[nsp] 1Mbps rate-limit - syntax help

[Christopher J. Wolff]

Hello,

I had a similar problem until the guru Rob Thomas set me straight on Cisco
CAR math.  The following line produces a razor sharp 4 meg chart.

rate-limit input 4000000 6000000 12000000 conform-action transmit
exceed-action drop

1. bits per second
2. Normal burst bytes = bits per second * 1.5
3. Maximum burst bytes = normal burst bytes * 2

Have fun!
-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Sean Mathias
Sent: Monday, March 01, 2004 5:03 PM
To: matthew zeier; cisco-nsp at puck.nether.net
Subject: RE: [nsp] 1Mbps rate-limit - syntax help

The counters from sh int are averaged over a 5 minute interval whereas the
CAR threshholds are checked per TC interval which is several times per
second.  So the average you see on the interface is just that, an average
and does not necessarily reflect the bursty nature of the traffic.  CAR sees
those bursts and drops anything that does not have enough accumulated credit
to be passed.

Sean 


Ignoring that 1,000,000 isn't 1Mbps, is this syntax correct for a 1Mbps
"cap" ?

 rate-limit input 1000000 1500 2000 conform-action transmit exceed-action
drop
 rate-limit output 1000000 1500 2000 conform-action transmit exceed-action
drop


The conformed rate is much lower than the input/output rate, yet I'm still
seeing a lot of exceeded matches.  'sh int' also showsa bit rate that's far
under the 1Mbps.

#sh in fa2/1 rate-limit

FastEthernet2/1   Input
    matches: all traffic
      params:  1000000 bps, 1500 limit, 2000 extended limit
      conformed 397 packets, 331656 bytes; action: transmit
      exceeded 35 packets, 46296 bytes; action: drop
      last packet: 16ms ago, current burst: 1434 bytes
      last cleared 00:00:05 ago, conformed 478000 bps, exceeded 66000 bps
  Output
    matches: all traffic
      params:  1000000 bps, 1500 limit, 2000 extended limit
      conformed 331 packets, 118316 bytes; action: transmit
      exceeded 15 packets, 20814 bytes; action: drop
      last packet: 20ms ago, current burst: 0 bytes
      last cleared 00:00:05 ago, conformed 170000 bps, exceeded 30000 bps


--
matthew zeier                        | "Nothing in life is to be feared.
InteleNet Communications, Inc.       |  It is only to be understood."
(949) 784-7904                       |       - Marie Curie

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