VS.RAB.FailEstabCS.IubFail increased too much only in 1 of 3 carriers in site when Iub is the same

The VS.RAB.FailEstabCS.IubFail increased too much only in 1 of 3 carriers in site. Why on only 1 carrier when Iub is the same for whole site?

Is the number of users the same in all carriers?

this counter has no relation to iub congestion

it will be related to some channels not enough on configuration

What is iub? Iub issue effects on site?!

Which channels do you mean, and which configuration ?

I don’t think so. We can configure the limit of users on every carrier…but the user behaviour is stochastic in nature

Try to balance the users for all carriers. Usually we configure 4 carriers and this never happens.
The Iub is ATM or IP?