As a business owner, you are constantly looking for ways to cut costs and reprioritize your spending. With all the services you are tasked with managing (merchant services, shipping services, payroll services, etc.) it’s understandable you haven’t mastered the knowledge of each industry. Maybe you’ve heard of SIP trunking, and maybe a friend of yours saves money by using it with his business, but you’d like to know more about how it works before you contact providers.

 

What Is SIP Trunking?

Session Initiation Protocol, or SIP, is the way you achieve a voice over IP (VoIP) call. It’s an application layer protocol for setting up real-time sessions of audio and/or video between two endpoints (phones). Simply put, SIP is the technology that creates, modifies, and terminates sessions with one or more parties in an IP network, whether a two-way call or a multi-party conference call.

 A SIP trunk is the virtual version of an analog phone line. Using SIP trunks, a SIP provider can connect one, two, or twenty channels to your PBX, allowing you to make local, long distance, and international calls over the Internet. If you have an on-premises PBX in your office, a SIP trunk provider can connect to you and allow you to make outbound calls on your existing system, without restrictions on the number of concurrent calls.

 

Important Considerations

The next step is to choose a SIP Trunk provider who will supply the necessary SIP Trunks. A few factors come into play when making this decision:

• Security – As SIP Trunks are exposed to the Internet, it is very important that the SIP Trunk has a well secured network and an anti fraud system in place. The anti fraud system must monitor the system and provide protection against call fraud.
• Own network – Does the SIP Trunk provider run its own network or is it a rebranded service? There are quite a few providers out there reselling SIP Trunks from other providers. Select a provider who has control over their service and network.
• Competitive Cost – Costs vary widely between services. Some vendors will overcharge for SIP Trunks. Look for competitive rates, but ensure that you are getting business quality SIP Trunk service. For example, telecom providers will provide a cheaper quality to Internet call shops. Be cost conscious, but expect to pay a bit more for business class service.
• Number Porting – Can the provider port your phone numbers? Ensure that you choose a provider who can port all the existing numbers – not all providers are able to do this for all regions.

 

How Much Does SIP Trunking Cost?

The cost of SIP trunking can vary depending on your business needs, but typically businesses can expect to pay a setup fee of $0-$150, and monthly costs of $25-$50 per trunk, but this is dependant on your carrier.

Some SIP trunking providers, such as ThinkTel, Broadconnect, BabyTel and many more, offer metered plans in addition to channelized plans:

Metered SIP trunking is delivered and charged on usage, so each minute will incur a charge. Metered trunking is very flexible in that there are no limitations to the number of concurrent calls, as you are just charged for each minute of each call. Metered services allow businesses the flexibility to dynamically add calls and just pay for the additional usage.

Channelized SIP trunking is a prepaid option that provides unlimited inbound and outbound local and long distance calls on per channel/call basis. Each Channel provides the ability to make or receive a single call. Once you have filled all of your channels you will be unable to make or receive additional calls. Channels can always be added for more capacity by contacting your provider. This type of SIP trunking service allows businesses a way to easily budget their telecom spending.

 

How Many Concurrent Calls Can Be On A Metered SIP Trunk? What About Bandwidth?

The limitation is based on Internet bandwidth capacity. Each non-compressed call uses approximately 85kbps of bandwidth. In most Internet connections your upload speed is normally your slower speed, so when determining the number of calls your connection will support, you should use your upload speed. If, for example, your upload speed on your Internet connection is 4Mbps, then the maximum number of calls would be 47 (4,000,000/85,000).

 

Number of Concurrent Calls During Busiest Hours

X

85~90 Kilobits per Second *

=

Bandwidth in Megabits per Second Required for SIP Trunking

 

Upgrading Internet connectivity

Once you have selected your SIP Trunk provider, consider a dedicated Internet line for the SIP Trunk. Most firewalls are able to handle multiple WAN connections, and, considering the low cost of an Internet line in most places, a separate VoIP connection will be the most reliable way to ensure the quality of your VoIP calls.

However, some SIP Trunk providers bundle their service with a dedicated Internet line. This keeps your voice traffic separate from your data traffic. Much will depend on the cost and your network infrastructure. Check that your firewall is up-to-date and will be capable of handling VoIP traffic correctly.