What is the Difference Between VoIP and SIP Trunking?

When shopping for IP telephony services, it is incredibly easy to get confused. Acronyms like VoIP, SIP, and others get tossed around, and it can be difficult for the non-techie to determine exactly what they need. Here is your guide to understanding when you need only VoIP Services, when to invest in SIP trunking, and what you can expect from each service.

What is Protocol?

voice transmissions

Protocol is the set of standards developers use to assure that voice transmissions over the Internet are consistent and understandable.

First, you need to understand what protocol is and why it is important. VoIP and SIP trunking allow users to use the Internet (which was designed for the transmission of data, which is technically different than the transmission of voice). A number of terms are used to discuss transmitting voice (a phone call) over the Internet, including IP telephony, Internet telephony, voice over broadband, broadband telephony, IP communications, and broadband phone service.

In order for computers or other digital devices to exchange messages coherently, it is necessary to establish a protocol system. The protocol is a well-defined format used by developers to exchange consistently understandable messages. The protocol defines the semantics, syntax, and synchronization of the messages communicated between parties, usually called endpoints. These protocols are so essential to reliable communication via the Internet that they become industry standards, allowing various vendors to develop endpoints for communications.

What is VoIP: Voice over Internet Protocol?

VoIP is one such protocol. Voice over Internet Protocol is a service based on IP. VoIP is offered by subscription, usually on a month to month basis. VoIP allows normal voice communications, like a phone call, to run over a network that was designed to transmit data. Essentially, it turns your average computer or Internet connected device into a device capable of acting like a TDM or circuit switched network, just like your ordinary land line telephone.

What is SIP Trunking: Session Initiation Protocol?

data transmission

SIP Trunking allows for the transmission of data such as video (not just voice messages) via the Internet.


If you are familiar at all with ordinary telephone technology, you can picture SIP trunking much like PBX trunks. SIP is capable of transmitting all types of media, not just voice. SIP trunks transmit packets of data, which can include voice as well as other data like video. SIP trunks are an actual physical connection.

An easy way to picture the difference is to consider the difference in the ability to make just a voice call from person to person versus the ability to make a video conference call. VoIP service would allow the voice conversation, but it would require SIP trunking to transmit the video required for a face to face conversation over the Internet. Most VoIP providers also offer SIP trunking so that customers can get everything they need in one convenient monthly service.

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