SIP and VoIP – Are the Terms Interchangeable?

sip vs. voip

All 911s are Porches, but not all Porches are 911s.

Sometimes I wonder if those of us in the technology industry, telecommunications in particular, know how confusing our acronyms and technospeak are for customers. We tend to throw arcane lingo around like it’s going out of style and often fail to explain what we are talking about in plain English. Worse yet, many of us are guilty of using the terms incorrectly, making it even more difficult for people who don’t live and breathe this stuff every day to figure out what in the hell we are talking about.  So, if you are confused about the difference between SIP and VoIP, it’s not your fault. Let’s see if I can clear it up with a minimum of nerd language.

Let’s start with Protocol

SIP, which I will describe in a bit, is a protocol. In computing, a protocol is a system of digital rules for message exchange within or between computers, phones or other devices. In the same way that having a common language makes is possible for two people to understand each other, the protocol provides common ground so that devices with different developers can communicate with each other. The developers of each connected device or software program must agree on the protocol. Since it is beneficial for devices to have the capability to connect to many other devices and applications, protocols often evolve into industry standards. This allows lots of vendors to create devices, also called endpoints, that can work together.


The term VoIP stands for Voice Over Internet Protocol.  Any time a voice signal is sent over the internet, rather than traditional telephone lines, it can be called VoIP. It is a broad term that encompasses a number of more specific protocols, SIP being one.  There are a bunch of other terms that are closely associated with and used interchangeably with VoIP. They include, IP telephony, voice over broadband, IP communications, internet phone service, cloud phone service, and others. They are all different ways of saying that calls are being transmitted via the internet.


Session Initiation Protocol (SIP) is a specific open standards protocol that is popular for managing multimedia communications including voice and video calls. SIP is one of the protocols that make VoIP possible. Just like all 911s are Porches, but not all Porches are 911s, SIP enables VoIP, but not all VoIP requires SIP. SIP controls the establishment, termination and other elements of a call. It was developed and standardized under the guidance of the Internet Engineering Task Force or IETF. (I swear, I am not paid by the acronym.)  In addition to voice, SIP is used for video conferencing, media distribution, instant messaging and other applications.

SIP trunking describes an implementation in which telephone services and other unified communications applications are delivered to customers with SIP-enabled telephony equipment, usually an IP-PBX (private branch exchange). The SIP trunks provide connectivity between the telephone system hardware and the public telephone network. This eliminates the need for traditional telephone lines. SIP can also be used with legacy analog phone systems, or key systems with the help of a device called an analog telephony adapter or ATA. SIP trunking is popular with businesses because it is extremely cost effective, flexible and generally easy to use.

So, although people in the industry make the mistake all the time, SIP and VoIP are not the same thing. SIP is an industry standard method of achieving VoIP.

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