VoIP & RTP Protocols

Voice Over Internet Protocol - A New Use of the Internet

VoIP or Voice over Internet Protocol is a signaling standard that is used to convert human speech, which is an analog signal into a digital signal. The signal is then sent over the Internet. This can reduce costs for businesses if they have an Internet connection because they can use the same connection not just for data transfers but also for voice transfers.

RTP

Real Time Transport Protocol - With Multiple Ports for Communication

Real Time Transport Protocol (RTP) facilitates real-time data transfer. RTP is a set of rules used to transfer data between computers or devices, in this case Internet phone devices. It enables VoIP communications, sending data through two ports in real time for communication. One port is for the media stream and one for control. The control protocol is RTCP.

UDP

UDP - A Delivery Service for RTP Packets

RTP works side-by-side with the signal set of the User Datagram Protocol to carry the phone message. VoIP communications use UDP because it transfers data quickly. First a conversion of Voice data from an analog (speech) signal into digital packets occurs. Then the RTP protocol incorporates the data packets into its format. The RTP packets transform into the UDP packets. They are then transmitted to the receiving device or computer.

RTCP

RTCP Monitors Transmissions

RTP works in conjunction with UDP and also with the RTP Control Protocol. RTP carries the media streams, such as audio and video and other out-of-band signal events, like e-mail, RTCP provides a way to monitor the transmission operation and statistics plus quality of service (QoS) information.

RSVP

Resource Reservation - Reserves Bandwidth For Signals and Prevents Decay

Resource Reservation Protocol, RSVP, is a VoIP signaling protocol that requests a certain amount of bandwidth at every network hop that supports it. This approach guarantees that a host will receive a specified amount of bandwidth from the network to support the data stream. This is otherwise known as quality of service, QOS. RSVP carries the reservation request through the network. At each hop, the network uses RSVP to carry the stream; it makes a resource reservation for the voice stream. This guarantees a certain bandwidth amount on the system so the quality of service, e.g., the quality of the signal, will continue with interruption, jitter, or delay.

H.323 Signaling Protocol

H.323 Allows Multiple Hardware Units to Communicate

The H.323 is another protocol; it provides a foundation for video, audio, and data communications across IP-based networks, including the Internet. H.323 acts as an umbrella that provides multimedia communications standards over Local Area Networks which do not provide the guaranteed Quality of Service that other protocols provide, like RSVP. H.323 standards, however, are the building blocks for a broad range of collaborative equipment, and LAN-based applications for multimedia communications. This will allow multiple hardware units to communicate with one another, if they use this protocol.

References

• RSVP Protocol Overview
• A Primer on the H.323 Series Standard
• VoIP Protocols