Multi-Path Aware Internet Transport Selection

When the Internet experiment started more than 30 years ago, no one could foresee its expansion — What started as an experiment to interconnect a few research computers has become an essential global infrastructure of humanity. Originally, there was usually only one way to transport data between two computers; this has changed dramatically — today’s Internet offers us way more diverse transport options: Most end hosts are connected via multiple paths to the Internet, most content on the Internet is available on multiple servers, and there is a variety of transport protocols available to meet the needs of different applications. In this thesis, we tackle the problem of how to exploit Internet transport diversity to improve applications’ performance. More specifically, we discuss how to choose among transport options, how to realize multi-path aware transport option selection at the clients’ operating system, and take a glimpse at the performance benefits we can achieve using transport option selection. To reason about transport options and how to choose among them, we characterize three dimensions of transport diversity on the Internet: paths, endpoints, and protocol alternatives. We analyze a representative set of Internet Protocols with regards to the functionality and the granularity of control they provide and how they can be combined. To realize multi-path aware transport option selection at the clients’ operating system (OS), the OS needs to know what to optimize for. Therefore, we introduce the concept of Socket Intents; a means for applications to share their knowledge about their communication pattern and express performance preferences in a generic and portable way. We sketch a generic policy framework that enables the OS to choose suitable transport options while taking the interests of stakeholders like users, vendors and network operators into account. To estimate the performance benefits we can achieve using pathselection, we analyze the benefits of using our Earliest Arrival First (EAF) path selection strategy for Web browsing. The EAF schedules the transfer over the path or path combination that minimizes the expected transfer time. We estimate the possible performance benefits in a custom simulator with a full factorial experimental design covering the Alexa Top 100 and Top 1000 Web sites and a small testbed study using our prototype and demonstrate significant performance benefits. We demonstrate the implementability of path selection and endpoint selection, we implement our Multi-Access Prototype as an extension to the BSD Socket API. Our prototype enables connection reuse via implicit connection pooling and can control the path-management of MPTCP, but also reveals limitations originating by the BSD Socket API. Finally, we give an outlook of the challenges for deploying automated transport option selection within commodity OSes and underline the need for a replacement of the BSD Socket API