Voice over Internet Protocol (VoIP), also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the internet. The terms Internet telephony, broadband telephony, and broadband phone service specifically refer to the provisioning of communications services (voice, fax, SMS voice-messaging) over the public Internet, rather than via the public switched telephone network (PSTN), also known as plain old telephone services (POTS).
1Core concepts of how Internet Protocol (IP) carries a VoIP packet
2Advantages and disadvantages of SIP Trunking
3Understand how DHCP and DNS supports IP telephony