Today, the Internet has become the most important communication infrastructure of our society. It enables worldwide users (individual, groups, and organizations) to access and exchange remote information scattered all over the world. Currently, due to the growing needs in telecommunications (Video on Demand, Video-Conference, VoIP, etc.) and the diversity of transported flows, the Internet still does not meet the requirements of integrated service networks that carry multimedia data traffic with a high quality of service (QoS). The main drivers of this evolution are the continuous growth of the bandwidth requests, the promise of cost improvements, and finally the possibility of increasing profits by offering new services. First, the Internet does not support resource reservation which is primordial to guarantee an end-to-end QoS (bounded delay, bounded delay jitter, and/or bounded loss ratio). Second, flow packets may be subjected to unpredictable delays and thus may arrive at their destination after the expiration time, which is undesirable for continuous real-time media. In this context, to optimize the financial investment of their networks, operators must use the same underlying Internet infrastructure to transport all types of flows including those associated with strict QoS requirements. Therefore, we need to develop high quality control mechanisms that can support efficient end-to-end QoS requirements. It is clear that the integration and support of these QoS parameters increases the complexity of current QoS routing algorithms and models. Many QoS challenges still exist in emerging hybrid networks often consisting of a highly heterogeneous mix of several different types of networks (wireless, broadcast, mobile, fixed, etc.) especially during the routing process which is central to the delivery of optimal performances in hybrid network environments. Providing a good QoS in heterogeneous networks for irregular traffic flows remains a significant challenge. A general problem of large-scale, distributed systems is the everincreasing complexity of their operations. This complexity is mainly driven by heterogeneity. The wide variety of underlying technologies deployed within a network and their different, if not proprietary, operational paradigms makes it hard for network operators to solve. Moreover, network operations are typically handled by one or more human operators. Manual control is time-consuming, expensive, and error-prone. Nevertheless, both technologies and needs continue to develop and grow. The risk is thus that complexity and cost become limiting factors in the evolution of networks in the future and for the enriched services these networks are expected to deliver. We have witnessed significant interests in recent years in the area of QoS routing algorithms that can support Ann. Telecommun. (2008) 63:543–544 DOI 10.1007/s12243-008-0066-x