Figure 1 shows this for a request of URL in the World Wide Web. Since the communication request to the proxy is encrypted, nobody can link a message processed by the proxy by simply comparing the messages on the incoming and outgoing link. Thus, a global observer is able to associate a communication relation to a certain client and server. The conclusion is that the existing concepts are not secure against powerful traffic analysis. Unfortunately, this concept is not directly usable for connection oriented communication.
All connection have an equal length.
A typical duration of a time slice in the ISDN-MIX concept is approx. A communication that needs longer than 1,2 seconds is composed from two or more time slices. It goes without saying that two ore more time slices of a certain user cannot be linked for the attacker. These concepts are very good applicable in the ISDN since the user is connected exclusively to the local switch, i.e. enough bandwidth for simultaneous dummy traffic and time slices to and from each user is provided. Unfortunately, the links in the Internet are shared with a large number of users, i.e. constant dummy traffic leads to a very increased signalling load or a decreased bandwidth efficiency.