Thomas Pfeiffenberger

Reliable and flexible communications for power systems: Fault-tolerant multicast with SDN/OpenFlow

Our work evaluates the use of software-defined networking (SDN) for reliable communication. Reliable communication has become an important topic in many areas, including energy communication networks or, more generally, automation control networks. Electrical grids are developing into smart grids, which depend heavily on reliability, robustness and optimized resource usage. On the other side, the separation of communication and network control proposed by SDN opens new possibilities for reliable and flexible networks. In this work, we show how OpenFlow, the leading SDN framework, could be used to solve the problem of robust multicast better than existing technologies used by substations. Our solution uses the fast-failover groups feature of OpenFlow to provide one-link fault tolerance with little packet loss and can provide routes that use resources efficiently and are less likely to fail. Robust shortest path routing and minimum spanning tree broadcast routing come as special cases. We also show how this solution can be extended to handle more link failures (even an arbitrary number of them) or to provide more efficient routes.

Evaluation of software-defined networking for power systems

A highly available and secure communication infrastructure is one of the major prerequisites for modern power systems. In this paper we evaluate the use of a software-defined networking infrastructure in the domain of energy communication networks. The advantages and potential risks of using software-defined networking at the current stage of development in productive networks are investigated. Test scenarios are defined based on IEC 61850 traffic specification to perform traffic measurements using the OpenFlow standard and real network devices. Software-defined networks have the potential to offer significant advantages over conventional networks. However, we will show through our analysis and measurements that there are still open issues that need to be solved before usage in a productive environment.

One-way-delay measurements with CM toolset

Internet Quality of Service (QoS) is an actual research topic. The need for more or less guaranteed transmission rates (e.g. for bulk-data transfer applications), upper bounds for transmission delay and jitter (e.g. for real time applications like IP telephony, video-conferencing) stimulated the development of QoS transmission technologies like ATM, IP-RSVP and the actual discussion about Diff-Serv mechanisms. This paper describes the implementation and the first measurement trials with the One-Way-Delay measurement components of CM-Toolset. The overall tool architecture consists of a distributed system of load generators and receivers (agents) and a measurement server, which stores the measurement results in a data-base. To measure the exact One-Way-Delay (OWD) the synchronised GPS clock system was integrated. The measurements were realised in a 4 hop heterogeneous IP and ATM network. The clock drift during the loop measurements was about 10 ms, linear and deterministic. So the drift could be eliminated by statistical computations. The measurements were made for UDP flows under different load situations( 1 UDP....5 UDP, TSDU size, interarrival time), and for n*UDP+1 TCP. The measurements show very clearly the interaction and dependencies between the number of flows, their load parameters and the QoS parameters like packet loss and one way delay. The measurements of UDP+TCP multiplexed flows explains, why the concept of flow separation is important for QoS guarantees. CM Toolset can be used by protocol engineers for the development of new QoS-based network technologies by collecting measurement data for modelling the network behaviour. Network managers can tune the operational network to improve the quality e.g. of IP-Telephon.

Dynamic Evacuation Guidance as Safety Critical Application in Building Automation

In building automation systems a bunch of very diverse applications have to be executed at the same time. This includes applications with special safety and security requirements. One of these applications is the dynamic evacuation guidance, i.e. electronic signs which show the direction of the most fortunate evacuation path from public buildings like schools, universities, office buildings or buildings of public authorities during emergency situations like fire or also terrorist attacks. In this context we explored the new and innovative solution Flexit, focussing on safety issues of the communication infrastructure.

Communication coverage awareness for self-aligning wireless communication in disaster operations

Broad band communication in international disaster response actions is becoming more and more important. The information exchange between field commanders and tactical commanders lead to a better situational awareness on all layers of disaster management. After large scale disasters the communication infrastructure is often destroyed. Setting up a communication infrastructure is essential in todays disaster response actions. As organizations in disaster response actions are not consisting of IT experts, the setup and installation has to be easy. For example [1] presents such a system. Furthermore the knowledge where to deploy wireless communication gateways and wireless relay nodes is essential. Consequently the positions of field commanders can not only be based on tactical needs but also on communication needs. In this paper we present a simulation based visualization tool which helps to evaluate deployment locations for communication equipment to achieve adequate communication coverage with respect to specific disaster related information. This allows an optimal positioning of relay nodes and field commanders in the field to ensure broad band communication in disaster response actions and thus faster help for the people.

CMT II: an agent based framework for comprehensive IP measurements

The Communication Measurement Tool II (CMT II) is a framework for comprehensive IP measurements. It is the next development stage of the succeeded measurement framework called CMToolset. The purpose of a distributed measurement framework, like CMT II, is to provide detailed information about the network for performance evaluation, network engineering or detecting network problems. Regarding this point CMT II operates on different layers of the OSI layer model, as well as it is designed in an open structure in order to allow further extensions for upcoming protocols, networks and applications. Furthermore CMT II is designed to conduct active as well as passive measurements. CMT II is based on the agent framework JADE, which allows the deployment of measurement agents on different platforms and the interaction with other agent frameworks. Unlike other measurement tools, CMT II can also be applied on wireless or mobile scenarios to study the influences of wireless and mobile data transmissions

Concepts for Reliable Communication in a Software-Defined Network Architecture

Not available services or service interruption could have different impact to our social life. Emails or messages which are not delivered in a proper time-frame could lead to omit a meeting or a discussion with colleagues. Interconnected CPS in different domains, like autonomous driving, smart grids, Industry 4.0, needs a guaranteed and safe delivery of information.

A New Agent-Based Approach towards Distributed IP Measurements

The Communication Measurement Tool II (CMT II) is a modular architecture for comprehensive IP measurements. The main objective of CMT II is to provide an overall quantitative and qualitative picture of a network. CMT II operates on different layers of the OSI layer model and its open standard based architecture is designed to allow further extensions for upcoming new protocols, networks and applications. Unlike other measurement tools, CMT II can be employed in wireless or mobile scenarios as well, in order to study the behavior of wireless and mobile data transmissions. This paper provides an introduction into the CMT II architecture, its measurement possibilities and the supported analysis methods.