Note: The following is an excerpt from the official IETF RFC. It is provided here as a convenience and is not authoritative. Refer to the original document as the authoritative reference.
The Internet Protocol is designed for use in interconnected systems of
packet-switched computer communication networks. Such a system has
been called a “catenet”
1). The internet protocol provides for
transmitting blocks of data called datagrams from sources to
destinations, where sources and destinations are hosts identified by
fixed length addresses. The internet protocol also provides for
fragmentation and reassembly of long datagrams, if necessary, for
transmission through “small packet” networks.