Multi-access connectivity in wireless networks is becoming widely available. Most handsets on the market today support connectivity to multiple access technologies such as HSPA, LTE or WiFi and can make use of some of them in parallel. By offering multiple access options, the available bandwidth and robustness of the connectivity can be increased. There is a large design space to take advantage of multiple connectivity. Various solutions and protocols at different layers and locations in the network exist, originating from different viewpoints and problem statements. They range from static low-layer tunneling approaches like IWLAN or Mobile-IP to dynamic transport layer approaches like multipath TCP up to highly sophisticated application-layer specific protocols.

Focusing on the network layer and above, we review a variety of these protocols and solutions by categorizing them, exhibiting their properties, reasoning about their potential behavior in the presence of Internet traffic and take a glimpse on their impact on the network.