Hi Marc, You definitely have enough information now for a PR. Would you please file all of this into a PR so one of the IP stack people can take a look?
Thanks, Adrian On 22 November 2012 07:42, Marc Peters <m...@mpeters.org> wrote: > On 11/22/2012 02:20 PM, Ingo Flaschberger wrote: >> Am 22.11.2012 13:38, schrieb Marc Peters: >>> interesting, the MTU is way lower, than i expected. Through the VPN >>> tunnel, only 1322 bytes are possible without fragmentation. ScreenOS >>> adds 42 additional bytes per paket and the FreeBSD box is receiving >>> 1364 bytes, according to tcpdump. From the outside (only one Netscreen >>> on the way), 1472 is the maximum possible size to send pakets without >>> fragmentation (-D). Which MTU would you suggest to use? Shouldn't the >>> MTU discovery of FreeBSD handle this correct? >> >> do you see fragmented tcp packets on the receiving site in tcpdump? > > nearly every packet is fragmented, if i read th [TCP segment of a > reassembled PDU] correct. Those have a length of 1364. Thera are also > lots of [TCP Window Update] (every two to three acks from the receiving > host, where the tcpdump took place). After some time, there were lots of > [TCP Dup ACK] from the receiving host and the throughput went to a crawl > and had lots of retransmissions. After 30 sec. everything went back to > "normal" as of transmitting pakets without dubs and retransmissions. > > The same tcpdump collect on the Linux hosts, the packets had a length of > 1514 and no dubs or retransmissions. > > I didn't get the option JUMBO_MTU removed, but removing TSO4 didn't > changed anything. > > Adding packetfiltering and the pipe didn't change anything, too. > >> >> When you load the tcpdump data (tcpdump -s 1500 -w filename ...) into >> wireshark, you can graph the speed (bit/sec, packets/sec) and do some >> more tcp analysis. >> >> Kind regards, >> Ingo Flaschberger >> _______________________________________________ >> freebsd-net@freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-net >> To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org" > > _______________________________________________ > freebsd-net@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-net > To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org" _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org"
