New transmission media have been proposed to provide higher bandwidth to the Internet – satellite links offer unidirectional and asymmetric access. Both unidirectional and asymmetric links should be integrated into the Internet transparently. However, there are some specific problems that must be solved in the case of unidirectional links. The UniDirectional Link Routing working group  focuses on supporting unidirectional links on top of bidirectional internetwork. In order to support unidirectional links, there are two approaches: 1) modifications to common Internet routing protocols (RIP, OSPF etc.), or 2) a new layer between the network interface and the routing software to emulate bi-directional links through tunnels.