The PMTUBHDetectEnabled property indicates whether detection of black hole routers occurs. Setting this parameter to TRUE ...

The PMTUBHDetectEnabled property indicates whether detection of black hole routers occurs. Setting this parameter to TRUE causes TCP to try to detect black hole routers while discovering the path of the Maximum Transmission Unit. A black hole router does not return ICMP Destination Unreachable messages when it needs to fragment an IP datagram with the Don't Fragment bit set. TCP depends on receiving these messages to perform Path MTU Discovery. With this feature enabled, TCP will try to send segments without the Don't Fragment bit set if several retransmissions of a segment go unacknowledged. If the segment is acknowledged as a result, the MSS will be decreased and the Don't Fragment bit will be set in future packets on the connection. Enabling black hole detection increases the maximum number of retransmissions performed for a given segment. The default value of this property is FALSE.