• Goal is to normalize traffic flow
    • Smooth out bursts
    • Prepare traffic for ingress policing.
    • Delay and Queue exceeding traffic.
  • Terminology
    • Access Rate – AR
      • Physical port speed
    • Committed Information Rate – CIR
      • Average rate the shaper is targetting.
    • Time Committed – Tc
      • Time interval in ms to emit traffic bursts
      • Bursts always emitted at Access Rate (AR)
    • Burst Committed – Bc
      • Amount of bits that could be sent every Tc
    • Burst Excessive – Be
      • Amount of bits over Bc that could be sent during Tc
      • Must be accumulated by idle periods.
  • Modular QoS Command line (MQC) Syntax
    • Configuration via MQC
      • ‘shape average <cir> [Bc][Be]
      • Tc is found implicitly as Bc/CIR
    • Default shaper queue is FIFO.
      • Can be turned into HQF by associating a child policy-map with shaped class.
      • Specify HQF settings in the child-policy
        • ie. nested policies.
          • ie. shaping could be on outside policy, fancy queueing is referenced in outer policy via ‘service-policy’ command.

Configuration:

Create new access-list referencing ICMP:

Create new class-map that references access-list ‘ICMP’:

Create new Policy-map that references Class-map ‘ICMP’:

Under the Policy-map ‘SHAPER’ we’re saying the shape average is target bit rate.

And lastly, apply to the desired interface.

Now when doing a normal ping and high repeat ping out interface gig0/3, we’ll see the latency is very low, then very high.

Our normal ping has an average latency to 4.4.4.4 of 3ms. The high repeat ping has an average latency of 689ms.

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