Disruption-tolerant networks (DTNs) have a wide range of applications, including emergencies where traditional communication infrastructure has been destroyed, remote rural deployments where communication infrastructure does not exist, and environmental monitoring in which animals are equipped with sensors and transmit data whenever they come into contact with a base station. Using the de-facto DTN protocol standard, Bundle Protocol version 7, nodes transmit data using Convergence Layer Protocols, which serve as abstractions for the underlying communication technology. In this article, we introduce QUICL, a novel convergence layer for disruption-tolerant networks. QUICL is built on the QUIC transport protocol, which offers advantages over TCP in a disruption-tolerant setting. In particular, it improves congestion control, supports multiplexing, ensures reliable transmission, effectively manages unstable networks, and encrypts traffic by default. Our implementation, already merged upstream, is based on the free and open-source DTN7-go-protocol suite and the QUIC-go-library. Our experimental evaluation shows that even in challenging situations such as bundle transmission over 63 hops with a packet loss of 30% on each hop, QUICL still delivers data where most other DTN software/convergence layer combinations fail to transmit any data.

Recent advances in low-cost microcontrollers have enabled innovative smart home applications. However, existing systems typically consist of single-purpose devices that only report sensed data to a controller. Given the potential for residential emergencies, we propose to integrate emergency detection systems into smart home environments. We present an ad-hoc distributed sensor network (DSN) designed to detect five common residential emergencies: fires, gas and water leakages, earthquakes, and intrusions. Our novel approach combines diverse sensors with a voting-based consensus algorithm among multiple nodes, improving accuracy and reliability over traditional alert systems. The consensus algorithm employs a majority rule with weighted votes, allowing adjustments for various scenarios. An experimental evaluation confirms our approach’s effectiveness in accurately detecting emergencies while demonstrating reliability in mitigating node failures, ensuring system longevity, and maintaining robust communication. Additionally, our approach significantly reduces power consumption compared to alternatives.

Wireless sensor networks (WSNs) can automate data sensing tasks. To ensure redundancy and manage network connectivity issues, a sensing node stores a copy of the gathered data. Since this data may contain sensitive personal or business information, protecting privacy and preventing unauthorized access is crucial. We introduce the Write-only File System (WoFS), a novel encryption system for WSNs that secures data without user interaction, even if a sensor node is stolen. WoFS utilizes either symmetric encryption with volatile keys via a ratchet mechanism or asymmetric encryption. Asymmetric encryption, while slower, allows operation post-reboot, unlike the ratchet-based method. Our experiments show that WoFS achieves write speeds of 200 MB/s or higher, making it suitable for WSN applications. All developed software and artifacts are available under a permissive open-source license.

Fires are among the most dangerous and life-threatening emergency situations that might occur in residential settings. Therefore, smoke detectors are required in many rooms of a house in many European countries, such as the Netherlands, the UK, Germany, and Austria. We present a novel smart smoke detector that can be used for communication in emergency situations. In addition to playing a sound when it detects smoke, it provides (i) an acoustic message interface to call for help or leave a message, (ii) a mesh-based wireless communication interface to allow communication even if infrastructure is damaged, and (iii) an accelerometer to detect earthquakes.

We present an approach to enable long-range device-to-device communication between smartphones in crisis situations. Our approach is based on inexpensive and readily available microcontrollers with integrated LoRa hardware that we empower to receive and forward messages via Bluetooth, Wi-Fi, or a serial connection by means of a dedicated firmware, called rf95modem. The developed firmware cannot only be used in crisis scenarios but also in a variety of other applications, such as providing a communication fallback during outdoor activities, geolocation-based games or broadcasting of local information. We present two applications to show the benefits of our approach. First, we introduce a novel device-to-device LoRa chat application that works on both Android and iOS as well as on traditional computers like notebooks using a console-based interface. Second, we demonstrate how other infrastructure-less technology can benefit from our approach by integrating it into the DTN7 delay-tolerant networking software. Furthermore, we present the results of an in-depth experimental evaluation of approach consisting of (i) real-world device-to-device LoRa transmissions in urban and rural areas and (ii) scalability tests based on simulations of LoRa device-to-device usage in a medium-sized city with up to 1000 active users. The firmware, our device-to-device chat application, our integration into DTN7, as well as our code fragments of the experimental evaluation and the experimental results are available under permissive open-source licenses.

We present a novel multi-hop data dissemination protocol for wireless networks that minimizes the total energy consumption across an entire network by minimizing the transmission power at each hop. It is based on a game-theoretic model, constructs a spanning tree topology in a decentralized manner, and is usable in practice. We evaluate the protocol via simulation and a pratical implementation on a testbed of 75 Raspberry Pis, demonstrating that a total energy reduction of up to 90% can be achieved compared to a simple broadcast protocol.

Disruption-tolerant networks (DTNs) have a wide range of applications, such as emergencies where traditional communication infrastructure has been destroyed, remote rural deployments where communication infrastructure has never existed, and environmental monitoring where animals are equipped with sensors and transmit data whenever they come into contact with a base station. Using the de-facto DTN protocol standard, i.e., Bundle Protocol version 7 (BPv7), nodes transmit data via so-called Convergence Layer Protocols (CLPs) that act as general abstractions for the underlying communication technologies. BPv7 specifies MTCP and TCPCL as the two current CLPs for DTNs. However, both of them have different but equally undesirable shortcomings in terms of functionality, complexity, performance, and reliability. In this paper, we present QUICL, a novel CLP for DTNs. QUICL is based on the QUIC transport protocol and fully leverages QUIC's advantages over TCP-based transport protocols in a DTN environment. In particular, QUICL provides improved congestion control, allows multiplexing, ensures reliable transmission, effectively manages unreliable links, and uses encryption by default. Our prototypical implementation, already merged upstream, is based on the free and open-source DTN7-go protocol suite and the QUIC-go implementation. Our experimental evaluation shows that even with 30% packet loss, QUICL can still deliver data with minimal CPU overhead in scenarios where most other DTN/CLP combinations fail to transmit any data successfully.

Several areas of wireless networking, such as wireless sensor networks or the Internet of Things, require application data to be distributed to multiple receivers in an area beyond the transmission range of a single node. This can be achieved by using the wireless medium's broadcast property when retransmitting data. Due to the energy constraints of typical wireless devices, a broadcasting scheme that consumes as little energy as possible is highly desirable. In this article, we present a novel multi-hop data dissemination protocol called BTP. It uses a game-theoretical model to construct a spanning tree in a decentralized manner to minimize the total energy consumption of a network by minimizing the transmission power of each node. Although BTP is based on a game-theoretical model, it neither requires information exchange between distant nodes nor time synchronization during its operation, and it inhibits graph cycles effectively. The protocol is evaluated in Matlab and NS-3 simulations and through real-world implementation on a testbed of 75 Raspberry Pis. The evaluation conducted shows that our proposed protocol can achieve a total energy reduction of up to 90% compared to a simple broadcast protocol in real-world experiments.

Existing routing algorithms for disruption-tolerant networking (DTN) have two main limitations: (a) a particular DTN routing algorithm is typically designed to achieve very good performance in a specific scenario, but has limited performance in other scenarios, and (b) DTN routing algorithms do not take advantage of network programmability to profit from its benefits. We present ProgDTN, a novel approach to support programmable disruption-tolerant networking by allowing network operators to implement and adapt routing algorithms without knowledge of a router's interior workings using the popular JavaScript language. To consider the specific properties of a particular application scenario, network operators can incorporate context information of DTN bundles and nodes in their routing algorithms. ProgDTN is based on DTN7, a flexible and efficient open-source, platform-independent implementation of the Bundle Protocol version 7. Our experimental evaluation demonstrates that using ProgDTN to tailor a routing algorithm to a particular scenario achieves excellent results of up to 99.9% delivery ratio while reducing unnecessary transmissions by 92.9%. ProgDTN's implementation, our tailored scenario-specific routing algorithm, and code/data fragments for our experiments are released under permissive open-source licenses.

A network for environmental monitoring typically requires a large number of sensors. If a longer service life is intended, it is essential that the deployed sensor systems can be upgraded without modifying hardware. Often, these networks rely on proprietary hardware/software components tailored to the desired functionality, but these could technically also be used for other applications. We present a demo of mechanism interception, a novel approach to unobtrusively add or modify the functionality of an existing networked system, in our case a TreeTalker, without touching any proprietary components. We demonstrate how a cloud infrastructure can be unobtrusively replaced by an edge infrastructure in a wireless sensor network. Our results indicate that mechanism interception is a compelling approach for our scenario to provide previously unavailable functionality without modifying existing components.

Networked systems and applications are often based on proprietary hardware/software components that manufacturers might not be willing to adapt or update if new requirements arise. We present mechanism interception, a novel approach to unobtrusively add or modify functionality to/of an existing networked system or application without touching any proprietary components. Behavioral changes are achieved by functionality-enhancing yet unobtrusive interceptors, i.e., components introduced between systems and their environments adding or updating mechanisms. We illustrate our approach by unobtrusively adding a vertical handover mechanism between Wi-Fi and LTE to a mobile end device without disconnecting TCP sessions. Our results indicate that mechanism interception is a compelling approach to achieve improved service quality and provide previously unavailable functionality.

Software-defined networking paradigms have found their way into wireless edge networks, allowing network slicing, mobility management, and resource allocation. This paper presents dynamic role assignment as a novel approach to software-defined network topology management for wireless edge devices, such as laptops, tablets and smartphones. It combines the centralized control of wireless Network Interface Controller (NIC) modes with Network Function Virtualization (NFV) to integrate network topology transitions as well as network service and application service placement within a single mechanism. Our proposal is evaluated with respect to latency, bandwidth, and power consumption of the edge nodes. The experimental results show significant differences in both bandwidth (up to 18%) and power consumption (up to 15%) for playing different roles, and when using (a) a web proxy and (b) an intrusion prevention system as examples of application services.