Need help with rate-limit on ethernet interface

[atrevido43]

Getting a 30MB ethernet handoff from our ISP and I want to rate limit a sub-interface (VLAN 100)  to 10M of it so that the group of people in that VLAN 100 do not suck up all 30MB with their downloads. 

Would this be what I need to put?

interface GigabitEthernet0/0.100

rate-limit input 10485760 20000 40000 conform-action transmit exceed-action drop

rate-limit output 10485760 20000 40000 conform-action transmit exceed-action drop

I don't really know exactly what the burst rate #'s are supposed to be or mean.  If anyone can explain that I'd appreciate it.  I just dreamed 20000 and 40000 up out of thin air.

[John Blakley]

Dawn,

Based on your calculation (and you can simplify this with 10000000), you would take your normal rate * .125 * 1.5. That would get:

10000000 * .125 * 1.5 = 1875000

Excess burst is 2 * normal burst:

1875000 * 2 = 3750000

So, you would put:

rate-limit input 10000000 1875000 3750000 conform transmit exceed drop

rate-limit output 10000000 1875000 3750000 conform transmit exceed drop

From the Cisco doc:

Burst size—Also called the Committed Burst (Bc)  size, it specifies in bits (or bytes) per burst how much traffic can be  sent within a given unit of time to not create scheduling concerns. (For  a shaper, such as GTS, it specifies bits per burst; for a policer, such  as CAR, it specifies bytes per burst.)

When extended burst is configured and this  scenario occurs, the flow is allowed to borrow the needed tokens to  allow the packet to be sent. This capability exists so as to avoid  tail-drop behavior, and, instead, engage behavior like that of Random  Early Detection (RED).

HTH,
John

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[atrevido43]

so what time period is the Burst allowed for?  5 seconds or 10 minutes or an hour?