Gateways exchange network routing information.
Currently, most gateways accept on faith that the
information provided about the state of the network is
correct. In the past this was not a big problem since
most of the gateways belonged to a single administrative
entity (DARPA). Now with multiple wide area networks
under different administrations, a rogue gateway
somewhere in the net could cripple the Internet.
There is design work going on to solve both the problem of
a gateway doing unreasonable things and providing enough
information to reasonably route data between multiply
connected networks (multi-homed networks).