• the utilization of class-default is recommeded
• the total amount of bandwidth allocated with CBWFQ cannot exceed 75% of the line rate
• when deploying CBWFQ on ATM, we need to associate a specific WFQ policy per VC, this means when having one or more VCs per interface, the recommended configuration is like the following:

  	pvc VPI / VCI 
    	 service-policy output 
  	

• you can use service-policy on an atm pvc only if you choose vbr or abr as your traffic model (reported by D.Matsakis)

EXAMPLE 1

class-map f
  class class1
    ban x
  class class-default
    ban y

int s1
  ban z
  service f


==> the requirement is (x+y)/z <= 0.75

policy-map wfq
 class wfq
    bandwidth 1300
    random-detect   <=== configure RED, this helps TCP

 class class-default
    bandwidth 200   <=== 1300+200=75%(2000)

==> this effectively means that you allocate 1300/1500=87% of the
    BW to the wfq class and 13% to the rest

!         
interface ATM1/0.8 point-to-point
 description to CERN (diffserv)
 bandwidth 2000
 ip address 192.168.60.6 255.255.255.252
 no ip directed-broadcast
 pvc 8/8  
  service-policy output wfq
  vbr-nrt 2000 2000 1
  encapsulation aal5mux ip
 !        
!