The OVS buffers are sized by packets, not by bytes.
On Sat, Apr 16, 2016 at 05:09:24PM +0000, Majid Taleqani wrote: > Thank you Ben for answering my questionBen you mentioned that OVS have the > capacity to buffer 256 packets per connection. i guess OVS buffer size should > be in byte not in packet count. i mean if i send 256 packets that each packet > size is 1024 byte should overflow OVS buffer sooner that sending 256 packets > with the size of 20 byte. also consider that these 256 packets do not match > flow table and therefore will be buffered and sent to controller and also > suppose that controller just drop Packt_IN messages to test overflowing OVS > buffer.am i right or OVS just care about packet count? > thank you > > > From: Ben Pfaff <b...@ovn.org> > To: Ali Volkan Atli <volkan.a...@argela.com.tr> > Cc: Majid Taleqani <majid.taleq...@yahoo.com>; "discuss@openvswitch.org" > <discuss@openvswitch.org> > Sent: Friday, 15 April 2016, 10:17:22 > Subject: Re: [ovs-discuss] open vSwitch port input buffer capacity > > OK, so you're asking how many packets does OVS buffer on an OpenFlow > connection? That was not clear from the question. It is documented in > ovs-vswitchd(8): > > Packet buffering. > The OpenFlow specification, version 1.2, says: > > Switches that implement buffering are expected to expose, > through documentation, both the amount of available buffering, > and the length of time before buffers may be reused. > > Open vSwitch maintains a separate set of 256 packet buffers for each > OpenFlow connection. Any given packet buffer is preserved until it is > referenced by an OFPT_FLOW_MOD or OFPT_PACKET_OUT request or for 5 sec‐ > onds, whichever comes first. > > Also, PKTBUF_CNT isn't 512, it's 256. > > On Fri, Apr 15, 2016 at 05:42:02AM +0000, Ali Volkan Atli wrote: > > Hi Ben > > > > No doubt you are a legend but you are wrong in this question or I'm > > totally screwed :) > > > > I think you did not understand the question correctly. OvS has a > > buffer mechanism for each controller. While trying to add a flow_mod > > with max_length is not OFPCML_NO_BUFFER, the packets are stored in the > > buffer. If the maximum capacity is exceeded, OvS start sending the > > whole packets instead of related parts in the packet-in > > messages. Finally, its size (PKTBUF_CNT) is 512. > > > > @Majid, just set max-lenght (different than 0xFFFF) and then drop the > > packet-in messages in the controller and then you'll see the whole packets > > after 512th packet-in. > > > > - Volkan > > > > ________________________________________ > > From: discuss [discuss-boun...@openvswitch.org] on behalf of Ben Pfaff > > [b...@ovn.org] > > Sent: Thursday, April 14, 2016 6:56 PM > > To: Majid Taleqani > > Cc: discuss@openvswitch.org > > Subject: Re: [ovs-discuss] open vSwitch port input buffer capacity > > > > On Thu, Apr 14, 2016 at 01:52:31PM +0000, Majid Taleqani wrote: > > > i am writing a DDOS mitigation for openflow networks using pox > > > controller and open vSwitch version 1.9. as DDOS attacks aim at > > > Flooding flow tables and input buffers, i wonder what is the maximum > > > capacity of each switch port input buffer. > > > > OVS ports themselves don't have buffers, so this is a question of your > > NIC driver's buffering strategy. > > > > > i know after the switch input buffer overflows then the switch sends > > > the whole packet to the controller > > > > No, that's wrong. Buffer overflow has nothing to do with sending > > packets to the controller. > > > > > and then the controller responses by sending packet out message which > > > contains the whole packet and also the action. i want to know how > > > much data and at what rate should a host send data to overflow a > > > switch port input buffer and if is it possible to change the switch > > > port input buffers? is it possible to change the amount of time that a > > > packet stays in buffer before timeouts? thanks > > _______________________________________________ > > discuss mailing list > > discuss@openvswitch.org > > http://openvswitch.org/mailman/listinfo/discuss > > > _______________________________________________ discuss mailing list discuss@openvswitch.org http://openvswitch.org/mailman/listinfo/discuss
