Jürgen Totzke

On traffic characteristics and bandwidth requirements of voice over IP applications

Voice over IP (VoIP) services will play an important role in future IP networks, promising cost savings and new revenue sources to operators and service providers. To provide quality of service guarantees, certain mechanisms need to be implemented which support predictable packet handling, bandwidth allocation, and call admission control. In order to configure these mechanisms, a solid understanding of VoIP traffic characteristics and its respective bandwidth requirements is necessary. In this paper, we characterize traffic traces generated by various VoIP applications. According to the H.323 standard, the characteristics are described by means of token bucket parameters, which are then used to derive the required service rates for individual traffic flows. While in most cases sources send out fairly steady packet streams, there are situations where software based clients emit rather bursty traffic resulting in unreasonably high bandwidth needs. On basis of these traffic flows, we investigate the effects that token bucket parameters have on the bandwidth demand and discuss tradeoff possibilities in order to reduce it.

An IN-based implementation of interactive video services

Interactive video services will be among the first broadband services to be offered to residential and business customers. This paper describes a full service network architecture based on the intelligent network (IN) which supports a large variety of services, including video on demand and other multimedia services. ATM will be deployed on an end-to-end basis, allowing standardised signalling protocols to be used. The target solution, however, requires special call and connection handling capabilities such as multi-connection calls and call transfer which are not covered by the current status of B-ISDN signalling protocols. Therefore, we introduce an alternative solution which is based on current standards and allows an evolution from a fast prototype implementation towards our target concept.

A Dimensioning Strategy for Almost Guaranteed Quality of Service in Voice over IP Networks

Providing hard quality of service guarantees for Voice over IP traffic in multi-service IP networks is quite costly in terms of network resources. However, if one is willing to slightly soften the guarantees and to accept a small probability of service degradation, the amount of capacity necessary for voice traffic can be greatly reduced. In this paper, we investigate the tradeoff between quality of service and the required bandwidth for voice traffic in IP networks taking into account different scheduling schemes. We propose a dimensioning strategy, which allows the worst-case packet delay to exceed a desired threshold with a certain probability. Based on simulations, it can be demonstrated that bandwidth is reduced while the quality of service is assured in most cases.

An object-oriented implementation of B-ISDN signalling

The implementation of the September 1992 version of CCITT Draft Recommendation Q.93B for B-ISDN Signalling is described after a brief overview of the architecture of the Siemens ATM Pilot System is given. It is shown how the software for dial-up connections has been integrated into the pre-existing object-oriented software for permanent virtual channel connections and permanent virtual paths exploiting the features of object-oriented technology. A call model is derived considering the call model for N-ISDN and the particularities of object-oriented design. The implementation of this call model is subsequently discussed. A very modular and clear structure of call-processing software has been achieved. By means of an example the extendability of the call model with respect to modifications is demonstrated. The impact on existing software is minimal due to the structure of the call model and also due to features of object-oriented technology.<<ETX>>

Agile Geschäftsprozesse durch integrierte mobile Kommunikation

Nicht-Routine-Geschaftsprozesse erfordern ein hohes Mas an Interaktion. Deshalb wird Kommunikation zunehmend in die Geschaftsprozesse integriert. Derartig erweiterte Geschaftsprozesse werden Communication Enabled Business Processes (CEBP) genannt. Dabei werden heute vorwiegend Computer Telephony Integration (CTI)-Losungen fur die Kommunikation verwendet. CTIbasierte Losungen sind jedoch hinsichtlich ihrer Funktionalitat begrenzt und relativ statisch. Die flexible Einbindung von mobilen Endgeraten ist unzureichend. Fortgeschrittene Business Process Modeling (BPM)-Plattformen hingegen erlauben eine wesentlich komfortablere Integration von Kommunikation in die Geschaftsprozesse. Besonders Service Oriented Architecture (SOA)-basierende Implementierungen von Unified Communication & Collaboration (UCC) erlauben an den Geschaftskontext angepasste Integration von Kommunikationsvorgangen auch im mobilen Umfeld. So wird benutzerzentrische, kontext- und ortsabhangige Modellierung von Geschaftsprozessen ermoglicht. Auserdem werden der Business Software ohne besonderen Integrationsaufwand die gesamte Funktionalitat von UCC und besonders deren mobile Erweiterungen zur Verfugung gestellt. Im Rahmen eines durchgefuhrten Innovationsprojektes wurden mobile Endgerate uber einen UCC-Kommunikationsserver an ein Business-Softwaresystem angebunden. Neben der Service-orientierten Anbindung der Kommunikationsdienste stand dabei vor allem eine Frage im Vordergrund: Wie wird sich die Einbindung von mobilen Endgeraten mit mobiler Erreichbarkeit und Lokalisations-Information auf die Agilitat der durchlaufenden Geschaftsprozesse auswirken? Das Ergebnis ist unerwartet positiv, weil klare Effizienzsteigerungen der betrachteten Geschaftsprozesse feststellbar sind; Eine Grosenordnung von 35 Prozent Effizienzsteigerung ist dabei durchaus realistisch. Der daraus kalkulierbare Return on Investment (ROI) rechtfertigt mogliche Investitionen in derartige Plattformen und Systeme. Der im Innovationsprojekt realisierte Prototyp hat bei den Betrachtern sofort vielfaltige Ideen fur neuartige Anwendungen ausgelost, was ein erhebliches Potenzial fur mobile Business-Applikationen erwarten lasst.