Which system should I use for a Callcentr with a 100 concurrent call system?

Question

Asterisk

Colleagues, good afternoon.
It is very likely that the task of implementing a telephony system for Callcentr with an automatic dialing system will have to be solved.
What is the essence of the task: the system calls the subscriber to the PSTN, and then connects to a free operator.
It is planned to use 100 operators, which means there will be 100 simultaneous connections. I always used Asterisk for such tasks with a set of self-written scripts (via AMI, Asterisk AGI), but I didn’t have to build systems of this scale.
On all implemented systems there were up to 25 simultaneous connections at the peak.
In this regard, the question is, how reliable is such a solution, in principle, on * ? What are the alternatives (paid software)
What do you like about Asterisk: unlimited flexibility, writing your own scripts, writing your own reports (php, javascript).
What confuses Asterisk : It is not clear how to scale the system with increasing load, is it enough to buy a new server with a lack of load, or Asterisk will still stall due to architectural limitations.
PS I have seen systems with 800 concurrent calls, but apparently the core of the system has been deeply redesigned

Answer 1

Indeed, 100 operators is not equal to 100 lines. You can use an effective solution based on a cloud-based PBX - then your channels will not be used at all, but only the channels of this PBX are used. For example, the Virtual Office Tools virtual PBX can do this, there is even a ready-made solution for Call Centers . As far as I know, it easily supports up to 2000 connections during peak loads!

Answer 2

From direct call center solutions - Oktell, Avaya (here it will be possible to bury money in the sand - the solution is insanely expensive). Of the free ones, there is a ready-made platform built on the same components that Sergey wrote above - it is called kazoo (Kamailio, freeswitch). There is a connection to call center chips - there are queues, agents, etc. Rich API, but this part is not fully developed (there is no mechanism for determining the operator's busy time). Calls can be queued and serviced by operators. Agents can be in multiple queues at the same time. You can make outgoing calls and bridge them with operators (here you will need to script a little using the API).
All systems scale very well and hold high loads.
If there is no money at all - dig from the side of freeswitch or kazoo. There is some money - take Oktell.
You can rent virtual PBXs (there are also a lot of systems - in Russia Mango, Zebratelecom, the same Octell).
If suddenly by chance you have several million - take Avaya.

Answer 3

100 operators does not always equal 100 concurrent connections, usually only at peak times.
If you need Asterisk scalability, dig towards OpenSER, Kamailio in conjunction with Asterisk.
There is an alternative to Asterisk - FreeSwitch is called. The platform is also not bad, it is also often used in conjunction with Asterisk to solve a number of problems.

Answer 4

If the question arises of further increasing the number of operators, it’s better to move towards soft switches, for example, as mentioned above, Freeswitch, since * is still a PBX with the “install, configure, forget it for n-years” approach.
From my experience I can say that with an increase in load, there will still be problems and all load management, call distribution, etc. in such cases should be moved to your application that works in conjunction with telephony.Then the possibility of horizontal scaling is no longer ghostly and predictable