Balancing outgoing calls via trunk

How to balance proceeding calls between trunks
We have 6 trunks / The provider allows you to make no more than 5 calls per minute
How to balance trunks by the amount of time?
Thank you very much!


You get a SIP Proxy/SBC that is designed for that because Asterisk is not. It cannot control calls by amount per seconds.

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Why can’t he just add all trunks in his outbound route? And once the first trunk becomes busy it’ll try the next one…

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Because thats not what the OP asked for. It is also not load balancing. While I think it is more a 5 per second limit as that is what CPS is, the provider isnt allowing more than 5 new calls at a time. This is not something Asterisk does.

I’m not in the line for that long, but I never heard of such a limitation. I only heard about concurrent calls. Why would a vendor now allow an amount of calls per seconds?

If that’s the case, then I think you are right, only a SIP Proxy/SBC would be able to do that, but if it’s a ‘5 concurrent calls’ limitation then adding all trunks to the outbound route would work.

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It’s called Calls Per Second (CPS) and it’s a limitation at the provider/carrier level. Carriers/Providers look at numerous factors for calls and sessions. The formula for that is ASR x ACD x CPS x .6

ASR = Average Seizure Rate (Answered Calls) - This is generally averaged at about 80-85%. The other 15-20% account for actual Busy’s, bad numbers, etc.

ACD = Average Call Duration - How long is the average call.

CPS = Calls Per Second

So if I was to send 5 calls per second to my provider with the idea that 80% are going to be answered and take 5 minutes, the maths are 80 x 5 x 5 x .6 = 1200 Active Calls.

This type of worry is generally reserved for those doing rather high outbound call volume such as an actual voice provider (at some level) or outgoing sales campaign people. The 5 minute marker was being generous as most calls in an outbound campaign are either to bad numbers, voicemails or hung up on pretty quickly.

The average SIP trunk user isn’t sending 5 CPS, they generally send 1 call per second so this isn’t really a consumer level service item they put out there. Only time is when the SIP trunk provider has some sort of “wholesale” structure.

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