[c-nsp] ASR920 Microbursts

Jordi Magrané Roig jordimagrane at hotmail.com
Tue Aug 4 10:46:30 EDT 2015

Dear Colleagues,


Recently I have installed one ASR920 and I have configured on 1G interface
one service instance with an outbound policy-map shaping to 30 Mbps. The
problem is that I noticed that the ASR920 has the same microburst issue than
the ME3600. I have tried to adjust the queue-limit in order to avoid drops
but then the latency increments. I have configured:



class class-default

  shape average 30000000


I have tried also with different classes of service but the issue still


I would like to know the recommendation about the queue-limit size, the
relation with the values of burst committed and then what should be the
recommended configuration of shaping, recommendations about fine tunning the
shaping. I have noticed that there Cisco platforms that shape better, for
example the ASR9001 or 7600 with ES+ shape better than ASR1000 with
SPA-5X1GE-V2 or ME3600.


Another problem is that I didn’t find enough information about QoS on ASR920
platform. Somebody knows the default queue size of 1G port? How the packet
buffer works? Is it like ME3600 (shared queue buffer per ASIC)?





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