Zero-Error communication investigates communication without any error. By defining channels without probabilities, results from Elias can be used to completely characterize which channel can simulate which other channels. We introduce the ambiguity of a channel, which completely characterizes the possibility in principle of a channel to simulate any other channel. In the second part we will look at networks of players connected by channels, while some players may be corrupted. We will show how the ambiguity of a virtual channel connecting two arbitrary players can be calculated. This means that we can exactly specify what kind of zero-error communication is possible between two players in any network of players connected by channels.