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auto qos voip cisco-phone and ingress queues

Hi everybody.

When we use " mls qos trust device cisco-phone', will it also set up ingress priority queues?

For e.g  consider the example below:

Switch-A(config)#interface fastEthernet 0/5
Switch-A(config-if)#auto qos voip cisco-phone


Switch-A#sh run int fa0/5Building configuration...

Current configuration : 487 bytes
!
interface FastEthernet0/5
 switchport access vlan 10
 switchport mode dynamic desirable
 switchport voice vlan 100
 mls qos trust device cisco-phone
 mls qos trust cos
 auto qos voip cisco-phone
 wrr-queue bandwidth 10 20 70 1
 wrr-queue min-reserve 1 5
 wrr-queue min-reserve 2 6
 wrr-queue min-reserve 3 7
 wrr-queue min-reserve 4 8
 wrr-queue cos-map 1 0 1
 wrr-queue cos-map 2 2 4
 wrr-queue cos-map 3 3 6 7
 wrr-queue cos-map 4 5
 priority-queue out spanning-tree portfast

Above " priority-queue out" is shown, Does it mean only egress priority queue not ingress priority, is configured as a result of using '

mls qos trust device cisco-phone" ? 

thanks and have a great weekend.
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14 ACCEPTED SOLUTIONS

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Highlighted
Hall of Fame Expert

auto qos voip cisco-phone and ingress queues

Hi Sarah,

That is correct.  The priority-queue out enable the egress queue.

from the config guide:

priority-queue out

Enable the egress expedite queue, which is disabled by default.

When you configure this command, the SRR weight and queue size ratios  are affected because there is one fewer queue participating in SRR. This  means that weight1 in the srr-queue bandwidth shape or the srr-queue bandwidth share command is ignored (not used in the ratio calculation).

here is the QOS config guide for more info:

http://www.cisco.com/en/US/docs/switches/lan/catalyst3750x_3560x/software/release/12.2_53_se/configuration/guide/swqos.html#wp1395244

HTH

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Highlighted
Participant

Re: auto qos voip cisco-phone and ingress queues

hello Sarah,

yes you are correct.

The Catalyst has 2 ingress queues, one can be used for priority. The switch also
has 4 egress queues where one can be used for priority. It is more likely to end
up with congestion on egress than ingress. Auto Mls Qos trust enable queue 2 for ingress for two queues and queue 1 for egress from 4 queues.

please check this doc and hopefuly it will help you.

thanks

View solution in original post

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Hall of Fame Expert

auto qos voip cisco-phone and ingress queues

Hi Sarah,

1)Do all ports on the switch use this common queues i.e 2 ingress queues  and 4 egress queues?  I mean it is not like that each port on the  switch has its own dedicated ingress and egress queues.

That is correct.  Usually all ports with the same speed they have the same common queues.

2)Do switches usually have this kind of architecture where ingress and egress queues are shared among all ports?

no, it depends on the switch.

3)My question is 20 percent of whch bandwidth? Is the 20 percent of bandwidth of backplane ?

Correct

from the command reference guide:

The priority queue is guaranteed part of the bandwidth on the internal  ring, which reduces the delay and jitter under heavy network traffic on  an oversubscribed ring (when there is more traffic than the backplane  can carry, and the queues are full and dropping frames).

Shaped round robin (SRR) services the priority queue for its configured weight as specified by the bandwidth keyword in the mls qos srr-queue input priority-queue queue-id bandwidth weight global  configuration command. Then SRR shares the remaining bandwidth with  both ingress queues and services them as specified by the weights  configured with the mls qos srr-queue input bandwidth weight1 weight2 global configuration command.

4)what do threshold1  34 and threshold2 64 for queue2 represent?

That is %34 of 100 and %64 of 100

see below example:

default:

Switch(config)#do sh mls qos input-q

Queue     :       1       2

----------------------------------------------

buffers   :      90      10

bandwidth :       4       4

priority  :       0      10

threshold1:     100     100

threshold2:     100     100

now, I configure Queue 1 for %50

mls qos srr-queue input threshold 1 50 50

Switch(config)#do sh mls qos input-q                    

Queue     :       1       2

----------------------------------------------

buffers   :      90      10

bandwidth :       4       4

priority  :       0      10

threshold1:      50     100

threshold2:      50     100

HTH

Reza

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Participant

auto qos voip cisco-phone and ingress queues

Hello Sarah,

Sorry for the delay answer , was bit sick

I think its depends on switch make and model about how many ingress and aggress queues they had. But QOS config will be same it just matter for having extra queues for more threshold and buffer. Like 2960 is different that 3560.

For threshold , please have a look at this pic,

Threshold 1 will start dropping packets when it reaches to its limit but threshold 2 will not drop any packets. It goes like this up to last threshold until it starts dropping all the traffic.

Here is another example.

You can change these threshold values if you want so it can process more traffic before start dropping any packet.

If you use shape instead of share that’s mean you reserving some bandwidth for that queue and others will not able to share that bandwidth if there is congestion. Like if you shape q1 with 10 % of bandwidth then even if there is no congestion but still q2 will not be able to borrow that 10 % if it need because that 10 % is reserved for q1.

Hope this will help.

thanks

View solution in original post

Highlighted
Participant

Re: auto qos voip cisco-phone and ingress queues

Hello Sarah,

yes i am feeling lot better now and back to work as well.

just found a good example about threshold

http://www.netcontractor.pl/blog/?p=538

thanks

View solution in original post

Highlighted
Participant

Re: auto qos voip cisco-phone and ingress queues

Hi Sarah,

Yes thats correct . in the first pic if the threshold is 40 percent and packets with cos 0-3 will start dropping. This 40 % will count any traffic from cos 0-7. Suppose the queue is already filled with 60%, and a new frame arrives. It contains CoS values 4 and 5 and drop and 0-3 cos packet.

In the second picture I was trying to explain that if threshold one reach to its limit then it will start dropping packets with cos 0-1 or 0-3 . user can change these settings according to there needs.

but threshold 2 will not drop any packets. It goes like this up to last  threshold until it starts dropping all the traffic.

this mean threshold 2 will not drop its packets until traffic reached to its configured limit. Once threshold 2 is full it will start dropping packets with cos mapped to threshold 2.

Then threshold 3 will be next until it reaches to its limit.

here is a new pic with diffrent values but same concept.

Let me know if you are still confused.

Sorry for the confusion

thanks

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Highlighted
Participant

Re: auto qos voip cisco-phone and ingress queues

Hello Sarah,

Yes you are correct. But its good to use threshold values to 100.

sh mls qos map cos-input-q
   Cos-inputq-threshold map:
             cos: 0   1   2   3   4   5   6   7
             ------------------------------------
 queue-threshold: 1-1 1-1 1-1 1-1 1-1 2-1 1-1 1-1

this will map Cos 5 to queue 2 and threshold1 but it’s always good to map cos 6 into the same queue as cos 5. You can select different threshold for cos 6 traffic.

Yes you are correct about input queues.

For egress queues, you are talking about shape command here not share ..

If you shape 25 % of bandwidth to q1 then other queues can’t take it if there is congestion. Because this actually reserve the amount of bandwidth for the queue so its always good to use share command.

Check this one for egress QOS

http://blog.ipexpert.com/2011/08/25/campus-qos-part-3-egress-queuing-dropping-and-scheduling/

thanks

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Highlighted
Participant

Re: auto qos voip cisco-phone and ingress queues

Hello Sarah,

i tried my best to explain all you questions but plz forgive if there is any mistake coz i am still learner.

but please ask as many question you want and will help you.

please check this attachment

thanks

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Highlighted
Participant

Re: auto qos voip cisco-phone and ingress queues

You can check this default behaviour by this command and see which queue that interface mapped.

Switch># show mls qos interface gigabitethernet1/0/2 queueing

GigabitEthernet1/0/2

Egress Priority Queue :enabled

Shaped queue weights (absolute) :  25 0 0 0

Shared queue weights  :  25 25 25 25

The port bandwidth limit : 100  (Operational Bandwidth:100.0)

The port is mapped to qset : 1

thanks

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Highlighted
Participant

Re: auto qos voip cisco-phone and ingress queues

hello Sarah,

hope fully this will help.

thanks

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Highlighted
Participant

Re: auto qos voip cisco-phone and ingress queues

Hello Sarah,

lets see if this helps.

please ask as many questions you want.

thanks

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Highlighted
Participant

Re: auto qos voip cisco-phone and ingress queues

Hello,

In Classification and Marking stage packets will get remarked according to the configured classification and policer information. All packets that belong to a classification can be remarked. When you configure a policer, packets that meet or exceed the permitted bandwidth requirements (bits per second) can be conditionally passed through, dropped, or reclassified

Switch(config)# policy-map Example
Switch(config-pmap)# class class-default
Switch(config-pmap-c)# set ip dscp 1
Switch(config-pmap-c)# exit
Switch(config-pmap)# class AF31-AF33
Switch(config-pmap-c)# set ip dscp 3
Switch(config-pmap-c)# exit
Switch(config-pmap)# exit
Switch(config)# interface fastethernet0/1
Switch(config-if)# service-policy input Example 
Switch(config-if)# exit
 
In this example by using command set ip
  dscp 1 you remarking the incoming packet.
As soon as packets comes in switch will
check  the cos or Dscp value and then
  remark it if there is any service
policy for classification and then
route it to its destination.
 
thanks

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Highlighted
Participant

Re: auto qos voip cisco-phone and ingress queues

Hello Sarah,

hope this will help.

thanks

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Highlighted
Participant

Re: auto qos voip cisco-phone and ingress queues

Hi Sarah,

You can also assign burst size with any police so it wont drop the packet straight way after reaching to police limit. In short cut, it is a bit extra bandwidth for the queue before it actually drops the packet.

Its always good to have some burst so packets wont drop soon in congested network.

Burst—defines the maximum amount of tokens the bucket can hold at any time. Supported bursts range from 8000 bytes to to 2000000 bytes, and increment by 64 bytes

Hope this will help.

thanks

View solution in original post

29 REPLIES 29
Highlighted
Hall of Fame Expert

auto qos voip cisco-phone and ingress queues

Hi Sarah,

That is correct.  The priority-queue out enable the egress queue.

from the config guide:

priority-queue out

Enable the egress expedite queue, which is disabled by default.

When you configure this command, the SRR weight and queue size ratios  are affected because there is one fewer queue participating in SRR. This  means that weight1 in the srr-queue bandwidth shape or the srr-queue bandwidth share command is ignored (not used in the ratio calculation).

here is the QOS config guide for more info:

http://www.cisco.com/en/US/docs/switches/lan/catalyst3750x_3560x/software/release/12.2_53_se/configuration/guide/swqos.html#wp1395244

HTH

View solution in original post

Highlighted
Participant

Re: auto qos voip cisco-phone and ingress queues

hello Sarah,

yes you are correct.

The Catalyst has 2 ingress queues, one can be used for priority. The switch also
has 4 egress queues where one can be used for priority. It is more likely to end
up with congestion on egress than ingress. Auto Mls Qos trust enable queue 2 for ingress for two queues and queue 1 for egress from 4 queues.

please check this doc and hopefuly it will help you.

thanks

View solution in original post

Highlighted
Contributor

auto qos voip cisco-phone and ingress queues

Thanks Singh and Reza

Highlighted
Contributor

auto qos voip cisco-phone and ingress queues

Hi Singh.

Thanks for the excellent  attachment. ; I am still reading it as it contains too much information ; I will  be posting a lot of questions once I am done.

thanks and have a great weekend.

Highlighted
Contributor

Re: auto qos voip cisco-phone and ingress queues

The Catalyst has 2 ingress queues, one can be used for priority. The switch also has 4 egress queues where one can be used for priority

1)Do all ports on the switch use this common queues i.e 2 ingress queues and 4 egress queues?  I mean it is not like that each port on the switch has its own dedicated ingress and egress queues.

2)Do switches usually have this kind of architecture where ingress and egress queues are shared among all ports?

Rack18SW1(config)#mls qos srr-queue input priority-queue 1 bandwidth ?
   enter bandwidth number [0-40]

Let say we use 20 bandwidth number in above command which means the queue can not use more than 20 percent of bandwidth.

3)My question is 20 percent of whch bandwidth? Is the 20 percent of bandwidth of backplane ?

Rack18SW2#sh mls qos input-queue
Queue     :       1       2
----------------------------------------------
buffers   :     67     33
bandwidth :     90     10
priority :       0     10
threshold1:       8     34
threshold2:     16     66

4)what do threshold1  34 and threshold2 64 for queue2 represent?

Back to my reading.

thanks

Highlighted
Hall of Fame Expert

auto qos voip cisco-phone and ingress queues

Hi Sarah,

1)Do all ports on the switch use this common queues i.e 2 ingress queues  and 4 egress queues?  I mean it is not like that each port on the  switch has its own dedicated ingress and egress queues.

That is correct.  Usually all ports with the same speed they have the same common queues.

2)Do switches usually have this kind of architecture where ingress and egress queues are shared among all ports?

no, it depends on the switch.

3)My question is 20 percent of whch bandwidth? Is the 20 percent of bandwidth of backplane ?

Correct

from the command reference guide:

The priority queue is guaranteed part of the bandwidth on the internal  ring, which reduces the delay and jitter under heavy network traffic on  an oversubscribed ring (when there is more traffic than the backplane  can carry, and the queues are full and dropping frames).

Shaped round robin (SRR) services the priority queue for its configured weight as specified by the bandwidth keyword in the mls qos srr-queue input priority-queue queue-id bandwidth weight global  configuration command. Then SRR shares the remaining bandwidth with  both ingress queues and services them as specified by the weights  configured with the mls qos srr-queue input bandwidth weight1 weight2 global configuration command.

4)what do threshold1  34 and threshold2 64 for queue2 represent?

That is %34 of 100 and %64 of 100

see below example:

default:

Switch(config)#do sh mls qos input-q

Queue     :       1       2

----------------------------------------------

buffers   :      90      10

bandwidth :       4       4

priority  :       0      10

threshold1:     100     100

threshold2:     100     100

now, I configure Queue 1 for %50

mls qos srr-queue input threshold 1 50 50

Switch(config)#do sh mls qos input-q                    

Queue     :       1       2

----------------------------------------------

buffers   :      90      10

bandwidth :       4       4

priority  :       0      10

threshold1:      50     100

threshold2:      50     100

HTH

Reza

View solution in original post

Highlighted
Contributor

Re: auto qos voip cisco-phone and ingress queues

Hi Reza

)Do all ports on the switch use this common queues i.e 2 ingress queues and 4 egress queues? I mean it is not like that each port on the switch has its own dedicated ingress and egress queues.

That is correct. Usually all ports with the same speed they have the same common queues

1)What about switches with ports 10/100 Mbits/sec?  Do such switches have common ingress and egress queues for such ports( 10/100 MBS) ?

2)Consider a switch with few 10/ 100 MBS ports and few 1000MBS ports, What about ingress/agress queues on this kind of switch ?

3)Switch(config)#do sh mls qos input-q

Queue : 1 2

----------------------------------------------

buffers : 90 10

bandwidth : 4 4

priority : 0 10

threshold1: 50 100

threshold2: 50 100

   I am sorry I still cannot understand what exactly threshold represent? I understand how we can change threshold value but what they actually mean  and What happens when these threshold reach?

4)Shaped round robin (SRR) services the priority queue for its configured weight as specified by the bandwidth keyword in the

mls qos srr-queue input priority-queue queue-id bandwidth weightglobal configuration command. Then SRR shares the remaining bandwidth with both ingress queues and services them as specified by the weights configured with the mls qos srr-queue input bandwidth weight1 weight2 global configuration command

Shaped round robin (SRR) services the priority queue for its configured weight as specified by the bandwidth keyword in the mls qos srr-queue input priority-queue  queue-id  bandwidth  weightglobal configuration command. Then SRR shares the remaining bandwidth with both ingress queues and services them as specified by the weights configured with the mls qos srr-queue input bandwidth weight1 weight2 global configuration command

Let say we have two ingress queues : q1 and q2

q2 is priority queue and it can can use upto 10 percent bandwidth, weight 50 percent

q1 has weight of 50 percent.

Let say q2 has reached its 10 percent bandwidth utilization ( i.e traffic from q2 is using upto 10 percent of backplane bandwidth). Upto this point,q2 get services first but once q2 starts using 10 percent of backplane bandwidth, q2 will no longer be serviced first  SRR will  service q1 and q2 according to their weights. Once q2 utilization of backplane falls below 10 percent, q2 will be serviced first again.

Is my understanding correct?

Thanks and have a great weekend.

Highlighted
Participant

auto qos voip cisco-phone and ingress queues

Hello Sarah,

Sorry for the delay answer , was bit sick

I think its depends on switch make and model about how many ingress and aggress queues they had. But QOS config will be same it just matter for having extra queues for more threshold and buffer. Like 2960 is different that 3560.

For threshold , please have a look at this pic,

Threshold 1 will start dropping packets when it reaches to its limit but threshold 2 will not drop any packets. It goes like this up to last threshold until it starts dropping all the traffic.

Here is another example.

You can change these threshold values if you want so it can process more traffic before start dropping any packet.

If you use shape instead of share that’s mean you reserving some bandwidth for that queue and others will not able to share that bandwidth if there is congestion. Like if you shape q1 with 10 % of bandwidth then even if there is no congestion but still q2 will not be able to borrow that 10 % if it need because that 10 % is reserved for q1.

Hope this will help.

thanks

View solution in original post

Highlighted
Contributor

Re: auto qos voip cisco-phone and ingress queues

Thanks Singh.

I hope you are feeling better now.   I am half way through that attachment you forwarded to me.   I will be posting questions as I read it.

thanks and have a great  evening.

Highlighted
Participant

Re: auto qos voip cisco-phone and ingress queues

Hello Sarah,

yes i am feeling lot better now and back to work as well.

just found a good example about threshold

http://www.netcontractor.pl/blog/?p=538

thanks

View solution in original post

Highlighted
Contributor

Re: auto qos voip cisco-phone and ingress queues

Hi Singh

Let say threshod1 is 40 percent. So what are we saying?  Are we saying once the  40 percent of queue is filled , packets with cos 0 -3  should be dropped.  This 40 percent of queue could be filled with any number of packets whose cos values are mapped to queue.

Is my understanding correct?

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

For threshold , please have a look at this pic,

threshold 1 will start dropping packets when it reaches to its limit but threshold 2 will not drop any packets. It goes like this up to last  threshold until it starts dropping all the traffic.

Please consider the highlighted text; you lost me here.

so far i understand:

threshold 1 40 means once the 40 percent queue is filled, start dropping packets whose COS mapped to threshold1

If the above is correct, then

threshold 2  65 should mean once the 65 percent queue is filled, start dropping packets with cos mapped to threshold 2

thanks

Highlighted
Participant

Re: auto qos voip cisco-phone and ingress queues

Hi Sarah,

Yes thats correct . in the first pic if the threshold is 40 percent and packets with cos 0-3 will start dropping. This 40 % will count any traffic from cos 0-7. Suppose the queue is already filled with 60%, and a new frame arrives. It contains CoS values 4 and 5 and drop and 0-3 cos packet.

In the second picture I was trying to explain that if threshold one reach to its limit then it will start dropping packets with cos 0-1 or 0-3 . user can change these settings according to there needs.

but threshold 2 will not drop any packets. It goes like this up to last  threshold until it starts dropping all the traffic.

this mean threshold 2 will not drop its packets until traffic reached to its configured limit. Once threshold 2 is full it will start dropping packets with cos mapped to threshold 2.

Then threshold 3 will be next until it reaches to its limit.

here is a new pic with diffrent values but same concept.

Let me know if you are still confused.

Sorry for the confusion

thanks

View solution in original post

Highlighted
Contributor

Re: auto qos voip cisco-phone and ingress queues

  Thanks Singh. I got it.

Back to my reading.

Highlighted
Contributor

Re: auto qos voip cisco-phone and ingress queues

Hi Singh

Please consider the following from the attachment:

Rack18SW1#sh mls qos map cos-input-q

   Cos-inputq-threshold map:

              cos:  0   1   2   3   4   6   7

              ------------------------------------

  queue-threshold: 1-1 1-1 1-1 1-1 1-1 2-1 1-1 1-1

Above Cos 5 is mapped to queue 2 and threshold1

Let see how much  threshold 1 is:

Rack18SW2#sh mls qos input-queue

Queue     :       1       2

----------------------------------------------

buffers   :      67      33

bandwidth :      90      10

priority  :       0      10

threshold1:       8      34

threshold2:      16      66

So threshold1 is 34 percent.

Based on the above configurations, only frames with cos 5 will use queue 2 ; Once the threshold1 is reached, frames with cos 5 will be dropped.

Did i get it right?

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

I am now reading about egress queues discussed in the attachment.

In case of ingress queues, we have queue2 as a priority queue . queue2 get serviced first as long it is not utilizing configured bandwidth.

for example.

Rack18SW2#sh mls qos input-queue

Queue     :       1       2

----------------------------------------------

buffers   :      67      33

bandwidth :      90      10

priority  :       0      10

threshold1:       8      34

threshold2:      16      66

       Above q2  can use upto 10 percent of backplane bandwidth.  after that traffic from all queues including q2 will be alowed to share backplane bandwidth according to their weights.

Let talk about egress queue now:

Now lets look at our options for egress queues. We have four queues

where every queue has three thresholds. We start by looking at the default settings.

Rack18SW1#sh mls qos map cos-output-q

   Cos-outputq-threshold map:

              cos:  0   1   2   3   4   5   6   7

              ------------------------------------

  queue-threshold: 2-1 2-1 3-1 3-1 4-1 1-1 4-1 4-1

Rack18SW1(config-if)#srr-queue bandwidth shape 25 0 0 0

How much bandwidth did we just assign to queue 1? 25 Mbit?

We assigned 4 Mbit since (1/25)*100 = 4. When we set the other queues to 0

I noticed  above once the q1 start using upto 25 percent of port bandwidth, packets from q1 will be dropped. If you compare this behavior to ingress queue 2 discussed above we see that once ingress priority queue has reached its configured bandwidth, packets from all ingress queues are allowed to use backplane' according to their configured weights.

But here in case of egress queue, we see that packets are simply dropped once egress queue 1 starts utilizing 25 percent of port bandwidth.

thanks

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