Ari Keränen

The ONE simulator for DTN protocol evaluation

Delay-tolerant Networking (DTN) enables communication in sparse mobile ad-hoc networks and other challenged environments where traditional networking fails and new routing and application protocols are required. Past experience with DTN routing and application protocols has shown that their performance is highly dependent on the underlying mobility and node characteristics. Evaluating DTN protocols across many scenarios requires suitable simulation tools. This paper presents the Opportunistic Networking Environment (ONE) simulator specifically designed for evaluating DTN routing and application protocols. It allows users to create scenarios based upon different synthetic movement models and real-world traces and offers a framework for implementing routing and application protocols (already including six well-known routing protocols). Interactive visualization and post-processing tools support evaluating experiments and an emulation mode allows the ONE simulator to become part of a real-world DTN testbed. We show sample simulations to demonstrate the simulators flexible support for DTN protocol evaluation.

Working day movement model

Abstract movement models, such as Random Waypoint, do not capture reliably the properties of movement in the real life scenarios. We present and analyse a movement model for delay-tolerant network simulations that is able to produce inter-contact time and contact time distributions that follow closely the ones found in the traces from the real-world measurement experiments. We validate the movement model using the ONE simulator.

Simulating Mobility and DTNs with the ONE (Invited Paper)

Delay-tolerant Networking (DTN) enables communication in sparse mobile ad-hoc networks and other challenged environments where traditional networking fails and new routing and application protocols are required. Past experience with DTN routing and application protocols has shown that their performance is highly dependent on the underlying mobility and node characteristics. Evaluating DTN protocols across many scenarios requires suitable simulation tools. This paper presents the Opportunistic Networking Environment (ONE) simulator specifically designed for evaluating DTN routing and application protocols. It allows users to create scenarios based upon different synthetic movement models and real-world traces and offers a framework for implementing routing and application protocols (already including six well-known routing protocols). Interactive visualization and post-processing tools support evaluating experiments and an emulation mode allows the ONE simulator to become part of a real-world DTN testbed. We examine a range of published simulation studies which demonstrate the simulator’s flexible support for DTN protocol evaluation.

Message fragmentation in opportunistic DTNs

Delay-tolerant networking is used for communication in challenged environments such as MANETs, in which links are unstable and end-to-end paths between communicating nodes may not exist. Messages may be significantly larger than packets in IP networks. Large messages lead to longer transfer times rendering it more likely that a link breaks in the middle of a message transfer. This motivates investigating how to support partial message transfers through fragmentation. In this paper, we formulate fragmentation independent of routing algorithms, introduce several fragmentation strategies, and evaluate these by simulations to derive recommendations for using fragmentation in DTNs.

Effect of non-cooperative nodes in mobile DTNs

When applying delay-tolerant networking concepts to communication in mobile ad-hoc networks formed between mobile users, a general assumption is that users are willing to share own resources to support communication between others. However, we cannot assume that all users are altruistic in their behavior; instead, we have to deal with users who only make a limited or no contribution to the mobile community. Nodes not participating in communication only reduce the effective node density, but do not consume resources. Others act as sources and sinks but perform only limited or no forwarding and thus may impact the overall network performance. When considering routing in mobile DTNs, such selfish nodes have to be considered. We introduce two types of selfish nodes and evaluate their impact on message delivery performance for different routing protocols by means of simulation in different synthetic mobility models and with real-world traces. We find that their impact can be surprisingly low in our scenarios, suggesting that DTN communication can be quite robust against selfishness and that controlled non-cooperative behavior may be a suitable way to overcome resource limitations, such as battery depletion.

End-to-end security for sleepy smart object networks

We develop a new secure and energy-efficient communication model for the Constrained Application Protocol (CoAP), a light-weight communication protocol designed for smart object networks. This architecture and the communication model ensures data integrity and authenticity over a multi-hop network topology. It provides a mirroring mechanism that uses a proxy to serve data on behalf of sleeping smart objects, thereby allowing them to act as always-online web servers. A working prototype implementation of the architecture is also developed. The security features in the architecture presented in this paper are based on using strong public-key cryptography. Contrary to popular belief, our performance evaluation shows that asymmetric public-key cryptography can be implemented on small 8-bit microcontrollers without modifying the underlying cryptographic algorithms using public libraries.

DTN over aerial carriers

Delay-tolerant Networking has been discussed for mobile environments, both with predictable (e.g., between buses) and unpredictable opportunistic (e.g., between people) contact schedules. While some research projects have envisioned the larger scale use of DTNs to perform message forwarding based upon social interactions between humans, the geographic dimension of simulations has mostly been limited to rather local areas such as (parts of) cities or modestly sized areas covered by public transportation. In this paper, we explore how messages could be carried over a realistic large scale global network, between airports based upon scheduled flight connections. We investigate the interaction with different routing protocols, the impact of scheduling uncertainties, and the limiting factors by means of simulations and analysis. While we do not consider in depth the integration of aerial-carrier-based DTN message delivery into regional and local social networks, we provide some initial approximation on this subject and discuss some potential roles for message forwarding based upon mass transportation.

Impact of Network Address Translator Traversal on Delays in Peer-to-Peer Session Initiation Protocol

Peer-to-Peer Session Initiation Protocol (P2PSIP) is a distributed communication system being standardized in the Internet Engineering Task Force (IETF). Since it uses the peer-to-peer paradigm, P2PSIP faces the problems created by Network Address Translators (NATs); even peers located behind NATs need to be able to not only initiate connections to other peers but also accept connections initiated by other peers. In this paper, we study the impact of standardized NAT traversal solutions, namely Session Traversal Utilities for NAT (STUN), Traversal Using Relays around NAT (TURN), and Interactive Connectivity Establishment (ICE), on delays in P2PSIP overlay networks. These delays are studied from the viewpoint of wireless and wired nodes acting as clients in a P2PSIP overlay network running in the PlanetLab. The delays are also compared to those of the traditional client/server Session Initiation Protocol (SIP).

Connecting IoT Sensors to Knowledge-based Systems by Transforming SenML to RDF

Abstract Applying Semantic Web technologies to Internet of Things (IoT) enables smart applications and services in a variety of domains. However, the gap between semantic representations and data formats used in IoT devices introduces a challenge for utilizing semantics in IoT. Sensor Markup Language (SenML) is an emerging solution for representing device parameters and measurements. SenML is replacing proprietary data formats and is being accepted by more and more vendors. In this paper, we suggest a solution to transform SenML data into a standardized semantic model, Resource Description Framework (RDF). Such a transformation facilitates intelligent functions in IoT, including reasoning over sensor data and semantic interoperability among devices. We present a fishery IoT system to illustrate the usability of this approach and compare the resource consumptions of SenML against other alternatives.

Reducing delays related to NAT traversal in P2PSIP session establishments

This paper focuses on reducing the Network Address Translator (NAT) traversal-related components of the session establishment delay in peer-to-peer Session Initiation Protocol (P2PSIP) overlays. To reduce the delay, we propose to group the management of different connections so that the (time-consuming) NAT traversal procedures performed for one connection can be reused when establishing other connections. To do this, we propose to use the Host Identity Protocol (HIP) to perform connection management in P2PSIP overlays. In order to evaluate the performance gains resulting from this approach, we have implemented a P2PSIP system whose modular design allows us to build overlay networks with and without HIP and measure their differences in performance. Our experiments show that grouping the management of different connections results in a significant reduction in the session establishment delay in the presence of NATs.