[Asterisk-Users] What route do diverted SIP calls travel?

[Andy Burns]

If I have inbound SIP calls arriving from a provider's gateway to an 
asterisk server on my LAN, which then routes the call back out via the 
provider's gateway to a PSTN number, once the call is answered do all 
the voice packets pass through my asterisk PBX, or is SIP intelligent 
enough to patch the two PSTN ends of the call direct to each other going 
only via two ports on the provider's gateway?