IP fragmentation

The Internet Protocol allows IP fragmentation so that datagrams can be fragmented into pieces small enough to pass over a link with a smaller MTU than the original datagram size.

RFC 1191 describes "Path MTU discovery", a technique for determining the path MTU between two IP hosts, so that IP fragmentation can be avoided.

The details of the fragmentation mechanism, as well as the overall archtectural approach to fragmentation, are different in IPv4, the current version of the Internet Protocol, and IPv6, the newer version.