Opportunity for ISPs and ITSPs. It can be used to increase the value of residential Internet or as a defensive move against competitors offering bundles.
SIP Trunking
SIP trunking is a B2B offer for businesses. Usually will be in the form of a certain amount of concurrent calls and phone numbers.
Click Here
Cloud PBXs
Cloud PBS is an opportunity for ISPs, ITSPs, MSPs and ISV's
EN 
PT