rate-limit command

[Stevep]

Todd,
I'm looking at this command on a Cisco 7200 and wondering what it does:

rate-limit input 3072000 2000000 2000000 conform-action transmit exceed-action drop
rate-limit output 3072000 2000000 2000000 conform-action transmit exceed-action drop

My understanding is that it rate shapes the interface to 3 Mbps normal, 2 Mbps normal burst and 2 Mbps max burst, while dropping anything that exceeds. Is the 2 Mbps normal burst above the 3 Mbps normal rate? And if so, how is the max burst rate figured into the problem?
Is there a limit to the burst rate allowed? Can a customer buy 8Mbps bandwidth and have it configured to allow a burst up to 15 Mbps ?

[lammle]

You have to control the burst...

You can purchase a 1k link and burst to OC12 speeds if you are permitted to.

Normal burst... I don't know if you can really determine a "Normal Burst".

I would think that the burst would be dependant on the type of traffic you are sending.

For instance ICMP traffic has a fixed packet size, right? There is not going to be a burst, right?

TCP traffic will try to take advantage of all the bw available and control lost packets with windowing, right?

UDP will try to take advantage of all the bw disregarding windowing, right?

So which one is normal?

I believe that is why in frame relay you mark certain frames with discard eligible so that if the ISP sees that you are bursting above "their configured burst" they will first drop the discard eligible frames instead of dropping random frames.