[QoS Question] LLQ function

[lvtquan1991]

Dear all, 

Please help me clear the unclear point regarding the QoS setting.

In case we have 1 circuit with 2Mbps bandwidth.

We setup the voice traffic (IPP 4) is 0.4Mbps LLQ.

(Suppose that the configuration is correct)

So, When we sent only 2Mbps traffic IPP4 over this link (no other traffic).

Does packet will drop?

Thank you. 

[paul driver]

Hello

When no congestion is occuring the priority queue will be allowed to utilise the exrta BW, When congestion occurs it will be rate limited to the specifc class value you specifed and if this is exceeded packets wil be dropped to allow others classes not to be starved of any BW.

res

Paul

[lvtquan1991]

Hi Paul, 

Thank you for your response,

I just checked the CiscoPress QoS document and see the picture which describe LLQ operator.

It seem that if we set up the voice traffic (IPP 4) is 0.4Mbps LLQ. And we sent 2Mbps IPP4 only (no other traffic). The traffic will drop due to it exceed the LLQ bandwidth even it does not exceed the total bandwidth.

Loda

[paul driver]

Hello

I understand what your saying posting that flow diagram, As its shows the LLQ flow IN times of congestion.

However If no congestion is occuring on the interface (And this is what your asking correct?)

And the only traffic at that time traversing the interface is what is matching your LLQ class , Then this traffic should not be dropped, Its only WHEN congestion occurs this should happen and not before.

Basically if your not experiencing congestion then QOS wont initate.

res

Paul
 

[lvtquan1991]

Dear Paul, 

Thank you so much for your information, 

Its seem that I already lack understanding.

"And the only traffic at that time traversing the interface is what is matching your LLQ class , Then this traffic should not be dropped, Its only WHEN congestion occurs this should happen and not before."

Could you help me provide the document or website for this?

Loda

[paul driver]

Hello

Have a look here  -  Cisco LLq

res

Paul