Real Time Transport Protocol (RTP) is used to offer real-time data transfer. It enables VoIP communication by sending data from two slots in real time.

Protocol
RTP is a protocol; set of rules used to transport information between PCs. VoIP uses a mixture of protocols to send phone data between PCs or from a PC to cell-phone or land-line phone.

Layers
VoIP information is changed from analog to digital signal. Leveled protocols send, receive and interpret the signal. RTP is a part of the transport layer.

UDP
RTP works in union with User Datagram Protocol to transport message. The UDP protocol is used in VoIP communications as it transfers data quickly.

Packets
Voice information is placed in data packets from RTP protocol. The RTP packets, with UDP packets inside, then sent to receiving device.

Application Layer
While data packets arrive at receiving PC, a program level reads signal. The data is then presented to user as a voice message from earphones or a USB phone.

Other Protocols
VoIP communications need using several protocols to offer clear communication. These involve Quality of Service protocols and Session Initiation protocols.