blished in 1996 [13]. By the early 2000s several VoIP services existed, specially targeted at the corporate market. A service ecosystem emerged to manage high quality VoIP services: for example Genista Corporation where the author worked in the early 2000s developed a tool to measure the perceptual quality of VoIP communications. However, the VoIP market size remained quite small until Skype was introduced. The Skype offering was revolutionary in several ways. One way was a simple user interface which made it easy for anyone to use the service. A second way was a peer-to- peer protocol which made it possible to place and receive calls from behind corporate firewalls, and which facilitated a decentralised database of on-line subscribers, a pro- tocol already used by Skype founders Friis and Zenstrom for their music file-sharing site KaZaa. However, the most important factor was the voice codec used to transfer analogue voice to digital stream. The quality of sound was very good compared with the international analogue telephony service. Added to this was the fact that one could make free international calls with ease. Skype was a great success: it was soon acquired by the on-line auction company eBay in 2006 for $2.6 billion to enhance their peer-to-peer sales platform. The company has changed and Skype is now owned by Microsoft after an $8.5 billion deal in 2012 again aimed at enhancing Microsoft applications such as internet messaging and email. Skype is reported to use a number of voice codecs including G.711 (64 kbps), G.729 (8 kbps), proprietary Content and services layer SVOPC (16 kbps) and AMR-WB (16 kbps). High quality voice source coding has been one of the most important Connectivity retail layer factors in maintaining Skype's customer base and continued success. Infrastructure layer Skype also offers phone services to and from landline and mobile telephones through its Skype-out/Skype-in ser- Subscriber/End-user vices. Skype and similar companies such as Viber, WhatsApp and WeChat are known as over-the-