SIP Trunking: Understanding the basics, benefits, and the transition process

You’ve likely heard the term SIP Trunking thrown around before. But what does it mean for businesses today?

SIP Trunking SIP stands for Session Initiation Protocol and is used to establish and control communication connections between different users and the public switched telephone network (PSTN).

With more and more companies making the jump to cloud communication platforms, it’s hard to ignore the benefits SIP Trunking offers.

Before we dive into the key benefits—let’s start with the basics of SIP Trunking.

What Is SIP Trunking? The Need-to-Know Basics

SIP Trunking uses SIP technology to establish connections via a data network. Using the existing data infrastructure SIP Trunking eliminates the need for physical phone connections, separate wiring, and hardware 

SIP Trunking isn’t new—it’s been around for years already—but there is still a significant embedded base of existing analog and PRI lines in use. 

We continue to see a significant demand for SIP Trunking and thought we would outline some of the benefits and best practices when looking to deploy SIP Trunking service.


Why Move to SIP Trunking?

First, let’s start with some of the advantages of SIP Trunking. This technology offers several advantages over traditional analog and PRI lines. 

However, the three biggest categories where SIP Trunking shines include the enhanced cost savings it offers, the simplicity of scaling, and the overall reliability and design of SIP systems.


Benefit #1: Cost Savings & Transparent Per Usage Pricing

This is usually the most common reason customers make the decision to move to SIP Trunking. Based on our experience, companies are often attracted to the cost savings offered by the following areas:

  • No Long Distance Charges: Most SIP Providers include long distance as part of the monthly recurring charge for sessions. This means all outbound domestic and long distance, including US and Canada, is included in the monthly session price. The only usage charges associated with a SIP Trunking service should be international and inbound toll-free.

  • Trunk Utilization: With SIP Trunking, you only need to purchase the number of trunks or sessions you need. This differs from traditional PRIs that come in 23-channel increments. The ability to optimize trunks allows you to purchase the capacity you require.

  • Leverage Your Existing Data or IP Connectivity: Because SIP can use your existing IP or data connections, there is no need to add additional phone lines. Using existing data connections reduces your costs for internal wiring, maintenance, and additional on-premise hardware.

Benefit #2: Flexibility & Ease of Scaling

  • On-Demand Scaling: Once you have established your SIP service, you can scale on-demand. This is a big advantage if your business is growing, or you have seasonal growth in your voice capacity requirements. 

  • Even More Flexibility: SIP Trunking is IP based, meaning it provides enhanced flexibility when managing multiple connections and rerouting numbers and traffic between IP providers. 

Benefit #3: Enhanced Reliability & Customized System Design

  • Network Redundancy & Reliability: SIP Trunking provides redundancy and reliability you don’t get with traditional phone lines or PRI’s. With SIP Trunks, your carrier can add multiple IP connections to the call routing. If you experience an outage with your data or IP connection, traffic can reroute to your backup IP connection. On the carrier side, if your IP PBX allows, you can even route to multiple IPs. Your SIP carrier will need to operate a geo-redundant network with multiple IPs or POPs for you to route traffic.
  • Architectural Optimization: If you have a multisite deployment and manage trunks across several locations and systems, SIP Trunking provides flexibility in the way you design your network. You can establish SIP Trunks from each location or route traffic back to a single location to and from the PSTN.

Keep in mind, these are only a few of the main benefits businesses receive when they switch to SIP Trunking. Your individual needs may vary depending on your use case.

How Can You Select the Right SIP Provider?

SIP Trunking is a popular service that’s offered by many SIP carriers. So, how can you choose the right one?

It’s important to select a provider that has extensive SIP experience, has the long-term customers to prove it, and provides the responsive customer support you need to manage your voice service.

As a proven SIP carrier to SMBs and enterprise, we recommend you look for the following:

  • Experience Delivering SIP Trunking: You want to make sure the SIP provider has extensive experience providing SIP Trunking services. This includes managing and operating the infrastructure, provisioning services, and the operations and technology team to provide on-going support and service.

  • Knowledgeable Engineering, Operations, & SIP Design Teams: The engineering and operations team should have experience turning up new trunks, designing failover for both customer and network facing sessions, number porting experience, and have a knowledgeable support staff that can quickly respond and resolve SIP-related issues.

  • Geo-Redundant Network Infrastructure: Confirm the provider operates a geo-redundant network and can provide failover to a geo-node if required. That way you can avoid service outages and ensure business continuity.

  • 911 Service & Expertise Deploying 911 Routing: Implementing and configuring your 911 system isn’t just important—it’s the law. Your SIP provider should walk you through the process, ensuring all locations are set up properly, that 911 calls are all routing to the proper 911 authorities, and 911 address information is presented properly.

  • Nationwide/Global Network Coverage: As you scale your business and expand, you may need nationwide and global network coverage. Make sure your SIP provider has nationwide DID coverage, and if needed, global DID reach.

  • International & Toll Free Services: Your SIP provider should be able to provide full international calling and inbound toll-free services. You should also discuss toll fraud protection with your SIP provider.

  • SIP/PRI Conversion: Your provider should be capable of supporting your technical requirements, such as native SIP or SIP to PRI conversion. Make sure the SIP provider is capable of supporting your current PBX requirements, and if you need a PRI hand-off, they have the option to convert the SIP to PRI.

  • Certifications With Major PBXs: Confirm the SIP provider is certified with the major PBX manufacturers. This SIP certification process will confirm the service providers’ infrastructure and platform supports any IP PBX SIP requirements.

  • Experienced & Knowledgeable Support Team: Voice service is critical to the success of your business, and you need a SIP provider with an experienced support team that can provide quality and timely support when needed. It’s also important to find a provider that’s staffed with experienced SIP technicians, so issues can get quickly resolved, targeting first call resolution.

  • Ancillary Services: You may need additional services in the future. Look for a SIP carrier that can provide other ancillary services, such as fax, fax to email, and even Cloud PBX services should you need to transition from your existing phone system.

  • Security & Toll Fraud Monitoring: Now more than ever, cybercrime is on the rise. Network hacks and toll fraud are very real and need to be monitored. If your SIP carrier provides you with international calling, you need to make sure they monitor international attempts and have alarms and/or alerts set for fraud attempts.

  • Pricing: SIP Trunking can provide significant cost savings when you find the right SIP carrier. Make sure you understand the pricing model of the SIP service, including a breakdown of any fees. Standard SIP Trunking fees may include: one-time porting, monthly recurring charges for per session, per DID, per 911 DID, outbound international usage per minute, and inbound toll-free usage per minute.

If there’s anything you’re unsure of, don’t hesitate to ask your SIP carrier. A reputable provider will be more than happy to answer your questions. After all, they want the best outcome for your business, because your long-term success is their success too.

How Does the SIP Trunking Transition Process Work?

Once you have made the decision to move forward and selected your SIP provider it’s time to turn-up your service. Making the transition to SIP Trunking isn’t hard when you’re working with an experienced provider. 

We put together this brief outline to guide you through the different steps involved in this process: 

  • SIP Technology Validation: Again, make sure your PBX is SIP-ready and is capable of bringing in native SIP. And if it isn’t capable, you’ll need a plan to convert SIP to PRI.

  • Data Capacity Requirements: Understand your current data utilization, and if you need additional IP capacity to support your voice deployment. Voice does not use a lot of bandwidth, but if you have other applications running simultaneously with your voice, you may want to set priorities for voice to avoid quality degradation.

  • Firewall Configuration: Take the time to review your current firewall configuration and your SIP settings. You should check with your SIP carrier and confirm if they have standard settings for your firewall.

  • Redundant IP: Determine if you want to set up a redundant IP connection. If you do, coordinate with your SIP carrier so they can route to both connections. Also, if your PBX has the ability to route to multiple IP’s and the SIP carrier you select operates a geo redundant infrastructure make sure you are set up to route to each geo-redundant node.

  • Data Gathering Process: Next, you need to identify your current DID inventory and determine how many numbers you will be porting. You will also need to confirm information, such as your current provider and any authorized signatures on your account. You will need to validate this with your current provider and communicate it with your new SIP carrier.

  • Trunk Turn Up and Testing: You should supply your IP information to your SIP provider so they can set up new trunks and work through the testing process. Once these trunks are set up, you can begin the testing process. Temporary DIDs can be loaded so you can start testing inbound and outbound calling. The SIP provider should be able to assist with this process, offer feedback, and provide release reasons from the platform, so you or your IP PBX support technician can make the necessary changes to get the SIP trunks up and operational.

You may find that your individual needs go beyond these basic steps, and that’s perfectly fine. Your SIP carrier will help you build a personalized transition plan that offers minimal disruption to your organization.

Are You Looking to Transition to SIP Trunking? Momentum Can Help

Momentum is a national leader in providing cost-effective and reliable SIP Trunking services to clients in a variety of industries. From healthcare to finance, we’ve done it all.

Are you interested in learning more about Momentum’s SIP Trunking service? Get in touch with a Momentum SIP specialist today by calling (877) 377-8750 (Option1) or by emailing

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