10-30-2009 12:54 PM - edited 03-06-2019 08:24 AM
I'm trying to understand how can the average shaping have a BE parameter? I thought average shaping does no allow for bursting.
shape {average | peak} cir [bc] [be]
Any help would be greatly appreciated.
Thank you,
TK
10-30-2009 01:04 PM
Tomasz,
First off, you must know what the paramters are.
- Line Rate/Access Rate. Let's say AR is 512 Kbps.
- CIR. Let's say CIR is 256 Kbps. This is what you want to shape.
- TC. Interval Time that you can send the packets. It's 1/8 second if BW of the link is under 768. If I recall.
- BC = Cir x TC
- BE = (AR - CIR) x TC. Yes. You can burst it if you didn't send packets in some time interval .
HTH,
Toshi
12-02-2009 12:34 PM
Average only includes Bc while peak includes Bc+Be. In other words, if you use average then only CIR and Bc are used.
If Bc is in bits, use the following to calculate the Bc value.
Bc=CIR * (ms/1000)
Example:
4ms is the minimum Tc value in IOS, which means CIR * .004 is the lowest value you can use for Bc.
10Mbps would be the following using a 4ms Tc
10000000 * .004 = 40000
shape average 10000000 40000
The lower the Tc the more smooth the traffic will be (shaped). This can also drive the CPU up a bit higher, so you should use caution if your CPU is already running high.
HTH
--Tim
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