Any good SIP server software or hardware that can be implement out of the box and easy to use?

What's SIP ?

SIP is Session Initiation Protocol.

Used for VoIP ;)

http://dictionary.reference.com/search?q=session%20initiation%20protocol

Yeap Session Initiation Protocol, having a big headache the good ones cost more than 10k the free ones needs to be configure intensively, looking for a middle of the line product.