Jan Späth

Evaluation of Reservation Mechanisms for Optical Burst Switching

Summary In this paper, we give an overview and classification of optical burst switching schemes and present burst reservation concepts. The performance of various basic reservation mechanisms proposed in literature is compared. Furthermore, a new analysis is introduced that allows to calculate the loss probabilities of a two-class system based on the reservation mechanism just-enough-time (JET) for arbitrary offsets. Finally, a variety of new results is presented including the dependence of burst loss probabilities on offset, burst length distribution, and interarrival distribution.

Study on the Implementation of Optical Transparent Transport Networks in the European Environment—Results of the Research Project COST 239

This paper reports the main results obtained in the framework of the COST239 project on the implementation of transparent optical network schemes to connect main European cities. The investigation on transmission limitations has shown that transmission systems, for which 1662:5 Gbit/s WDM systems are used due to traf®c reasons, have a maximum range shorter than 1000 km. This condition does not allow a completely transparent network. Two solutions, the partitioned and the gridconnected network architecture, are proposed, described, and compared in the paper.

Dynamic routing and resource allocation in WDM transport network

Abstract This contribution concentrates on dynamic routing in Wavelength Division Multiplexing (WDM) networks. It is shown that a strategy based on pre-calculated alternatives and an adaptive dynamic path search performs very well over a wide load range. Moreover, specific effects for the impact of resource allocation strategies in photonic WDM networks are highlighted, especially the influence of wavelength converter usage strategies in networks with partial conversion. The paper also investigates the way non-Poisson traffic behaviour affects performance of routing strategies and presents how the results from dynamic routing investigation can help to optimise the network planning process.

An efficient method to estimate transponder count in multi-layer transport networks

The cost of a multi-layer transport network comprising a WDM layer and an SDH/SONET/OTN layer is in many cases dominated by the number of electro-optical converters (transponders) in the network. An efficient method to estimate the transponder count required in multi-layer networks, consisting of opaque, transparent, or hybrid nodes, is proposed. The method is based on analytical approximations which take only a small number of characteristic network topology and traffic parameters as input and are therefore easy to apply to many network scenarios. It is shown that the approximations match the results achieved by optimisation algorithms with very good accuracy. This enables comparison of network architectures and transponder technologies in a very general way. As an example for the application to a relevant practical issue, the paper analyses cost efficiency of a 40G transponder deployment.

Performance Evaluation of Photonic Networks Under Dynamic Traffic Conditions

This paper focuses on two aspects of photonic network traffic performance investigation. Two different modelling approaches for the evaluation of network nodes under dynamic traffic conditions are described. This allows to evaluate how suitable different node architectures are for networks carrying dynamic traffic. Furthermore, routing strategies are becoming more important with increasing dynamic. A lot of work reported in literature deals with “wavelength routing”. In most cases however, this means static wavelength assignment to routes and not dynamical routing of random wavelength path requests. This paper now considers dynamic traffic aspects of wavelength routing where many analogies to classical routing strategies can be observed. Therefore, a short overview of routing methods is given before we describe our modelling approach and present some case studies and results.

Next-generation transport solutions for IP backbone networks: benefits of an ASTN-based multilayer OTN network

This paper concentrates on solutions for next-generation IP (Internet Protocol) backbone networks. This is a key issue for many network operators since IP will be the dominating network layer technology on which an ever increasing number of applications with growing bandwidth requirements will be based. Without new network solutions, this trend would lead to a strong increase in number and size of IP routers while already today’s requirements make it difficult to realise large-scale IP backbone networks in a stable and cost-efficient way. This paper investigates the benefits that an appropriate transport network based on ASTN (Automatic Switched Transport Network) and OTN (Optical Transport Network) technology can bring to future IP backbone networks - providing the stable basis on which next generation IP networks can be built. Network modelling is used to show that in addition to qualitative benefits a transport network based IP backbone solution can lead to a significant reduction of network equipment cost.

IP over OTH/ASTN: from concepts to real deployments

This paper highlights advantages of Optical Transmission Network (OTN) standards, explains its benefits in combination with IP networks and discusses potential introduction strategies. Furthermore a practical introduction example is presented.

Performance Analysis of a Combined WDM/TDM Network Based on Fixed Wavelength Assignment

Photonic telecommunication networks gain increasing importance in various fields extending from access to wide area networks. Due to limitations of fast all-optical switching technology, many promising concepts are based on circuit switching. In this paper, we propose a new and simple star topology using fixed wavelength assignment and a combination of wavelength and time division multiplexing. Owing to the fixed assignment, no tunable components or wavelength converters are needed in the central star element. For this system architecture, we present a performance evaluation based on a probabilistic method to calculate call blocking probabilities, which is validated by simulation and compared to a rough approximation based on a simple loss system. The results allow to evaluate the trade-off between capacity increase either by additional wavelengths or additional time slots in the system.