Transmission Control Protocol (TCP) accepts data from a data stream, 'segments' it into chunks, and adds a TCP header creating a TCP segment. The TCP segment is then encapsulated, into an IP datagram. A TCP segment is "the packet of information that TCP uses to exchange data with its peers." [1] Note that the term TCP packet is now used interchangeably with the term TCP segment. [2][3] Although in the original RFC segment usually referred to the TCP unit of data, datagram[4] to the IP unit and packet to the data communications network unit:
Processes transmit data by calling on the TCP and passing buffers of data as arguments. The TCP packages the data from these buffers into segments and calls on the internet module [e.g. IP] to transmit each segment to the destination TCP.[5]
For detailed information on TCP segments See: TCP segment structure
