5000 concurrent calls

is asterisk capable enough to support 5000 concurrent calls? the requirement is that each call needs to be answered, the caller is engaged with an IVR, and then the call is transferred. transcoding is also involved as the end points might not be using the same codecs every time. can asterisk be used for this purpose? if so, how many asterisk servers are needed? what should be the resources of the server? will a proxy server be needed to be used with asterisk configuration? and is asterisk the only solution available?

That’s so far outside the size range for which I have experience that I won’t try to be quantitative. I suspect that is true for most or everyone else here.

You gave clues that you are talking about a SIP system, but didn’t say so. You will need around 1Gb/s of total network throughput.

Really though, something like this needs a lot of background on the application as a solution based on the abstract problem will need to make lost of worst case assumptions. One would also need to know about the upstream and downstream environments. An example of something that might make a big difference is if the IVR stage is short and the upstream will accept a re-direct to the final destination.