Microsoft has certified Interoute as the first European service provider to supply Session Initiation Protocol (SIP) trunking for Microsoft Office, and thus enabling business-class unified communications to compete directly with Skype for corporate users. Enterprises looking to benefit from business quality VoIP can now use Interoute One to make free computer to computer calls and dramatically cheaper telephone calls from and to virtually any communications device. Businesses can also avoid international roaming charges on all other calls, enabling international communication at a fraction of the price of traditional telephony.