In some previous article, I explained how to configure a Frame-Relay Hub and Spoke network environment. Based on that example, I will show you today how you can implement traffic shaping over the Frame-Relay Hub and Spoke.You can have a look at the topology that we will use here.
A note from the beginning. Since I do not have a traffic generator, I cannot really prove that the traffic is shaped, you’ll just have to believe me or to try on your own.
Let’s assume that we have an excessive amount of packet loss between R1 and R2 from the topology and the R1 is overwhelming the Frame-Relay connection to R2. R1 has a port speed of 512Kbps and we have to assure that R1 is sending traffic at 384Kbps. In case that the connection get congested R1 should throttle down the CIR to 256Kbps. R1 should be permitted to burst in case it accumulate credit and to minimize the delay due to serialization the interval (Tc) should be 10ms.
-we have a CIR of 384Kbps; CIR = 384Kbps
-when congested CIR throttle down to 256Kbps; minCIR = 256 Kbps
-time interval is 10ms; Tc = 10ms
-burst size, based on the date above is 3840 bps; Bc=CIR*Tc=384000*0.01=3840; (note that CIR has to be in bps and time in seconds)
-also R1 is allowed to send burst in excess in case of accumulated credit, so excess burst is 1280 bps; Be=(AR-CIR)*Tc=(512000 – 384000) * 0.01=1280 (AR is the port speed 512Kbps)
After we have gathered all this data let’s proceed to the Cisco device configuration. Please see the presentation below: