A method and mechanism for determining when to transmit a probe packet to detect increases in path maximum transmission unit (PMTU) in a network having a host and a target interconnected by the network. Calculate a utility variable corresponding to a number of packets to be transmitted from the host to the target which are greater than a predetermined amount of a known PMTU for the target. When the utility variable is greater than a predetermined utility threshold, sending instructions to the host to send a probe packet to detect increases in PMTU for the target. Storing the previous state of the internet path with respect to PMTU in a variable PPMTU and tracking it during decreases so that a restoration of the PMTU can be verified by sending probes. PMTU is treated as a resource which is either fully or partially used by an application.