Regarding the Internet, one should note that there were efforts to provide certain QoS options in IP standards from the start. IPv4 (IP and IPv4 are used interchangeably in the following text) has a type of service (ToS) field in which it can specify QoS requirements on precedence, delay, throughput, and reliability. In a similar manner, IPv6 has a DSCP (differentiated service code point) field which can provide support for QoS per flow on the network layer. Neither IPv4 nor IPv6 guarantees the actual end-to-end QoS as there is no reservation of network resources, which is something that should be provided by other mechanisms in IP-based networks. What about the main Internet architecture? The Internet is built on the basis of autonomous systems (ASs). Each AS is in fact an autonomous administrative domain and it is identified by a 16-bit or 32-bit AS number, which is allocated by the IANA (Internet Assigned Numbers Authority), a department of the ICANN (Internet Cor- poration for Assigned Names and Numbers), which governs the Internet in terms of domain naming and IP addressing, as well as other well-known numbers from various standardized protocols for IP-based networks (e.g. port numbers for different 1 Introduction protocols on the application layer). The autonomous system is called "autonomous" for a reason, that is, it can apply within its administrative domain the traffic management schemes and routing protocols independently from other ASs, which directly impact the QoS. However, one company or operator can have several ASs and can apply similar traffic management and QoS functions in them. In general, the Internet and the global telecommunication networks are based on IP networks consisting of about 50,000-100,000 active ASs (this number is constantly increasing) [8], which are interconnected. Every AS is connected with either one other AS (e.g. so-called stub AS), or with several adjacent ASs, thus creating the global telecommunication network of today (which is completely based on Internet networking t