What is QoS?

For many businesses, the internet has become integral within day-to-day operations. Email, web-based interfaces for applications, and now Voice over IP and streaming video put increasing demands on a fixed resource: bandwidth. Bandwidth can always be increased, yet there will always be times when the bandwidth available is less than enough to prevent packets from being dropped.

Prioritization

QoS can be used to prioritize traffic so that during times of congestion we gain some control over what happens to different priorities of traffic. In the case of interactive applications, like VoIP, you may want to guarantee that no packets are dropped. To do this you would create a priority for VoIP that is assigned a bandwidth guarantee. This guarantee should be calculated on your maximum VoIP usage so that VoIP is allowed to take as much bandwidth as needed, when needed.

QoS is NOT Throttling

An important concept is to differentiate between QoS and simple throttling. Throttling typically slices up bandwidth, giving each class a segment of the total. QoS in our usage here is dynamic and can allow even the lowest priority class to use all of the available bandwidth so long as another class does not need any bandwidth.