Internet has shown to be the major enabler for a large variety of services via a common infrastructure. Since early applications such as remote login, e-mail, file transfer and web browsing, many new applications and services have entered the stage, where overlay networks play an important role. When broadband access technologies reached private users, file sharing became popular. Telecommunication providers have discovered internet technology as a cost-saving alternative to classical telecom technology. 3GPP has standardised the IP multimedia system (IMS), which is nowadays also used in the world of fixed access networks to handle the coexistence of voice, TV and internet (so-called Triple Play) on access links. New application domains such as e-health, e-government, e-tourism, etc., have emerged. Many new services use other services, forming composite services or service supply chains based on internet. So, the ‘anything-over-IP-over-anything’ principle has become a reality. This emergence of new applications raises challenges. The internet has never been designed for fulfilling all imaginable application’s needs, nor to maximise user’s quality of experience (QoE). During the years, the basic best-effort paradigm has been enhanced by network-level quality of service (QoS) measures. Still, internet packet delivery cannot be guaranteed. Applications try to adapt themselves to these volatile conditions, e.g., by modifying the intensity of the data flows or adding some kind of redundancy to be used for error correction, which fits the internet principle of end-to-end control. However, in order to reach the right interplay between applications and services and the internet infrastructure, a good understanding of the characteristics of both is mandatory. On this background, this special issue focuses on performance assessment of contemporary, new and emerging applications and services using the internet.