text: EarthLink offers VoIP service (MacCentral) MacCentral - Internet service provider (ISP) EarthLink Inc. on Tuesday announced the launch of EarthLink Free Online Calling, a Voice over Internet Protocol (VoIP) service that enables their Mac and PC to make calls over the Internet free of charge. Based on Session Initiation Protocol (SIP), the service works with a Mac or PC equipped with a headset or an Analog Telephone Adapter (ATA). Users can make unlimited calls to other SIP users, and can also listen to voicemail via e-mail. The service also offers an online calling log and online account management. ...