巴黎地铁系统在网络上的应用:

随着互连网的发展，单一的计费方式既不利于网络服务商的利益最大化，也不能满足一些网络的高级应用的需要。

把网络进行划分，各个分区相同或不同的服务能力，但是它们有不相的价格。因此相对价格较高的服务分区由于选择的人比较少而负载轻，因而有较少的时延。由于不同服务有不同的QoS要求，如网络视频，电话需要较高的带宽要求，所以必需选用价格较高的网络分区才能满足需要，而像下载，网页浏览对QoS的要求相对较低，因此可以选用价格较低的网络分区。其主要原理把是把网络时延作为网络一种内在的价值。其应用的基础在于其本身的简单性，易于实现。

-Abstract—Paris Metro Pricing (PMP) is a simple multi-class

fl at-rate pricing scheme already practiced by transport systems,

specifi cally by the Paris Metro at one time. The name is coined

after Andrew Odlyzko proposed it for the Internet as a simple

way to provide differentiated services. Subsequently, there were

several analytical studies of this promising idea. The central issue

of these studies is whether PMP is viable, namely, whether it

will produce more profi t for the service provider, or whether it

will achieve more social welfare. The previous studies considered

similar models, but arrived at different conclusions. In this

paper, we point out that the key is how the users react to

the congestion externality of the underlying system. We derive

suffi cient conditions of congestion functions that can guarantee

the viability of PMP, and provide the relevant physical meanings

of these conditions.