Are there alternatives to SIP Trunking?
<p>I'm not sure if this is a stackoverflow question but,</p>

<p>To my understanding SIP Trunking is a VOIP protocol that 
allows a person to call through a phoneline and than some datacenter will convert that into an internet call. </p>

<p>My question is, is it the only protocol? Are there other protocols that can be used for VOIP?</p>