Investigating TCP/MPTCP Support for Drop Computing in User Space Network Stacks

The tremendous growth of smart devices in the past few years has brought new computational, storage and networking resources at the edge of the Internet. Using the recently-developed Drop Computing paradigm, these devices can be interconnected in an ad-hoc network, using said resources beyond local barriers in order to improve the latency and to remove the pressure from the core Internet network caused by the intensive usage of a centralized cloud architecture. In order to use the networking capabilities of the devices registered in a Drop Computing network in an optimal manner, multi-path TCP (MPTCP) is the key technology which allows the concurrent usage of all the devices’ networking interfaces, leading to a smoother reaction to failures, improved latency, and better throughput. Because of the high variety of devices in Drop Computing, some low-end devices can have stripped network stacks with many missing features, but the Linux Kernel Library (LKL) or User Mode Linux (UML) implementations are able to offer MPTCP and other features directly in user space.In this paper, we assess the feasibility and analyze the behaviour of TCP and MPTCP in Drop Computing-specific scenarios, using the Linux native network stack or the LKL/UML user space network stack. We demonstrate that MPTCP can be used successfully over any of them and that the most suitable one should be selected based on the hardware profile of the device used and the target software application. Furthermore, we prove that LKL and UML can be successfully utilised on low-end devices in order to allow them to use all their network interfaces and have a better failure handover solution.