Date: Sun, 10 Dec 2017 21:20:26 +0100 From: Michael Grimm <trashcan@ellael.org> To: Eugene Grosbein <eugen@grosbein.net> Cc: freebsd-net@FreeBSD.org Subject: Re: [IPsec] Weird performance issue via IPsec/racoon tunnel Message-ID: <FF3F1C00-97B0-43C3-B32B-F4546D71D781@ellael.org> In-Reply-To: <5A2D93BA.9020709@grosbein.net> References: <7A6EF712-920E-40BF-B155-113EE6C00AEA@ellael.org> <5A2D703F.8040004@grosbein.net> <3B480730-FF34-45B8-8636-9FCD4E97A2B9@ellael.org> <5A2D93BA.9020709@grosbein.net>
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Eugene Grosbein <eugen@grosbein.net> wrote: > 11.12.2017 2:54, Michael Grimm wrote: >> *BUT* if I do boot with the default 1500 setting, >> changing the MTU to e.g. 1450 and *immediately* back to 1500 = manually, >> I do not encounter any performance loss at all. Why? >> Even when booting 1490 and immediately setting the MTU manually to = 1500 I do not see any performance loss. Strange. >=20 > Interface MTU is used to assing 'mtu' attribute to corresponding route = in the system routing table. > Lowering interface MTU lowers route mtu, but raising interface MTU = does *not* raises route mtu, > use "route -n get" command to check it out. So, you still use low mtu = really. Bingo!=20 NEW> ifconfig vtnet0 vtnet0: flags=3D8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> = metric 0 mtu 1490 NEW> route -n get freebsd.org ... recvpipe sendpipe ssthresh rtt,msec mtu weight = expire 0 0 0 0 1490 1 = 0=20 NEW> ifconfig vtnet0 mtu 1500 up NEW> ifconfig vtnet0 vtnet0: flags=3D8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> = metric 0 mtu 1500 NEW> route -n get spiegel.de ... recvpipe sendpipe ssthresh rtt,msec mtu weight = expire 0 0 0 0 1490 1 = 0=20 I didn't know that. And that explains all my observations. >> Hmm, how would one check that? The output is to fast for me ;-) = Seriously, how should one check this? >=20 > With your eyes :-) Use tcpdump -c flag to limit number of lines, = redirect output to a file > and carefully compare some packets using their ID that tcpshow shows. Ok. I will do that at some later time ;-) I'd like to thank you again for your input and with kind regards, Michael
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