Specifications

Sample Scenarios 69
4.1.9 CIR Monitoring
CIR monitoring is an optional frame relay feature that you can set for each
interface to prevent the router from creating congestion conditions in the FR
network. CIR monitoring allows the IR for a VC to range between the configured
minimum and maximum IR. CIR monitoring is configured with the
enable
cir-monitor configuration
command and is disabled by default. CIR monitoring,
when enabled, overrides congestion monitoring. You can also dynamically enable
and disable CIR monitoring using the
enable cir-monitor and disable cir-monitor
console commands.
4.1.10 Congestion Monitoring
Congestion monitoring is an optional feature, set per interface, that allows the
VIR of VCs to vary in response to network congestion. The VIR assumes values
between the minimum IR and a maximum IR of the line speed. Congestion
monitoring is enabled by default. It can be disabled with the
disable
congestion-monitor
configuration command and re-enabled with the enable
congestion-monitor
command. You can also dynamically enable and disable
congestion monitoring using the
enable congestion-monitor and disable
congestion-monitor
console commands. CIR monitoring, if enabled, overrides
congestion monitoring. If both CIR monitoring and congestion monitoring are
disabled, the VIR for each VC on the interface is set to the line speed and does
not decrease in response to network congestion.
Figure 38. Frame Relay CIR Monitoring and Congestion Monitoring
4.1.11 Discard Eligibility (DE)
The frame relay network may discard transmitted data exceeding CIR on a PVC.
1.5Mbps
64kbps
64kbps
64kbps
CIR=16kbps
0
10
20
30
40
50
60
70
80
Time
Information Rate
CIR monitor
enable
CIR monitor
disable
CIR=16
12%inclease
CIR monitor : enable
MIR=Line Speed=1.5bps
CIR monitor: disable
BECN=1
25% decrease
25% of CIR=4kbps
2212 HQ
IBM 2212
IBM 2212
IBM 2212
IBM 2212
IBM 2212
2212 HQ Information Rate and Time
BECN=0
MIR=(Bc+Be)/Tc=64Kbps