quality of service - Computer Definition
As demand for bandwidth in networks continues to grow, the competition between different applications and protocols for these resources will continue to grow as well. Certain applications, such as Voice over IP (VoIP) and Video Conferencing, require guaranteed minima of resources so that users will not experience unacceptable delays or dropouts during their communications. The Internet Protocol in its currently used version 4 does not provide a formal mechanism for applications to reserve these resources on the network. With version 6 of IP—as well as in a number of other network protocols—the notion of Quality of Service has been formally introduced, meaning that a mechanism to solve this problem has been provided.