Overview of QoS Basic

Definition

Quality of service (QoS) is a mechanism that provides end-to-end service quality assurance to meet different requirements of various services. It allows different traffic to compete for network resources based on their priorities, thereby using existing resources more effectively instead of increasing network bandwidth. In this way, voice, video, and important data applications can be preferentially processed on network devices.

Purpose

As networks rapidly develop, services on the Internet become increasingly diversified. Apart from traditional applications such as WWW, email, and File Transfer Protocol (FTP), the Internet has expanded to encompass other services such as IP phones, e-commerce, multimedia games, e-learning, telemedicine, videophones, videoconferencing, video on demand (VoD), and online movies. In addition, enterprise users use virtual private network (VPN) technologies to connect their branches in different areas so that they can access each other's corporate databases or manage remote devices through Telnet.

Figure 1 Internet services

Diversified services enrich users' lives but also increase the risk of traffic congestion on the Internet. In the case of traffic congestion, services can encounter long delays or even packet loss. As a result, services deteriorate or even become unavailable. Therefore, a solution to resolve traffic congestion on the IP network is urgently needed.

The best way to resolve traffic congestion is actually to increase network bandwidths. However, increasing network bandwidths is not practical in terms of operation and maintenance costs.

This has subsequently led to the development of QoS technology. QoS has played an overwhelmingly important role on the Internet. Without QoS, service quality cannot be guaranteed.