Routing

Hi

I want to creat policer to limit traffic to 1mb on one interface of J-6350. Below is my configuration:

policer rate-limitor-policer {
    if-exceeding {
        bandwidth-limit 1m;
        burst-size-limit <>;
    }
    then discard;
}

But I am confused about burst-size-limit. Can any one explain this parameter in simple words and how to calculate this value for 1mb traffic?

Many thanks in advance

To determine the burst parameter, use this equation:

burst = (rate [bps]) * 0.00025 [sec/interval]) or (maximum packet size [bits]), whichever is greater.

On your case if you want to calculate the minimum burst value needed to sustain a rate of 1mbps on an ethernet network, the rate is defined as 1mbps and the maximum ethernet packet size is 1518 bytes. The equation is:

burst = (1,000,000 bps * 0.00025) or (1518 bytes * 8 bits/byte) = 250 or 12144.

The larger result is 12144, which you round to 13 kbps.

Hi Masood

Thanks a lot for reply.

1- But when we congiure burst-size-limit this parameter should be in bytes.

2- Other thing is that the formula should be burst = (rate [bps]) * 0.00025 [sec/interval])  OR burst = (rate [bps]) * 0.0025 [sec/interval])

3- In Juniper document i read it was saying the minimum burst-size-limit should be the 10 times MTU and recommended value is calculated from the below formula:

burst = (rate [bps]) * 0.005 [sec/interval])  and result of this should be divided by 8 to convert answer in to bytes.

I really confused 😞 what burst-size-limit parameters specifies? its rate above than 1mbps which traffic can get or some other thing?

Many thanks in advance

Yeah, it should be in bytes. I believe bits/bytes conversion is not the problem. So if you got the bits you got the bytes 🙂

There are two ways to calculate burst size. So you either go one of two ways – MTU of the traffic on the interface by 10 (For example, the burst size for an MTU of 1500 would be 15,000 bytes) or burst = (rate [bps]) * 0.00025 [sec/interval]). You can now choose whichever method suits you best 🙂

Thanks masood