QOS scheduling: 1p3q8t

Unanswered Question
Nov 9th, 2010

Hi, I'm investigating if it is necessary to configure extra queuing options, other than the default on uplink ports which have to trust dscp.

For instance the interface below supports 1p3qt scheduling, which I think it will be active when enabling mls qos global on the switch and configuring mls qos trust dscp on the interface level. Please look at the picture below, which is included in the Medianet Campus QoS Design 4.0. Is this the default behaviour of 1p3q8t scheduling? And is this activated without adding additional interface commands? Or do I have to enable auto-qos on the interface?

Regards, Peter

show int gi5/1 cap:

GigabitEthernet5/1
  Model:                 WS-SUP32-GE-3B
  Type:                  1000BaseLH
  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-(2q8t), tx-(1p3q8t)
  QOS queueing mode:     rx-(cos), tx-(cos)
  CoS rewrite:           yes
  ToS rewrite:           yes
  Inline power:          no
  Inline power policing: no
  SPAN:                  source/destination
  UDLD                   yes
  Link Debounce:         yes
  Link Debounce Time:    yes
  Ports on ASIC:         1-9
  Remote switch uplink:  yes
  Dot1x:                 yes
  Port-Security:         yes

1P3Q8T.png

I have this problem too.
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pverstegen Tue, 11/09/2010 - 04:33

Thanks for your answer.

So if I only configure "mls qos trust dscp" on the uplink, Real Time EF class traffic will not automatically be forwarded in the Priority Queue? Is that true? Is this behaviour the same for layer 2 switches and layer 3 routed interfaces?

Is it recommendable to use the "auto-qos" interface command in this situation?

Best regards, Peter

Lei Tian Tue, 11/09/2010 - 06:31

Hi Peter,

You are correct, with qos enabled and trust dscp on the port, traffic marked as EF will be forwarded in strict priority queue by default. However, the recommendation has some changes on other important parameters. Like, COS to egress queue map, queue size for each output queue, weight assigned to each queue, drop threshold.. Here is the default value on 1p3q8t; you can use it as reference to compare the difference between the default and recommended value.

I am not familiar with the default commands added by auto-qos, so I cannot say what will be changed using auto-qos.


HTH,
Lei Tian

1p3q8t Transmit Queues

Feature
Default Value

Standard transmit queue 1
(lowest priority)

Threshold 1

CoS

0

Tail-drop

Disabled; 70%

WRED-drop

Enabled; 40% low, 70% high

Threshold 2

CoS

1

Tail-drop

Disabled; 100%

WRED-drop

Enabled; 70% low, 100% high

Threshold 3

CoS

None

Tail-drop

Disabled; 100%

WRED-drop

Enabled; 70% low, 100% high

Threshold 4

CoS

None

Tail-drop

Disabled; 100%

WRED-drop

Enabled; 70% low, 100% high

Thresholds 5-8

CoS

None

Tail-drop

Disabled; 100%

WRED-drop

Enabled; 50% low, 100% high

Standard transmit queue 2
(medium priority)

Threshold 1

CoS

2

Tail-drop

Disabled; 70%

WRED-drop

Enabled; 40% low, 70% high

Threshold 2

CoS

3 and 4

Tail-drop

Disabled; 100%

WRED-drop

Enabled; 70% low, 100% high

Thresholds 3-8

CoS

None

Tail-drop

Disabled; 100%

WRED-drop

Enabled; 70% low, 100% high

Standard transmit queue 3
(high priority)

Threshold 1

CoS

6 and 7

Tail-drop

Disabled; 100%

WRED-drop

Enabled; 70% low, 100% high

Thresholds 2-8

CoS

None

Tail-drop

Disabled; 100%

WRED-drop

Enabled; 70% low, 100% high

Strict-priority transmit queue

CoS

5

Tail-drop

100% (nonconfigurable)

pverstegen Thu, 11/11/2010 - 00:19

Hi, thanks again.

Where can I lookup this table with default values?

Is there an IOS show command that shows me the same?

Best regards, Peter

Lei Tian Thu, 11/11/2010 - 10:49

Hi Peter,

Yes, you can verify those information from 'show interface capability' and 'show queueing interface'.

Regards,

Lei Tian

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