An Internet telephone and video calling service from Skype Technologies S.A.R.L., Luxembourg City, Luxembourg (www.skype.com), a division of Microsoft. Being software based, calls from Skype subscribers originate from their computers or mobile devices, and if the recipient is using a computer or mobile, voice and video calls are free. Access to regular telephones is also available. For outgoing calls, users can dial a landline or cellphone for a low per-minute or monthly charge, and subscribers can obtain a Skype number to receive calls from landlines and cellphones worldwide. In 2010, Skype introduced its group service that lets five people have a videoconference.
Introduced in 2004, within a year, more than a hundred million people downloaded the software. In the fall of 2005, Skype claimed 40 million active users and was acquired by eBay for $2.6 billion. By late 2008, an average of 10 million users were using Skype simultaneously. Skype was acquired by private investors a year later with eBay retaining a major equity position. In 2011, Microsoft bought Skype and partnered with Facebook to allow its members to make video calls.
Instead of using standard voice over IP (VoIP) protocols such as SIP and H.323, Skype originally used proprietary protocols that incorporated a peer-to-peer architecture. If Skype could not make a direct connection between users, it might have elicited one of its users who has the Skype application loaded to become a "supernode" and relay the call. Only a fraction of Skype users ever become supernodes at any given time, and in the early 2010s, the supernode architecture was dropped. See Skype for Business