ICTM - Soutenance publique de thèse - M. Christoph PAASCH

The Internet is ever increasing since its creation in the early 70s.
Nowadays, it is interconnecting billions of digital devices. From
smartphones to huge servers, providing content to millions of users.
In order to cope with the increasing amount of traffic, redundancy and load-balancing
is the rule on the Internet. Indeed, there often exist many different paths between
any two pair of hosts connected to the Internet. Further, end-user devices also have
muliple paths to the Internet. E.g., smartphones are typically equipped with a WiFi and
a 3G/4G interface. This allows to still be connected to the Internet, even if the
next WiFi access point is far away.

The Internet's architecture as well as the devices connected to it offer a large
number of paths between the end hosts. An attempt to use these multiple paths is
done by Multipath TCP, a major extension to TCP. Multipath TCP allows to transmit
a single byte stream across different paths. This kind of multipath transmission
has several benefits. First, it increases the resilience to failures. If a link
disappears, Multipath TCP can simply continue the transmission on another one -
without disrupting the application. Second, it allows to increase the performance
by pooling the resources. Indeed, the different paths may be constrained by
distinct bottlenecks, each offering a different capacity to the flow.
Multiplexing a byte stream across these different bottlenecks effectively
allows to pool their capacities and thus increase the overall goodput for the
byte stream transmission.

This thesis is a contribution to make multipath communication not an exception,
but the rule by improving Multipath TCP and its Linux Kernel implementation.
First, this thesis applies an Experimental Design approach to the evaluation of Multipath TCP.
This kind of approach allows to have statistical confidence in the evaluation and allows
to have a good overview of Multipath TCP's performance. Next, the thesis tries to
improve the performance in heterogeneous environments by applying a reactive
strategy. Third, the thesis describes the implementation in the Linux Kernel and how
it has been designed to be scalable while reducing its impact on regular TCP. Finally,
we take a step back and reconsider some of the design decisions of Multipath TCP,
taking into account the lessons learned through these last years.

Membres du jury :

Pr. Olivier Bonaventure (Advisor) - UCL/ICTEAM, Belgium
Pr. Marco Canini - UCL/ICTEAM, Belgium
Dr. Ramin Khalili - T-Labs/TU-Berlin, Germany
Pr. Charles Pecheur (Chair) - UCL/ICTEAM, Belgium
Pr. Costin Raiciu - Universitatea Politehnica din Bucuresti, Romania
Pr. Laurent Schumacher - UNamur, Belgium