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What is SIP trunk?

In simple words, it is a virtual communication channel between the provider (operator) and of IP-telephony (the office IP-PBX of the client). It allows connecting any number of telephone numbers. In turn, each of such number may have an unlimited number of channels (the number of simultaneous conversations on a single number).

SIP trunk for ringing uses SIP 2.0, VoIP telephony, described in RFC 3261 and its add-ons (RFC 2976, RFC 3262, RFC 3265, RFC 3428, RFC 3515, RFC 3903).

Having connected the SIP trunk from the telephony provider, the company does not limit itself in data exchange (voice, video, and chat), unlike traditional analog telephony. It allows abandoning the multi-pair physical cable lines connecting it with the urban PBX. Moreover, your provider providing an external number can be located territorially in another state.

The second type of SIP trunk is a virtual channel between two IP-PBXs, if necessary, physically spaced apart physically. This makes it possible to organize the total internal, numbered capacity of both PBXs and use common external lines for outgoing and incoming communications.

Each telephone number in the trunk is called and identified as a DID (Direct Inward Dialing), which is assigned to you by a VoIP telephony operator or VoIP wholesale providers.

Advantages of SIP trunks

The main advantage for the company from the shift from analog telephony to SIP trunks is:

  • Low subscription fee per channel and DID number. That means the subscriber fee for voice channels and DID numbers are significantly lower than the fee for the same number of analog lines.
  • The high quality of provided services. Digital data transmission protocols are used for the establishment of connection and voice, video transfer. This gives high quality of voice and high speed of the connection.
  • Saving single number with changing the office. This feature means that your SIP trunk is not tied to your office. You can move to another office, saving your previous number. Accordingly, you do not need to notify customers about the new number, change advertising, business cards and pay the operator for the installation of redirection and connect new numbers.
  • No need to purchase a VoIP gateway. SIP trunks save you from having to purchase and support VoIP gateways. Calls from the telephone network come directly through the SIP protocol. In addition, the lack of technology conversion (from analog to IP) provides a higher quality of communication.
  • The scalable capacity of channels. If you have increased the number of calls, you can quickly and easily add additional voice channels to an existing SIP trunk. Compare this with the time spent on ordering and laying additional analog lines, installing expansion cards and programming an analog PBX!