Stateless multicast forwarding with RPL in 6LowPAN sensor networks

Recent research efforts have resulted in efficient support for IPv6 in Low power Wireless Personal Area Networks (6LoWPAN), with the "IPv6 Routing Protocol for Low power and Lossy Networks" (RPL) being on the forefront as the state of the art routing approach. However, little attention has been paid to IPv6 multicast for networks of constrained devices. The "Multicast Forwarding Using Trickle" (Trickle Multicast) internet draft is one of the most noteworthy efforts, while RPL's specification also attempts to address the area but leaves many questions unanswered. In this paper we expose our concerns about the Trickle Multicast (TM) algorithm, backed up by thorough performance evaluation. We also introduce SMRF, an alternative multicast forwarding mechanism for RPL networks, which addresses TM's drawbacks. Simulation results demonstrate that SMRF achieves significant delay and energy efficiency improvements at the cost of a small increase in packet loss. We have extended the TCP/IP engine of the Contiki embedded Operating System to support both algorithms. Both implementations have been made available to the community. © 2012 IEEE

Experiences from porting the Contiki operating system to a popular hardware platform

In contrast to original belief, recent work has demonstrated the viability of IPv6-based Wireless Sensor Networks (WSNs). This has led to significant research and standardization efforts with outcomes such as the "IPv6 over Low-Power Wireless Personal Area Networks " (6LoWPAN) specification. The Contiki embedded operating system is an important open source, multi-platform effort to implement 6LoWPAN functionality for constrained devices. Alongside its RFC-compliant TCP/IP stack (uIP), it provides support for 6LoWPAN and many related standards. As part of our work, we have made considerable fixes and enhancements to one of Contiki's ports. In the process, we made significant optimizations and a thorough evaluation of Contiki's memory and code footprint characteristics, focusing on network-related functionality. In this paper we present our experiences from the porting process, we disclose our optimizations and demonstrate their significance. Lastly, we discuss a method of using Contiki to deploy an embedded Internet-to-6LoWPAN router. Our porting work has been made available to the community under the terms of the Contiki license

Ad-Hoc networking with OWL-S and CSP

In order to achieve a ubiquitous ad-hoc environment suitable for any kind and number of compute devices, information concerning device usability must be stored and manipulated. Take, for example the home where a large number of devices - heating, cooking, lighting, entertainment, security all cooperate to provide a suitable environment for a home resident. This paper proposes a representation of home devices as OWL-S (Web service ontology) services, capable of being implemented by means of the formal algebra CSP (communication sequential process). Because of the ontological nature of OWL-S and the possibility of translating CSP equations to lightweight implementations, this proposal allows a rich semantic description of services capable of being hosted by a wide range of devices, including such ones with low computational resources. The paper describes the procedure of developing a service in OWL-S, its translation to CSP and its implementation in occam, an efficient CSP-based languag

On the combined effects of Bit Error Rate and delay-distribution tail on TCP performance

The original design of the TCP retransmission timeout was implemented ignoring the recent measurement studies on the dynamics and features of network traffic and delay. Such studies have reported the highly variable characteristics of network delay, considered to be heavy-tailed distributed. Accordingly, depending on the heavy characteristics of the tail of the delay distribution, the actual implementation of TCP's retransmission timeout might be too conservative, or rather insufficient. This work aims to assess the optimal design of the retransmission timeout when heavy-tailed delay profiles are present. In our experiments, we have considered the case of low-bit error rate scenarios typical from wired networks as well as the high bit-error rates, typical from wireless networks. We show that the current implementation of the retransmission timeout is in broad terms very conservative, except in cases with extremely heavy tails

Weibull mixture model to characterise end-to-end Internet delay at coarse time-scales

Traces collected at monitored points around the Internet contain representative performance information about the paths their probes traverse. Basic measurement attributes, such as delay and loss, are easy to collect and provide a means to both build and validate empirical performance models. However, the task of analysis and extracting performance conclusions from measurements remains challenging. Ideally, performance modelling aims to find a set of self-contained parameters to describe, summarise, profile and easy display network performance status at a time. This can result in the provision of meaningful information to address applications in fault and performance management, hence providing input to network provisioning, traffic engineering and performance prediction. In this work we present the Weibull Mixture Model, a method to characterise endto- end network delay measurements within a few simple, accurate, representative and handleable parameters using a finite combination of Weibull distributions, with all the aforementioned benefits. The model parameters are related tomeaningful delay characteristics, such as average peak and tail behaviour in a daily profile, and can be optimally found using an iterative algorithm known as Expectation Maximisation. Studies on such parameter evolution can reflect current workload status and all possible network events impacting packet dynamics, with further applications in network management. In addition, a self-sufficient procedure to implement the Weibull Mixture Model is presented, along with a set of matching examples to real GPS synchronised measurements taken across the Internet, donated by RIPE NCC

IPv6 multicast forwarding in RPL-based wireless sensor networks

In wireless sensor deployments, network layer multicast can be used to improve the bandwidth and energy efficiency for a variety of applications, such as service discovery or network management. However, despite efforts to adopt IPv6 in networks of constrained devices, multicast has been somewhat overlooked. The Multicast Forwarding Using Trickle (Trickle Multicast) internet draft is one of the most noteworthy efforts. The specification of the IPv6 routing protocol for low power and lossy networks (RPL) also attempts to address the area but leaves many questions unanswered. In this paper we highlight our concerns about both these approaches. Subsequently, we present our alternative mechanism, called stateless multicast RPL forwarding algorithm (SMRF), which addresses the aforementioned drawbacks. Having extended the TCP/IP engine of the Contiki embedded operating system to support both trickle multicast (TM) and SMRF, we present an in-depth comparison, backed by simulated evaluation as well as by experiments conducted on a multi-hop hardware testbed. Results demonstrate that SMRF achieves significant delay and energy efficiency improvements at the cost of a small increase in packet loss. The outcome of our hardware experiments show that simulation results were realistic. Lastly, we evaluate both algorithms in terms of code size and memory requirements, highlighting SMRF's low implementation complexity. Both implementations have been made available to the community for adoption

Adaptive intelligent middleware architecture for mobile real-time communications

Provision of instantaneous, mobile and dependable communications in military and safety-critical scenarios must overcome certain wireless network issues: lack of reliable existing infrastructure, immutability of mission-critical protocols and detrimental wireless dynamics with contributing factors including hidden transmitters and fading channels. Benchmarked approaches do not fully meet these challenges, due to reliance on addressing Quality of Service (QoS) at a layer-specific level rather than taking a system of systems approach. This paper presents an adaptive middleware methodology to provide timely MANET communications through predictive selection and dynamic contention reduction, without invasive protocol modification. This is done using ROAM, the proposed, novel Real-time Optimised Ad hoc Middleware based architecture. Extensive simulation results demonstrate the adaptability and scalability of the architecture as well as capability to bound maximum delay, jitter and packet loss in complex and dynamic MANETs

Processing network delay measurements into network events

Network performance monitoring is an ongoing process as networks and their users are constantly changing. Networks are subject to various changes, some of which are controlled by the network providers (such as upgrades or re-routes) and some are not (equipment failure, usage). Network monitoring may include the detecting of such changes. These changes can be referred to as network event

Drop-burst length evaluation of urban VANETs

Networks performance is traditionally evaluated using packet delivery ratio (PDR) and latency (delay).We propose an addition mechanism the drop-burst length (DBL). Many traffic classes display varying application-level performance according to the pattern of drops, even if the PDR is similar. In this paper we study a number of VANET scenarios and evaluate them with these three metrics. Vehicular Ad-hoc Networks (VANETs) are an emerging class of Mobile Ad-hoc Network (MANETs) where nodes include both moving vehicles and fixed infrastructure. VANETs aim to make transportation systems more intelligent by sharing information to improve safety and comfort. Efficient and adaptive routing protocols are essential for achieving reliable and scalable network performance. However, routing in VANETs is challenging due to the frequent, high-speed movement of vehicles, which results in frequent network topology changes. Our simulations are carried out using NS2 (for network traffic) and SUMO (for vehicular movement) simulators, with scenarios configured to reflect real-world conditions. The results show that OLSR is able to achieve a best DBL performance and demonstrates higher PDR performance comparing to AODV and GPSR under low network load. However, with GPSR, the network shows more stable PDR under medium and high network load. In term of delay OLSR is outperformed by GPSR

Evaluating VANET routing in urban environments

Vehicular Ad-hoc Networks (VANETs) are a class of Mobile Ad-hoc Networks (MANETs) incorporated into moving vehicles. Nodes communicate with both and infrastructure to provide Intelligent Transportation Systems (ITS) for the purpose of improving safety and comfort. Efficient and adaptive routing protocols are essential for achieving reliable and scalable network performance. However, routing in VANETs is challenging due to the high-speed movement of vehicles, which results in frequent network topology changes. This paper provides an in-depth evaluation of three well-known MANET routing protocols, AODV, OLSR and GPSR, in VANET with urban environment setup. We compare their performance using three metrics: drop burst length (DEL), delay and delivery ratio (PDR). The simulations are carried out using NS2 and SUMO simulators platforms, with scenarios configured to reflect real-world conditions. The results show that OLSR is able to achieve a shorter DEL and demonstrates higher PDR performance comparing to AODV and GPSR under low network load. However, with GPSR, the network shows more stable PDR under medium and high network load. In term of delay it is outperformed by GPSR, which delivers packets with the shortest delay