VoIP is partially allowed in India and unless it involves tariff loss to the telecom operators it is considered a lawful means of communication. Computer to computer VoIP service is allowed but these services cannot be encrypted over permissible strengths without the approval of Government Authorities. Additional compliances such as an ‘Other Service Provider’ [OSP] Registration from the DoT may also be required for setting up VoIP communications at an Indian data centre.
On the question of logical partitioning, Indian regulations require that Voice over IP [VoIP] systems be physically separate from PSTN interconnect systems. Regulations of the Telecom Regulatory Authority of India [TRAI] require that voice traffic over the enterprise data network and the Public Switched Telephone Network [PSTN] must be strictly separated and no mixing of calls between the two networks can occur for the purpose of toll bypass.
While following TRAI regulations and avoiding toll bypass, a single-line phone should be able to reach outside VoIP [closed user group [CUG]] or PSTN networks, provided that the guidelines are met.