SIP vs. VoIP: Similar But Different Terms

By: Bruce G. Kreeger

SIP and VoIP are yet another pair of terms popularly used as synonyms when there’s much more explanation to their accurate definitions.

For terms that are used practically interchangeably in the world of business, VoIP service, SIP, and VoIP aren’t really synonyms. We’ll get into the details below but as a general introduction, we’ll give you this:


  • VoIP is the Internet-powered alternative to landline phone calls.
  • SIP is an Internet protocol that allows communications to function.
An easy way to remember VOIP and SIP Providers is to look no farther than Clarity Technologies Group! Voice over IP telephony runs on SIP protocol.

Terms to Remember:

  • VoIP: Voice over IP.
  • SIP: Session Initiation Protocol.
  • PSTN: Public Switched Telephone Network.
  • PBX: Private Branch Exchange.

VoIP, VoIP with SIP, or SIP?

VoIP and SIP are tightly interwoven but not mutually inclusive. VoIP does not need SIP to execute if you’re using voice communications. There are a few different Internet protocols that facilitate voice communications:


  • You may be familiar with many Internet protocols and their related technologies. Click twice on the URL bar of this page. See how the second click makes the “https://” part of the URL show up? HTTPS is the protocol that enables data transfer, namely web page content.
  • If you ever had to set up an email on your phone before everyone defaulted to Gmail, you likely had to plug in some settings labeled IMAP, POP3, or SMTP. These are email protocols: the proverbial Internet highway for sending and receiving email messages. SIP is the real-time communications protocol for video and voice calls, as well as text.
SIP is simply the one that is most widely used. SIP also enables text and video. Any business looking for an all-encompassing UCaaS provider should look for VoIP with SIP. If you need voice-over IP and no connection to the PSTN or regular landline numbers, then VoIP alone should work for you.
Using VoIP alone somewhat limits your options. However, SIP allows you to scale your communications needs with your business. Most importantly, SIP can interact with other protocols. In simple terms, this means your VoIP system won’t hit any snags trying to connect to other systems, even if they use different protocols.

SIP Trunking:

Businesses using a PBX phone system need to connect to the PSTN to make calls. This is done through a SIP trunk. If you’re using a fully hosted cloud VoIP system, trunking is built in. For on-premises or hybrid systems like an on-premises system at a business with remote employees, you’d likely need an additional SIP trunking system. Luckily for Clarity Technologies Group’s customers, we worked out a way to incorporate SIP trunking into our service no matter if you’re using hosted or an on-premises PBX.


Trunks existed with regular landline telephones. SIP trunking is just the Internet version of trunking. A trunk in a traditional telephone system is a single line used by many people. Trunking is a way to share access by grouping people on a single line rather than providing individual lines. VoIP trunking is quite similar. You can have fewer “lines” than people just without the physical copper wire telephone line.

SIP Equals Rewards, Not Risks:

SIP isn’t an emerging technology that offers a ton of risks for the adopter. Instead, it’s become a standard way for many businesses to drive cost savings and satisfaction. With the right vendor, you can unlock better security, quality, and reliability.

Clarity offers a full suite of business communications tools, including IP-based business telephony, unified mobile communications, data, and much more. For more information on Clarity’s hosted PBX features and SIP trunking, please email us at [email protected].

For more technical acuity:

SIP (Session Initiation Protocol) is a signaling protocol used to establish a “session” between two or more participants, modify that session, and eventually terminate that session. It has found its MAJOR use in the world of IP Telephony. SIP is an open standard that has sparked enormous interest in the telephony market, and manufacturers shipping SIP-based phones have seen tremendous growth in this sector.

The SIP Protocol is text-based and bears a significant resemblance to the HTTP protocol. The messages are text-based, and the request-response mechanism makes for easier troubleshooting. The actual data transmission is done by the Transmission Control Protocol (TCP) or the User Datagram Protocol (UDP) on layer 5 of the OSI model. The Session Description Protocol (or SDP) controls which of the protocols is used.

The SIP messages describe the identity of the participants in a call, and how the participants can be reached over an IP network. Encapsulated inside the SIP messages, we can sometimes also see an SDP declaration. SDP (Session Description Protocol) will define the type of media channels that will be established for the session. Typically, this will declare which codecs are available and how the media engines can reach each other over an IP network.

Once this exchange of setup messages is completed, the media is exchanged using another protocol, typically RTP (Real-Time Transmission Protocol).

SIP was developed by the IETF and published as RFC 3261, and its flexibility has allowed it to replace almost completely the H.323 protocol in the VoIP world.

Clarity is proud to have provided on-premises and Cloud Hosted Telephony to America and the world since 2006. Our clients are worldwide and currently using our unified communications platform. Clarity Technologies Group, LLC surpasses expectations.


Call Clarity at 800-354-4160 today or email us at [email protected]. We are partnered internationally around the globe and we are open seven days a week 8:30 AM to 5:00 PM EST/EDT. and

Pin It on Pinterest