A question about CAR configuration

Question

I read the configuring CAR on CCO. I'm a little confused about the conform value. here the URL of the article:
http://www.cisco.com/en/US/partner/products/sw/iosswrel/ps1835/products_configuration_guide_chapter09186a00800c75ce.html
per the article, to limit a speed of a interface:
Router(config-if)# rate-limit {input | output} bps burst-normal burst-max conform-action action exceed-action action
here is it's 1st sample:
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
interface hssi 0/0/0
rate-limit output 15000000 2812500 5625000 conform-action transmit exceed-action drop
ip address 10.1.0.9 255.255.255.0
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
The CIR is setup to 15Mbps, the normal burst size is 2812500bytes(22.5Mbits), excessed burst size is 5625000bytes(45Mbits)
I think it's mean during a long-term, the average transmit speed is limited to 15Mbps, but at a specific time, the traffic
can be allowed to 22.5Mbits. and a specific time, 44.99Mbits can be allowed as long as the CIR is under 15Mbps.
but below is another sample:
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
interface Fddi2/1/0
rate-limit input access-group rate-limit 100 80000000 64000 80000 conform-action transmit exceed-action drop
ip address 200.200.6.1 255.255.255.0
access-list rate-limit 100 00e0.34b0.7777
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
here, it wants to limit a specific host. the CIR is 80Mbps. normal burst size is 64000bytes(512kbits), exceeded burst size
is 80000bytes(640kbits).
then at a specific time, the traffic can't pass 640kbits, if it pass, will be dropped. My question is since no time the
traffic can more than 640kbits, what's the CIR 80Mbps for?
Thank you a lot.
Regards,
Sha

Answer 1

see the following example. This may help
Chris
Subrate IP Services Example
The following example illustrates how to configure a basic CAR policy that allows all IP traffic. In the example, the network operator delivers a physical T3 link to the customer, but offers a less expensive 15 Mbps subrate service. The customer pays only for the subrate bandwidth, which can be upgraded with additional access bandwidth based on demand. The CAR policy limits the traffic rate available to the customer and delivered to the network to the agreed upon rate limit, plus the ability to temporarily burst over the limit.
interface hssi 0/0/0
rate-limit output 15000000 2812500 5625000 conform-action transmit exceed-action drop
ip address 10.1.0.9 255.255.255.0
Input and Output Rate Limiting on an Interface Example
In this example, a customer is connected to an Internet service provider (ISP) by a T3 link. The ISP wants to rate limit transmissions from the customer to 15 Mbps of the 45 Mbps. In addition, the customer is allowed to send bursts of 2,812,500 bytes. All packets exceeding this limit are dropped. The following commands are configured on the High-Speed Serial Interface (HSSI) of the ISP connected to the customer:
interface Hssi0/0/0
description 45Mbps to R1
rate-limit input 15000000 2812500 2812500 conform-action transmit exceed-action drop
ip address 200.200.14.250 255.255.255.252
rate-limit output 15000000 2812500 2812500 conform-action transmit exceed-action drop
The following sample output shows how to verify the configuration and monitor CAR statistics using the show interfaces rate-limit command:
Router# show interfaces hssi 0/0/0 rate-limit
Hssi0/0/0 45Mbps to R1
Input
matches: all traffic
params: 15000000 bps, 2812500 limit, 2812500 extended limit
conformed 8 packets, 428 bytes; action: transmit
exceeded 0 packets, 0 bytes; action: drop
last packet: 8680ms ago, current burst: 0 bytes
last cleared 00:03:59 ago, conformed 0 bps, exceeded 0 bps
Output
matches: all traffic
params: 15000000 bps, 2812500 limit, 2812500 extended limit
conformed 0 packets, 0 bytes; action: transmit
exceeded 0 packets, 0 bytes; action: drop
last packet: 8680ms ago, current burst: 0 bytes
last cleared 00:03:59 ago, conformed 0 bps, exceeded 0 bps
it's from the article you were looking at near the bottom..
Chris