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What is SIP Trunking ?

SIP (Session Initiation Protocol) is the protocol used by VoIP (Voice over Internet Telephony) systems to manage the VoIP phone calls. Because VoIP calls work differently from ordinary circuit-switched phone calls, different protocols are used to accomplish basic tasks such as establishing and terminating phone calls. SIP trunking is the method used when the VoIP network has to communicate with the Public Switched Telephone Network (PSTN).

If your VoIP system is used only internally, no SIP trunking is needed, because the PSTN is not a factor. But in reality, most VoIP installations are meant to seamlessly replace conventional telephony, and using it only for internal calls would not be taking full advantage of the power of VoIP. SIP trunking is what allows you to use your VoIP phone to make a phone call to someone outside of your enterprise, through the PSTN. You can think of SIP trunking as an adapter between VoIP and the PSTN.

SIP Trunking

SIP trunking starts at the IP PBX. The PBX should include a SIP trunking interface. Although an IP PBX is preferred, an analog system can be used instead if an Integrated Access Device (IAD) is added. Through this interface, the PBX is attached to a firewall. The firewall must be one that supports SIP, to facilitate SIP traffic. Outside the firewall, the enterprise is then connected to the Internet via a VoIP service provider. On their end, the VoIP service provider will have an interface to the PSTN, although the enterprise need not be concerned with that. The end result is that the person using a VoIP phone is able to call any number, anywhere, whether it is on a VoIP service or not.

Ultimately, SIP trunking eliminates the need to deploy alternative technologies such as PSTN gateways or PRIs (Primary Rate Interfaces). In general, SIP trunking is a far less costly solution, highly efficient, and easier to manage, since fewer pieces of hardware are required. Since SIP trunks can be purchased incrementally, cost savings is increased compared to PRIs, which must be purchased by 23 channels at a time.

If an enterprise is using a hosted VoIP solution, SIP trunking is unnecessary. Should an enterprise make the decision to use an on-premises VoIP solution, then SIP trunking should be considered.

Submit a SIP Trunking VoIP quote request today for your business and save up to 80% on your monthly phone bills.

Business SIP Trunking Service

Businesses are saving up to 80% on their monthly phone bills by switching to a SIP Trunking VoIP phone service. Receive FREE SIP Trunking service quotes by completing the short form below, takes less than 1 minute to complete. Alternatively, use our Popular Business SIP Trunking Providers comparison table below to select a SIP Trunking service provider.