|Title||Evaluation and Optimisation of Multi-Path Transport using the Stream Control Transmission Protocol|
|Afilliation||Networks, Communication Systems, Communication Systems|
|Project(s)||NorNet, The Center for Resilient Networks and Applications|
|Year of Publication||2012|
|Publisher||University of Duisburg-Essen, Faculty of Economics, Institute for Computer Science and Business Information Systems|
|Keywords||Dissimilar Paths, Evaluation, Fairness, Multi-Path Transport, Optimisation, Stream Control Transmission Protocol (SCTP)|
The Stream Control Transmission Protocol (SCTP) as defined in RFC 4960 is an advanced Transport Layer protocol that provides support for multi-homing. That is, SCTP endpoints may simultaneously use multiple Network Layer addresses, which allows to connect the endpoints to multiple networks for redundancy purposes. However, for the transfer of user data, only one of the possible paths is currently used at a time. All other paths remain as backup and are only used for retransmissions. Clearly, the existence of multiple paths has led to the idea of applying load sharing among the paths. An extension to SCTP – denoted as Concurrent Multipath Transfer (CMT) – realises this load sharing functionality. While this approach works well for similar paths, i.e. paths having similar characteristics regarding bandwidths, bit error rates and delays, the use of dissimilar paths does not work that neatly. In this thesis, the issues of dissimilar paths for CMT-based load sharing will be demonstrated first. The reasons for these issues will be identified and solutions proposed. These solutions will be evaluated in simulations, as well as partially also in a real-world Internet testbed setup, in order to show their effectiveness. In particular, it will be shown that a combination of multiple mechanisms is necessary to make CMT work as expected under a wide range of network and system parameters. Furthermore, the fairness of CMT-based transport – in concurrency to classic non-CMT flows – will be analysed. The usage of plain CMT leads to an overly aggressive bandwidth occupation on so-called shared bottlenecks. As a countermeasure, the idea of Resource Pooling will be utilised. For this purpose, two new and one adapted congestion control approach – all based on the Resource Pooling principle – will be introduced and examined in similar as well as dissimilar path setups, in order to show how to fairly deploy CMT transport in the Internet. The results of this work have also been contributed to the ongoing IETF standardisation process of SCTP and its extensions.