04-12-2014 11:16 PM - edited 03-07-2019 07:04 PM
We have many portchannels running between our core switches and access switches. Those portchannel members are getting QoS queueing drops intermittently and it is not happening to specific interfaces. Since it is production environment, we are unable to do any diagnostics.
Current Interface Queueing config...
-------------------------------
wrr-queue bandwidth 30 30 30
wrr-queue queue-limit 40 30 15
wrr-queue threshold 2 60 80 100 100 100 100 100 100
wrr-queue threshold 3 60 80 100 100 100 100 100 100
wrr-queue random-detect min-threshold 1 40 60 80 80 80 80 80 80
wrr-queue random-detect max-threshold 1 70 80 100 100 100 100 100 100
no wrr-queue random-detect 2
no wrr-queue random-detect 3
wrr-queue cos-map 1 2 0
wrr-queue cos-map 1 3 1
wrr-queue cos-map 2 1 2
wrr-queue cos-map 3 2 3
wrr-queue cos-map 3 3 6 7
priority-queue cos-map 1 4 5
Drops on Queue
-------------------------
CORESW#sh queueing int Gi6/14
Interface GigabitEthernet6/14 queueing strategy: Weighted Round-Robin
Port QoS is enabled
Trust boundary disabled
Trust state: trust DSCP
Extend trust state: not trusted [COS = 0]
Default COS is 0
Queueing Mode In Tx direction: mode-cos
Transmit queues [type = 1p3q8t]:
Queue Id Scheduling Num of thresholds
-----------------------------------------
01 WRR 08
02 WRR 08
03 WRR 08
04 Priority 01
WRR bandwidth ratios: 30[queue 1] 30[queue 2] 30[queue 3]
queue-limit ratios: 40[queue 1] 30[queue 2] 15[queue 3] 15[Pri Queue]
queue tail-drop-thresholds
--------------------------
1 70[1] 100[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]
2 60[1] 80[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]
3 60[1] 80[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]
queue random-detect-min-thresholds
----------------------------------
1 40[1] 60[2] 80[3] 80[4] 80[5] 80[6] 80[7] 80[8]
2 40[1] 70[2] 70[3] 70[4] 70[5] 70[6] 70[7] 70[8]
3 70[1] 70[2] 70[3] 70[4] 70[5] 70[6] 70[7] 70[8]
queue random-detect-max-thresholds
----------------------------------
1 70[1] 80[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]
2 70[1] 100[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]
3 100[1] 100[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]
WRED disabled queues: 2 3
queue thresh cos-map
---------------------------------------
1 1
1 2 0
1 3 1
1 4
1 5
1 6
1 7
1 8
2 1 2
2 2
2 3
2 4
2 5
2 6
2 7
2 8
3 1
3 2 3
3 3 6 7
3 4
3 5
3 6
3 7
3 8
4 1 4 5
Queueing Mode In Rx direction: mode-cos
Receive queues [type = 1q8t]:
Queue Id Scheduling Num of thresholds
-----------------------------------------
01 WRR 08
WRR bandwidth ratios: 100[queue 1]
queue-limit ratios: 100[queue 1]
queue tail-drop-thresholds
--------------------------
1 100[1] 100[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]
queue thresh cos-map
---------------------------------------
1 1 0 1 2 3 4 5 6 7
1 2
1 3
1 4
1 5
1 6
1 7
1 8
Packets dropped on Transmit:
BPDU packets: 0
queue dropped [cos-map]
---------------------------------------------
1 13191 [0 1 ]
2 0 [2 ]
3 0 [3 6 7 ]
4 0 [4 5 ]
Packets dropped on Receive:
BPDU packets: 0
queue dropped [cos-map]
---------------------------------------------
1 0 [0 1 2 3 4 5 6 7 ]
CORESW#sh int Gi6/14 capabilities
GigabitEthernet6/14
Model: WS-X6724-SFP
Type: 1000BaseSX
Speed: 1000
Duplex: full
Trunk encap. type: 802.1Q,ISL
Trunk mode: on,off,desirable,nonegotiate
Channel: yes
Broadcast suppression: percentage(0-100)
Flowcontrol: rx-(off,on,desired),tx-(off,on,desired)
Membership: static
Fast Start: yes
QOS scheduling: rx-(1q8t), tx-(1p3q8t)
QOS queueing mode: rx-(cos), tx-(cos)
CoS rewrite: yes
ToS rewrite: yes
Inline power: no
SPAN: source/destination
UDLD yes
Link Debounce: yes
Link Debounce Time: yes
Ports-in-ASIC (Sub-port ASIC) : 1-24 (13-24) <-- groups in this module Po5[1-4], Po6[5-8], Po11[13-16] & Po12[17-20]
Remote switch uplink: no
Dot1x: yes
Port-Security: yes
04-14-2014 05:55 AM
Okay, you're getting intermittent QoS queue drops. Your question is?
04-14-2014 05:59 AM
Hi Joseph
Thanks for your attention..........My question why those drops occurs? is it related to configuration/HW issue?
04-14-2014 09:00 AM
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In brief, most often drops are caused by a burst of traffic exceeding the egress bandwidth. When that happens, packets queue, but queues only hold so many packets. When queues overflow, you get drops.
Depending on your device capabilities, you might reduce drops by increasing queuing resources (adds to latency, though) or by using a "better" drop strategy. (Basically, some flows, e.g. react to drops. So, by dropping sooner, they slow, and you avoid an all out-of-hand drop situation. You still gets drops, but less.)
To do it "right", you need to understand your traffic, and your device capabilities. Malcolm's reference looks to be a nice starting point.
To be clear, there's often much you can do with QoS settings, but understanding device capabilities extends to fully understanding all your hardware's features. For example, your 6724-SFP is one of the better cards for the 6500 series. It's major limitation is, for raw performance, it's slightly oversubscribed, i.e. 24:20. Some other 6500 line cards, though, do support more buffering per port. (Whether that is really of benefit, depends on the needs of your traffic.)
04-14-2014 07:20 AM
We have the same issue. See this post, as it sounds similar to your issue.
http://www.reddit.com/r/networking/comments/1t5r0z/high_outdiscards_where_do_i_begin/
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