What does this accomplish " PPP Multilink queue depth qos <number>" ?

Answered Question
Aug 3rd, 2010
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Guys,

I have a router with 2 serials configure, they are both bonded with a multilink interface. I noticed a command under the "interface multilink 1" command, "ppp multilink queue depth qos 3".  What does this command do?


Thanks

BV

Correct Answer by abaskara about 6 years 11 months ago

Hi,


I am not aware of a specific doc for this.


tx_limited = 1(2) << the number in the paranthesis is what I was referring to.

Yes, with qos (service-policy) applied, IOS will autmatically tune it down to 2 packets, per my earlier comment.

-Arun

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abaskara Tue, 08/03/2010 - 13:34
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  • Cisco Employee,

Hello,


When you have qos configured, it takes effect only when there is "congestion" on the interface. Congestion is detected when the queue gets filled up. Having a lower queue depth is a good idea when you have RTP (Voice) type of traffic, so that QOS kicks in quickly to service the latency sensitive traffic. By default, when you apply a service-policy to the Multilink, the queue depth is 2 packets.


To take it further, you can do "sh controller | in tx_limit" and you will see this number reflected, when you have qos configured.


The default for FIFO is 8 packets.


HTH.


-Arun

Bobby Villegas Wed, 08/04/2010 - 07:51
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abaskara,


Is there any docs on this? I did issue show command you stated on the last reply. This is what I got:


chip_state = 2, ds->tx_limited = 0
  chip_state = 3, ds->tx_limited = 0
tx_limited = 1(2), errata19 count1 - 0, count2 - 0
tx_limited = 1(2), errata19 count1 - 0, count2 - 0


You stated "To take it further, you can do "sh controller | in tx_limit" and you  will see this number reflected, when you have qos configured", where is the 2 packets reflected? tx_limited = 1(2) or count2.


I did remove " ppp multilink queue depth qos 3" from the multlink interface. The above output is after I removed the depth command.


I do have a service policy with voip class maps on the multilink interface.


Thanks

Correct Answer
abaskara Wed, 08/04/2010 - 08:10
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  • Cisco Employee,

Hi,


I am not aware of a specific doc for this.


tx_limited = 1(2) << the number in the paranthesis is what I was referring to.

Yes, with qos (service-policy) applied, IOS will autmatically tune it down to 2 packets, per my earlier comment.

-Arun

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