Stefan Bodamer

A new efficient integrated routing scheme for SDH/SONET-WDM multilayer networks

This paper presents and evaluates the new weighted integrated routing scheme to solve the problem of dynamic routing and grooming in meshed SDH/SONET-WDM multilayer networks. Its performance is compared to other integrated and nonintegrated schemes using a cost model.

A new scheduling mechanism to provide relative differentiation for real-time IP traffic

Design alternatives for supporting real-time traffic in a differentiated services IP network node are studied. A scheduling algorithm called weighted earliest due date (WEDD) is proposed that provides tunable delay differentiation for applications like video or voice over IP. WEDD enhances the earliest due date (EDD) scheduling mechanism in such a way that not only different delay bounds but also different deadline violation probabilities are provided. The ratios of violation probabilities in different classes are easily specified by a set of parameters. Simulation studies are performed to show that the scheduler is able to maintain the specified ratios under various traffic conditions in short as well as in long time scales.

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.

A scheduling algorithm for relative delay differentiation

An important issue in the design of multi-service IP networks is to find appropriate mechanisms to provide different levels of quality of service (QoS) for different types of applications. In this paper, scheduling mechanisms for real-time traffic in a differentiated services IP network are studied. A new scheduling algorithm called weighted earliest due date (WEDD) is proposed that provides tunable delay differentiation for real-time applications like voice over IP. WEDD is an enhancement of the earliest due date (EDD) scheduler in the sense that not only different deadlines but also different deadline violation probabilities are provided. The ratios of the violation probabilities are directly defined by a set of parameters. Simulation studies are performed to show that the scheduler is able to maintain the specified ratios under various load conditions.

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.

Dienstgütemetriken für elastischen Internetverkehr

ZUSAMMENFASSUNG Mit der zunehmenden Bedeutung des Internet als Basis für eine Vielzahl von Kommunikationsdiensten und -anwendungen wird der Ruf nach einer Unterstützung von Dienstgüteanforderungen immer lauter. Allerdings stellt sich häufig die Frage, wie sich Dienstgüte quantifizieren lässt, um einerseits solche Anforderungen formulieren zu können und andererseits die Leistungsfähigkeit bestehender und geplanter Netze und Netzkomponenten beurteilen zu können. In diesem Beitrag wird aufgezeigt, dass eine Konzentration auf klassische Metriken der Paketebene nicht genügt, sondern dass auch Einflüsse auf höheren Ebenen der Kommunikation, z.B. der Transportebene, bei der Definition geeigneter Dienstgütemaße berücksichtigt werden müssen. Dies gilt insbesondere für elastischen Verkehr, zu dem auch der im heutigen Internet dominierende WWW-Verkehr zählt. Für die Transportebene werden eine Reihe relevanter Leistungsmaße beschrieben, deren praktische Anwendung anhand eines typischen Beispiels gezeigt wird.

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.