[ovs-discuss] LACP test with two vswitches in a single hosts

[Ethan Jackson]

Please keep replies on the list.

> That's a good point for why a TCP flow cannot be distributed
> to different links simultaneously. Thanks a lot.
> But the TCP SACK mode can handle the out of order issue, isn't it?

I'm not a tcp expert.  My understanding is that out of order packets
typically cause tcp backoffs. I may be wrong on this point, but in
general networking equipment tries to deliver packets in order for
this reason.  Even if tcp can handle it gracefully, a bonding
implementation that consistently delivers packets out of order is
incorrect.

Ethan


>
> 2012/4/7 Ethan Jackson <ethan at nicira.com>
>>
>> >> OVS can't distribute packets of the same flow to different interfaces.
>>
>> As far as I know, this is typical of all bonding implementations.  If
>> you send packets from the same flow down different links, they may
>> arrive at the destination out of order.  This can wreak havoc on tcp
>> stacks.
>>
>> >> OVS can't really achieve balance/fairness between flows.
>> >> OVS can't dynamically switch a flow between different interfaces on the
>> >> fly based on the bandwidth utilization.
>>
>> This isn't true,  if one slave is receiving quite a bit more traffic
>> than another, some flows will be rebalanced to the less loaded one.
>> By default this is done once every 10 seconds, but that's
>> configurable.
>>
>> >> So it means the LACP implemented in OVS is not mature?
>> >> Or it's just the nature of LACP? It needs extra QoS scheme to achieve
>> >> real balance and full bandwidth utilization?
>>
>> This is just the nature of bonding implementations.
>>
>> Ethan
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>
>