RTCP information isn’t mixed with the RTP data stream and is delivered through separate sessions that run parallel to the RTP streams. Using RTCP details, the service quality of sessions can be monitored.

RTP works alongside the RTP control protocol (RTCP), which exchanges information related to service quality, including the number of data packets exchanged, number of packets lost, and round-trip lag time. RTP sessions run parallel to SIP sessions, unlike SDP, which is a payload of SIP. It lowers the audio quality to reduce the amount of transmitted data and the resulting bandwidth consumption.Įncoded packets of audio data are carried by the real-time transport protocol (RTP), a specialized application layer protocol used for real-time streaming of audio and video data. G.729 codec: Used for compressed voice.

Audio quality is better than other codecs, but it uses more bandwidth. G.711 codec: Used for uncompressed digital voice.Many codecs are used for this purpose, but the two most common are: Instead, session descriptions are included as a payload of SIP messages.īefore being transported over the network, voice information is encoded using codecs that translate audio signals into binary data. SDP doesn’t transport these details itself. It sends three types of information: session description, time description, and media description. While SIP communicates with IP endpoints to exchange signaling details, SDP conveys session-related information to help participants join or receive details of the session. The session description protocol (SDP) is one such protocol. Several other protocols work along with it to ensure voice data reaches its destination. SIP doesn’t work alone during VoIP calls. We’ll leave the other uses of SIP aside for now and focus on how the protocol works during a voice call. That’s why it can be used for video conferencing and instant messaging as well as making phone calls over the internet. SIP doesn’t encode, decode, or transport any information during these sessions. Gary Audin, tech writer, expert in VoIP and IP telephony SIP tells you the presence of the other party, makes a connection and lets you do whatever you want over the connection, but it has no idea of what’s going over the connection. The OSI model with locations of protocols involved in VoIP technology ( Source ) Multiple protocols work simultaneously by building on top of each other in layers, collectively known as a “protocol stack.” Different models explain how protocols layer on top of each other, but the Open Systems Interconnection (OSI) model, developed by the International Organization for Standardization (ISO), is the most commonly used. Instead, it’s an umbrella term for all the technologies involved in transporting voice and video information using IPs.Ĭommunication between networked devices on the internet doesn’t just involve a single protocol. It is important to remember that VoIP isn’t a protocol itself. Systems that enable the transmission of voice and video calls through internet networks are known as VoIP or business phone systems. This is known as Voice over Internet Protocol (VoIP) technology. To keep things simple, we’re going to focus on protocols that are involved in making and receiving voice and video calls over the internet.

A protocol is a set of rules that defines how two or more computing devices (laptops, smartphones, routers, network switches, etc.) communicate with each other.

It sip definition