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New Contributor

policies explanation

- Commited rate

- Commited burst

- peak rate

- peak burst

- excess burst

- one-rate or two-rate rate limit

thank's

3 REPLIES 3
Occasional Contributor

Re: policies explanation

Hi Kisito,

I'm not familiar with how these apply to UAC, but in general terms, what you're describing is a form of two rate three colour marking (with some bursts).

Imagine that you define two rates (Rc and Rp). If we're talking leaky bucket mechanisms, then the rate is related to the size of the hole in the bucket (i.e. the rate at which traffic can be transmitted).

While traffic is being transmitted at a rate below Rc, that is considered to be within the Committed Rate.

Between Rc and Rp the traffic is considered to be above the Committed Rate but within the Peak Rate.

Above Rp, the traffic is considered to be in excess.

Going back to the leaky bucket mechanism, bursts are usually used to define the size of the bucket. So, you can fill the bucket up to the maximum burst size (i.e. instantaneously, you receive N packets, which fill the bucket. From that point on, you will empty the bucket at Rate and you can refill it at Rate, but if you exceed Rate at all, the packets are dropped. If you go below Rate for a period, then you have some of your burst back).

Committed burst, Peak burst and excess burst are just the burst sizes that are available while you are in each of those states with your general traffic flow.

With two rates, you can effectively get three colours (or classes) If Actual Rate = Ra, you have

Ra < Rc = within Committed Rate

Rc < Ra < Rp = within Peak Rate

Rp < Ra = within Excess Rate

With one rate, you can only create two colours (or classes)

Ra < Rp = Within Allowed (peak) Rate

Ra > Rp = Within Excess Rate.

Hope that helps.

Guy

New Contributor

Re: policies explanation

Thank's Guyi think, i understood. But I'd like a clarification

>but if you exceed Rate at all, the packets are dropped

What would happen if the packets are dropped? if I surf the Web, and packets are dropped. My connection is interrupted? My connection is slow?

Thank's

Occasional Contributor

Re: policies explanation

Hi Kisito,

The answer is "it depends" :-)

If you are on a voice call and the packets are dropped, you're likely to hear a "click" or a pause. If a large number of packets get dropped, eventually the call will be dropped.

If you are on a web browser looking at a web page, then the TCP session will detect the packet loss and the packet will be retransmitted. If there is sustained loss, then you'll most likely see the page will be delayed in coming up on your browser.

If you're talking about email, the chances are that you won't ever notice. It will just be handled in the background when the congestion has gone away.

Rgds,

Guy