What is SIP Trunking?

Session Initiation Protocol (SIP) Trunking allows you to connect your onsite private branch exchange (PBX) to the public telephone exchange so you can use voice over IP (VoIP) services and reach mobile and landline customers with your business phone service. SIP trunking is used to connect either a hosted cloud PBX or a traditional onsite PBX to the main public phone system, but this term is mainly used to refer to connecting PBX systems that operate onsite at a business. If you have a hosted PBX, your vendor will also typically take care of the SIP trunking for you.

Advantages of SIP Trunking:

  • Access Advanced VoIP Features
  • Connect with Plain Old Telephone Service (POTS) Subscribers
  • Link Your PBX to the Internet

In this article, we will provide you with an overview of what SIP trunking is, how it works and what features it offers for businesses. We will also explain how SIP trunking is different from getting a hosted cloud PBX.

  1. How Does SIP Trunking Work?
  2. What Equipment Do I Need for SIP Trunking?
  3. SIP Trunking Features
  4. Is SIP Trunking Right for My Business?

1. How Does SIP Trunking Work?

SIP trunking connects a PBX to the Internet instead of using the traditional POTS infrastructure. Rather than rely on miles of copper wires, SIP trunking uses the Internet as the “trunk” transporting phone signals. Used in conjunction with VoIP service, SIP trunking enables you to use the Internet to connect your business telecommunications system to the landline and cellphone system many people associate the most with phone services.

This means your company can reach or receive calls from people with traditional phone technology while still generating significant cost savings from using VoIP services. With VoIP’s greater efficiency and lower costs, you can accomplish more with your business successfully.

SIP trunking is also used with cloud hosted PBX systems, since this method is used to connect any PBX to the Internet. In that case, however, your hosting vendor also takes care of the SIP trunking connection.

Businesses looking to save money on incoming toll-free calls, large call volumes and international calls may find SIP trunking particularly useful, since SIP trunking with a local PBX allows you to work with multiple VoIP service vendors. This is one of the more attractive features of SIP trunking for many companies.

2. What Equipment Do I Need for SIP Trunking?

To begin, you will need a PBX system. Many businesses, particularly large corporations and organizations with a large phone call volume, have their own PBX gateway boxes onsite. There are numerous advantages to this approach. Some companies choose cloud hosting instead and have their hosting and VoIP vendor manage the SIP trunking process for them instead.

Typical SIP Trunking Equipment:

  • PBX Gateway—You may need a gateway of some kind. Typically, you will have an onsite traditional PBX gateway. Depending on your system, this is usually a box full of electronic and computer components needed to manage your phone system internally. A PBX manages call queues, runs multiple phone lines or extensions and keeps phone traffic running smoothly, similarly to how a phone switchboard operates. Rather than being a switchboard with human operators as in the early days of phone service, today’s PBX units use computers to manage the phone system.
  • Phones—You need phones compatible with your other equipment. Depending on the type of PBX you have, your VoIP vendor and other considerations, your phone equipment may differ. Phones should be compatible with SIP and meet your other requirements. IP phones, traditional analog handsets and computer phones are all possibilities depending on your system. If you have questions about specific equipment needs, your VoIP vendor may be able to help you pick the right phones. With a SIP compatible phone, router or appliance, you may not need additional hardware to access VoIP and you may be able to establish a VoIP connection as-is.

3. SIP Trunking Features

SIP trunking with a local PBX allows you to control your system directly, improve security and generate cost savings by using multiple vendors. You get to take advantage of VoIP phone services without missing out on the advantages of an onsite PBX. You also get to save money if you happen to make or receive a lot of phone calls.

Common Advantages of SIP Trunking an onsite PBX:

  • Improved Security—While cloud hosted PBX systems are typically very secure, many companies prefer to maintain direct control over their PBX systems. Having an onsite PBX means you have complete say over how your system is secured and you can readily confirm that your PBX is still secure. Monitoring your PBX is easy when it is onsite and you can immediately see it.
  • Control—If you have an onsite PBX, you can decide when it is upgraded, maintained and monitored. You have control and you can make changes to the PBX whenever you want.
  • Cost Savings—If you have high call volumes, SIP trunking can help you reduce your costs by enabling you to switch VoIP vendors as needed based on traffic and other conditions. You can use existing equipment in many cases, saving even more money. Use the phones you already have and avoid buying new ones.
  • Virtual Numbers in Other Locales—You can set up virtual extensions and phone numbers locally in another physical location and route this phone traffic through the Internet via VoIP, allowing you to appear local and choose your area code.
  • Achieve Other Benefits of Hosted VoIP—Without getting a cloud hosted VoIP service, you can achieve many of the benefits of hosted VoIP by using SIP trunking.

If you think your business could benefit from this method of accessing VoIP services, you should consider doing your own research. You may need to shop around and asking several vendors

4. Is SIP Trunking Right for My Business?

If your business uses a lot of phone services, receives a lot of toll-free phone calls or spends a significant amount on phone service, then SIP trunking might be right for your business. For small businesses, cloud hosted PBX service might be a better fit. SIP trunking can significantly benefit your business, but it also has associated upfront costs if you do not have existing equipment.

  • Small to Medium-Sized Business (SMB)—You may benefit more from a cloud-hosted PBX service, so you can minimize your equipment investment. If you already have equipment, then SIP trunking might be right for you.
  • Call Center or Large Business—You may benefit more from SIP trunking since you can save on phone service costs by using multiple vendors. You can also control your own PBX directly.

For many businesses, SIP trunking is worth the investment. If you are still unsure if SIP trunking is appropriate for or relevant to your business communications, your VoIP vendor may help you understand how to use SIP trunking and what your options are. Many vendors have plenty of great information available and can help you apply various VoIP tools and techniques as part of your business communications strategies. You may save money, become more efficient or become capable of reaching more customers and potential clients by using SIP trunking with your business.