[openstack-dev] [neutron] vm can not transport large file under neutron ml2 + linux bridge + vxlan
Hello, Right now, we test neutron under havana release. We configured network_device_mtu=1450 in neutron.conf, 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 then scp display 'stalled'. And iperf is also can not completed. If we configured vm's mtu to 1450, then iperf, scp all is ok. If we iperf with -M 1300, then the iperf is ok too. 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. Thanks. -- Best Li Tianqing___ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
Re: [openstack-dev] [neutron] vm can not transport large file under neutron ml2 + linux bridge + vxlan
Hi Tangqing, This is a well-known problem, it is because GRE/VxLan 's packet header use some bytes, length of data packet should reduced. You can get refer to bellow pages: http://www.chriscowley.me.uk/blog/2014/03/31/openstack-neutron-performance-problems/ https://ask.openstack.org/en/question/25947/openstack-neutron-stability-problems-with-openvswitch/ https://openstack.redhat.com/forum/discussion/302/quantumneutron-and-ip-packet-mtus-questions-answers-and-suggestions/p1 Hope it helps, Damon 2014-10-27 9:18 GMT+08:00 Li Tianqing : > Hello, > Right now, we test neutron under havana release. We configured > network_device_mtu=1450 in neutron.conf, >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 >then scp display 'stalled'. And iperf is also can not completed. >If we configured vm's mtu to 1450, then iperf, scp all is ok. >If we iperf with -M 1300, then the iperf is ok too. >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. > > > Thanks. > > > > > -- > Best > Li Tianqing > > > > ___ > OpenStack-dev mailing list > OpenStack-dev@lists.openstack.org > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev > > ___ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
Re: [openstack-dev] [neutron] vm can not transport large file under neutron ml2 + linux bridge + vxlan
Thanks, it helps a lot. But i want to know, why the mtu discovery can not find the appropriate mtu to send? In http://www.chriscowley.me.uk/blog/2014/03/31/openstack-neutron-performance-problems/, it says that "Everything matches, however I was using GRE tunnels, which add a header to each frame. This was pushing them over 1500 on entry to br-tun causing massive network fragmentation, which basically destroyed Openvswitch every time I performed a large transfer. It showed up when deploying an image, because that is hitting the Glance API over http." Dose it means that the pmtu is not work? At 2014-10-27 09:51:31, "Damon Wang" wrote: Hi Tangqing, This is a well-known problem, it is because GRE/VxLan 's packet header use some bytes, length of data packet should reduced. You can get refer to bellow pages: http://www.chriscowley.me.uk/blog/2014/03/31/openstack-neutron-performance-problems/ https://ask.openstack.org/en/question/25947/openstack-neutron-stability-problems-with-openvswitch/ https://openstack.redhat.com/forum/discussion/302/quantumneutron-and-ip-packet-mtus-questions-answers-and-suggestions/p1 Hope it helps, Damon 2014-10-27 9:18 GMT+08:00 Li Tianqing : Hello, Right now, we test neutron under havana release. We configured network_device_mtu=1450 in neutron.conf, 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 then scp display 'stalled'. And iperf is also can not completed. If we configured vm's mtu to 1450, then iperf, scp all is ok. If we iperf with -M 1300, then the iperf is ok too. 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. Thanks. -- Best Li Tianqing ___ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev ___ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
Re: [openstack-dev] [neutron] vm can not transport large file under neutron ml2 + linux bridge + vxlan
-BEGIN PGP SIGNED MESSAGE- Hash: SHA512 On 27/10/14 02:18, Li Tianqing wrote: > Hello, Right now, we test neutron under havana release. We > configured network_device_mtu=1450 in neutron.conf, 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 then scp display 'stalled'. > And iperf is also can not completed. If we configured vm's mtu to > 1450, then iperf, scp all is ok. If we iperf with -M 1300, then the > iperf is ok too. 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. There is a neutron spec currently in discussion for Kilo to finally fix MTU issues due to tunneling, that also tries to propagate MTU inside instances: https://review.openstack.org/#/c/105989/ /Ihar -BEGIN PGP SIGNATURE- Version: GnuPG/MacGPG2 v2.0.22 (Darwin) iQEcBAEBCgAGBQJUThORAAoJEC5aWaUY1u571u4H/3EqEVPL1Q9KgymrudLpAdRh fwNarwPWT8Ed+0x7WIXAr7OFXX1P90cKRAZKTlAEEI94vOrdr0s608ZX8awMuLeu +LB6IA7nMpgJammfDb8zNmYLHuTQGGatXblOinvtm3XXIcNbkNu8840MTV3y/Jdq Mndtz69TrjTrjn7r9REJ4bnRIlL4DGo+gufXPD49+yax1y/woefqwZPU13kO6j6R Q0+MAy13ptg2NwX26OI+Sb801W0kpDXby6WZjfekXqxqv62fY1/lPQ3oqqJBd95K EFe5NuogLV7UGH5vydQJa0eO2jw5lh8qLuHSShGcDEp/N6oQWiDzXYYYoEQdUic= =jRQ/ -END PGP SIGNATURE- ___ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
Re: [openstack-dev] [neutron] vm can not transport large file under neutron ml2 + linux bridge + vxlan
On Mon, Oct 27, 2014 at 4:42 AM, Ihar Hrachyshka wrote: > -BEGIN PGP SIGNED MESSAGE- > Hash: SHA512 > > On 27/10/14 02:18, Li Tianqing wrote: >> Hello, Right now, we test neutron under havana release. We >> configured network_device_mtu=1450 in neutron.conf, 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 then scp display 'stalled'. >> And iperf is also can not completed. If we configured vm's mtu to >> 1450, then iperf, scp all is ok. If we iperf with -M 1300, then the >> iperf is ok too. 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. > > There is a neutron spec currently in discussion for Kilo to finally > fix MTU issues due to tunneling, that also tries to propagate MTU > inside instances: https://review.openstack.org/#/c/105989/ > This is something which would be quite fantastic to land in Kilo, as multiple people have been bit by this particular issue. > /Ihar > -BEGIN PGP SIGNATURE- > Version: GnuPG/MacGPG2 v2.0.22 (Darwin) > > iQEcBAEBCgAGBQJUThORAAoJEC5aWaUY1u571u4H/3EqEVPL1Q9KgymrudLpAdRh > fwNarwPWT8Ed+0x7WIXAr7OFXX1P90cKRAZKTlAEEI94vOrdr0s608ZX8awMuLeu > +LB6IA7nMpgJammfDb8zNmYLHuTQGGatXblOinvtm3XXIcNbkNu8840MTV3y/Jdq > Mndtz69TrjTrjn7r9REJ4bnRIlL4DGo+gufXPD49+yax1y/woefqwZPU13kO6j6R > Q0+MAy13ptg2NwX26OI+Sb801W0kpDXby6WZjfekXqxqv62fY1/lPQ3oqqJBd95K > EFe5NuogLV7UGH5vydQJa0eO2jw5lh8qLuHSShGcDEp/N6oQWiDzXYYYoEQdUic= > =jRQ/ > -END PGP SIGNATURE- > > ___ > OpenStack-dev mailing list > OpenStack-dev@lists.openstack.org > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev ___ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
Re: [openstack-dev] [neutron] vm can not transport large file under neutron ml2 + linux bridge + vxlan
-- Best Li Tianqing At 2014-10-27 17:42:41, "Ihar Hrachyshka" wrote: >-BEGIN PGP SIGNED MESSAGE- >Hash: SHA512 > >On 27/10/14 02:18, Li Tianqing wrote: >> Hello, Right now, we test neutron under havana release. We >> configured network_device_mtu=1450 in neutron.conf, 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 then scp display 'stalled'. >> And iperf is also can not completed. If we configured vm's mtu to >> 1450, then iperf, scp all is ok. If we iperf with -M 1300, then the >> iperf is ok too. 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. > >There is a neutron spec currently in discussion for Kilo to finally >fix MTU issues due to tunneling, that also tries to propagate MTU >inside instances: https://review.openstack.org/#/c/105989/ The problem is i do not know why the vm with 1500 mtu can not send large file? I found the packet send out all with DF, and is it because the DF set default by linux cause the packet be dropped? And the application do not handle the return back icmp packet with the smaller mtu? > >/Ihar >-BEGIN PGP SIGNATURE- >Version: GnuPG/MacGPG2 v2.0.22 (Darwin) > >iQEcBAEBCgAGBQJUThORAAoJEC5aWaUY1u571u4H/3EqEVPL1Q9KgymrudLpAdRh >fwNarwPWT8Ed+0x7WIXAr7OFXX1P90cKRAZKTlAEEI94vOrdr0s608ZX8awMuLeu >+LB6IA7nMpgJammfDb8zNmYLHuTQGGatXblOinvtm3XXIcNbkNu8840MTV3y/Jdq >Mndtz69TrjTrjn7r9REJ4bnRIlL4DGo+gufXPD49+yax1y/woefqwZPU13kO6j6R >Q0+MAy13ptg2NwX26OI+Sb801W0kpDXby6WZjfekXqxqv62fY1/lPQ3oqqJBd95K >EFe5NuogLV7UGH5vydQJa0eO2jw5lh8qLuHSShGcDEp/N6oQWiDzXYYYoEQdUic= >=jRQ/ >-END PGP SIGNATURE- > >___ >OpenStack-dev mailing list >OpenStack-dev@lists.openstack.org >http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev ___ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
Re: [openstack-dev] [neutron] vm can not transport large file under neutron ml2 + linux bridge + vxlan
Path MTU discovery works on a path - something with an L3 router in the way - where the outbound interface has a smaller MTU than the inbound one. You're transmitting across an L2 network - no L3 routers present. You send a 1500 byte packet, the network fabric (which is not L3, has no address, and therefore has no means to answer you) does all that it can do with that packet - it drops it. The sender retransmits, assuming congestion, but the same thing happens. Eventually the sender decides there's a network problem and times out. This is a common problem with Openstack deployments, although various features of the virtual networking let you get away with it, with some configs and not others. OVS used to fake a PMTU exceeded message from the destination if you tried to pass an overlarge packet - not in spec, but it hid the problem nicely. I have a suspicion that some implementations will fragment the containing UDP packet, which is also not in spec and also solves the problem (albeit with poor performance). The right answer for you is to set the MTU in your machines to the same MTU you've given the network, that is, 1450 bytes. You can do this by setting a DHCP option for MTU, providing your VMs support that option (search the web for the solution, I don't have it offhand) or lower the MTU by hand or by script when you start your VM. The right answer for everyone is to properly determine and advertise the network MTU to VMs (which, with provider networks, is not even consistent from one network to the next) and that's the spec Kyle is referring to. We'll be fixing this in Kilo. -- Ian. On 27 October 2014 20:14, Li Tianqing wrote: > > > > > > -- > Best > Li Tianqing > > > At 2014-10-27 17:42:41, "Ihar Hrachyshka" wrote: > >-BEGIN PGP SIGNED MESSAGE- > >Hash: SHA512 > > > >On 27/10/14 02:18, Li Tianqing wrote: > >> Hello, Right now, we test neutron under havana release. We > >> configured network_device_mtu=1450 in neutron.conf, 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 then scp display 'stalled'. > >> And iperf is also can not completed. If we configured vm's mtu to > >> 1450, then iperf, scp all is ok. If we iperf with -M 1300, then the > >> iperf is ok too. 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. > > > >There is a neutron spec currently in discussion for Kilo to finally > >fix MTU issues due to tunneling, that also tries to propagate MTU > >inside instances: https://review.openstack.org/#/c/105989/ > > The problem is i do not know why the vm with 1500 mtu can not send large file? > I found the packet send out all with DF, and is it because the DF set default > by linux cause the packet > be dropped? And the application do not handle the return back icmp packet > with the smaller mtu? > > > > >/Ihar > >-BEGIN PGP SIGNATURE- > >Version: GnuPG/MacGPG2 v2.0.22 (Darwin) > > > >iQEcBAEBCgAGBQJUThORAAoJEC5aWaUY1u571u4H/3EqEVPL1Q9KgymrudLpAdRh > >fwNarwPWT8Ed+0x7WIXAr7OFXX1P90cKRAZKTlAEEI94vOrdr0s608ZX8awMuLeu > >+LB6IA7nMpgJammfDb8zNmYLHuTQGGatXblOinvtm3XXIcNbkNu8840MTV3y/Jdq > >Mndtz69TrjTrjn7r9REJ4bnRIlL4DGo+gufXPD49+yax1y/woefqwZPU13kO6j6R > >Q0+MAy13ptg2NwX26OI+Sb801W0kpDXby6WZjfekXqxqv62fY1/lPQ3oqqJBd95K > >EFe5NuogLV7UGH5vydQJa0eO2jw5lh8qLuHSShGcDEp/N6oQWiDzXYYYoEQdUic= > >=jRQ/ > >-END PGP SIGNATURE- > > > >___ > >OpenStack-dev mailing list > >OpenStack-dev@lists.openstack.org > >http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev > > > > > ___ > OpenStack-dev mailing list > OpenStack-dev@lists.openstack.org > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev > > ___ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
Re: [openstack-dev] [neutron] vm can not transport large file under neutron ml2 + linux bridge + vxlan
The problem is that it is not at the begining to transmit large file. It is after some packets trasmited, then the connection is choked. After the connection choked, from the bridge in compute host we can see the sender send packets, and the receiver can not get the packets. If it is the pmtud, then at the very begining, the packet can not transmit from the begining. At 2014-10-28 14:10:09, "Ian Wells" wrote: Path MTU discovery works on a path - something with an L3 router in the way - where the outbound interface has a smaller MTU than the inbound one. You're transmitting across an L2 network - no L3 routers present. You send a 1500 byte packet, the network fabric (which is not L3, has no address, and therefore has no means to answer you) does all that it can do with that packet - it drops it. The sender retransmits, assuming congestion, but the same thing happens. Eventually the sender decides there's a network problem and times out. This is a common problem with Openstack deployments, although various features of the virtual networking let you get away with it, with some configs and not others. OVS used to fake a PMTU exceeded message from the destination if you tried to pass an overlarge packet - not in spec, but it hid the problem nicely. I have a suspicion that some implementations will fragment the containing UDP packet, which is also not in spec and also solves the problem (albeit with poor performance). The right answer for you is to set the MTU in your machines to the same MTU you've given the network, that is, 1450 bytes. You can do this by setting a DHCP option for MTU, providing your VMs support that option (search the web for the solution, I don't have it offhand) or lower the MTU by hand or by script when you start your VM. The right answer for everyone is to properly determine and advertise the network MTU to VMs (which, with provider networks, is not even consistent from one network to the next) and that's the spec Kyle is referring to. We'll be fixing this in Kilo. -- Ian. On 27 October 2014 20:14, Li Tianqing wrote: -- Best Li Tianqing At 2014-10-27 17:42:41, "Ihar Hrachyshka" wrote: >-BEGIN PGP SIGNED MESSAGE- >Hash: SHA512 > >On 27/10/14 02:18, Li Tianqing wrote: >> Hello, Right now, we test neutron under havana release. We >> configured network_device_mtu=1450 in neutron.conf, 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 then scp display 'stalled'. >> And iperf is also can not completed. If we configured vm's mtu to >> 1450, then iperf, scp all is ok. If we iperf with -M 1300, then the >> iperf is ok too. 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. > >There is a neutron spec currently in discussion for Kilo to finally >fix MTU issues due to tunneling, that also tries to propagate MTU >inside instances: https://review.openstack.org/#/c/105989/ The problem is i do not know why the vm with 1500 mtu can not send large file? I found the packet send out all with DF, and is it because the DF set default by linux cause the packet be dropped? And the application do not handle the return back icmp packet with the smaller mtu? > >/Ihar >-BEGIN PGP SIGNATURE- >Version: GnuPG/MacGPG2 v2.0.22 (Darwin) > >iQEcBAEBCgAGBQJUThORAAoJEC5aWaUY1u571u4H/3EqEVPL1Q9KgymrudLpAdRh >fwNarwPWT8Ed+0x7WIXAr7OFXX1P90cKRAZKTlAEEI94vOrdr0s608ZX8awMuLeu >+LB6IA7nMpgJammfDb8zNmYLHuTQGGatXblOinvtm3XXIcNbkNu8840MTV3y/Jdq >Mndtz69TrjTrjn7r9REJ4bnRIlL4DGo+gufXPD49+yax1y/woefqwZPU13kO6j6R >Q0+MAy13ptg2NwX26OI+Sb801W0kpDXby6WZjfekXqxqv62fY1/lPQ3oqqJBd95K >EFe5NuogLV7UGH5vydQJa0eO2jw5lh8qLuHSShGcDEp/N6oQWiDzXYYYoEQdUic= >=jRQ/ >-END PGP SIGNATURE- > >___ >OpenStack-dev mailing list >OpenStack-dev@lists.openstack.org >http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev ___ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev ___ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
Re: [openstack-dev] [neutron] vm can not transport large file under neutron ml2 + linux bridge + vxlan
Hi, Currently OpenStack have any framework to notify the Tennant/Service-VM for such kind of notification based on VM’s interest ? VM may be very much interested for such kind of notification like 1. Path MTU. 2. Based on specific incoming Tennant traffic, block/Allow particular traffic flow at infrastructure level itself, instead of at VM. This may require OpenStack infrastructure notification support to Tenant/Service VM. … Thanks & regards, Keshava From: Ian Wells [mailto:ijw.ubu...@cack.org.uk] Sent: Tuesday, October 28, 2014 11:40 AM To: OpenStack Development Mailing List (not for usage questions) Subject: Re: [openstack-dev] [neutron] vm can not transport large file under neutron ml2 + linux bridge + vxlan Path MTU discovery works on a path - something with an L3 router in the way - where the outbound interface has a smaller MTU than the inbound one. You're transmitting across an L2 network - no L3 routers present. You send a 1500 byte packet, the network fabric (which is not L3, has no address, and therefore has no means to answer you) does all that it can do with that packet - it drops it. The sender retransmits, assuming congestion, but the same thing happens. Eventually the sender decides there's a network problem and times out. This is a common problem with Openstack deployments, although various features of the virtual networking let you get away with it, with some configs and not others. OVS used to fake a PMTU exceeded message from the destination if you tried to pass an overlarge packet - not in spec, but it hid the problem nicely. I have a suspicion that some implementations will fragment the containing UDP packet, which is also not in spec and also solves the problem (albeit with poor performance). The right answer for you is to set the MTU in your machines to the same MTU you've given the network, that is, 1450 bytes. You can do this by setting a DHCP option for MTU, providing your VMs support that option (search the web for the solution, I don't have it offhand) or lower the MTU by hand or by script when you start your VM. The right answer for everyone is to properly determine and advertise the network MTU to VMs (which, with provider networks, is not even consistent from one network to the next) and that's the spec Kyle is referring to. We'll be fixing this in Kilo. -- Ian. On 27 October 2014 20:14, Li Tianqing mailto:jaze...@163.com>> wrote: -- Best Li Tianqing At 2014-10-27 17:42:41, "Ihar Hrachyshka" mailto:ihrac...@redhat.com>> wrote: >-BEGIN PGP SIGNED MESSAGE- >Hash: SHA512 > >On 27/10/14 02:18, Li Tianqing wrote: >> Hello, Right now, we test neutron under havana release. We >> configured network_device_mtu=1450 in neutron.conf, 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 then scp display 'stalled'. >> And iperf is also can not completed. If we configured vm's mtu to >> 1450, then iperf, scp all is ok. If we iperf with -M 1300, then the >> iperf is ok too. 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. > >There is a neutron spec currently in discussion for Kilo to finally >fix MTU issues due to tunneling, that also tries to propagate MTU >inside instances: https://review.openstack.org/#/c/105989/ The problem is i do not know why the vm with 1500 mtu can not send large file? I found the packet send out all with DF, and is it because the DF set default by linux cause the packet be dropped? And the application do not handle the return back icmp packet with the smaller mtu? > >/Ihar >-BEGIN PGP SIGNATURE- >Version: GnuPG/MacGPG2 v2.0.22 (Darwin) > >iQEcBAEBCgAGBQJUThORAAoJEC5aWaUY1u571u4H/3EqEVPL1Q9KgymrudLpAdRh >fwNarwPWT8Ed+0x7WIXAr7OFXX1P90cKRAZKTlAEEI94vOrdr0s608ZX8awMuLeu >+LB6IA7nMpgJammfDb8zNmYLHuTQGGatXblOinvtm3XXIcNbkNu8840MTV3y/Jdq >Mndtz69TrjTrjn7r9REJ4bnRIlL4DGo+gufXPD49+yax1y/woefqwZPU13kO6j6R >Q0+MAy13ptg2NwX26OI+Sb801W0kpDXby6WZjfekXqxqv62fY1/lPQ3oqqJBd95K >EFe5NuogLV7UGH5vydQJa0eO2jw5lh8qLuHSShGcDEp/N6oQWiDzXYYYoEQdUic= >=jRQ/ >-END PGP SIGNATURE- > >___ >OpenStack-dev mailing list >OpenStack-dev@lists.openstack.org<mailto:OpenStack-dev@lists.openstack.org> >http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev ___ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org<mailto:OpenStack-dev@lists.openstack.org> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev ___ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
Re: [openstack-dev] [neutron] vm can not transport large file under neutron ml2 + linux bridge + vxlan
lan, you are right, the receiver only receive packet that small than 1450. Because the sender does not send large packets at the begining, so tcpdump can catch some small packets. Another question about the mtu, what if we clear the DF in the ip packets? Then l2 can split packets into smaller mtu size? At 2014-10-28 15:15:51, "Li Tianqing" wrote: The problem is that it is not at the begining to transmit large file. It is after some packets trasmited, then the connection is choked. After the connection choked, from the bridge in compute host we can see the sender send packets, and the receiver can not get the packets. If it is the pmtud, then at the very begining, the packet can not transmit from the begining. At 2014-10-28 14:10:09, "Ian Wells" wrote: Path MTU discovery works on a path - something with an L3 router in the way - where the outbound interface has a smaller MTU than the inbound one. You're transmitting across an L2 network - no L3 routers present. You send a 1500 byte packet, the network fabric (which is not L3, has no address, and therefore has no means to answer you) does all that it can do with that packet - it drops it. The sender retransmits, assuming congestion, but the same thing happens. Eventually the sender decides there's a network problem and times out. This is a common problem with Openstack deployments, although various features of the virtual networking let you get away with it, with some configs and not others. OVS used to fake a PMTU exceeded message from the destination if you tried to pass an overlarge packet - not in spec, but it hid the problem nicely. I have a suspicion that some implementations will fragment the containing UDP packet, which is also not in spec and also solves the problem (albeit with poor performance). The right answer for you is to set the MTU in your machines to the same MTU you've given the network, that is, 1450 bytes. You can do this by setting a DHCP option for MTU, providing your VMs support that option (search the web for the solution, I don't have it offhand) or lower the MTU by hand or by script when you start your VM. The right answer for everyone is to properly determine and advertise the network MTU to VMs (which, with provider networks, is not even consistent from one network to the next) and that's the spec Kyle is referring to. We'll be fixing this in Kilo. -- Ian. On 27 October 2014 20:14, Li Tianqing wrote: -- Best Li Tianqing At 2014-10-27 17:42:41, "Ihar Hrachyshka" wrote: >-BEGIN PGP SIGNED MESSAGE- >Hash: SHA512 > >On 27/10/14 02:18, Li Tianqing wrote: >> Hello, Right now, we test neutron under havana release. We >> configured network_device_mtu=1450 in neutron.conf, 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 then scp display 'stalled'. >> And iperf is also can not completed. If we configured vm's mtu to >> 1450, then iperf, scp all is ok. If we iperf with -M 1300, then the >> iperf is ok too. 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. > >There is a neutron spec currently in discussion for Kilo to finally >fix MTU issues due to tunneling, that also tries to propagate MTU >inside instances: https://review.openstack.org/#/c/105989/ The problem is i do not know why the vm with 1500 mtu can not send large file? I found the packet send out all with DF, and is it because the DF set default by linux cause the packet be dropped? And the application do not handle the return back icmp packet with the smaller mtu? > >/Ihar >-BEGIN PGP SIGNATURE- >Version: GnuPG/MacGPG2 v2.0.22 (Darwin) > >iQEcBAEBCgAGBQJUThORAAoJEC5aWaUY1u571u4H/3EqEVPL1Q9KgymrudLpAdRh >fwNarwPWT8Ed+0x7WIXAr7OFXX1P90cKRAZKTlAEEI94vOrdr0s608ZX8awMuLeu >+LB6IA7nMpgJammfDb8zNmYLHuTQGGatXblOinvtm3XXIcNbkNu8840MTV3y/Jdq >Mndtz69TrjTrjn7r9REJ4bnRIlL4DGo+gufXPD49+yax1y/woefqwZPU13kO6j6R >Q0+MAy13ptg2NwX26OI+Sb801W0kpDXby6WZjfekXqxqv62fY1/lPQ3oqqJBd95K >EFe5NuogLV7UGH5vydQJa0eO2jw5lh8qLuHSShGcDEp/N6oQWiDzXYYYoEQdUic= >=jRQ/ >-END PGP SIGNATURE- > >___ >OpenStack-dev mailing list >OpenStack-dev@lists.openstack.org >http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev ___ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev ___ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
Re: [openstack-dev] [neutron] vm can not transport large file under neutron ml2 + linux bridge + vxlan
On 28 October 2014 00:18, A, Keshava wrote: > Hi, > > > > Currently OpenStack have any framework to notify the Tennant/Service-VM > for such kind of notification based on VM’s interest ? > It's possible to use DHCP or RA to notify a VM of the MTU but there are limitations (RAs don't let you increase the MTU, only decrease it, and obviously VMs must support the MTU element of DHCP) and Openstack doesn't currently use it. You can statically configure the DHCP MTU number that DHCP transmits; this is useful to work around problems but not really the right answer to the problem. > VM may be very much interested for such kind of notification like > > 1. Path MTU. > This will be correctly discovered from the ICMP PMTU exceeded message, and Neutron routers should certainly be expected to send that. (In fact the namespace implementation of routers would do this if the router ever had different MTUs on its ports; it's in the kernel network stack.) There's no requirement for a special notification, and indeed you couldn't do it that way anyway. > 2. Based on specific incoming Tennant traffic, block/Allow > particular traffic flow at infrastructure level itself, instead of at VM. > I don't see the relevance; and you appear to be describing security groups. > This may require OpenStack infrastructure notification support to > Tenant/Service VM. > Not particularly, as MTU doesn't generally change, and I think we would forbid changing the MTU of a network after creation. It's only an initial configuration thing, therefore. It might involve better cloud-init support for network configuration, something that gets discussed periodically. -- Ian. > > > … > > Thanks & regards, > > Keshava > > > > *From:* Ian Wells [mailto:ijw.ubu...@cack.org.uk] > *Sent:* Tuesday, October 28, 2014 11:40 AM > *To:* OpenStack Development Mailing List (not for usage questions) > *Subject:* Re: [openstack-dev] [neutron] vm can not transport large file > under neutron ml2 + linux bridge + vxlan > > > > Path MTU discovery works on a path - something with an L3 router in the > way - where the outbound interface has a smaller MTU than the inbound one. > You're transmitting across an L2 network - no L3 routers present. You send > a 1500 byte packet, the network fabric (which is not L3, has no address, > and therefore has no means to answer you) does all that it can do with that > packet - it drops it. The sender retransmits, assuming congestion, but the > same thing happens. Eventually the sender decides there's a network > problem and times out. > > This is a common problem with Openstack deployments, although various > features of the virtual networking let you get away with it, with some > configs and not others. OVS used to fake a PMTU exceeded message from the > destination if you tried to pass an overlarge packet - not in spec, but it > hid the problem nicely. I have a suspicion that some implementations will > fragment the containing UDP packet, which is also not in spec and also > solves the problem (albeit with poor performance). > > The right answer for you is to set the MTU in your machines to the same > MTU you've given the network, that is, 1450 bytes. You can do this by > setting a DHCP option for MTU, providing your VMs support that option > (search the web for the solution, I don't have it offhand) or lower the MTU > by hand or by script when you start your VM. > > The right answer for everyone is to properly determine and advertise the > network MTU to VMs (which, with provider networks, is not even consistent > from one network to the next) and that's the spec Kyle is referring to. > We'll be fixing this in Kilo. > -- > > Ian. > > > > On 27 October 2014 20:14, Li Tianqing wrote: > > > > > > -- > > Best > > Li Tianqing > > > > > At 2014-10-27 17:42:41, "Ihar Hrachyshka" wrote: > > >-BEGIN PGP SIGNED MESSAGE- > > >Hash: SHA512 > > > > > >On 27/10/14 02:18, Li Tianqing wrote: > > >> Hello, Right now, we test neutron under havana release. We > > >> configured network_device_mtu=1450 in neutron.conf, 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 then scp display 'stalled'. > > >> And iperf is also can not completed. If we configured vm's mtu to > > >> 1450, then iperf, scp all is ok. If we iperf with -M 1300, then the > > >> iperf is ok too. The vms path mtu discovery is set by default. I do > > >> not
Re: [openstack-dev] [neutron] vm can not transport large file under neutron ml2 + linux bridge + vxlan
On 28 October 2014 00:30, Li Tianqing wrote: > lan, you are right, the receiver only receive packet that small than 1450. > Because the sender does not send large packets at the begining, so > tcpdump can catch some small packets. > > Another question about the mtu, what if we clear the DF in the ip > packets? Then l2 can split packets into smaller mtu size? > Routers can split packets. L2 networks don't understand IP headers and therefore can't fragment packets. DF doesn't change that. (DF is there to make PMTU discovery work, incidentially; it's what prompts routers to return PMTU exceeded messages.) -- Ian. At 2014-10-28 15:15:51, "Li Tianqing" wrote: > > The problem is that it is not at the begining to transmit large file. It > is after some packets trasmited, then the connection is choked. > After the connection choked, from the bridge in compute host we can see > the sender send packets, and the receiver can not get the packets. > If it is the pmtud, then at the very begining, the packet can not transmit > from the begining. > > At 2014-10-28 14:10:09, "Ian Wells" wrote: > > Path MTU discovery works on a path - something with an L3 router in the > way - where the outbound interface has a smaller MTU than the inbound one. > You're transmitting across an L2 network - no L3 routers present. You send > a 1500 byte packet, the network fabric (which is not L3, has no address, > and therefore has no means to answer you) does all that it can do with that > packet - it drops it. The sender retransmits, assuming congestion, but the > same thing happens. Eventually the sender decides there's a network > problem and times out. > > This is a common problem with Openstack deployments, although various > features of the virtual networking let you get away with it, with some > configs and not others. OVS used to fake a PMTU exceeded message from the > destination if you tried to pass an overlarge packet - not in spec, but it > hid the problem nicely. I have a suspicion that some implementations will > fragment the containing UDP packet, which is also not in spec and also > solves the problem (albeit with poor performance). > > The right answer for you is to set the MTU in your machines to the same > MTU you've given the network, that is, 1450 bytes. You can do this by > setting a DHCP option for MTU, providing your VMs support that option > (search the web for the solution, I don't have it offhand) or lower the MTU > by hand or by script when you start your VM. > > The right answer for everyone is to properly determine and advertise the > network MTU to VMs (which, with provider networks, is not even consistent > from one network to the next) and that's the spec Kyle is referring to. > We'll be fixing this in Kilo. > -- > Ian. > > > On 27 October 2014 20:14, Li Tianqing wrote: > >> >> >> >> >> >> -- >> Best >> Li Tianqing >> >> >> At 2014-10-27 17:42:41, "Ihar Hrachyshka" wrote: >> >-BEGIN PGP SIGNED MESSAGE- >> >Hash: SHA512 >> > >> >On 27/10/14 02:18, Li Tianqing wrote: >> >> Hello, Right now, we test neutron under havana release. We >> >> configured network_device_mtu=1450 in neutron.conf, 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 then scp display 'stalled'. >> >> And iperf is also can not completed. If we configured vm's mtu to >> >> 1450, then iperf, scp all is ok. If we iperf with -M 1300, then the >> >> iperf is ok too. 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. >> > >> >There is a neutron spec currently in discussion for Kilo to finally >> >fix MTU issues due to tunneling, that also tries to propagate MTU >> >inside instances: https://review.openstack.org/#/c/105989/ >> >> The problem is i do not know why the vm with 1500 mtu can not send large >> file? >> I found the packet send out all with DF, and is it because the DF set >> default by linux cause the packet >> be dropped? And the application do not handle the return back icmp packet >> with the smaller mtu? >> >> > >> >/Ihar >> >-BEGIN PGP SIGNATURE- >> >Version: GnuPG/MacGPG2 v2.0.22 (Darwin) >> > >> >iQEcBAEBCgAGBQJUThORAAoJEC5aWaUY1u571u4H/3EqEVPL1Q9KgymrudLpAdRh >> >fwNarwPWT8Ed+0x7WIXAr7OFXX1P90cKRAZKTlAEEI94vOrdr0s608ZX8awMuLeu >> >+LB6IA7nMpgJammfDb8zNmYLHuTQGGatXblOinvtm3XXIcNbkNu8840MTV3y/Jdq >> >Mndtz69TrjTrjn7r9REJ4bnRIlL4DGo+gufXPD49+yax1y/woefqwZPU13kO6j6R >> >Q0+MAy13ptg2NwX26OI+Sb801W0kpDXby6WZjfekXqxqv62fY1/lPQ3oqqJBd95K >> >EFe5NuogLV7UGH5vydQJa0eO2jw5lh8qLuHSShGcDEp/N6oQWiDzXYYYoEQdUic= >> >=jRQ/ >> >-END PGP SIGNATURE- >> > >> >___ >> >OpenStack-dev mailing list >> >OpenStack-dev@lists.openstack.org >> >http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev >> >> >> >> >> ___ >> OpenStack-dev mailing list >> OpenStack-dev@list
Re: [openstack-dev] [neutron] vm can not transport large file under neutron ml2 + linux bridge + vxlan
One more question. Vxlan use udp, how can vxlan promise reliability. 在 2014-10-28 15:51:02，"Ian Wells" 写道： On 28 October 2014 00:30, Li Tianqing wrote: lan, you are right, the receiver only receive packet that small than 1450. Because the sender does not send large packets at the begining, so tcpdump can catch some small packets. Another question about the mtu, what if we clear the DF in the ip packets? Then l2 can split packets into smaller mtu size? Routers can split packets. L2 networks don't understand IP headers and therefore can't fragment packets. DF doesn't change that. (DF is there to make PMTU discovery work, incidentially; it's what prompts routers to return PMTU exceeded messages.) -- Ian. At 2014-10-28 15:15:51, "Li Tianqing" wrote: The problem is that it is not at the begining to transmit large file. It is after some packets trasmited, then the connection is choked. After the connection choked, from the bridge in compute host we can see the sender send packets, and the receiver can not get the packets. If it is the pmtud, then at the very begining, the packet can not transmit from the begining. At 2014-10-28 14:10:09, "Ian Wells" wrote: Path MTU discovery works on a path - something with an L3 router in the way - where the outbound interface has a smaller MTU than the inbound one. You're transmitting across an L2 network - no L3 routers present. You send a 1500 byte packet, the network fabric (which is not L3, has no address, and therefore has no means to answer you) does all that it can do with that packet - it drops it. The sender retransmits, assuming congestion, but the same thing happens. Eventually the sender decides there's a network problem and times out. This is a common problem with Openstack deployments, although various features of the virtual networking let you get away with it, with some configs and not others. OVS used to fake a PMTU exceeded message from the destination if you tried to pass an overlarge packet - not in spec, but it hid the problem nicely. I have a suspicion that some implementations will fragment the containing UDP packet, which is also not in spec and also solves the problem (albeit with poor performance). The right answer for you is to set the MTU in your machines to the same MTU you've given the network, that is, 1450 bytes. You can do this by setting a DHCP option for MTU, providing your VMs support that option (search the web for the solution, I don't have it offhand) or lower the MTU by hand or by script when you start your VM. The right answer for everyone is to properly determine and advertise the network MTU to VMs (which, with provider networks, is not even consistent from one network to the next) and that's the spec Kyle is referring to. We'll be fixing this in Kilo. -- Ian. On 27 October 2014 20:14, Li Tianqing wrote: -- Best Li Tianqing At 2014-10-27 17:42:41, "Ihar Hrachyshka" wrote: >-BEGIN PGP SIGNED MESSAGE- >Hash: SHA512 > >On 27/10/14 02:18, Li Tianqing wrote: >> Hello, Right now, we test neutron under havana release. We >> configured network_device_mtu=1450 in neutron.conf, 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 then scp display 'stalled'. >> And iperf is also can not completed. If we configured vm's mtu to >> 1450, then iperf, scp all is ok. If we iperf with -M 1300, then the >> iperf is ok too. 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. > >There is a neutron spec currently in discussion for Kilo to finally >fix MTU issues due to tunneling, that also tries to propagate MTU >inside instances: https://review.openstack.org/#/c/105989/ The problem is i do not know why the vm with 1500 mtu can not send large file? I found the packet send out all with DF, and is it because the DF set default by linux cause the packet be dropped? And the application do not handle the return back icmp packet with the smaller mtu? > >/Ihar >-BEGIN PGP SIGNATURE- >Version: GnuPG/MacGPG2 v2.0.22 (Darwin) > >iQEcBAEBCgAGBQJUThORAAoJEC5aWaUY1u571u4H/3EqEVPL1Q9KgymrudLpAdRh >fwNarwPWT8Ed+0x7WIXAr7OFXX1P90cKRAZKTlAEEI94vOrdr0s608ZX8awMuLeu >+LB6IA7nMpgJammfDb8zNmYLHuTQGGatXblOinvtm3XXIcNbkNu8840MTV3y/Jdq >Mndtz69TrjTrjn7r9REJ4bnRIlL4DGo+gufXPD49+yax1y/woefqwZPU13kO6j6R >Q0+MAy13ptg2NwX26OI+Sb801W0kpDXby6WZjfekXqxqv62fY1/lPQ3oqqJBd95K >EFe5NuogLV7UGH5vydQJa0eO2jw5lh8qLuHSShGcDEp/N6oQWiDzXYYYoEQdUic= >=jRQ/ >-END PGP SIGNATURE- > >___ >OpenStack-dev mailing list >OpenStack-dev@lists.openstack.org >http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev ___ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev __
Re: [openstack-dev] [neutron] vm can not transport large file under neutron ml2 + linux bridge + vxlan
Hi, Pl find my reply . Regards, keshava From: Ian Wells [mailto:ijw.ubu...@cack.org.uk] Sent: Tuesday, October 28, 2014 1:19 PM To: OpenStack Development Mailing List (not for usage questions) Subject: Re: [openstack-dev] [neutron] vm can not transport large file under neutron ml2 + linux bridge + vxlan On 28 October 2014 00:18, A, Keshava mailto:keshav...@hp.com>> wrote: Hi, Currently OpenStack have any framework to notify the Tennant/Service-VM for such kind of notification based on VM’s interest ? It's possible to use DHCP or RA to notify a VM of the MTU but there are limitations (RAs don't let you increase the MTU, only decrease it, and obviously VMs must support the MTU element of DHCP) and Openstack doesn't currently use it. You can statically configure the DHCP MTU number that DHCP transmits; this is useful to work around problems but not really the right answer to the problem. VM may be very much interested for such kind of notification like 1. Path MTU. This will be correctly discovered from the ICMP PMTU exceeded message, and Neutron routers should certainly be expected to send that. (In fact the namespace implementation of routers would do this if the router ever had different MTUs on its ports; it's in the kernel network stack.) There's no requirement for a special notification, and indeed you couldn't do it that way anyway. In the network interface/router going down is common scenario. In that case the packet will take different path which may have different MTU. In that case the PATH MTU calculated at the source may be different and should be notified dynamically to VM. So that VM can originate the packet with requirement MTU size . If there is no notification mechanism ( as per this reply): If there is no such dynamic PATH MTU change notification to VM, how VM can change the packet size ? Or Do we expect ICMP too big message reaches all the way to VM ? Or VM itself the run the PATH MTU ? 2. Based on specific incoming Tennant traffic, block/Allow particular traffic flow at infrastructure level itself, instead of at VM. I don't see the relevance; and you appear to be describing security groups. This may require OpenStack infrastructure notification support to Tenant/Service VM. Not particularly, as MTU doesn't generally change, and I think we would forbid changing the MTU of a network after creation. It's only an initial configuration thing, therefore. It might involve better cloud-init support for network configuration, something that gets discussed periodically. -- Ian. … Thanks & regards, Keshava From: Ian Wells [mailto:ijw.ubu...@cack.org.uk<mailto:ijw.ubu...@cack.org.uk>] Sent: Tuesday, October 28, 2014 11:40 AM To: OpenStack Development Mailing List (not for usage questions) Subject: Re: [openstack-dev] [neutron] vm can not transport large file under neutron ml2 + linux bridge + vxlan Path MTU discovery works on a path - something with an L3 router in the way - where the outbound interface has a smaller MTU than the inbound one. You're transmitting across an L2 network - no L3 routers present. You send a 1500 byte packet, the network fabric (which is not L3, has no address, and therefore has no means to answer you) does all that it can do with that packet - it drops it. The sender retransmits, assuming congestion, but the same thing happens. Eventually the sender decides there's a network problem and times out. This is a common problem with Openstack deployments, although various features of the virtual networking let you get away with it, with some configs and not others. OVS used to fake a PMTU exceeded message from the destination if you tried to pass an overlarge packet - not in spec, but it hid the problem nicely. I have a suspicion that some implementations will fragment the containing UDP packet, which is also not in spec and also solves the problem (albeit with poor performance). The right answer for you is to set the MTU in your machines to the same MTU you've given the network, that is, 1450 bytes. You can do this by setting a DHCP option for MTU, providing your VMs support that option (search the web for the solution, I don't have it offhand) or lower the MTU by hand or by script when you start your VM. The right answer for everyone is to properly determine and advertise the network MTU to VMs (which, with provider networks, is not even consistent from one network to the next) and that's the spec Kyle is referring to. We'll be fixing this in Kilo. -- Ian. On 27 October 2014 20:14, Li Tianqing mailto:jaze...@163.com>> wrote: -- Best Li Tianqing At 2014-10-27 17:42:41, "Ihar Hrachyshka" mailto:ihrac...@redhat.com>> wrote: >-BEGIN PGP SIGNED MESSAGE- >Hash: SHA512 > >On 27/10/14 02:18, Li Tianqing wrote: >> Hello,
Re: [openstack-dev] [neutron] vm can not transport large file under neutron ml2 + linux bridge + vxlan
On Tue, Oct 28, 2014 at 08:32:11, Li Tianqing wrote: > One more question. > Vxlan use udp, how can vxlan promise reliability. > It can't, but that doesn't matter. VXLAN emulates a single layer 2 broadcast domain: conceptually, a series of machines all plugged into the same Ethernet switch. This kind of network *isn't* reliable: you can lose Ethernet frames. There's no reason to require reliability from VXLAN, and it would increase VXLAN's overhead to add it in. If you need reliability, the encapsulated transport will provide it for you exactly as it does on a non-encapsulated network. ___ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
