1. Cisco Visual Networking Index: Forecast and Trends, 2017–2022 White Paperhttp://goo.gl/X3efVF
2. VoIP Attacks on the Risehttps://www.nettitude.com/uk/
3. Voice over internet protocol (VOIP): Overview, direction and challenges;Alo;J. Inf. Eng. Appl.,2013
4. RTP: A Transport Protocol for Real-Time Applicationshttps://tools.ietf.org/html/rfc3550
5. SIP: Session Initiation Protocolhttps://tools.ietf.org/html/rfc3261