SIP trunk providers are VoIP providers who utilize the Session Intiation Protcol.
Sip Trunk Provider Overview
SIP trunking is a method used when the VoIP network has to communicate with the PSTN.
SIP Trunk Providers – A Closer Look
SIP trunk providers utilize SIP, pure IP connections that can offer your company significant cost savings by eliminating the need for local PSTN gateways, costly ISDN BRIs (Basic Rate Interfaces) or PRIs (Primary Rate Interfaces).
SIP Trunk Provider – AVOXI
AVOXI can meet your SIP trunking needs, as well as your SIP phone requirements with softphones or Polycom IP phones.