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Cisco Bug: CSCuo64537 - Typhoon - improve burst behavior in low-burst mode

Last Modified

Jul 20, 2018

Products (6)

  • Cisco ASR 9000 Series Aggregation Services Routers
  • Cisco ASR 9922 Router
  • Cisco IOS XR Software
  • Cisco ASR 9010 Router
  • Cisco ASR 9006 Router
  • Cisco ASR 9001 Router

Known Affected Releases

4.3.1.FWDG

Description (partial)

Symptom:
On typhoon, shaping at parent and grand-parent level exceeds the configured burst size. While the overall shaper rate is still maintained over time, there is initial burst, as well as sustained burst, when measured over smaller intervals. This can cause a policer on the other end to drop packets, depending on the burst size (CBS) configured on the policer. Configuring low-burst mode improves the burst behavior significantly, but it may still not be enough if the policer CBS is very low (< 1 ms).
Conditions:
A two-level or three-level policy is configured, with shaping action in parent-level or grand-parent level. The shaper burst is configured to be as low as possible - 500us. low-burst mode is enabled, and the line-card rebooted for the low-burst mode to take effect. 

Mixed priority traffic is sent to through the shaper at high enough rate for the shaper to kick-in, and the traffic coming out is either
1. Captured and analyzed for burst or 
2. A policer is configured on the other end with the required burst, and check for drops.
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Bug Details Include

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