[ovs-discuss] Basic Questions about Queues in OVS

[Chien Hsin]

Peter Nase <pet.nase at ...> writes:

> 
> Hello all,
> 
> i have a basic question about queue(s) in ovs.
> 
> As a example my Mininet-Network consists of one switch (s1) and three 
> hosts (h1, h2, h3).
> The links between the hosts and the switch are configured as 10000 Mbps
> and communication works fine. I started iperf in server mode on h3 and
> use h1, h2 as clients at the same time. Both clients send with full
> speed (2x times 10000 Mbps) to h3, but the link of h3 can only process
> 10000 Mbps.
> 
> For my understandig there must exist a queue that fills, because host 3
> can handle only 10000 Mbps. Am i'm right?
> 
> Where is this queue exactly located?
> Is there one (default) queue in the switch which holds all packets to be
> forwarded or is there one queue per port?
> How can i get the stats of such a queue to see if it gets filled up and
> see if packets are dropped because the queue is full?
> 
> I read about QoS-Queues which i can configure per port, but what about
> if i do not do this. What is the default behaviour if my two hosts h1,
> h2, overloads the link of h3?
> 
> If my understanding is wrong, please correct me.
> Thanks for clarifying my questions.
> Greetings
> 

Hello Peter,

Did you limit the bandwidth via tclink?
If so, you probably got involved in the bug of the mininet.
This bug has been issued here https://github.com/mininet/mininet/issues/91.
You can solve it by using kernel mode switch, i.e. --switch=ovsk.

Regards,
Chien Hsin