[OpenSIPS-Users] Is opensips a front end to asterisk?

[lists at grounded.net]

I've come across this project a few times but have been having a bit of a time confirming just what the project does. I thought perhaps the best way would be to join the list and ask.

My task is to put together a scalable asterisk based pbx system. Because the boxes will initially have more than they really should installed on them, we need to limit the number of users per box to perhaps 50. 

Right now, the plan calls for every box to have a second one for redundancy. I was planning on manually redirecting connections (for now) but it sounds like opensips could take care of a number of issues.

I have multiple providers (WANs) at one location but was thinking that for highest reliability, that I might have three locations to be safe unless there are better ideas.

One would be the location where the initial user connection is made, such as a proxy/load balancer.
Then, two separate physical locations and networks for redundancy. The front end could use both sites as needed but if something went down, could re-route users/sessions to the redundant location.

This of course is where my questions about opensips come in.

-From what I can tell, opensips could act as a pbx on it's own but it can act as a proxy/load balancer/gateway to asterisk systems as well. 

-If this is the case, would there be a way of creating a distributed environment, like as in a web server farm, making scaling quite easy.

-Does opensips handle only new incoming connections or could it actually move sessions from a down server to another which is still up?

-Would there be any control, or even any need depending on how the back end can be set up, by which to control which pbx/pair that someone registers to?

-Would I have some method of controlling how many people can register on any one box?

Thank you very much for this information as it will help to first understand what the project can do.

Mike