A packet is a basic unit of communication over a digital network. A packet is also called a datagram, a segment, a block, a cell or a frame, depending on the protocol. When data has to be transmitted, it is broken down into similar structures of data, which are reassembled to the original data chunk once they reach their destination.
Packets and protocols
Packets vary in structure depending on the protocols implementing them. VoIP uses the IP protocol, and hence IP packets. On an Ethernet network, for example, data is transmitted in Ethernet frames.
The structure of a packet depends on the type of packet it is and on the protocol. Normally, a packet has a header and a payload.
The header keeps overhead information about the packet, the service and other transmission-related things. For example, an IP packet includes
- The source IP address
- The destination IP address
- The sequence number of the packets
- The type of service
The payload is the data it carries.