On Mon, Mar 09, 2015 at 02:41:52PM -0500, swair shah wrote:
> >
> > I don't see how that can solve the problem that he is reporting.  Did
> > you read his whole scenario?  If we knew how to handle the packet in the
> > datapath at the beginning of the scenario then we would not be sending
> > it to the controller.
> >
> > I doubt that this is a real problem that needs to be solved, because
> > it's been in the back of my mind since about 2008 as a possible concern
> > but this is the first time I remember anyone actually voicing it.  Swair
> > hasn't explained how it actually shows up as a problem in practice.
> > Swair?
> 
> I ran into this case when running some tests with streams of UDP datagrams.
> Clearly in case of TCP, the flow would gradually build up and this case
> would not occur as only the first 'ack' would not be followed by any
> packets before the handshake is done. I am not sure how significant this
> problem would be in real world scenarios.

I guess I don't count this as a real problem then.

> Can this be done:
> If we define flow as the set of packets with 'similar' header (I am not
> sure on the granularity with which one would define 'similar' in this
> case), then after the first packet buffer each subsequent packet in a
> ordered list (and probably don't send Packet_In, for subsequent packets;
> but this can be a configuration). In response to packet_out for first
> packet forward all the packets from that list.
> 
> Again, the issue is how would you decide if two packets are 'similar', i.e.
> are to be queued in the same list.
> 
> Another probably highly inefficient way to do is to check all the buffered
> packets in response to every packet_in.

I think that's the same as what I proposed.
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