BIOLOGICAL TOOLS FOR WATER SECURITY IN THE NORTHERN GREAT PLAINS

Rivers and streams are a critical component of Northern Great Plains ecosystems and an extremely valuable source of surface water. Despite their importance, these waterbodies have traditionally received much less scientific attention than forested regions. This thesis provides insight into what best available natural communities may still exist, and how alterations in the physical characteristics of rivers and streams can push communities outside of their range of natural variation. Specifically, I show that since the construction of a hydroelectric dam on a large Northern Great Plains river densities of benthic macroinvertebrates have increased significantly through time in the river downstream relative to reference sites and pre-dam conditions. My findings indicate that although there is a notable loss in sensitive taxa such as mayflies and stoneflies, other midge taxa colonize this unique, cold water habitat and create a new community of benthic macroinvertebrates. Further, reaches downstream of the dam are significantly cooler than reference through the summer into August and do not reach the temperature optima of reference reaches. I use these results to develop a reference condition model that assesses current condition and can be used to monitor recovery through mitigation of these perturbations. My results have implications primarily for understanding and quantifying the ecosystem impacts of hydroelectric energy production, but also range expansion of cold-water tolerant taxa, the life-history of select groups of invertebrates, and ultimately the forage resources available to the fish assemblages of this river system. Further, as Northern Great Plains rivers are typified by considerable flow variability, particularly in the presence of water control structures, fine sediment (<63μm) is readily suspended, especially during periods of high discharge. Assessment of the impacts to biota by anthropogenic stressors must therefore occur within the context of dynamic turbidity and background flow conditions. I developed a model in which discharge is a principal determinant of in-stream suspended sediment. This relationship was explored with a case study showing that macroinvertebrate community structure is strongly correlated with suspended sediment gradients and ultimately predicted by discharge. Factors affecting sediment loads and ecosystem responses in managed systems should be considered so that in-stream water quantity and quality needs are met. This new understanding should allow for the development of improved ecosystem based flow management objectives. Finally, I develop a multivariate and predictive model based on the reference condition approach for the Northern Great Plains region of Saskatchewan from benthic macroinvertebrate communities and environmental abiotic data collected at 280 reference sites and 10 test sites. Reference sites were classified into groups characterized by similar macroinvertebrate communities. This model predicted 68.7% of the sites correctly using cross-validation. Of the 10 test sites, two were stressed (one waste water and one urban site) while three were classified as impaired (one waste water and two reservoirs). These models are effective tools that provide a practical means of evaluating biotic condition of streams in the Northern Great Plains

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

FASER: Binary Code Similarity Search through the use of Intermediate Representations

Being able to identify functions of interest in cross-architecture software is useful whether you are analysing for malware, securing the software supply chain or conducting vulnerability research. Cross-Architecture Binary Code Similarity Search has been explored in numerous studies and has used a wide range of different data sources to achieve its goals. The data sources typically used draw on common structures derived from binaries such as function control flow graphs or binary level call graphs, the output of the disassembly process or the outputs of a dynamic analysis approach. One data source which has received less attention is binary intermediate representations. Binary Intermediate representations possess two interesting properties: they are cross architecture by their very nature and encode the semantics of a function explicitly to support downstream usage. Within this paper we propose Function as a String Encoded Representation (FASER) which combines long document transformers with the use of intermediate representations to create a model capable of cross architecture function search without the need for manual feature engineering, pre-training or a dynamic analysis step. We compare our approach against a series of baseline approaches for two tasks; A general function search task and a targeted vulnerability search task. Our approach demonstrates strong performance across both tasks, performing better than all baseline approaches.Comment: 10 pages, Proceedings of the Conference on Applied Machine Learning in Information Security (CAMLIS

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

Drop-Burst Length Evaluation of Urban VANETs

This is an Open Access Article. It is published by International Science and Engineering Society under the Creative Commons Attribution-ShareAlike 4.0 International Licence (CC BY-SA). Full details of this licence are available at: http://creativecommons.org/licenses/by-sa/4.0/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

Discrete-time heavy-tailed chains, and their properties in modeling network traffic

This is the author's version of the work. It is posted here for your personal use. Not for redistribution. The definitive Version of Record was published in ACM Transactions on Modeling and Computer Simulation , http://dx.doi.org/10.1145/10.1145/1276927.1276930The particular statistical properties found in network measurements, namely self-similarity and long-range dependence, cannot be ignored in modeling network and Internet traffic. Thus, despite their mathematical tractability, traditional Markov models are not appropriate for this purpose, since their memoryless nature contradicts the burstiness of transmitted packets. However, it is desirable to find a similarly tractable model which is, at the same time, rigorous at capturing the features of network traffic. This work presents discrete-time heavy-tailed chains, a tractable approach to characterize network traffic as a superposition of discrete-time “on/off” sources. This is a particular case of the generic “on/off” heavy-tailed model, thus shows the same statistical features as the former, particularly self-similarity and long-range dependence, when the number of aggregated sources approaches infinity. The model is then applicable to characterize a number of discrete-time communication systems, for instance, ATM and optical packet switching, to further derive meaningful performance metrics such as average burst duration and the number of active sources in a random instant.The authors would like to acknowledge the support of the UKLight MASTS project (EPSRC, UK) and the DIOR project (MEC, Spain) to this work

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