Multipath TCP

Networks have become multipath: mobile devices have multiple radio interfaces, datacenters have redundant paths and multi-homing is the norm for big server farms. Meanwhile, TCP is still only single-path and this makes it very difficult for endpoints to take advantage of network-level redundancy. There are numerous examples of problems caused by this mismatch: for instance, TCP connections are reset when a mobile device exits WiFi coverage despite the availability of 3G connections; and in datacenters random load-balancing often overloads a subset of links leaving parts of the network underutilized.