Scheduler Functions

As described in Section Overview, Chimera supports automatically turning the impairments on and off with the configured distribution using a per impairment scheduler.

The scheduler is configured depending on the distribution type which is applied to the impairment. There are 2 types of distributions:

• Continuous distributions

• Burst distributions

Table 78 illustrates Bursty and Continuous distributions.

Table 78 Distributions overview

Continuous	Bursty
Random Burst	Fixed burst
Fixed Rate	Accumulate & Burst
Random Rate
Bit Error Rate
Gilbert-Elliot
Uniform
Gamma
Gaussian
Poisson
Step
Custom distribution

Notice that for latency / jitter, only the Accumulate & Burst supports a scheduler. If other distributions are applied to latency / jitter, only continuous mode is supported.

Continuous Distributions

For continuous distributions, the scheduler can work in 2 modes:

• Continuous: When started, the impairment is applied continuously with the configured distribution until it is manually stopped.

The example below illustrates how to configure the scheduler in continuous mode for drop with fixed rate distribution of 1.23%.

PED_SCHEDULE[fid,0] 1 0
PED_FIXED   [fid,0] 12300

• Repeat Pattern: When started, the impairment is applied with the configured distribution in a repeated pattern. First it will be applied for a configurable duration and then turned off. It will be restarted for every repeat period.

This is illustrated in Fig. 263.

Fig. 263 Scheduler function Repeat Pattern

The example below illustrates how to configure the scheduler for duration = 1.20 sec and a repeat period = 5.2 sec, applying drop with random rate distribution of 3.3421 %.

PED_SCHEDULE[fid,0] 1200 5200
PED_RANDOM  [fid,0] 33421

Bursty Distributions

The bursty distributions are characterized by being bursty by nature, i.e. they will automatically terminate if not restarted. E.g., a fixed burst of 8 packets will automatically stop after dropping 8 packets.

For bursty distributions, the scheduler can work in 2 modes.

• One-Shot: When started, the impairment will be applied for the duration of the burst. When the burst terminates, the impairment is turned off.

The example below illustrates how to configure the scheduler for in shot mode for drop with a fixed burst distribution of 10 packets.

PED_SCHEDULE  [fid,0] 1 0
PED_FIXEDBURST[fid,0] 10

• Repeat Burst: When started, the impairment will be applied for the duration of the burst. The burst will be restarted every Repeat period.

This is illustrated in Fig. 264.

Fig. 264 Scheduler function Repeat Burst.

The example below illustrates how to configure the scheduler to restart the Accumulate & Burst every 2.36 sec with a Burst Delay of 0.654 sec.

PED_SCHEDULE[fid,2] 1 2360
PED_ACCBURST[fid,2] 654000