"The routers get involved in this and they know that on the path between this router and that router a certain percentage of the bandwidth is reserved to these things and a certain percentage of it is allowed on a first come first served basis"

This quote by Jon Postel is referring to the function of routers in network traffic management. Routers are responsible for directing data packages from one network to another. In order to guarantee that the network runs efficiently, routers should have the ability to allocate bandwidth to different types of traffic. In this quote, Postel is recommending that routers can be configured to schedule a particular portion of the available bandwidth for certain types of traffic, while the remaining bandwidth is assigned on a very first preceded served basis. This ensures that the most crucial traffic is provided priority, while other traffic is still able to access the network. By utilizing this method, routers can ensure that the network is running efficiently and that all kinds of traffic have the ability to access the network.