3. Packets

A packet is a unit of data that is routed between an origin and destination on the internet or other packet switched network. Each packet has a header and a trailer. The header usually consist of the sources and destination address. It may also provide error checking . The trailer usually consists of check sum and error detection function. In VoIP, a voice packet usually consists of several protocol such as Internet Protocol(IP), User Datagram Protocol (UDP) and Real-time Transport Protocol (RTP).

Another similar term to packet is called Datagram which is used in User Datagram protocol. Packet is usually transported using IP, and the re sequencing is usually done by Transmission Control Protocol.

The following diagram show the IP Packet format: