To be able to provide VoIP services several protocols need to be employed. On
this page we focus on the four most common ones used to describe VoIP connections.
Protocol is a generic term, a standard that describes how the respective participants
communicate with each other. For transmitting audio and video packets between
communicating computers Real-Time Protocol (RTP) is used worldwide. But before
audio or video media are transmitted between computers other protocols need to
be used to find the remote device and to define the means by which media will be
transmitted between the two devices. These are call-signaling protocols, such as
Session Initiation Protocol (SIP).
VoIP connections are basically described with the following protocols:
SDP: Session Description Protocol
It describes media components and conciliates between participants (codecs and
transfer protocols)
RTP: Real-time Transport Protocol
It transmits audio and video packets between communicating computers over the network.
To identify packages it uses time stamps and ordinal numbers.
