[c-nsp] Tx Queue for 7609 WS67xx cards

[Victor Lyapunov]

Hello all

Got a question about queuing functionality in WS67xx cards. We have a
typical 7609 setup with TenG uplink and GigE downlink interfaces.

During the day we see an increase in packet drops on the GigE downlink
interfaces. The average bandwidth is kept around 750Mbps but I suppose
short bursts may result in dropped packets. Is there any way to improve
this behavior? (e.g increase output buffer?)

The current state of the interfaces is following:


=====================================================================================================================
We have enabled mls qos for the 7609


interface GigabitEthernet1/22
 description test
 switchport
 switchport trunk encapsulation dot1q
 switchport trunk allowed vlan 1100
 switchport mode trunk
 mtu 9216
 load-interval 30
 speed nonegotiate
 mls qos trust dscp
 no cdp enable


GigabitEthernet 1/22 is up, line protocol is up (connected)
  Hardware is C7600 1Gb 802.3, address is f8687.f2da.ea01 (bia
f8687.f2da.ea01)
  Description: test
  MTU 9216 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
     reliability 255/255, txload 181/255, rxload 28/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 1000Mb/s, media type is SX
  input flow-control is off, output flow-control is off
  Clock mode is auto
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input never, output never, output hang never
  Last clearing of "show interface" counters 40d07h
  Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops:
2845472
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
<<<<========================================================
  30 second input rate 110375000 bits/sec, 48500 packets/sec
  30 second output rate 713714000 bits/sec, 81902 packets/sec

lab7609#sh mls qos queuing interface g1/22
 Weighted Round-Robin
  Port QoS is enabled
  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:  100[queue 1] 150[queue 2] 200[queue 3]
    queue-limit ratios:     50[queue 1]  20[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     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]

    queue random-detect-min-thresholds
    ----------------------------------
      1    40[1] 70[2] 70[3] 70[4] 70[5] 70[6] 70[7] 70[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] 100[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:

    queue thresh cos-map
    ---------------------------------------
    1     1      0
    1     2      1
    1     3
    1     4
    1     5
    1     6
    1     7
    1     8
    2     1      2
    2     2      3 4
    2     3
    2     4
    2     5
    2     6
    2     7
    2     8
    3     1      6 7
    3     2
    3     3
    3     4
    3     5
    3     6
    3     7
    3     8
    4     1      5

    Queueing Mode In Rx direction: mode-cos
    Receive queues [type = 2q8t]:
    Queue Id    Scheduling  Num of thresholds
    -----------------------------------------
       01         WRR                 08
       02         WRR                 08

    WRR bandwidth ratios:  100[queue 1]   0[queue 2]
    queue-limit ratios:    100[queue 1]   0[queue 2]

    queue tail-drop-thresholds
    --------------------------
    1     100[1] 100[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]
    2     100[1] 100[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]

    queue random-detect-min-thresholds
    ----------------------------------
      1    40[1] 40[2] 50[3] 50[4] 50[5] 50[6] 50[7] 50[8]
      2    100[1] 100[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]

    queue random-detect-max-thresholds
    ----------------------------------
      1    70[1] 80[2] 90[3] 100[4] 100[5] 100[6] 100[7] 100[8]
      2    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
    2     1
    2     2
    2     3
    2     4
    2     5
    2     6
    2     7
    2     8


  Packets dropped on Transmit:

    queue     dropped  [cos-map]
    ---------------------------------------------
    1                  2845981  [0 1 ]
    2                        0  [2 3 4 ]
    3                        0  [6 7 ]
    4                        0  [5 ]

  Packets dropped on Receive:
    BPDU packets:  0

    queue              dropped  [cos-map]
    ---------------------------------------------------
    1                        0  [0 1 2 3 4 5 6 7 ]
    2                        0  []
lab7609#          sh run int g1/22


No fabric drops

========================================================================================================

Is the output queue (even when we enable mls qos) 40 packets long (have
read that Tx buffer length is around 1Mbyte)?
In mls mode can we configure its length using "hold-queue <len>" ?

The traffic in our network is mostly best effort (not care much about
additional delay). Is there a way to decrease output packet drops
for WS67xx cards operating in mls qos?

(If this has already been addressed in the past please provide reference to
previous thread)

Thanx

Victor