What are CIR and PIR?

2024-01-18 09:01:44 SPOTO Club Cisco 4869

Table of Contents


In frame relay networks, a committed information rate (CIR) is considered to be the bandwidth, which would be expressed in bits per second, which would be associated with a logical connection in PVC (permanent virtual circuit). Frame relay networks are believed to be the digital networks in which different logical connections share the same physical path, as well as some logical connections, would be given higher bandwidths than others. For instance, a connection would be conveying a high proportion of video signals, which would be requiring high bandwidth, could be set up for certain workstations in a company or on a larger network as well as other connections which would be requiring less bandwidth could be set up for all other workstations. Utilizing statistical multiplexing, FRADs (frame relay assemblers and dissemblers), the devices that would be interconnecting to the frame relay network, managing the logical connections so that, for instance, those with the video signals and higher CIRs gain more use of the paths. Because the CIR would be defined in software, the network's mixture of traffic bandwidths could be redefined in a relatively short amount of time. Before we discuss the PIR, if you wish to have much more knowledge about the CIR, you should gain the study dumps, which would be offered at the SPOTO Club


Peak information rate or shortly known as the PIR is a burst-able rate set on routers and/or switches that would be allowing throughput overhead. Related to CIR (committed information rate) which is a committed rate speed capped/guaranteed. For instance, a CIR of 10 Mbit/s PIR of 12 Mbit/s would be allowing you to gain access to 10 Mbit/s minimum speed with burst/spike control that would be allowing a throttle of an additional 2 Mbit/s; this would be allowing for data transmission to "settle" into a flow. PIR would be defined in MEF Standard 10.4 Subscriber Ethernet Service Attributes. Excess information rate or shortly known as EIR is the magnitude of the burst above the CIR that means that EIR plus CIR is equal to PIR. Maximum information rate or shortly known as MIR, in reference to broadband wireless which would be referred to maximum bandwidth the subscriber unit would be delivered from the wireless access point in kbit/s. When you would be gaining a subscription from an ISP, you would be paying for the bitrate that you would desire, for instance, 5, 10 or 20 Mbit. The fiber connection, however, would be capable of sending traffic at a much higher bitrate, for example, 100 Mbit. In this case, the ISP will “limit” your traffic to whatever you would be paying for. The contract that you would be having with the ISP is often known as the traffic contract. The bitrate that you would be paying for at the ISP is often known as the CIR (Committed Information Rate). Limiting the bitrate of a connection would be done with shaping or policing. The difference between the two is that policing would be dropping the exceeding traffic and shaping would be buffering it. The logic behind policing would be completely different than shaping. In order to check if traffic matches the traffic contract the policer would be measuring the cumulative byte-rate of arriving packets and the policer could take one of the following actions:

  • Allowing the packet to pass.
  • Dropping the packet.
  • Remarking the packet with a different IP or DSCP precedence value.

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