Starting with the imminent roll-out of the IP Multimedia Subsystem (IMS) and fourth-Generation
networking technology Next Generation Networks (NGN) are gradually becoming reality with
charging and Quality-of-Service (QoS) issues as two of the key drivers for the evolution toward
the convergent all-IP network of the future. Therefore the 6th International Workshop on
Internet Charging and QoS Technology (ICQT 2009) was devoted to discussing the most recent
approaches models and mechanisms in this highly interesting and important research area. The
present volume of the Lecture Notes in Computer Science series includes those papers presented
at ICQT 2009-collocated this year with the IFIP Networking 2009 conference-taking place on May
15 2009 in Aachen Germany and hosted by the Rheinisch-Westfälische Technische Hochschule
(RWTH Aachen). For the commercial success of future QoS-enabled communication services the
emergence of viable business models pricing schemes and charging and accounting mechanisms is
of paramount importance. Problems in this domain can only be addressed through a broad
interdisciplinary approach linking together a variety of technical and economic perspectives
which are constantly driving a plethora of relevant research t- ics for application developers
business architects network providers service providers and customers. Within the current
trend toward a convergent NGN architecture compe- tion modeling pricing mechanisms and the
economics of inter-domain traffic are of specific importance and urgency. Thus they
determined-in the form of three technical sessions-the core of the ICQT 2009 program.
