Committed information rate
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Committed information rate or CIR in a Frame relay network is the average bandwidth for a virtual circuit guaranteed by an ISP to work under normal conditions. At any given time, the bandwidth should not fall below this committed figure. The bandwidth is usually expressed in kilobits per second (kbit/s).
Above the CIR, an allowance of burstable bandwidth is often given, whose value can be expressed in terms of additional rate (known as the Excess Information Rate, EIR) or as its absolute value (Peak Information Rate, PIR). The provider guarantees that the connection will always support the CIR rate, and sometimes the EIR rate provided that there is adequate bandwidth. The PIR, i.e. the CIR plus excess burst rate (EIR), is either equal to or less than the speed of the access port into the network. Frame relay carriers define and package CIRs differently, and CIRs are adjusted with experience.
CIR is derived from the term Committed Data Rate or CDR, and is used in similar fashion, but refers also to voice and non-data packets and not only to data packets as in CDR.
- The relationship is: PIR = CIR+EIR
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