Friday, October 16, 2009

Frame Relay Traffic Shapping Terms

I was reading about traffic shaping & policing and the acronyms in the book they were as clear as mud, but now Ive written them down and understand them they are really really simple. I put a few formulas on for them aswell, but havnt checked them so please correct me if im wrong, oh and I have presumed that you are attempting to traffic shape to the CIR.

Tc – This is a time interval in milliseconds when a Committed Burst (Bc) can get sent. Usually Tc = Bc / CIR

Bc – Committed Burst this is the amount of data in bits which can bet sent every Tc. Usually Bc = CIR / Tc

Be – Excess Burst is the number of bits the Bc can be exceed by if no data has been sent if no data has been sent in previous Tcs. EDIT: As commented by Jeriel Atienza the formula is Be = (Ar – CIR) * Tc/1000

CIR – Committed Information Rate this is the bandwidth of a link or VC in bps which the Service Provider guarantees to provide. Quite often the CIR is lower than the full capabilities of a link which is the main reason why traffic should be shaped & policed. CIR = Bc * Tc

Shaped Rate – This is the rate of the traffic which is being shaped in bps, it normally matches the CIR. Usually CIR = Shaped Rate!

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