Throughput Management

PBXs are not designed to handle the volume of throughput generated by a predictive dialer.

Take, for example, 300 agent stations with 600 trunks. In this set-up you can expect Softdial CallGem™ to dial around 30 calls per second. With varying dialing conditions throughout the day, this might peak at 150 calls per second. If you only have a PBX with a rating limit of 40 calls per second then you will encounter problems.

When dialing, Softdial CallGem™ sends a Call Initiate [CI] message, requesting the switch to dial the number. If there are resources available then the number will be dialled. However, if all the resources are currently being used then the number will be put in a queue (consisting of numbers to be dialed). When resources become available, the number will be dialed and a Delay Notification [DN] message is sent back to Softdial CallGem™.

From V9.2.0.18 - Softdial CallGem™ makes launch attempts at whatever interval is necessary to keep agents busy. The maximum number of simultaneous outbound calls that can be supported will be determined by the number of trunks that are available but this may be reduced depending on restrictions imposed by a local gateway or the network itself. This may cause problems for legacy PBX and central office switching equipment. In order to support working within the constraints imposed by the local telephony gateway, or the local exchange company, the Calls per Second (CS) parameter in the Trunks Open [TO] message provides a means to set a throttle to limit the number of call launch attempts in a given second.

Softdial CallGem™ deals with limiting capacity by tenant / campaign, so if a tenant is at capacity, Softdial CallGem™ will defer launch of calls until there is free capacity for that tenant or campaign.

Call launch rate throttling may be specified in Softdial Telephony Gateway™ using the maxCallsPerSecond element in the STG configuration file.

The value specified is used in the Calls per Second (CS parameter sent to Softdial CallGem™ in the Trunks Open [TO] message.

With TDM networks where network capacity is not normally an issue, setting launch rate throttling is not a normal dialer tuning exercise. You should only constrain launch rates when the call launch rate has been verified as being a source of problem, and only with the prior agreement of Sytel.

Most vendors quote ability to handle call launches in busy hour call attempts (BHCA). As a rule, if you need to implement launch rate throttling, you can take this value, divide by 3600 and round up to an integer, then use this value to limit the call launch rate.

For information on establishing appropriate call launch rates when using SIP Trunking, see Telephony Issues.

Launch rate limits, if set incorrectly, can and will impact call center performance adversely. The effects of throttling can be observed using Softdial Sim (see Demonstration of Softdial Contact Center™).