for the given media type, such as audio or video). The over- all end-to-end application factors directly influence the perceived quality, which may be measured and discussed only end-to-end, at the point where the user is located. So, one may note that there is some interrelationship among QoS parameters on different protocol layers. Traffic Management Techniques When there is heterogeneous traffic over the same IP network, the issue is what to do with different traffic types on public or/and non-public networks. On one side, the Inter- net was initially designed to provide best-effort service, i.e. all IP packets are treated in the same manner. On the other side, not all packets are the same. For example, the Web as an interactive application is delay sensitive, but voice is more sensitive to delay and jitter. Video requirements are highest regarding bitrate because video is one of the most demanding traffic types on the Internet. Also, online games are delay and jitter sensitive, even more than voice. Some P2P applications for file sharing, where BitTorrent was the most used at the beginning of the twenty-first century [17], are generally insensitive to delay and jitter, while bandwidth does not matter a lot for them, although it is still impor- tant (e.g. file transfer will finish eventually, but having higher average download bitrate will help the user to be more satisfied with it). There are other examples, but the main points are given. This "big picture" refers to the public Internet, which is also referred to as Internet access service by many regulators and telecom operators. When all IP traffic is multiplexed onto the same IP-based links and IP networks, including traditional telephony (as VoIP) and television (as IPTV), then the network needs to have techniques to give better quality to some packets for certain types of applications/services. 2 Internet QoS 2.5.1 Classification of IP Packets How do we classify IP packets? Well, it depends on the approach used, and there are different options on the tab