Switch port QoS settings for an AP flexconnect local switching

[Clem58]

Hello,

We have a remote WLC 5520 (fw 8.2.130.0), some 3802E and I APs in flexconnect mode, local switching.

On our WS-C3650-48PD switches, we have this configuration for APs ports:

interface GigabitEthernet1/0/48
description AP PORT
switchport trunk native vlan 8
switchport mode trunk
switchport nonegotiate
auto qos trust
spanning-tree bpduguard enable
service-policy input AutoQos-4.0-Trust-Cos-Input-Policy
service-policy output AutoQos-4.0-Output-Policy
end

We have a voice WLAN with platinum profile applied on WLC.

We have an "office laptop" WLAN with silver profile applied on WLC.

We also have a "handheld scanners" WLAN with silver profile applied on WLC.

If we check the QoS statistics, we can see a lot of drops in class-default class policy:

Class-map: class-default (match-any)
0 packets
Match: any
Queueing

(total drops) 33414092
(bytes output) 196106103408
bandwidth remaining 25%
queue-buffers ratio 25

According to the Cisco best-practice, when we have a flexconnect AP with local switching connected on a switch port, this one must be configured with "auto qos trust cos". Currently the port is configured with "auto qos trust", does that make a difference ?

Any thoughts ?

[Rasika Nayanajith]

Change it to "auto qos trust cos" at switchport is trunk & wireless SSID traffic comes with vlan tag ID on that trunk link (so QoS label - CoS will be on ethernet header.

This post may help you to get the concept right

https://mrncciew.com/2013/07/23/qos-for-h-reap/ 

HTH

Rasika

*** Pls rate all useful responses ***

[Clem58]

Thanks for your answer, I've put auto qos trust cos, but we still have some outdiscards errors on the port.

I've investigated more:

GigabitEthernet1/0/48 is up, line protocol is up (connected)
Hardware is Gigabit Ethernet, address is ***.***.*** (bia ***.***.***)
Description: *** : *** : TRUNK
MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 1000Mb/s, media type is 10/100/1000BaseTX
input flow-control is on, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input never, output 00:00:00, output hang never
Last clearing of "show interface" counters never
Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 33898088
Queueing strategy: Class-based queueing
Output queue: 0/40 (size/max)
5 minute input rate 29000 bits/sec, 38 packets/sec
5 minute output rate 2938000 bits/sec, 289 packets/sec
97507311 packets input, 50860682469 bytes, 0 no buffer
Received 1262416 broadcasts (436436 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 436436 multicast, 0 pause input
0 input packets with dribble condition detected
238713116 packets output, 212462618658 bytes, 0 underruns
0 output errors, 0 collisions, 2 interface resets
85571 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out

If I enter this command: show controllers ethernet-controller Gi1/0/48

Transmit GigabitEthernet1/0/48 Receive
212464643699 Total bytes 50861135351 Total bytes
177463948 Unicast frames 96247199 Unicast frames
207674333034 Unicast bytes 50715290086 Unicast bytes
37754887 Multicast frames 436457 Multicast frames
2840869675 Multicast bytes 68021309 Multicast bytes
23502559 Broadcast frames 825985 Broadcast frames
1949440990 Broadcast bytes 77823956 Broadcast bytes
0 System FCS error frames 0 IpgViolation frames
0 MacUnderrun frames 0 MacOverrun frames
0 Pause frames 0 Pause frames
0 Cos 0 Pause frames 0 Cos 0 Pause frames
0 Cos 1 Pause frames 0 Cos 1 Pause frames
0 Cos 2 Pause frames 0 Cos 2 Pause frames
0 Cos 3 Pause frames 0 Cos 3 Pause frames
0 Cos 4 Pause frames 0 Cos 4 Pause frames
0 Cos 5 Pause frames 0 Cos 5 Pause frames
0 Cos 6 Pause frames 0 Cos 6 Pause frames
0 Cos 7 Pause frames 0 Cos 7 Pause frames
0 Oam frames 0 OamProcessed frames
0 Oam frames 0 OamDropped frames
2035873 Minimum size frames 48290446 Minimum size frames
81843643 65 to 127 byte frames 12688080 65 to 127 byte frames
3982149 128 to 255 byte frames 3817937 128 to 255 byte frames
1965689 256 to 511 byte frames 2224329 256 to 511 byte frames
26553605 512 to 1023 byte frames 1664709 512 to 1023 byte frames
7130068 1024 to 1518 byte frames 635144 1024 to 1518 byte frames
115210367 1519 to 2047 byte frames 28188996 1519 to 2047 byte frames
0 2048 to 4095 byte frames 0 2048 to 4095 byte frames
0 4096 to 8191 byte frames 0 4096 to 8191 byte frames
0 8192 to 16383 byte frames 0 8192 to 16383 byte frames
0 16384 to 32767 byte frame 0 16384 to 32767 byte frame
0 > 32768 byte frames 0 > 32768 byte frames
0 Late collision frames 0 SymbolErr frames
33898088 Excess Defer frames 0 Collision fragments

0 Good (1 coll) frames 0 ValidUnderSize frames
0 Good (>1 coll) frames 0 InvalidOverSize frames
0 Deferred frames 0 ValidOverSize frames
0 Gold frames dropped 0 FcsErr frames
0 Gold frames truncated
0 Gold frames successful
0 1 collision frames
0 2 collision frames
0 3 collision frames
0 4 collision frames
0 5 collision frames
0 6 collision frames
0 7 collision frames
0 8 collision frames
0 9 collision frames
0 10 collision frames
0 11 collision frames
0 12 collision frames
0 13 collision frames
0 14 collision frames
0 15 collision frames
0 Excess collision frames

Could these "Excess Defer frames" disrupt any traffic from a computer (webex, video streaming, website app, files transfers on a remote server ...)?

[patoberli]

An AP can drop a fairly high amount of packets, if the traffic is high. Simply because it's attached with 1 Gbps but can only forward the packets with maybe 400 Mbit/s. Once the buffers are full, packets get dropped.
But you currently have around 15% dropped, which I find fairly high.

I don't use any QoS on the wired side. This here is the statistics of my probably highest loaded AP:

show int g1/0/44
GigabitEthernet1/0/44 is up, line protocol is up (connected) 
  Hardware is Gigabit Ethernet, address is 34f8.e733.d02c (bia 34f8.e733.d02c)
  MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec, 
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 1000Mb/s, media type is 10/100/1000BaseTX
  input flow-control is off, output flow-control is unsupported 
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:01:05, output 00:00:01, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 748037
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 1141000 bits/sec, 456 packets/sec
  5 minute output rate 7000000 bits/sec, 1194 packets/sec
     2009997310 packets input, 915385169633 bytes, 0 no buffer
     Received 1058043 broadcasts (1057682 multicasts)
     0 runts, 0 giants, 0 throttles 
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 1057682 multicast, 0 pause input
     0 input packets with dribble condition detected
     6351888611 packets output, 4886813263541 bytes, 0 underruns
     0 output errors, 0 collisions, 1 interface resets
     0 unknown protocol drops
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 0 pause output
     0 output buffer failures, 0 output buffers swapped out

     Transmit GigabitEthernet1/0/44           Receive
   3654272748 Bytes                        575037729 Bytes                    
   2010110067 Unicast frames              2009025047 Unicast frames           
     36222427 Multicast frames               1057701 Multicast frames         
     10880716 Broadcast frames                   361 Broadcast frames         
            0 Too old frames               355288438 Unicast bytes            
            0 Deferred frames              219640203 Multicast bytes          
            0 MTU exceeded frames             109088 Broadcast bytes          
            0 1 collision frames                   0 Alignment errors         
            0 2 collision frames                   0 FCS errors               
            0 3 collision frames                   0 Oversize frames          
            0 4 collision frames                   0 Undersize frames         
            0 5 collision frames                   0 Collision fragments      
            0 6 collision frames       
            0 7 collision frames             1355218 Minimum size frames      
            0 8 collision frames           411292338 65 to 127 byte frames    
            0 9 collision frames          1058536470 128 to 255 byte frames   
            0 10 collision frames           49556869 256 to 511 byte frames   
            0 11 collision frames           29597495 512 to 1023 byte frames  
            0 12 collision frames          459744719 1024 to 1518 byte frames 
            0 13 collision frames                  0 Overrun frames           
            0 14 collision frames                  0 Pause frames             
            0 15 collision frames      
            0 Excessive collisions                 0 Symbol error frames      
            0 Late collisions                      0 Invalid frames, too large
            0 VLAN discard frames                  0 Valid frames, too large  
            0 Excess defer frames                  0 Invalid frames, too small
   2454176334 64 byte frames                       0 Valid frames, too small  
    193816848 127 byte frames          
    538540980 255 byte frames                      0 Too old frames           
     64667787 511 byte frames                      0 Valid oversize frames    
     40202401 1023 byte frames                     0 System FCS error frames  
   3060776156 1518 byte frames                     0 RxPortFifoFull drop frame
            0 Too large frames         
            0 Good (1 coll) frames     
            0 Good (>1 coll) frames    

One thing to mention, you currently use the fairly old (and deferred) software 8.2.130.0 which has plenty of bugs with the 3800 AP series. I suggest you upgrade to the latest 8.2 release first. 

Release Notes: https://www.cisco.com/c/en/us/support/wireless/5500-series-wireless-controllers/products-release-notes-list.html

[Clem58]

Thanks for your answer, it's planned to upgrade our WLC.