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Cisco BTS 10200 Softswitch Troubleshooting Guide, Release 5.0.x
OL-8723-19
Appendix C Overload Control
Detecting Overload
Detecting Overload
In the detection phase of Overload Control any one of three factors can have the highest MCL. This value
dictates the MCL for the entire system. The three factors are:
•
Critical processes CPU usage—The olm.cfg configuration file has UNIX “nice” values. BTS uses
these values to calculate CPU utilization for critical processes over a small period of time (2 seconds
minimum). Values for each process should be at or below the set value.
•
Critical process queue lengths—The olm.cfg configuration file has critical queue lengths for BTS
processes like BCM, MGA, SGA, SIA, ISA and H3A. You can define multiple (32 factors total)
critical queues for any BTS process. BTS monitors the usage proportion of each critical IPC queue.
•
IPC buffer pool usage—BTS monitors the proportion of available buffers in the IPC buffers pool,
this reflects MCL: the higher the usage, the greater the congestion.
BTS detects its own MCL in five levels:
•
MCL0—No congestion and no need for any abatement.
•
MCL1—Mild congestion. Call rejection starts as configured in olm.cfg.
•
MCL2—Moderate congestion. Call rejection increases as configured in olm.cfg.
•
MCL3—Severe congestion. Call rejection increases still more as configured in olm.cfg.
•
MCL4—Emergency congestion. BTS rejects all calls including emergency calls.
Computing MCL
BTS computes factor levels by calculating averages for each factor. The rate of sampling (number of
slots) can be configured per factor (3–10 slots). The MCL is set according to a factor level. In
thresholds are set to 70, 80, 90, and 95 percent.
Table C-2
MCL Thresholds
Onset /abatement thresholds
Factor Level
MCL
-
0–69
MC0
level_1_threshold = 70
70–79
MC1
level_2_threshold = 80
80–89
MC2
level_3_threshold = 90
90–95
MC3
level_4_threshold = 95
95–100
MC4