[ovs-discuss] packet reorderoing

Ben Pfaff blp at nicira.com
Fri Feb 27 00:21:21 UTC 2015


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.



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