Advances in QoS

he burstincss of traffic gencrated by multimedia U applications is difficult to describe hy a static set of traffic paramctcrs, and yet the dcmand for a dynamic and efficient usage of network resources is one of the fundamental aspects in the current evolution of the Internet. It is widely recognized that to support both existing and emerging (mobile, peer-to-peer, ad hoc, etc.) multimedia applications, additional nctwork services and architectures are nccded. Moreover, driven by the current trends in the industry, there is a growing business requirement for a markct-enabling technology that allows providers of networks and services to interact with users i n a seamless transparent manner for the sale and delivery of a widc range of services with guaranteed quality of scrvice (QoS). The articles in this feature topic address a number of critical and relevant issues occurring within this evolving environmcnt. The issues arisc csscntially from the design and implementation of QoS services and architectures in the real world, and from their cocxistence with traditional best effort scrvices and architectures. For scveral applications, premium IP networks promise convenicnt QoS-enabled communication. We expect this area to grow in the next years, with wider support for QoS serviccs and architccturcs by network operators. The introductory article, by S . Giordano, S. Salsano, S. Van den Berghc, G . Ventre , and D. Giannakopoulos, describes thc current evolution of QoS architecturcs, mcchanisms, and protocols in the Internet, as i t is taking place within the framework of t h e European Union funded research projects on premium IP networks. After a critical review of the proposed standard approachcs to QoS, they discuss the state-of-the-art architcctures, mainly based on DiffServ concepts, analyzing the implementation issues of these architecturcs in the real world. The article then discusses the existing results and current direction of European research and development in thcsc arcas. Following this introduction, E. Mykoniati, P. Georgatsos, T. Damilatis, D. Godcris, P. Trimintzios, G. Pavlou, D. Griffin, and C. Charalampous present the principles and basic operation of the servi.ce admission control scheme for QoS delivcry in IP DiffServ networks, as developed in the IST TEQUILA project. Admission control is positioned in a unified architccture, where traffic cnginccring and service manGiorgio Ventre