2.4 FRTS - What's Lowest Possible Tc, and Default Tc?

Requirenments:

  • DLCI 204 should get lowest possible Tc.
  • Other DLCIs should get Tc.

 

IEWB used legacy FRTS, and lead to:

  • 10ms as lowest possible Tc for DLCI 204 (CIR 128000, Bc 1280)
  • 125ms as default Tc for other DLCIs (CIR 192000, Bc 24000)

 

Now I'm REAAALLLY confused. I configured it using MQC and I got different results:

  • 7ms a lowest possible Tc for DLCI 204 (CIR 128000, Bc 1000)
  • I did not set Bc value. I just set CIR value, and let IOS assign its DEFAULT values. The outcome was: Tc 41ms, Bc 7872.

 

 

 

-------- REFERENCE IF READER INTRESTED ---------

My configs (only for R2 for sake of simplexity):

class-map match-all DLCI-201-203
 match fr-dlci 201
 match fr-dlci 203
class-map match-all DLCI-204
 match fr-dlci 204
!
!
policy-map QoS
 class DLCI-204
  shape average 128000 1000 0
 class DLCI-201-203
  shape average 192000
 class class-default

 

My outputs:

RSRack2R2(config-pmap-c)#do s policy-map int s1/0

 Serial1/0

  Service-policy output: QoS

    Class-map: DLCI-204 (match-all)
      0 packets, 0 bytes
      5 minute offered rate 0 bps, drop rate 0 bps
      Match: fr-dlci 204
      Traffic Shaping
           Target/Average   Byte   Sustain   Excess    Interval  Increment
             Rate           Limit  bits/int  bits/int  (ms)      (bytes) 
           128000/128000    125    1000      0         7         125     

        Adapt  Queue     Packets   Bytes     Packets   Bytes     Shaping
        Active Depth                         Delayed   Delayed   Active
        -      0         0         0         0         0         no

    Class-map: DLCI-201-203 (match-all)
      0 packets, 0 bytes
      5 minute offered rate 0 bps, drop rate 0 bps
      Match: fr-dlci 201
      Match: fr-dlci 203
      Traffic Shaping
           Target/Average   Byte   Sustain   Excess    Interval  Increment
             Rate           Limit  bits/int  bits/int  (ms)      (bytes) 
           192000/192000    1968   7872      7872      41        984     

        Adapt  Queue     Packets   Bytes     Packets   Bytes     Shaping
        Active Depth                         Delayed   Delayed   Active
        -      0         0         0         0         0         no

    Class-map: class-default (match-any)
      1194 packets, 21780 bytes
      5 minute offered rate 0 bps, drop rate 0 bps
      Match: any

 

 

--------------------END OF REFERENCE --------------------

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