When a fragmented IP packet is reassembled, the Microsoft stack look for a reassembly header to fill the fragmented packets into the buffer in the correct order. If necessary, the stack creates missing reassembly headers.

Starting with Windows NT 4.0 SP5 and above, including Windows 2000 (NT 5.0), the stack has a default limit of 100 reassembly packets. If the limit has been reached, new fragmented packets are silently dropped.

You can change the limit by using Regedt32 to navigate to HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters. On the Edit menu, Add Value name MaximumReassemblyHeaders, a REG_DWORD data type, and set the data value to any Decimal number between 100 and 65535. After exiting the registry editor, restart your computer.