Cisco QoS
Switch Verify Commands
show mls qos
show mls qos interface gi0/1 statistics
show platform port-asic stats drop gi0/1
Router Verify Commands
show service policy-map interface gi0/1
Switch Commands
the command 'mls qos map cos-dscp' allows you to map COS to DSCP. the auto qos command will map a range of COS values to DSCP values. mls qos map cos-dscp 0 8 16 24 32 46 48 56
this maps COS 0 to DSCP 0-7, then COS 1 to DSCP 8-15, COS 2 to DSCP 16-23, COS 3 to DSCP 24-31, and so on. Policing Notes
On trunks ports 'mls qos trust dscp' The single bucket would be viewed as a conform action where once the bucket has been consumed traffic will be dropped. In the two bucket model the first bucket remains for your conform action, and the second bucket will be for the exceed action. Bucket one is known as Bc bucket two is known as Be
Policy-map restrict-traffic
Class restricted-traffic
Police 15000 conform-action transmit exceed-action set-prec-transmit 0 vilate-action drop
The router will auto-fill Bc=4687 bytes Be=4687 bytes
This is an example of a three-bucket model where we allow up to 15000bps if exceed we reset the ip precedence, if the traffic continues to exceed the set limit we drop traffic
Shaping Notes
Shaping will put traffic into the memory buffers and cannot reclassify traffic, shaping can be done per class of traffic. CIR = Tc * Bc or Bc = CIR / Tc Tc = time committed Bc = committed Burst = translates to the CIR Be = exceeded burst The router will transmit your CIR per time frame. Would see a burst of traffic per time increment then nothing for the remainder of the time increment The committed burst is accessible if a given Tc went unused and the following Tc needed more traffic. the Be is the cap that the ISP will enforce for any given Tc Shaping Graph
If you shape based off the peak the traffic can / will be dropped Shaping based on the average put traffic into the discard-eligible
This would be a method to shape data that can be re-transmitted (at a 500kbs rate)
Policy-map Shape
Class Data
Shape peak 500000
This would be a method to shape data at a peak rate (that cannot be re-transmitted (at a 500kbs rate)) this will use Bc Priority can be given to voice traffic with win the shape map
Class-map Data
match ip dscp 0
Class-map Voice
match ip dscp ef
!
class-map All-Data
match class data
match class voice
!
policy-map Priority
class Voice
priority 50000
class Data
bandwidth 50000
class class-default
fair-queue
!
Policy-map Shape
Class All-Data
Shape average 500000
Service-policy Priority
!
Interface X
Servicei-policy output Shape