Nowadays a growing number of mobile devices are in use, and the internet connections with mobile devices are increasingly important for the everyday life of the global population. As a result, applications and use cases of different requirements including high throughput, reliability and continuous connection have emerged for mobile device connections. Multipath transport located on the transport layer of the TCP/IP model has been proposed as a solution for providing better throughput, reliability and smooth handovers for mobile devices. Multiple network interfaces are present in current mobile devices, and multipath protocols can utilize them to transfer data through multiple paths inside one connection. Multipath protocols of parallel functionality have been proposed over the years, and relevant protocol versions include multipath extensions for well-known transport layer protocols.
The aim of the thesis is to provide an overview of three multipath protocols, MPTCP, CMT-SCTP and MPQUIC and the advantages and limitations they have when used for mobile connectivity through a literature review. First the challenges of multipath transport and requirements specific for mobile device usage are identified, and an overview of the protocols and their features are discussed. Then the protocols are compared in the context of the identified challenges and mobile device use.
MPTCP is the only transport layer multipath protocol currently deployed and in use, while CMT-SCTP faces problems with deployability. MPQUIC shows promise for having initially comparable performance and deployability with MPTCP. Transport layer multipath protocols are currently not optimal for interactive applications and have suboptimal performance in heterogeneous network conditions. Conversely, they can provide a boost for throughput with data intensive applications and can be helpful for providing smoother handovers, but at the cost of higher energy consumption.
