Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 
Community Member

QoS Calculations For CIR, Burst and Policing

Ive spent alot of time recently getting to grips with QoS but as yet i have been unable to find a definitive method for calculating traffic rates, CIR Values and Burst values specially for policing on differing links speeds.

For example i have a 2Mbit/s leased line and im configuring QoS on an ASA, ive configured a class for voice and used the class-default for all other traffic, in the policy map i have set priority on the voice class and policed traffic for the best effort class at 1536000 and a burst of 1500 bytes which is 3/4 of the link speed and based on the assumption that i should leave room for voice traffic even though it is priority queued, but i am unsure whether the full link speed on 2000000 should be specified and let the priority handle voice traffic.


access-list voice extended permit tcp any host eq sip

access-list voice extended permit udp any host eq sip

access-list voice extended permit udp any host range 16384 32767


priority-queue outside


class-map inspection_default

match default-inspection-traffic

class-map qos-voice-class

match access-list voice


policy-map qos-outside-pol

class qos-voice-class


class class-default

police output 1536000 1500

police input 1536000 1500


service-policy qos-outside-pol interface outside

Any help would be much appreciated.


CreatePlease to create content