[ovs-discuss] Basic Questions about Queues in OVS

[Peter Nase]

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

[Peter Nase]

Hello all,

i have a basic question about queue(s) in ovs.

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
Petrus

[Ben Pfaff]

Post by Peter Nase
i have a basic question about queue(s) in ovs.
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?

There is undoubtedly a queue but it is probably not an OVS queue. For
established flows, the OVS kernel module doesn't queue packets
internally but just passes them directly onward to the operating
system network stack output driver.