QOS Statistics

[gilou_1973]

Hello,

I configured QOS on Cisco 3750G used as distribution switches in Buildings.

I'm running IOS 12.2(46)SE.

Everything seems to work fine but I need some explanations about the results returned by the following command:

DISTRI1_T211#sh mls qos interface gigabitEthernet 1/0/12 statistics

  dscp: incoming
-------------------------------

  0 -  4 :   293227780        0        22909         0       143678

  5 -  9 :             0            0            0       306206       0
10 - 14 :           0            0            0            0            0
15 - 19 :           0           26            0           0            0
20 - 24 :           0            0            0            0            0
25 - 29 :           0            0            0            0            0
30 - 34 :           0            0            0            0            0
35 - 39 :           0            0            0            0            0
40 - 44 :           0            0            0            0            0
45 - 49 :           0            0            0      1383236        0
50 - 54 :           0            0            0            0            0
55 - 59 :           0            0            0            0            0
60 - 64 :           0            0            0            0
  dscp: outgoing
-------------------------------

  0 -  4 :   500001468        0            0            0            0
  5 -  9 :           0              0            0     79508489      0
10 - 14 :           0            0            0            0            0
15 - 19 :           0     44086709      0            0            0
20 - 24 :           0            0            0            0            0
25 - 29 :           0            0            0            0            0
30 - 34 :           0            0            0            0            0
35 - 39 :           0            0            0            0            0
40 - 44 :           0            0            0            0            0
45 - 49 :           0           15           0      1707220        0
50 - 54 :           0            0            0            0            0
55 - 59 :           0            0            0            0            0
60 - 64 :           0            0            0            0
  cos: incoming
-------------------------------

  0 -  4 :   295166613            0            0            0            0
  5 -  7 :           0                  0            0
  cos: outgoing
-------------------------------

  0 -  4 :   499990150     79519854     44086730            0            0
  5 -  7 :          15           1707221            0
Policer: Inprofile:            0 OutofProfile:            0

In fact, if I understand,  it seems that a lot of incoming packets are dropped on this interface.
Do I need to change parameters on this interface. I mean, should I change the configuration of the input queue.
The QOS configuration for this interface is here below:

DISTRI1_T211#sh mls qos input-queue
Queue     :       1       2
-----------------------------------
buffers   :      90      10
bandwidth :   4       4
priority  :       0      10
threshold1:     100     100
threshold2:     100     100

Thanks by advance for your assistance

[tprendergast · Accepted solution]

If you do the math, that's not very many packets considering that TCP will handle retransmits if tail-drops are happening...

143678 / 293227780 = 0.0489%

So roughly 0.05% of your packets (1 out of every 2000) are being dropped by that queue. I don't think that is terrible, but in some environments it may be unacceptable if you are running a lot of UDP/RTP/etc. You should make the call if that is within acceptable parameters, or if you need to adjust your queueing...or even adjust your QoS so more things are marked out of dscp0-4 and up to another dscp that may get better queuing behavior.

[gilou_1973]

Hi Tim,

Yes, you're right it's not a so high level and my network doesn't host VOIP applications.

I'll keep an eye on those counters and check that the percentage doesn't increase.

Thanks for your help.