MTU
The Maximum Transfer Unit (MTU) is a term for the size of the largest datagram that can be passed by a layer of a communications protocol. In the Internet Protocol the 'path MTU' of an Internet transmission path is defined to be the smallest MTU of any of the IP hops.The Internet Protocol allows IP fragmentation so that datagram 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.
