| |||
| 会话初始协议中继 (A mechanism for connecting the voice network of an enterprise to a service provider that offers public switched telephone network (PSTN) origination, termination, and emergency services without deploying PSTN gateways) | |||
| |||
| 会话初始协议中继 (A mechanism for connecting the voice network of an enterprise to a service provider that offers public switched telephone network (PSTN) origination, termination, and emergency services without deploying PSTN gateways) | |||
