Asterisk termination to PSTN question

we are working on a 5000 line asterisk arrary to get terminated to PSTN. I am new to this field and so far my understanding is

  1. I need a SBC to take care of asterisk SIP NAT issues to communiate with VoIP terminator.

Some one told me I dont need SBC at all and asterisk takes care of all this.

Can anyone provide some info on this or direct me to a documentation?

thanks
Sid

Who is SBC?

If array = ext lines then yes
If SBC = PBX then * is a PBX