[ovs-discuss] packet reorderoing

Ben Pfaff blp at nicira.com
Wed Mar 4 16:51:05 UTC 2015


On Wed, Mar 04, 2015 at 04:42:36PM +0000, Gray, Mark D wrote:
> > 
> > On Wed, Feb 25, 2015 at 11:28:56AM -0600, swair shah wrote:
> > > When packets which does not match any rule in ovs, are buffered at the
> > > ingress switch, say first n packets are buffered. Switch sends a
> > > flow_mod and message and packet_out for the buffered packets,
> > > meanwhile if some more packets of the same flow arrive (say n+1 to m),
> > > they'll also get buffered (as flow_mod) hasn't arrived yet.
> > >
> > > Once flow_mod message arrives at the switch then subsequent packets of
> > > the flow will be forwarded but packets (n+1 to m) will still be
> > > buffered waiting for their packet_outs. This results in reordering of
> > packets.
> > >
> > > Is there a way around this, besides from proactively setting up a flow?
> > >
> > > Is there a way to match flow_mod to existing buffered packets?
> > 
> > Reordering can happen.  There isn't a way to avoid it entirely (besides
> > proactive flow setup).  It isn't usually a problem, though, because most
> > protocols only send one packet before they receive a reply from the
> > opposite end.
> 
> The only way that I can think to nail up a flow is via dpctl. Is this how you
> suggest to do this?

Can you be more specific about what you want to do?  I can think of a
few possibilities.



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