VoIP or Voice over IP enables telephones, fax and other communications devices to initiate and receive calls over a VoIP network using VoIP protocols. VoIP works with Internet and mobile services to send/receive voice calls as digital signals over the Internet using voice over IP technology.
There is a variety of software/hardware solutions and applications that can adapt mobile or landline phones and other devices to access VoIP services. The figure shows an example of a hybrid network depicting different ways of accessing an IP network for the purpose of using voice services.
There are two major protocols that support VoIP.
- H.323
- SIP (Session Initiation Protocol)
Both protocols differ in flexibility, format, scalability and other aspects. H.323 is a vertically integrated suite of protocols for voice, video, fax and data communication over packet-based networks while SIP provides a more flexible standard for initiating multimedia sessions between endpoints, including video, chat, interactive games, and virtual reality.