What does a SIP trunk do?

A SIP trunk, or Session Initiation Protocol trunk, is a telephone technology that supports Voice over Internet Protocol (VoIP), enabling businesses to make voice connections over the Internet.
A SIP trunk transmits calls as data and uses a packet-switched model to make connections.

More enterprises are adopting SIP trunking technology these days to reduce costs, enhance productivity and improve enterprise telephony capabilities. But what does a SIP trunk do, exactly, and how does it provide advantages to an organization? Here’s a short download on “What does a SIP trunk do?” that offers some answers.

A SIP trunk, or Session Initiation Protocol trunk, is a phone system connection type that uses SIP and Voice over Internet Protocol (VoIP) to deliver voice services over the Internet. A SIP trunk relies on Ethernet or fiber connections to transmit voice calls as data, using a packet-switched model to make phone connections.

What does a SIP trunk do vs. a PRI trunk?

While a SIP trunk provides a virtual connection to the Public Switch Telephone Network (PSTN), a PRI trunk provides a physical connection using copper wire – usually a T-1 line in the U.S. Each line can only accommodate 23 simultaneous calls, requiring larger companies to add additional PRI lines at an additional cost. With a SIP trunk, on the other hand, lines can be ordered in any increment and adding lines is as easy as calling a provider to purchase more virtual connections.

What does a SIP trunk do to improve scalability?

While adding more PRI lines requires new infrastructure that can take days or weeks to deploy, adding or removing lines on a SIP trunk is quick and easy, enabling organizations to scale up or down to accommodate business requirements while paying only for the services they use.

What does a SIP trunk do to increase reliability?

Because a SIP trunk runs over a data network, it can be subject to packet loss, interference and jitter, which is why companies where voice services are mission-critical will often opt for PRI trunking. But when provided by a reliable vendor using fiber-optic connectivity and multiple route failover, a SIP trunk can be just as reliable as a PRI trunk.

What does a SIP trunk do to reduce costs for enterprise telephony?

A SIP trunk tends to be less costly than a PRI trunk, as it requires no trunk-specific hardware to purchase or maintain and the cost of placing long-distance or international calls is cheaper.

What does a SIP trunk do to ensure security?

While a SIP trunk may route calls over the public Internet, enterprises can secure SIP calls through network security measures.