On Mar 9, 2010, at 09:20 , Martin Casado wrote:

> Teemu Koponen wrote:
>> On Mar 8, 2010, at 21:32 , kk yap wrote:
>> 
>>  
>>> I might be wrong, but from my understanding there is nothing in
>>> OpenFlow that dictates reliable execution of commands received.
>>>    
>> 
>> btw; I can't resist and comment this by saying that unreliable (silently 
>> dropped) control plane operations of OF complicate development of any 
>> controller quite a bit.  To this date, I haven't heard a valid reason why 
>> the protocol semantics should be such for any of the OF messages.  No, 
>> overload conditions are not such a reason.
>>  
> I absolutely agree, this needs to be fixed in the OpenFlow specification.  
> Else, it is near impossible to build scalable controllers who maintain 
> consistent state.  The only caveats to consider would be for packet ins (we 
> can maintain the best effort delivery model for datagram forwarding) and 
> potentially flow expirations due to inactivity timers.

Packet-ins definitely belong to the data plane and can be reliable but flow 
expirations are definitely a part of control plane operations which should be 
reliable. 
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