When you provide QoS to the network, the packets are marked so you can tell what kind of treatment they deserve. We generally refer to that as coloring the packets. Then, you need to look at the network and decide if you can even apply QoS to it. If you have a router in the middle of the network that doesn t have the capability of offering a QoS, then you have a weak link in the chain. You have to think of it as a chain.
Every network element is a link in that chain.
You have to look at the service itself. Let s say they ve got 200,000 homes and they want to offer telephony service. They have to know how to activate QoS on all the individual routers, but they also need to make sure the routers themselves can offer enough QoS for all the potential traffic that might be generated by these 200,000 people. So, they re really taking a service view. There s a traffic engineering function here that you have to go through.