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IP Trunking vs. SIP Trunking: What’s the Difference and Which is Best?

IP Trunking vs. SIP Trunking: What’s the Difference and Which is Best?

IP Trunking vs. SIP Trunking:  Which is best? Let's find out.

As cloud communication tools become the mainstream, businesses worldwide are exploring ways that cloud-based business phone service, fiber internet connectivity, and cloud backups can drive business value. This is especially true as the number of remote workers continues to rise.

Between 2005 to 2017, there was a 159% increase in remote work according to FlexJobs, an online resource for all things remote work. As of February 13, 2020, FlexJobs estimated there were 4.7 million remote workers in the United States. With the pandemic, many companies have gone remote for the foreseeable future.

The point is, the business world has become more mobile, and your company’s phone system needs to evolve beyond the desk phone. Enter the world of IP and cloud-based phone services.

Two common terms that you may encounter when exploring IP and cloud-based phone service for the enterprise are SIP Trunking and IP Trunking. If you’re new to VoIP, you may be wondering what the difference is between IP vs. SIP trunking, and which is better.

Let’s walk through what SIP Trunking and IP Trunking are, the pros and cons of each, and the best use cases for each solution.

What is SIP Trunking?

SIP trunking is based on session initiation protocol (SIP), a set of communications protocols that are a standard approach for managing the transmission of multimedia communications. SIP protocols are used to perform key actions necessary for placing and receiving calls, including establishing the call, terminating the call, and transmitting information during the call. VoIP telephony supported by SIP trunking could either be hosted on-premises or in the cloud via a vendor partnership.

SIP trunking is not an alternative to IP trunking. It’s an alternative to PRI trunking. For organizations who want to achieve the benefits of VoIP and make the transition to Unified Communications tools, SIP trunking is likely to be among the technologies used.

While IP trunking could be accomplished through a media gateway and PBX, an IP trunking implementation could involve SIP trunks and call routing through a session border controller (SBC). SBCs are a complex piece of equipment that is used and maintained by VoIP vendors to act as a SIP application and perform other key actions, including access control, call accounting, and quality of service management.

The Pros and Cons of SIP Trunking


  • SIP has the flexibility to support many media types
  • As an open standard, SIP can be used for integration with relative ease
  • SIP can simultaneously support multiple, multimedia data transmission

To learn more, check out Why SIP? 10 Benefits of SIP Trunking.


  • Skilled SIP trunking experts can be rare, which is why many organizations are choosing hosted IP trunking
  • Processing SMS messages places a higher load on SBCs
  • Not all SIP features are open standard

The 5 Best Use Cases for SIP Trunking:

  1. The potential for massive cost savings on scaling phone systems and adding lines compared to installing cabling for analog phones.
  2. SIP can support scaling without the need to purchase expensive additional equipment, unlike TDM phone systems.
  3. Ability to scale a single phone system across multiple business sites or support employee mobility.
  4. Save costs on long distance and international calling.
  5. Add support for Unified Communications, including collaboration tools like file sharing, desktop sharing, video conferencing, and more.


What is IP Trunking

IP trunking is large-scale VoIP deployments at organizations, including corporations or institutions. This term is relatively rare, and may be interchangeably used with “VoIP implementation,” or depending on the inclusion of multimedia features, “Unified Communications.”

IP trunking is different than plain old telephones (PoTs) services because voice transmissions are treated as data, and transmitted via data connectivity instead of analog phones, which transmit electrical-based signals through traditional telephone lines. IP trunking is also different than consumer VoIP products, including Skype and Vonage, which are generally not designed to meet the security and reliability needs of the enterprise.

To learn the differences in VoIP solutions designed for business and home use, look into the Atlantech blog Decoding Business Class Cloud-Based Phone Service (Benefits vs. Cost).

IP trunking may be deployed at an enterprise in a number of ways, including an on-premises solution that is owned and managed by the organization, or a subscription to cloud-based VoIP service. It may also rely on either PBX trunks or SIP trunks. While a private branch exchange (PBX) is designed to support the transmission of voice as data, a SIP trunk can handle multimedia data, including voice, conferencing, emails, instant messaging, presence, and more.

IP Trunking vs. Alternatives

IP trunking, defined as enterprise deployments of VoIP, is not an alternative to SIP trunking. IP trunking is an alternative to publicly-switched telephone networks. Evaluating how IP trunking stacks up against alternative options requires comparing the solution to analog phones.


  • Lower Cost Savings
  • Superior Scalability
  • Can Include Sophisticated Multi-Media Communication Features
  • Can Quickly Add & Remove Phone Lies
  • Better Business Continuity & Lower Risk
  • Mobility


  • Requires Sufficient Data Connectivity for Quality of Service (QoS)
  • Desk Handsets May Not Working During Power Outages
  • May Not Operate Optimally with Public Internet Connectivity

The 6 Best Use Cases for IP Trunking

Organizations in all industries are driving value with VoIP. Highly-regulated firms are turning to Unified Communications as a Service (UCaaS) to diminish the administrative burden and skyrocketing costs of compliance. Educational institutions, like Montgomery College, are starting to realize that VoIP offers a pathway to next-generation, multi-campus connectivity.

While the following use cases are not a comprehensive representation of the full potential of IP Trunking, they’re worth noting:

  1. Reduce monthly phone bills by 20-30 percent or more
  2. Extend the life of legacy systems through hybrid VoIP-analog phones
  3. Improve employee productivity through mobility
  4. Increase information security
  5. Cloud adoption through implementation of Unified Communications as a Service (UCaaS)
  6. Reduce IT burden by outsourcing communication tools management via cloud VoIP or UCaaS

From Legacy PBX to UCaaS

Wait, so is SIP Trunking or IP Trunking the Best?

SIP trunking is a technology used to power internet-based phone service and multi-media communications for businesses. SIP trunks are a component in many VoIP or IP trunking implementations, which replace the need for analog phone lines.SIP trunking can act as one form of support for business communications in an environment with VoIP or other unified communications tools, giving SIP trunking users the ability to select from a wide variety of multimedia cloud communication tools.

While VoIP is a well-established technology, the “right” way to drive value with VoIP and other Unified Communications tools ultimately depends on your businesses’ requirements, budget, and goals. If your organization wants to work more collaboratively, streamline your communications technology and save costs, you’re likely a good candidate for VoIP phone service. However, the exact features you should deploy ad the right approach to implementation can vary.

While SIP trunking and IP trunking are both terms from the VoIP ecosystem, they’re not quite the same thing or alternatives to each other. Organizations who want to move their communications tools to the cloud should consider all of their options, including SIP trunking, and select the method that is most beneficial.

As with any business investment, you need to make the right choice. Get in touch with us to talk with one of our representatives. They will help you understand your options and make the right choice for your business.

Tom Collins
Post by Tom Collins
October 24, 2017
Tom is the Director of Enterprise Sales & Marketing for Atlantech Online. He has over 20 years of professional experience in the Internet Service Provider industry and is known for translating technology into positive results for business. A native of Washington, DC, a graduate from University of Maryland (degrees in Government & Politics and Secondary Education), Tom is also a five-time Ironman finisher.