 and improved uplink and downlink perfor- mance suggest that satellites will play an increasingly positive role in future terrestrial mobile broadband service provision. At the very least, satellites need to be more actively factored into present and future cellular and terrestrial broadcast business planning. Telstar marked the start of a new technical and commercial era in telecoms. 19 Sixty years on it feels that the story has only just begun. 19 Incidentally, July 2011 was the 50th anniversary of Yuri Gagarin's flight almost coinciding with the last planned mission of the American Shuttle. Part Four Network Software Network Software - The User Experience Back to earth again, the next five chapters address various aspects of network software. Chapter 18 of 3G Handset and Network Design looked at traffic-shaping protocols in some detail. This chapter provides a short reprise of traffic shaping and tracks the changes that have taken place over the past eight years. In 2002 the discussion revolved around the scale of the efficiency gain potential of IP networks and specifically IP networks with a radio network attached. At the time, Nortel were claiming that the 3 G air interface combined with an IP network would reduce delivered cost per bit by a factor of twenty. This was absurd. Nortel is no longer in business, a salutary warning to companies that allow marketing to become disconnected from engineering reality. The issue was that while it is very possible to achieve performance gain there is normally an associated performance cost in some other area that is often not factored into the marketing message. In this case, the performance cost of the theoretical efficiency gain was a loss of network determinism. In January 2003 after the book was published we wrote a technology topic on IP network processor performance limitations. The summary of this is as follows. 17.1 Definition of a Real-Time Network The IEEE defines a real-time operating system as 'A system that responds to external asyn- chronous events in a p