05-02-2013 10:11 AM - edited 03-07-2019 01:09 PM
We're trying to troubleshoot some performance problems on a stack of 3750. We initially noticed lots of output queue drops (no input drops, no errors).
I've followed this technote: http://www.cisco.com/en/US/products/hw/routers/ps133/products_tech_note09186a0080094791.shtml
Eventually I also looked at qos drops, and I see lots of drops
dscp: incoming
-------------------------------
0 - 4 : 1457734311 0 2154834 0 2649209
5 - 9 : 0 0 0 0 0
10 - 14 : 0 0 0 0 0
15 - 19 : 0 0 0 0 0
20 - 24 : 0 0 0 0 3196936291
25 - 29 : 0 5003169 0 0 0
30 - 34 : 0 0 22316 0 0
35 - 39 : 0 1 0 0 0
40 - 44 : 0 0 0 0 0
45 - 49 : 0 2512040185 0 74672627 0
50 - 54 : 40 0 0 0 3
55 - 59 : 0 0 0 0 0
60 - 64 : 0 0 0 0
dscp: outgoing
-------------------------------
0 - 4 : 360986293 15 16189 0 83333
5 - 9 : 0 0 0 8519 0
10 - 14 : 195960893 0 3 8 0
15 - 19 : 0 122 0 22750877 0
20 - 24 : 4 0 2 2 3642595093
25 - 29 : 0 7574890 0 22 0
30 - 34 : 0 0 502252620 0 7
35 - 39 : 0 47816 0 6 0
40 - 44 : 0 0 0 0 0
45 - 49 : 0 5266457 0 181700371 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 : 54270256 0 0 3201939457 22317
5 - 7 : 2512040177 75355489 14772028
cos: outgoing
-------------------------------
0 - 4 : 711773765 195969423 27760830 3650170005 502300449
5 - 7 : 4244506266 181700371 191977167
output queues enqueued:
queue: threshold1 threshold2 threshold3
-----------------------------------------
queue 0: 2 0 4244506267
queue 1: 43692439 45670782 4023848561
queue 2: 0 0 530061259
queue 3: 164 195969259 651039679
output queues dropped:
queue: threshold1 threshold2 threshold3
-----------------------------------------
queue 0: 0 0 0
queue 1: 2747 2794 162044
queue 2: 0 0 0
queue 3: 43 20903265 2849834164
Policer: Inprofile: 0 OutofProfile: 0
So that has me thinking we have a qos problem. I believe I need to assign more bandwidth to queue 4? (read this article https://supportforums.cisco.com/community/netpro/network-infrastructure/switching/blog/2011/04/11/output-drops-due-to-qos-on-296035603750-switches)
show mls qos queue-set
Queueset: 1
Queue : 1 2 3 4
----------------------------------------------
buffers : 10 10 26 54
threshold1: 138 138 36 20
threshold2: 138 138 77 50
reserved : 92 92 100 67
maximum : 138 400 318 400
Queueset: 2
Queue : 1 2 3 4
----------------------------------------------
buffers : 16 6 17 61
threshold1: 149 118 41 42
threshold2: 149 118 68 72
reserved : 100 100 100 100
maximum : 149 235 272 242
But as a side note, I'm also seeing some asic drops, I'm not sure if this is related?
Port-asic Port Drop Statistics - Summary
========================================
RxQueue Drop Statistics Slice0
RxQueue 0 Drop Stats Slice0: 0
RxQueue 1 Drop Stats Slice0: 0
RxQueue 2 Drop Stats Slice0: 0
RxQueue 3 Drop Stats Slice0: 0
RxQueue Drop Statistics Slice1
RxQueue 0 Drop Stats Slice1: 0
RxQueue 1 Drop Stats Slice1: 0
RxQueue 2 Drop Stats Slice1: 1
RxQueue 3 Drop Stats Slice1: 0
Port 0 TxQueue Drop Stats: 61335
Port 1 TxQueue Drop Stats: 0
Port 2 TxQueue Drop Stats: 0
Port 3 TxQueue Drop Stats: 0
Port 4 TxQueue Drop Stats: 0
Port 5 TxQueue Drop Stats: 0
Port 6 TxQueue Drop Stats: 0
Port 7 TxQueue Drop Stats: 0
Port 8 TxQueue Drop Stats: 0
Port 9 TxQueue Drop Stats: 0
Port 10 TxQueue Drop Stats: 0
Port 11 TxQueue Drop Stats: 0
Port 12 TxQueue Drop Stats: 0
Port 13 TxQueue Drop Stats: 0
Port 14 TxQueue Drop Stats: 69127
Port 15 TxQueue Drop Stats: 0
Port 16 TxQueue Drop Stats: 0
Port 17 TxQueue Drop Stats: 0
Port 18 TxQueue Drop Stats: 0
Port 19 TxQueue Drop Stats: 0
Port 20 TxQueue Drop Stats: 0
Port 21 TxQueue Drop Stats: 0
Port 22 TxQueue Drop Stats: 0
Port 23 TxQueue Drop Stats: 0
Port 24 TxQueue Drop Stats: 0
Port 25 TxQueue Drop Stats: 0
Port 26 TxQueue Drop Stats: 0
Port 27 TxQueue Drop Stats: 0
Supervisor TxQueue Drop Statistics
Queue 0: 0
Queue 1: 0
Queue 2: 0
Queue 3: 0
Queue 4: 0
Queue 5: 0
Queue 6: 0
Queue 7: 0
Queue 8: 0
Queue 9: 0
Queue 10: 0
Queue 11: 0
Queue 12: 0
Queue 13: 0
Queue 14: 0
Queue 15: 0
Are those relatd to my QoS problems? And any suggestions on how to redistribute my queue-set?
Thanks
Bill
Solved! Go to Solution.
05-02-2013 12:59 PM
Remove all QoS configuration, that is totally unnecessary on LAN, and all your problems will be solved.
05-02-2013 05:44 PM
Hi Bill,
As Paolo suggested kindly remove the QOS and update us the result.
If you are not supposed to remove then check the following things;
Output qos drops in many networks are expected and the best solution is
to increase the line speed, which is not the feasible solution here.
Here we need to apply some solution to control output drops, based on
the trail and run method by implementing various bandwidth ratios and
threshold values for the traffic that gets affected. From the queueing
interface output all drops occurred in Queue 1. Queue 1 handles traffic
mapped with COS values 0 1. No drops are reported for other queues,
queues 1 and 3. Lets not consider Queue 4 which is a priority queue and
is always dedicated to drop sensitive traffic such voice and video.
Packets dropped on Transmit:
BPDU packets: 0
queue dropped [cos-map]
---------------------------------------------
1 0 [0 1 ]
2 1477 [2 3 4 ]
3 0 [6 7 ]
4 0 [5 ]
- Identify what type of traffics are classified for COS 2, 3,
4.
- Suppose lets say, if more traffic are expected with a cos
value of 2, then its a best practice to dedicate one queue for that
traffic. In this case, other traffic cos 3 and 4, depending upon the
needs, they can be put to be handled by different queues.
- Accordingly MAP the cos values to the appropriate queued ID,
to minimize drops.
- Use "wrr-queue cos-map" command to map the appropriate cos to
a particular queue.
- You may also try increasing the buffer ratios and increase
its wrr threshold values for a particular queue to see if that would
help.
- Use "wrr-queue bandwidth" command to increase the bandwidth
percentage of a particular queue.
- Use "wrr-queue queue-limit" command to increase the transmit
queue ratio.
- Use "wrr-queue random-detect min-threshold" & w"wrr-queue
random-detect max-threshold" commands to configure the drop minimum and
maximum thresholds of a particular queue.
- Refer the link below to know the usage of all the above
commands in detail.
http://www.cisco.com/en/US/products/hw/switches/ps700/products_tech_note
09186a008015bf98.shtml
HTH
Regards
Inayath
Please rate all usefull posts.
05-02-2013 05:52 PM
Disclaimer
The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.
Liability Disclaimer
In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.
Posting
Indeed what you've posted shows drops. Your queue set parameters are (cough) "interesting".
The problem with the 2960/3560/3750 egress queuing architecture, is when you enable QoS it, by default, evenly provisions 4 egress queues with the resources that were devoted to just 1 egress queue. This commonly results in drops, not seen before QoS was enabled. (This is one reason Paolo is advising disabling QoS. However, you can still have congestion on a port with the non-QoS single egress queue, and if you do, and if you have "special" traffic performance requirements, then disabling QoS might not be a good option.)
If you really need QoS, then you likely will need to also tune it for your requirements. As your existing queue set configurations are non-default, I would presume someone has been trying to tune the QoS configuration.
Unfortunately, QoS tuning often is time consuming, as you need to monitor to determine if your are getting the performance from it your traffic requires.
Also unfortunately, understanding the queue set parameters, and how then interrelate, can be confusing (at least I had found them so).
There's another QoS document on these support forums, that has lots of good info about 3750 QoS: https://supportforums.cisco.com/docs/DOC-8093
05-02-2013 12:59 PM
Remove all QoS configuration, that is totally unnecessary on LAN, and all your problems will be solved.
05-02-2013 05:44 PM
Hi Bill,
As Paolo suggested kindly remove the QOS and update us the result.
If you are not supposed to remove then check the following things;
Output qos drops in many networks are expected and the best solution is
to increase the line speed, which is not the feasible solution here.
Here we need to apply some solution to control output drops, based on
the trail and run method by implementing various bandwidth ratios and
threshold values for the traffic that gets affected. From the queueing
interface output all drops occurred in Queue 1. Queue 1 handles traffic
mapped with COS values 0 1. No drops are reported for other queues,
queues 1 and 3. Lets not consider Queue 4 which is a priority queue and
is always dedicated to drop sensitive traffic such voice and video.
Packets dropped on Transmit:
BPDU packets: 0
queue dropped [cos-map]
---------------------------------------------
1 0 [0 1 ]
2 1477 [2 3 4 ]
3 0 [6 7 ]
4 0 [5 ]
- Identify what type of traffics are classified for COS 2, 3,
4.
- Suppose lets say, if more traffic are expected with a cos
value of 2, then its a best practice to dedicate one queue for that
traffic. In this case, other traffic cos 3 and 4, depending upon the
needs, they can be put to be handled by different queues.
- Accordingly MAP the cos values to the appropriate queued ID,
to minimize drops.
- Use "wrr-queue cos-map" command to map the appropriate cos to
a particular queue.
- You may also try increasing the buffer ratios and increase
its wrr threshold values for a particular queue to see if that would
help.
- Use "wrr-queue bandwidth" command to increase the bandwidth
percentage of a particular queue.
- Use "wrr-queue queue-limit" command to increase the transmit
queue ratio.
- Use "wrr-queue random-detect min-threshold" & w"wrr-queue
random-detect max-threshold" commands to configure the drop minimum and
maximum thresholds of a particular queue.
- Refer the link below to know the usage of all the above
commands in detail.
http://www.cisco.com/en/US/products/hw/switches/ps700/products_tech_note
09186a008015bf98.shtml
HTH
Regards
Inayath
Please rate all usefull posts.
05-02-2013 05:52 PM
Disclaimer
The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.
Liability Disclaimer
In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.
Posting
Indeed what you've posted shows drops. Your queue set parameters are (cough) "interesting".
The problem with the 2960/3560/3750 egress queuing architecture, is when you enable QoS it, by default, evenly provisions 4 egress queues with the resources that were devoted to just 1 egress queue. This commonly results in drops, not seen before QoS was enabled. (This is one reason Paolo is advising disabling QoS. However, you can still have congestion on a port with the non-QoS single egress queue, and if you do, and if you have "special" traffic performance requirements, then disabling QoS might not be a good option.)
If you really need QoS, then you likely will need to also tune it for your requirements. As your existing queue set configurations are non-default, I would presume someone has been trying to tune the QoS configuration.
Unfortunately, QoS tuning often is time consuming, as you need to monitor to determine if your are getting the performance from it your traffic requires.
Also unfortunately, understanding the queue set parameters, and how then interrelate, can be confusing (at least I had found them so).
There's another QoS document on these support forums, that has lots of good info about 3750 QoS: https://supportforums.cisco.com/docs/DOC-8093
05-03-2013 07:12 AM
Thank you all for the excellent advice, +5
My first step will be to remove QoS and monitor. To remove QoS do I just "no" all the mls qos commands individually? Or is there one global command to rip it all out (no mls qos)?
Sorry for asking a question I should be able to test myself -- but unfortunately I don't currently have a lab box.
05-03-2013 07:19 AM
Hi Bill,
Command to remove the QOS is:
Config t
no mls qos
Ref:
To enable the quality of service (QoS) functionality globally, use the mls qos command in global configuration mode. To disable the QoS functionality globally, use the no form of this command.
mls qos
no mls qos
HTH
Regards
Inayath
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