Did you try tweaking ip_no_pmtu_disc and run your tests? I played a bit with the openssl test client/server and it seems to respect ip_no_pmtu_disc. Test goes

Did you try tweaking ip_no_pmtu_disc and run your tests? I played a bit with the openssl test client/server and it seems to respect ip_no_pmtu_disc. Test goes something like this: 1) In one window run openssl s_server 2) In another window run openssl s_client -connect localhost:4433 3) In another window run tcpdump -nvi lo port 4433 Try twiddling the ip_no_pmtu_disc sysctl and see what happens.