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SIP/SIP Trunking

What is SIP/SIP Trunking?

A SIP Trunk is primarily a concurrent call that is routed over Citynet's IP backbone using VoIP technology. SIP Trunks are used in conjunction with an IP-PBX and are thought of as replacements for traditional PRI or analog circuits. The popularity of SIP Trunks is largely due to the cost savings of SIP, along with increased reliability.

The Session Initiation Protocol (SIP) is widely used for controlling multimedia communication sessions such as voice and video calls over Internet Protocol (IP). The protocol can be used for creating, modifying and terminating two-party (unicast) or multiparty (multicast) sessions consisting of one or several media streams. The modification can involve changing addresses or ports, inviting more participants, and adding or deleting media streams. IT allows for video conferencing, streaming multimedia distribution, instant messaging, presence information, file transfer and online games.

For those organizations wanting to make full use of their installed IP-PBXs and not only communicate over IP within the enterprise, but also outside the enterprise, a SIP Trunk provided by Citynet to connect to the traditional PSTN network is a great solution. A SIP trunk allows you to replace these traditional fixed PSTN lines with PSTN connectivity via our SIP Trunking Service. This service allows those businesses that have a PBX installed to use Voice-over-IP (VoIP) outside the enterprise network by using the same connection as the Internet connection.

SIP Trunking Benefits

Many enterprises are already using VoIP, however, many are only using it for communication on the enterprise LAN. In this scenario VoIP is only being used as a one-to-one replacement for traditional wireline telephony. For all calls made to the outside of the LAN a PSTN gateway on the enterprise edge is used. These businesses realize a solid return on investment (ROI) just by lowering administrative costs and the costs associated with calls made within the company. With SIP trunking, the potential for ROI is far greater because SIP trunking takes the idea of VoIP a step further, beyond this LAN application. The full potential for IP communications can be realized only when the communication is taken outside of the corporate LAN. 

  • Eliminates costly BRIs (Basic Rate Interfaces) and PRIs (Primary Rate Interfaces) subscriptions
  • No need to invest in PSTN gateways and additional line cards as you grow
  • Edge devices offer low investment path in adding new lines as they are typically cheaper per line than the corresponding PSTN gateway
  • Optimal utilization of bandwidth by delivering both data and voice in the same connection
  • Maximum flexibility in dimensioning and usage of lines as you avoid having to buy capacity in chunks of 23 (T1) or 30 (E1) lines
  • Flexible termination of calls to preferred providers; calls to anywhere worldwide can be made for the cost of a local one

Advantages of SIP Trunks Over Analog Circuits

  • SIP Trunks are less expensive than analog circuits; yet they maintain the same service/line quality that businesses expect.
  • Long-distance termination charges associated with SIP Trunks are also less expensive than traditional analog or TDM rates.
  • Provide increased reliabiilty.

Advantages of SIP Trunks Over PRIs

  • SIP Trunks realize their primary benefit over PRIs from cost savings.
  • SIP Trunks can be purchased in increments of one; PRIs have to be purchased in increments of 23 channels

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