<div dir="ltr"><div><div><div><div>Hi Tangqing,<br><br></div>This is a well-known problem, it is because GRE/VxLan 's packet header use some bytes, length of data packet should reduced.<br></div>You can get refer to bellow pages:<br><a href="http://www.chriscowley.me.uk/blog/2014/03/31/openstack-neutron-performance-problems/">http://www.chriscowley.me.uk/blog/2014/03/31/openstack-neutron-performance-problems/</a><br><a href="https://ask.openstack.org/en/question/25947/openstack-neutron-stability-problems-with-openvswitch/">https://ask.openstack.org/en/question/25947/openstack-neutron-stability-problems-with-openvswitch/</a><br><a href="https://openstack.redhat.com/forum/discussion/302/quantumneutron-and-ip-packet-mtus-questions-answers-and-suggestions/p1">https://openstack.redhat.com/forum/discussion/302/quantumneutron-and-ip-packet-mtus-questions-answers-and-suggestions/p1</a><br><br></div>Hope it helps,<br></div>Damon<br></div><div class="gmail_extra"><br><div class="gmail_quote">2014-10-27 9:18 GMT+08:00 Li Tianqing <span dir="ltr"><<a href="mailto:jazeltq@163.com" target="_blank">jazeltq@163.com</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="line-height:1.7;color:#000000;font-size:14px;font-family:Arial"><div>Hello,</div><div>    Right now, we test neutron under havana release. We configured network_device_mtu=1450 in neutron.conf, </div><div>   After create vm, we found the vm interface's mtu is 1500, the ping, ssh, is ok. But if we scp large file between vms</div><div>   then scp display 'stalled'. And iperf is also can not completed.</div><div>   If we configured vm's mtu to 1450, then iperf, scp all is ok.</div><div>   If we iperf with -M 1300, then the iperf is ok too.</div><div>   The vms path mtu discovery is set by default. I do not know why the vm whose mtu is 1500 can not send large file.</div><div><br></div><div><br></div><div>Thanks.</div><br><br><br><br><div>--<br><div>Best</div><span class="HOEnZb"><font color="#888888"><div>    Li Tianqing</div></font></span></div></div><br><br><span title="neteasefooter"><span></span></span><br>_______________________________________________<br>
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