The services provided by professionals in particular field. For example, a company may charge a certain sum of money for the certain tasks their consultant accomplished for the company who ordered the service.
IDC projected over 9 billion minutes of voice traffic to travel over worldwide packet networks in 2000, exceeding 135 billion minutes in 2004. Service revenue is projected at 1.6 billion in 2000 and 18.7 billion in 2004.