ernames instead of a telephone number which made it difficult to communicate with many subscribers. A second generation of mobile apps entered the market in early 2010 which allowed for short messaging across a mobile telecommunications network and used telephone numbers instead of usernames. A number of these apps have greatly grown in popu- larity. In particular Skype, WhatsApp and WeChat count their subscriber numbers in the order of several hundred millions. This has led to multi-billion dollar valuations for these companies as shown in Table 14.1 [3, 4, 5, 6, 7]. A common feature of these apps is short messaging, but they differ in the features and functions they provide. Some offer telephony and gaming services while others focus on short messaging. Furthermore, some services are offered for free while some are charged. In parallel some smart phones have started to include these OTT services within the operating system, such as iOS Facetime and iMessage. Moreover, a social networking app such as Facebook may also be considered an OTT as it provides many connectivity values traditionally provided by the (mobile) telephony networks. With the exception of a few global networks (Facebook messaging, iMessage) most OTT apps are concentrated in a few markets: WhatsApt dominates in the US, WeChat in China, Line in Japan and Korea and SO on. This may be explained by the social net- working nature of these apps. We connect with people we know, who are likely to live where we do. While all these apps may be installed freely, we tend to communicate on platforms which are used by our social network. Moreover, the platform created by Table 14.1 OTT services and valuations OTT Service Valuation (year) Skype $8.5 B (2011) WhatsApp $16 B (2014) WeChat $60 B (2014) $10 B (2014) Kakao Talk $8.5 B (2014) Broadband Telecommunications Technologies and Management these apps works to ensure we stay within the network for most of our social needs such as gaming, news and photo sharing, trading and SO on. WeChat platform Application