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New Member

Comparing the bandwidth and priority in policy-map


I read the documentation about to configure a Policy-Map for to give priority at voice traffic over data traffic. I have a dubt, the bandwidth that I assign with the PRIORITY command is always reserved to the class where I configure this parameter or in case of congestion the traffic that I configure with the BANDWIDTH parameter can use it.

For example in the following mini configuration:

class-map voice-traffic

match access-group 125



policy-map Voice-Priority

class voice-traffic

priority 1000

class class-default


the 1000 Kbit are always for voice traffic or if there is congestion in the class-default is it possibile to use these 1000Kbits for exceed traffic?

Thank you in advance



Re: Comparing the bandwidth and priority in policy-map

When you write "priority" it means you're now using LLQ instead of CBQWF. And the main difference is that both queueing methods assign a defined bandwidth to a traffic class but with LLQ, you create a priority queue besides the other CBWFQ classes. Just like priority queueing, this prioritized queue will be serviced first and always until it's emptied. Once it's empty, the other CBWFQ classes will be serviced according to their bandwidth statements. So besides assigning a bandwidth, you assign an absolute service priority (and minimum delay) for this class. For CBWFQ or LLQ configured bandwidth value is the "minimum" assigned bandwidth to this class during "congestion" periods. In non-congestion periods all classes shares the remaining bandwidth proportionally their configured bandwidth.

Best Regards.

New Member

Re: Comparing the bandwidth and priority in policy-map

Thank you for your response. My doubt is just this, if I need bandwidth for the classes in the CBWFQ and the priority traffic doesn't use all its bandwidth is the free priority bandwidth available for CBWFQ?

If I understand right, the bandwidth assigned to the priority queue is not share with the classes in the CBWFQ.

Best Regards


Re: Comparing the bandwidth and priority in policy-map

if traffic assigned to the proirity class doesn't fill the assigned bandwidth, this capacity can be used by other classes. Same for the other CBWFQ classes but as I mentioned earlier, service priority for this class is different.


New Member

Re: Comparing the bandwidth and priority in policy-map

Thank You very much and Merry Christmas

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