[c-nsp] Tail drops on ME3600 with shaping policy

[CiscoNSP List]

Hi Everyone,



We've run into a problem with tail drops on a couple of service on ME3600's....our "usual" shaping policy (For example 10Mb) would be:




policy-map CUSTA_10M


 class class-default


  shape average 9800000




int foo


 service instance 1065 ethernet


  description CUST_A


  encapsulation dot1q 1065


  rewrite ingress tag pop 1 symmetric


  service-policy output CUSTA_10M


  bridge-domain 1065




Which has worked historically without problem....but now we are seeing tail drop/poor performance on "some" of these services with shaping....Ive been doing some reading, and adjusting queue limit alleviates the issue?



Ive tried adding "queue-limit percent 100" to the shaping policy, but it gets rejected:



QOS: queue-limit command not supported in non-leaf classes


QoS: Policy attachment failed for policymap CUSTA_10M



Ive had a bit of a google, and have seen examples where people have used a "dummy class"



class-map match-all CM-DUMMY  <--  Had to create this or policy map complained and would not apply it


policy-map MB_TEST_10Mb


 class CM-DUMMY


 class class-default


  shape average 9800000


  queue-limit percent 100



but attempting to apply to a service instance I am still getting the "QOS: queue-limit command not supported in non-leaf classes"



Any help is greatly appreciated.


Cheers