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Frame-Relay Traffic Shaping

Can somebody explain :

Frame relay CIR

Minumum CIR




I heard Tc is fixed 125 Ms now we can calculate Bc=Tc*CIR

But how to calculate Be=??is it CIR/8.

Community Member

Re: Frame-Relay Traffic Shaping


some explainations below, hope they help.

CIR (Committed Information Rate) The average rate at which you want to transmit.

This is the rate at which you want to send in periods of noncongestion.

MinCIR (Minimum CIR) The minimum amount of data to send during periods of congestion. This is usually what you get from the telco. MinCIR defaults to one-half of CIR.

Bc (Committed Burst) The amount of data to send in each Tc interval.

Be (Excessive Burst) The amount of excess data allowed to be sent during the

first interval once credit is built up. Transmission credit is built up during periods of nontransmission. The credit is the burst size. Full credit is typically CIR / 8.

Tc (Committed Rate Measurement Interval) The Bc / CIR time interval. The time interval shouldn?t exceed 125 ms (almost always 125 ms).

Interval Bc / CIR. The maximum is 125 ms, or 1/8 second.

Re: Frame-Relay Traffic Shaping


in addition to the other post, have a look at this link as well, which is (I think) an excellent presentation on Frame Relay Traffic Shaping:

Understanding Frame Relay Traffic Shaping



Re: Frame-Relay Traffic Shaping

In follwing configuration

Map-class frame-relay MYCLASS

frame-relay cir 192000

frame-relay bc 24000

frame-relay be 24000

frame-relay mincir 128000

frame-relay adaptive-shaping becn

By default Be value is =0 when Be=Bc or Be=2Bc In some examples .So what does it mean this value depends upon what.

Community Member

Re: Frame-Relay Traffic Shaping

Even though your config gives a Be value, it has to be earnt first. Your right with respect that Be defaults at 0 and this value will go up and down as you use your link.

The less you use your circuit the more credit that is built up so the more bursty traffic you will be able to send during your more busier periods (above the guarenteed rate (minCIR)).



Re: Frame-Relay Traffic Shaping

The TC is only 1/8 or 125ms for circuts below 650k. This value is reduced as the circuit speed increases.

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