Tx Queue Counters

[r.shummoogum]

Hi:

Port       Tx-Bytes-Queue-1  Tx-Bytes-Queue-2 Tx-Bytes-Queue-3  Tx-Bytes-Queue-4
Gi5/1         1459590763386                 0        268216384        1121015619
Gi5/2          966733771123                 0        276715904        8606992753
Gi5/3         1225105180974                 0        264713024        1081019735
Gi5/4          233557012810                 0         56389056         275140576
Gi5/5         3330069008576                 0        471037116        2301340873
Gi5/6         2663327711813                 0        353952668        2233192511
Gi5/7         1480488611179                 0        293005900        2260786915
Gi5/8          102424987009                 0         60324704         571296312
Gi5/9          568953444459                 0                0        1547451226
Gi5/10         535769353882                 0                0        9076726125
Gi5/11        1275963209612                 0                0        1536418957
Gi5/12           1400121448                 0                0         398183157
Gi5/13         312164517008                 0                0         699206125
Gi5/14         478387537981                 0                0         699206632

The above are access ports on a catalyst 4507 sup4.

Question 1.Why would I see traffic in the above Qs. I don;t believe there are any congestions.

Even on very low volume traffic I see those counters incrementing.

I just did a clear counter on gig 5/25 and few sec later

Gi5/25              1017986                 0              576              2219

sh qos int gig 5/25
QoS is enabled globally
Port QoS is enabled
Administrative Port Trust State: 'untrusted'
Operational Port Trust State: 'untrusted'
Trust device: none
Default DSCP: 0 Default CoS: 0
Appliance trust: none
Tx-Queue   Bandwidth   ShapeRate   Priority   QueueSize
             (bps)       (bps)                (packets)
  1        N/A         disabled    N/A        240     
  2        N/A         disabled    N/A        240     
  3        N/A         disabled    normal     240     
  4        N/A         disabled    N/A        240    

sh run int gig 5/25
interface GigabitEthernet5/25
  switchport access vlan 444
switchport mode access

Question 2:

Why is Q2 empty?

Take note that the traffic is DSCP 0  or 16. No marking is done.

And the mapping is default as shown:

DSCP-TxQueue Mapping Table (dscp = d1d2)
d1 : d2  0  1  2  3  4  5  6  7  8  9
-------------------------------------
0 :    01 01 01 01 01 01 01 01 01 01
1 :    01 01 01 01 01 01 02 02 02 02
2 :    02 02 02 02 02 02 02 02 02 02
3 :    02 02 03 03 03 03 03 03 03 03
4 :    03 03 03 03 03 03 03 03 04 04
5 :    04 04 04 04 04 04 04 04 04 04
6 :    04 04 04 04

Thanks

[andrew.prince]

Why  is Q2 empty?

*** Take note that the traffic is DSCP 0  or 16. No  marking is done ***

And the mapping is default as shown:

DSCP-TxQueue  Mapping Table (dscp = d1d2)
d1 : d2  0  1  2  3  4  5  6  7  8  9
-------------------------------------
0 :    01 01 01 01 01 01 01 01 01 01 = DSCP 0 - 9
1 :    01 01 01 01 01 01 02  02 02 02 = DSCP 10 - 19
2 :    02 02 02 02 02 02 02 02 02 02 = DSCP 20 - 29
3 :    02 02 03  03 03 03 03 03 03 03 = DSCP 30 - 39
4 :    03 03 03 03 03 03 03 03 04 04 = DSCP 40 - 49
5  :    04 04 04 04 04 04 04 04 04 04 = DSCP 50 - 59
6 :    04 04 04 04 = DSCP 60 - 64

Answer below:-

DSCP 0 - 16 is in Queue 01.

DSCP 17 - 31 is in Queue 02

DSCP 32 - 47 is in Queue 03

DSCP 48 - 63 is in Queue 04

If you are not marking any traffic with DSCP values 17 to 31 then you will see no traffic in Queue 02.

HTH>

[r.shummoogum]

Andrew:

If you look carefully DSCP 0 to 15 goes in Q1 and DSCP 16 to 31 goes to Q2.

The output in not alligned properly.

Why do I see traffic in Q3 and Q4 (even Q1)at an output packet rate of 235 per sec. ( 0.34Mbps)

. I clear the counter and issue the command within 8 seconds

Port       Tx-Bytes-Queue-1  Tx-Bytes-Queue-2 Tx-Bytes-Queue-3  Tx-Bytes-Queue-4
Gi5/1                342092                 0                              64               270

Are those Queues an indication on congestion

Thanks

[andrew.prince]

No the queues are not congested - they are just receving packets that are are marked/being queued with marking.