Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

Frame Relay LFI Calculations

OK So I know the formula for find the fragment size which is CIR * Delay / 8 but how do you figure out the portion for the map-class?

Say I have a 384k CIR how do I know what my Bc needs to be set too? I can’t find a clear explanation for this.

1 ACCEPTED SOLUTION

Accepted Solutions
Purple

Re: Frame Relay LFI Calculations

Hi,

Given a CIR of 384000bps and a Bc of 3840, the Tc is calculated as follows:

Tc = Bc/CIR = 3840/384000 = 0.01 seconds

0.01 seconds is equal to 10 milliseconds so that is quite correct.

Hope that helps - pls rate the post if it does.

Paresh

4 REPLIES

Re: Frame Relay LFI Calculations

You configure Bc to force the shaping interval (Tc) that you want. The formula is Tc = Bc/CIR. If your CIR is 384k and you want Tc to be 10ms then Bc would need to be 3840. Please see the following link for confirmation.

http://www.cisco.com/en/US/tech/tk1077/technologies_configuration_example09186a0080101210.shtml#17

Hope this helps. If so, please rate the post.

Brandon

New Member

Re: Frame Relay LFI Calculations

That is what I found already but if I divide 384000 by 3840 I get 100 not 10. Is Tc measured differently?

Purple

Re: Frame Relay LFI Calculations

Hi,

Given a CIR of 384000bps and a Bc of 3840, the Tc is calculated as follows:

Tc = Bc/CIR = 3840/384000 = 0.01 seconds

0.01 seconds is equal to 10 milliseconds so that is quite correct.

Hope that helps - pls rate the post if it does.

Paresh

New Member

Re: Frame Relay LFI Calculations

Dang I feel like an idiot. You are absolutely right. I kept saying Kilobits in my head when 384000 is bits not kilobits. :) Thanks for the clarification.

177
Views
0
Helpful
4
Replies