On Mon, Jun 20, 2016 at 8:40 AM, Jeroen van Bemmel <jvb...@gmail.com> wrote: > Hello, > > When using VXLAN over Internet connections, Openvswitch TCP > performance is currently limited due to IP fragmentation: The Internet > MTU is (at most) 1500 bytes, and the typical TCP MSS value of 1460 > bytes used by clients becomes 1460+40+50 VXLAN = 1550 bytes. > > The attached patch addresses this issue, by modifying the TCP MSS > option in TCP SYN and SYN+ACK packets to account for VXLAN overhead. > It only applies to packets sent to or from VXLAN ports ( though could > be applied to other tunnel types as well ). > > I realize there are many things wrong about the patch, it's not > properly formatted and we would want the feature to be configurable ( > per port perhaps ). But before I go ahead and polish things up, I'd > like to collect some feedback on the general approach and desirability > of this feature. > > I built another patch to create a custom tcp-mss-rewrite Openflow > action, but I think for many applications this would complicate things > as flows have to be explicitly programmed. By making it part of the > standard output action, it can simply be dropped in and existing > applications can take advantage of the feature without modifications > to their code
I think you might have forgotten to attach the patch or it got clipped off by a mail server somewhere. In general, I think automatically clamping MSS for output actions doesn't really seem like a good idea. Even if it only applied to tunnel ports, OVS shouldn't change users' packets by itself. There was a thread about different ways to deal with MTU and tunnels. It didn't really lead to a conclusion yet but I think figuring out a way to make it work is the best way to solve this problem. http://openvswitch.org/pipermail/discuss/2016-May/021151.html _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
