Internet Protocol And VoIP
Internet data is made up of packets that contain a payload, and extra information that determines where and how that payload will be delivered. For VoIP, this payload is composed of five separate layers -- known as the Internet Protocol Suite (IPS) -- that together make a phone call possible.
The top layer of the IPS is the application layer. In VoIP, this is the Session Initiation Protocol (SIP), which specifies the type of connection the caller wants to make and identifies the recipient with a unique number.
The transport layer is the Real-time Transport Protocol (RTP) in conjunction with UDP (the User Datagram Protocol) to control data flow. RTP identifies the payload and provides sequencing information and UDP provides a fast method of delivery.
Next is the Network Layer, which is the Internet Protocol (IP), used to set up a path between the caller and the recipient.
The two physical layers of the Internet Protocol Suite are the Data Link layer (Ethernet) and the Physical Layer – a twisted-pair cable that connects the network card, routers, modems, Analogue Telephone Adaptors (ATAs) and IP phones.
Voice data packets originate in computer's sound hardware. Sound is converted into digital bits, then compressed by the VoIP software, divided into packets and transmitted through the twister-pair cable to the Internet connection. And the process is reversed at the other end.
