Jan Skodzik

Survey on real-time communication via ethernet in industrial automation environments

For companies in the automation industry, the development of real-time Ethernet to connect devices is of high economic interest to replace conventional fieldbus systems. Therefore, many approaches for adapting Ethernet to real-time requirements come from industrial applications. This is a challenging task as the original Ethernet standard IEEE 802.3 was not designed for real-time data transmission. Likewise, protocols basing on Ethernet like TCP, UDP, and IP do typically not consider real-time requirements. Hence, adaptations on several OSI layers become necessary to make the industrial system meet hard real-time requirements. For this purpose, a multitude of realtime capable Industrial Ethernet systems has been developed, which solve the problems of standard Ethernet- and TCP/IP- or UDP/IP-based communication in a variety of ways. This paper gives a summary of different Industrial Ethernet protocols for the real-time data transmission via Ethernet in automation environments. Advantages and disadvantages of these protocols are analyzed with regard to their sustainability in terms of their realtime capability, reliability, scalability, self-configuration of the network, and hardware requirements. Against the background of connected devices tremendously growing in number and computational power in the prospective “Industrial Internet”, consequences for future developments are drawn.

Investigation of the use of embedded Web Services in smart metering applications

The actual situation in smart metering is characterized by a coexistence of a large number of proprietary and open standards for wired as well as wireless communication. These standards show low or no interoperability to each other. Therefore, it is very difficult to integrate multi-vendor solutions using one sustainable holistic approach. The proposed approach is to use Web Service technology as an open widespread Internet standard for the creation of a heterogeneous network for smart metering devices. Smart metering is an emerging topic for realizing modern energy policies. Monitoring, analyzing, and controlling of power consumption is the precondition for optimizing energy strategies. This work focuses on the integration of Web Service technology in the area of smart meter communication. Furthermore, mechanisms for reducing Web Service traffic overhead by over 90% is presented.

HaRTKad: A hard real-time Kademlia approach

The Internet of Things is becoming more and more relevant in industrial environments. As the industry itself has different requirements like (hard) real-time behavior for many scenarios, different solutions are needed to fulfill future challenges. Common Industrial Ethernet solution often leak scalability, flexibility, and robustness. Most realizations also require special hardware to guarantee a hard real-time behavior. Therefore, an approach is presented to realize a hard realtime network for automation scenarios using Peer-to-Peer (P2P) technology. Kad as implementation variant of the structured decentralized P2P protocol Kademlia has been chosen as base for the realization. As Kad is not suitable for hard real-time applications per se, changes of the protocol are necessary. Thus, Kad is extended by a TDMA-based mechanism. Additionally, to evaluate the performance an prototype is presented, which is realized on an embedded platform with a real-time operating system. Thereby, with the presented approach and a realized prototype it is possible to investigate the performance of a Kad network with hard real-time capabilities.

DuDE: A distributed computing system using a decentralized P2P environment

The P2P-based system for the distributed computing of statistics called DuDE is presented. High scalability and failure resilience features of P2P are exploited to achieve a high-performance distributed system, which avoids the bottlenecks of a centralized computing system. To ensure high data availability, a sophisticated algorithm for distributed data storage is integrated. Furthermore, an algorithm for global peer discovery is presented, which allows for finding all data assigned to peers without the need for a central instance. For the realization of DuDE, common working stages of distributed computing are extended to enable a highly scalable computing system based on P2P technology. Generated results from a test system show a nearly perfect linear speedup for distributed computing as well as high processor and memory relief compared to a centralized solution.

Time synchronization in the DHT-based P2P network Kad for real-time automation scenarios

In this paper, an approach to synchronize the P2P network Kad to be applied in automation scenarios is presented. The approach bases on a deterministic algorithm to synchronize the network, which is required for hard real-time applications. Todays Industrial Ethernet solutions include and support machine to machine communication in automation scenarios. However, instead of allowing direct communication, the communication relies on centralized structures, which are deficient in resilience and scalability However, instead of allowing direct communication, the communication relies on centralized structures. The presented decentralized approach benefits from nodes helping to synchronize the network. However, the higher the number of helping nodes the higher is the time deviation on the nodes of the network, which contrary results in a higher time error. Therefore, a trade-off between synchronization performance and time error has to be determined to meet predefined constraints depending on the application scenario. Moreover, the individual clock drift of every device is considered to define necessary re-synchronization intervals of the network. Additionally, the optimum number of nodes to synchronize the Kad based network has been identified and the resulting synchronization performance and generated traffic are determined. Furthermore, an approach is presented to handle the dynamic churn of nodes.

A Highly Integrable FPGA-Based Runtime-Configurable Multilayer Perceptron

In this paper, a highly integrable Field Programmable Gate Array-based hardware design of multilayer perceptron as a realization of an artificial neural network is presented. Such a hardware solution ensures a deterministic behavior required for any hard real-time compositions. The integration into existing systems is achieved by the application of UDP/IP. %A developed protocol enables the hardware solution to act as a stand-alone device with no need for an additional host PC. Additionally, the presented design is highly flexible due to a parameterizable multilayer perceptron approach. However, most reconfigurations usually require a hard coded reimplementation, resynthesis, and the download of a new bit file to the target platform, which also requires an additional host PC. Contrary with the presented solution, it is possible to configure the multilayer perceptrons parameters during runtime via a software interface. This approach allows the multilayer perceptron to be adapted to nearly any application. The developed design combines the flexibility of a software solution to generate and comfortably reconfigure the multilayer perceptron as well as the high performance of a hardware solution. %The investigation of hardware utilization and performance of a running prototype stützt%Finally, the hardware utilization and performance are investigated. As proof of concept, a running prototype has been realized, which shows the design to be highly flexible and with good performance while the hardware resource consumption is kept minimal.

Extensive analysis of the Kad-based distributed computing system DuDE

The distributed computing of data is a challenging task in terms of the self-organizing task distribution and computing, especially if distributed computing systems are becoming very large and complex. Therefore, the distributed hash table (DHT)-based P2P system called DuDE has been developed to compute statistics of access nodes of Internet service providers in an efficient way. DuDE exploits the high failure resilience and scalability features of the DHT network Kad to achieve a high-performance distributed system, which avoids the bottlenecks of a centralized computing solution. To ensure highly available data, Reed-Solomon codes for reliable distributed data storage are utilized. For implementing DuDE, usual working steps of distributed computing have been extended to realize a highly scalable computing system. We have developed a simulation model for a large-scale DuDE network consisting of up to 9,000 access nodes for computing statistics. In this paper, simulation results are presented, which demonstrate that DuDE is able to almost linearly accelerate the distributed computing compared to a centralized solution while introducing low traffic overhead.

CoHaRT: A P2P-based deterministic transmission of large data amounts using CoAP

In Industrial Ethernet environments, usually only small amounts of data are transmitted. These transmissions must be deterministic to meet hard real-time requirements. But prospectively, also the deterministic transmission of high amounts of data and data streams is required. In this paper, a system based on the modified Peer-to-Peer network Kad called HaRTKad combined with the standardized protocol CoAP is presented to fulfill these requirements. The HaRTKad network bases on UDP. Because of the limited size of UDP packets, only small amounts of data can be transmitted and interpreted. Therefore, CoAP was chosen as protocol on top of HaRTKad. A highlight of CoAP is its applicability on constrained devices like embedded systems in automation environments. It has a very low overhead, high simplicity, and is very effective and well suited for the intended domain. CoAP enables the transmission and interpretation of big data amounts using the blockwise transfer. Thereby, HaRTKad ensures the deterministic data transmission of the packets. The combination of CoAP and HaRTKad is called CoHaRT. Besides the described concept of CoHaRT, real measurements from a running prototype are presented to demonstrate the performance of the data transmission.

Emulation of SDN-supported automation networks

Software-defined networking (SDN) is a principle for the flexible configuration of networks, which recently has aroused an increasing interest of researchers and companies. Today, the operation and configuration of networks as well as their adaptation to changing requirements represent a major challenge if legacy network management protocols are used due to their inability to provide network-wide configuration. Compatibility issues with legacy protocols or even proprietary protocols have further contributed to hardly reconfigurable and inefficient networks and thus prepare the way for the new concept called SDN. SDN implementations are mainly in the data center today. Implementations will find their way into broader networking applications over the next few years. However, even automation networks with highest QoS requirements can benefit from SDN support by achieving significantly more devices that meet these requirements. Therefore, this paper addresses the emulation of SDN-supported automation networks to examine possible design options. Limitations and possibilities when using the popular and widely accepted SDN emulator Mininet are analyzed.

P-DONAS: A P2P-Based Domain Name System in Access Networks

The domain name system (DNS) includes infrastructures deployed by Internet service providers (ISPs) and third-party suppliers to ensure high responsiveness, resilience, and load sharing. This equipment implies high effort and energy for 24/7 operation. To facilitate cost reductions in this regard, P-DONAS—a peer-to-peer (P2P)-based DNS—organizes access nodes (ANs) of an ISP’s access network, which possess available resources, into a decentralized, self-organizing distributed hash table--based P2P network. Each AN acts as traditional DNS server and solely stores a piece of DNS data. DNS requests issued to an AN are resolved via P2P lookups while maintaining full compatibility with traditional DNS. The article discusses the application of P-DONAS as both a complement and an alternative to traditional DNS. Results from both simulations and a practical test arrangement prove P-DONAS’ high scalability and its performance comparable to that of a commercial DNS name server relieving this name server by 53% to 75% of DNS traffic.