A large fraction of the communication in the Internet is handled by the Transmission Control Protocol (TCP). Since the first deployments of this protocol more than 30 years ago, the spectrum of applications as well as the structure of the network have developed at a fast pace. For example, today's network devices, like smartphones and laptops -- i.e.\ particularly many devices in the area of mobile computing -- frequently have an interesting property: the existence of multiple IP addresses (IPv4 and/or IPv6). The addresses may even change due to mobility. This property, denoted as multi-homing, can be utilised for multi-path transport, i.e. the simultaneous usage of multiple paths in the network to improve performance. Multi-path transport is a hot topic in the Internet Engineering Task Force (IETF), which is the standardisation organisation for the Internet.
This talk provides an overview of the work in the areas of multi-homing and multi-path transport, with focus on the area of the protocols TCP and Stream Control Transmission Protocol (SCTP) with their experimental extensions Multi-Path TCP (MPTCP) and Concurrent Multi-Path Transfer for SCTP (CMT-SCTP). It particularly shows the sequence of research and selected results, beginning from a simple simulation model, via lab setups and small Internet scenarios, up to the large-scale, international testbed project NorNet. NorNet, and particularly its landline network part NorNet Core, is furthermore described in some detail. Based on NorNet, it is finally possible to validate simulation results in real-world, multi-homed networks, in order to provide valuable input to the ongoing IETF standardisation processes of MPTCP and CMT-SCTP. Particularly, it will also show how the NorNet testbed can be utilised for research at Hainan University.