Resolution:

On Linux, you can disable DF system-wide by writing a "1" to /proc/sys/net/ipv4/ip_no_pmtu_disc or per-socket by using the SOL_IP socket option IP_MTU_DISCOVER (=>ip(7)).

RV daemon does not set DF. It is enabled on Linux by default. To verify the setting on Linux, run the following:

$ more /proc/sys/net/ipv4/ip_no_pmtu_disc

"0" means “Don't fragment” . To disable the DF, run the following:

$ Echo 1 >/proc/sys/net/ipv4/ip_no_pmtu_disc 

By default on Windows, the DF is not set.