Acknowledgements

I would like to thank my supervisors Susan Eisenbach and Jeff Magee for their help and guidance during the course of this work, and for finding me a position in the department when my attempt at riding the dotcom wave took a turn for the worse, and then convincing me to work towards a Ph.D.

I am also very grateful to Jeff Kramer and Sebastian Uchitel for their help and advice. Discussions with them led to a clearer understanding of problems discussed in this work - and sometimes solutions. Being part of their research group has provided the opportunity to work on some interesting problems - and to visit some nice places!

Thanks to the SLURP group for their time and entertaining discussions. Sophia Drossopoulou was the inspiration for the goldfish example. Matthew Smith helped greatly in the production of some of the diagrams in this thesis during his time as a drawing tool. Thanks to Johnny Knottenbelt and William Lee for their sound technical advice.

I have had the opportunity to meet and work with some great people from other parts of the world. Thanks to my colleagues in the STATUS project, especially Natalia Juristo, Ana Moreno, Xavier Ferre and Dimitris Tsirikos. I am also indebted to Jamieson Cobleigh and Dimitra Giannakopoulou at NASA, my foremost testers and bug reporters.

Thanks to my friends from the department for all of the discussions that we have had and for making me want to come in to work every day (well, most days): Chris A, Matthew, Johnny, Will, Ash, Nick, Gulden, Xiang, Alex A, Alex B and everyone else.

For helping take my mind off work when not in the office, to Paul, Marcus, Richard and all at ICSO; Sarah, Lev and all at RO (and lots of other people) ``thankyou for the music''. Lastly, a big thankyou must go to Jane for all her support.

For financial support, I would like to acknowledge the European Union for funding under grant STATUS (IST-2001-32298), without which this work would not have been possible.