Joachim Scharf

Comparison of contention resolution strategies in OBS network scenarios

Optical burst switching (OBS) has attracted interest as a transport network architecture for the future optical Internet. As OBS relies on statistical multiplexing efficient contention resolution is a key issue in order to achieve a low burst loss probability. Basically, contentions can be resolved by wavelength conversion, deflection routing and delaying the burst in a fiber delay line or a combination of these schemes. This paper compares the basic and combined contention resolution strategies in two reference core network scenarios with respect to burst loss probability and end-to-end transfer delay. We show that the effectiveness of those contention resolution schemes highly depends on the load offered to the network and the dimensioning of specific nodes and links. For high load, contention resolution schemes applying deflection routing have an end-to-end transfer time increase in the order of 10-60% depending on the scheme.

Ethernet – A Survey on its Fields of Application

During the last decades, Ethernet progressively became the most widely used local area networking (LAN) technology. Apart from LAN installations, Ethernet became also attractive for many other fields of application, ranging from industry to avionics, telecommunication, and multimedia. The expanded application of this technology is mainly due to its significant assets like reduced cost, backward-compatibility, flexibility, and expandability. However, this new trend raises some problems concerning the services of the protocol and the requirements for each application. Therefore, specific adaptations prove essential to integrate this communication technology in each field of application. Our primary objective is to show how Ethernet has been enhanced to comply with the specific requirements of several application fields, particularly in transport, embedded and multimedia contexts. The paper first describes the common Ethernet LAN technology and highlights its main features. It reviews the most important specific Ethernet versions with respect to each application fields requirements. Finally, we compare these different fields of application and we particularly focus on the fundamental concepts and the quality of service capabilities of each proposal.

IKR Simulation Library

The Simulation Library (SimLib) of the Institute of Communication Networks and Computer Engineering (IKR) [216] at the University of Stuttgart is a tool for event-driven simulation of complex systems in the area of communications engineering. The first version of the IKR SimLib was implemented in Pascal in the 1980s. Later in 1993, during his dissertation [256] Hartmut Kocher redesigned the Pascal simulation library and developed an objectoriented class library of the IKR SimLib in C++.

Efficiency analysis of distributed dynamic optical bypassing heuristics

The energy consumption of transport networks gets more and more attention as it is expected to become a problem with future traffic increase. Dynamic optical bypassing is a promising approach to tackle increasing energy consumption as well as growing resource usage. Performance evaluations are necessary in order to find suitable bypassing approaches. Recently, distributed approaches for bypass establishment and teardown have been proposed. There is so far no comprehensive performance evaluation available. In this paper, we present four different distributed heuristics for bypassing. We implemented a simulation framework for the performance evaluation of these heuristics. Two approaches without dynamic bypassing serve as reference. The results show benefits of dynamic bypassing with respect to required energy and resources. We relate these benefits to the necessary switching operations.

Optimized Frame Packing for OFDMA Systems

Orthogonal frequency division multiple access (OFDMA) is the basis for several emerging wireless systems, such as 802.16e (WiMAX) or 3GPP long term evolution (LTE). In OFDMA, different users are multiplexed in time and frequency. In the 802.16e adaptive modulation and coding (AMC) downlink, the data bursts for a particular terminal have a rectangular shape and need to be placed in the two-dimensional time/frequency plane. The position and shape of the rectangles is arbitrary, and it is the task of the frame packer to pack the frame efficiently, wasting as little space as possible. In this paper, we treat the frame packing problem as a strip-packing problem. We solve this combinatorial optimization problem by developing a suitable representation for a genetic algorithm. This algorithm can reach within 5% of the theoretical lower bound for the packing efficiency.

OBS vs. OpMiGua - A Comparative Performance Evaluation

Optical Burst Switching (OBS) and Optical Migration Capable Networks with Service Guarantees (OpMiGua) are two all-optical network architectures. In this paper we compare both by means of a quantitative performance evaluation based on simulations. In order to achieve a maximum of comparability both models are chosen as similar as possible and especially are fed with identical traffic. Results show differences regarding loss probabilities at which OpMiGua has a better performance.

Performance Issues in Optical Burst/Packet Switching

This chapter summarises the activities on optical packet switching (OPS) and optical burst switching (OBS) carried out by the COST 291 partners in the last 4 years. It consists of an introduction, five sections with contributions on five different specific topics, and a final section dedicated to the conclusions. Each section contains an introductive state-of-the-art description of the specific topic and at least one contribution on that topic. The conclusions give some points on the current situation of the OPS/OBS paradigms.

Software Tools and Methods for Research and Education in Optical Networks

Recent advances in photonic communication networks require planning, modelling and simulation tools of ever increasing scope and complexity. Based on valid and credible models, simulators are used heavily to investigate and assess new solutions before implementing testbeds and field trials. On the other hand, tools relying on heuristics algorithms or analytical models are widely used for network planning and dimensioning. This chapter reviews some recent trends in conception and utilisation of tools for modelling and planning, and reports several developments performed with commercial or academic tools and frameworks within the COST action 291.

Experimental Validation and Assessment of Multi-domain and Multi-layer Path Computation

Within the framework of the BONE European Network of Excellence, we setup a multi-domain multi-layer testbed covering three different networks at two distinct locations in Europe. The testbed includes two Ethernet switched client networks, which are interconnected by a wavelength switched server network. Each of these networks is operated by a GMPLS control plane and implements a path computation entity, following either the IETF PCE proposal or the DRAGON NARB. Since the communication protocols of IETF PCE and DRAGON NARB are incompatible, we propose and develop an application layer gateway, enabling inter-domain path calculation.