> On Dec 8, 2016, at 12:33 AM, durga <[email protected]> wrote:
> 
> Hi All,
> 
> I have configured a very basic topology in mininet with 2 switches and a 
> couple of hosts.
> I have configured tc on all the 4 ports of both the switches and set the tc 
> rate set at 1Mbps. Qdisc is htb. 
> 
> Now, as I incrementally generate traffic , though I observe drops via iperf, 
> I fail to observe any drops  on ovs portswhen I use 'ovs-ofctl dump-ports sw'
> 
> Am I looking at wrong places are putting things together incorrectly?
> 
> Can someone help me understand why I don't notice any drops when using 
> ovs-ofctl ?
> 
> Few logs:
> 
> UDP client:
> root@vd-Veriton-M200-A780:~# iperf -c 10.0.0.2 -u -b 10Mbps
> ------------------------------------------------------------
> Client connecting to 10.0.0.2, UDP port 5001
> Sending 1470 byte datagrams
> UDP buffer size:  208 KByte (default)
> ------------------------------------------------------------
> [ 15] local 10.0.0.1 port 53217 connected with 10.0.0.2 port 5001
> [ ID] Interval       Transfer     Bandwidth
> [ 15]  0.0-10.0 sec  12.5 MBytes  10.5 Mbits/sec
> [ 15] Sent 8922 datagrams
> [ 15] Server Report:
> [ 15]  0.0-11.5 sec  10.7 MBytes  7.78 Mbits/sec   0.503 ms 1306/ 8921 (15%)
> [ 15]  0.0-11.5 sec  1 datagrams received out-of-order
> 
> 
> OVS output:
> 
> root@vd-Veriton-M200-A780:~# ovs-ofctl dump-ports s33
> OFPST_PORT reply (xid=0x2): 3 ports
>   port LOCAL: rx pkts=0, bytes=0, drop=5, errs=0, frame=0, over=0, crc=0
>            tx pkts=0, bytes=0, drop=0, errs=0, coll=0
>   port  1: rx pkts=885787, bytes=33619595672, drop=0, errs=0, frame=0, 
> over=0, crc=0
>            tx pkts=403525, bytes=26653335, drop=0, errs=0, coll=0
>   port  2: rx pkts=403521, bytes=26652615, drop=0, errs=0, frame=0, over=0, 
> crc=0
>            tx pkts=884488, bytes=33617623003, drop=0, errs=0, coll=0
> 
> 
> TC qdsic output:
> 
> root@vd-Veriton-M200-A780:~# tc -s -d class show dev s33-eth2
> class htb 2:1 root prio 0 quantum 100000 rate 8Mbit ceil 8Mbit linklayer 
> ethernet burst 1600b/1 mpu 0b overhead 0b cburst 1600b/1 mpu 0b overhead 0b 
> level 0 
>  Sent 25232342 bytes 16683 pkt (dropped 1307, overlimits 0 requeues 0) 
>  rate 0bit 0pps backlog 0b 0p requeues 0 
>  lended: 12183 borrowed: 0 giants: 0
>  tokens: 15781 ctokens: 15781

The port stats are showing the statistics on the NIC.  However, when QoS is 
configure on OVS, it's just configuring the tc (traffic control) system in the 
kernel.  That implements a software-based limiter, so the packets are being 
dropped before they hit the NIC.  It looks like your tc output is showing 
dropped packets.

--Justin



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