Thanks for the reply. I should've checked the man page first.

I am working with Mininet and Floodlight. I'm trying to dimension a network 
with limited capacity to compare two routing algorithms, with respect to packet 
loss. 
I am using D-ITG traffic generator to put traffic in the network. 
I would like to get statistics in the controller about the packet loss per 
port, using the OF statistics request message. 
Now I'm using a very simple scenario with one OVS and two hosts (scenario 
created using the mininet API). 
UDP flows are sent from one host to the other and the traffic generator reports 
significant packet loss because the links have only 10mbps capacity in mininet. 
I was expecting to find this packet loss on the Tx ports of the OVS. I 
understand now that the packets may be dropped somewhere outside of OVS (maybe 
on the virtual links create by mininet).

How should I dimension a network of OVSs (manually, not through mininet) such 
that the Tx port capacity (outgoing links) is limited, so I can get the packet 
loss on the port and not on other parts of the software emulation?


Regards,
Cosmin

-----Original Message-----
From: Justin Pettit [mailto:[email protected]] 
Sent: 6. marts 2014 19:16
To: Cosmin Marius Caba
Cc: [email protected]
Subject: Re: [ovs-discuss] "lost" counter in the ovs-dpctl

On Mar 6, 2014, at 5:56 AM, Cosmin Marius Caba <[email protected]> wrote:

> What does the lookups entry mean? More specifically the lost counter?

From the ovs-dpctl man page:

              The  "lookups"  row  displays three stats related to flow lookup
              triggered by processing incoming packets in the datapath.  "hit"
              displays number of packets matches existing flows. "missed" dis‐
              plays the number of packets not matching any existing  flow  and
              require  user space processing.  "lost" displays number of pack‐
              ets destined for user space  process  but  subsequently  dropped
              before reaching userspace. The sum of "hit" and "miss" equals to
              the total number of packets datapath processed.

> Is the lost counter in the lookups entry related to the number of dropped 
> packets that I see at the end-points of a traffic low?

Most likely.  There are other places in the network where packets can get lost, 
too.

> If yes, then why there are no dropped packets on any of the ports?

Which ports?  It sounds like you are experiencing packet loss.

By the way, starting in OVS 1.11, the number of "lost" packets in most 
deployments should be substantially reduced.

--Justin


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