What is QoS?

This is Quality of Service. It is available on some of the newer routers, and also on the open source firmware available..

Quality of Service is about giving different types of network traffic a different priority. Imagine a freeway with limited lanes. Cars in the high occupany vehicle/carpool lane, are given a higher QoS with the limited freeway space. Similarly, police cars and ambulances are supposed to get higher QoS - they get priority over other cars.

On a network with limited space, a router can give preference to network traffic of a certain type or originating from a particular computer, or application. A company could have a critical system which will receive network traffic preference over those packets coming from a user just browsing the internet. The CEO’s computer might have a high QoS.

Is it useful for home? People have mentioned uses with Voice over IP, if you are using Vonage, etc.. You want your phone call to sound good. I can’t think of another reason…QoS is important within the home network - that is really all you can control now, once your packet goes out on the internet, there is no guarantee anyone will give your packet a particular priority. Companies that control the network, like Comcast, etc… can now manage QoS on their network, and then that leads to some aspect of the controversy of net-neutrality.

QoS is not important when you have a lot of bandwith on the network and very little traffic. Just like an empty street on which cars drive.

Similarly, if you have such limited bandwith that even your highest priority packets cannot get the bandwith they need, QoS does no good.

Right now, this is not QoS I think, but DSL or Cable companies advertise a particular speed that they sell you, for example 3 Mbps download, but I am not sure how or if they guarantee it. ie ,if they miss that level of service, is it a breach of contract?

That type of service guarantee is for enterprise level systems..

If they did offer that type of thing, they might then also limit bandwith or cap your speed, the sword cuts both ways.