portInfoPhyIfMtu 1.3.6.1.4.1.11.2.3.7.11.33.1.2.1.3.2.1.1.8

The size of the largest datagram which can be sent/received on the interface, specified in octets. For interfaces that are used for transmitting network datagrams, this is the size of the largest network datagram that can be sent on the interface.