with a single root, at which the majority of the traffic flows terminate, and assumes restrictions on network dynamics and traffic generality, in order to satisfy strict constraints on router state and processing. This paper investigates the efficient network-wide broadcast mechanisms in WSNs, using the logical structure already established by RPL. The aim hereof is to impose minimal additional state requirements on WSN routers, beyond that already maintained by RPL. This paper presents a selection of such broadcast mechanisms for RPL routed WSNs, and evaluates their performances. As part of this evaluation, the paper compares with MPR Flooding - an established efficient flooding optimization, widely used in MANETs.

Multipoint-to-Point and Broadcast in RPL

Recent trends in Wireless Sensor Networks (WSNs) have suggested converging to such being IPv6-based. To this effect, the Internet Engineering Task Force has chartered a Working Group to develop a routing protocol specification, enabling IPv6-based multi-hop Wireless Sensor Networks. This routing protocol, denoted RPL, has been under development for approximately a year, and this paper takes a critical look at the state of advancement hereof: it provides a brief algorithmic description of the protocol, and discusses areas where -- in the authors view -- further efforts are required in order for the protocol to become a viable candidate for general use in WSNs. Among these areas is the lack of a proper broadcast mechanism. This paper suggests two such broadcast mechanisms, both aiming at (i) exploiting the existing routing state of RPL, while (ii) requiring no additional state maintenance, and studies the performance of RPL and of these suggested mechanisms.

Vulnerability analysis of the optimized link state routing protocol version 2 (OLSRv2)

Mobile Ad hoc NETworks (MANETs) are leaving the confines of research laboratories, to find place in real-world deployments. Outside specialized domains (military, vehicular, etc.), citywide community-networks are emerging, connecting regular Internet users with each other, and with the Internet, via MANETs. Growing to encompass more than a handful of “trusted participants”, the question of preserving the MANET network connectivity, even when faced with careless or malicious participants, arises, and must be addressed.

OpenADR 2.0 deployment architectures: Options and implications

OpenADR 2.0, an internationally-recognized standard for Automated Demand Response (ADR), defines the interaction between an ADR server and client, but does not specify all the possible multi-tier deployment architectures that are valid relative to the standards specification. In this paper, we analyze the properties of a number of OpenADR-based architectures that have been proposed for deployment by ADR vendors, in terms of interoperability (compliance with the standard), scalability, complexity, and security, with the goal of helping utilities and third party DR aggregators make informed decisions about their planned ADR deployments to ensure high performing, future-proof, and secure DR services.

Enhancing Demand Response signal verification in automated Demand Response systems

Demand Response (DR) is a promising technology for meeting the worlds ever increasing energy demands without corresponding increase in energy generation, and for providing a sustainable alternative for integrating renewables into the power grid. As a result, interest in automated DR is increasing globally and has led to the development of OpenADR, an internationally recognized standard. In this paper, we propose security-enhancement mechanisms to provide DR participants with verifiable information that they can use to make informed decisions about the validity of received DR event information.

Study of multipoint-to-point and broadcast traffic performance in the “IPv6 Routing Protocol for Low Power and Lossy Networks”

Recent trends in Wireless Sensor Networks (WSNs) have suggested converging to such being IPv6-based. To this effect, the Internet Engineering Task Force has chartered a Working Group to develop a routing protocol specification, enabling IPv6-based multi-hop Wireless Sensor Networks. This routing protocol, denoted “IPv6 Routing Protocol for Low Power and Lossy Networks” (RPL), has been under development for approximately a year, and this paper takes a critical look at the state of advancement hereof: it provides a brief algorithmic description of the protocol, and discusses areas where—in the authors view—further efforts are required in order for the protocol to become a viable candidate for general use in WSNs. Among these areas is the lack of a proper broadcast mechanism. This paper suggests several such broadcast mechanisms, all aiming at (1) exploiting the existing routing state of RPL, while (2) requiring no additional state maintenance, and studies the performance of RPL and of these suggested mechanisms.

Performance Evaluation of Using a Dynamic Shortest Path Algorithm in OLSRv2

MANET routing protocols are designed to scale up to thousands of routers with frequent changes of the topology. In preference, MANET routing protocols should also support constrained low-power devices. One of the bottlenecks of scalability in link-state routing protocols is the performance of the shortest path algorithm (e.g. Dijkstra). In this paper, we investigate the in-node performance of OLSRv2 and, in particular, study the benefits of using a dynamic shortest path (DSP) algorithm for this routing protocol. A DSP algorithm is an algorithm that adds or removes edges in the routing tree incrementally and calculates shortest paths, also incrementally. The performance in OLSRv2 with classic Dijkstra vs. DSP is evaluated, by comparing the CPU time for calculating paths in a large emulated network. Additionally, it is demonstrated that frequent topology changes due to mobility in MANETs lead to frequent routing table recalculations with only few routes updated each time. This property of MANETs makes the use of a DSP in OLSRv2 appropriate.

Development Framework for Supporting Java NS2 Routing Protocols

This paper presents a framework for developing and executing Java routing protocol implementations within the network simulator NS2. NS2 provides extensive support for developing C++ routing protocols, but has no Java support. In this paper, we describe extensions we have made to the AgentJ toolkit that enable routing protocols to be integrated directly into NS2 without needing to extend the internals of NS2 for each new protocol. The framework defines a reusable AgentJ routing protocol definition that can be used to register new protocols dynamically from within Java code. The actual routing protocol can then leverage the AgentJ toolkit for executing unmodified Java applications in NS2. By means of aspect-oriented byte-code rewriting, AgentJ allows preexisting Java routing protocols, which run on the Internet, to run unmodified within NS2. This powerful system also helps researchers to both understand high-level and algorithmic properties of a given Java routing protocol through the analysis of an NS2 simulation and to rapidly develop and debug new routing protocols through prototyping and experimentation.