Internet routing and transmission control protocols have been designed to optimize the transmission assuming bidirectional symmetric communication links. Recently, new transmission media are proposed to provide higher bandwidth to the Internet. Satellite links with receive only antennas and cables offer respectively unidirectional and asymmetric access to the Internet are proposed. Both offer high speed bandwidth downstream, with zero bandwidth upstream for the satellite link and a lower bandwidth upstream for cables. There is a need to integrate both unidirectional and asymmetric links in the Internet transparently.
Unidirectional links are a priori a special case of asymmetric links.
We do not consider the case of bidirectional islands connected via unidirectional links nor the general case of asymmetric and possibly unidirectional links. In addition, we focus on routing related problems. Concerning the short term case, there are two proposed approaches. The second is to add a layer between the network interface and the routing software to emulate bi-directional links through tunnels. This second approach consists in masking the underlying unidirectionality with a tunneling mechanism under the network level.