[Asterisk-Users] Using Asterisk as simple proxy

[junk at lexon.ws]

I was thinking about this.
Configure asterisk to use SIP provider.
Set extensions, etc.

Give other parties outside (my network) ids and passwords so they can
register with asterisk assuming that there is no firewall on their side.
This configuration would support up to 10-15 clients.

Would asterisk work in such configuration?
Do I need an extra software?
Do I need a separate proxy for this?

I am aware that asterisk is not a proxy, but something between.
But if it works internally, would not it work also with outside clients.

Lets also assume that I have enough bandwith.

Thanks