  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.
