SIP Trunking Providers

SIP Trunking is a communication service that utilizes VoIP to enable any on-premise PBX (Private Branch eXchange) to direct calls over the Internet instead of only using the PSTN. SIP Trunking Providers allow a business to keep it's existing phone infrastructure while significantly reducing calling expenses. Use the best SIP provider comparison table below to get pricing and/or access user reviews.

If your business does not already use SIP trunks for phone calls then it is likely worth a few minutes of time to get some price quotes to determine the potential savings. Use our free quote tool below to get comparison price quotes with one simple form:

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Finding the Best SIP Trunk Providers

SIP stands for Session Initiation Protocol while the "Trunking" part is somewhat older terminology that is used to describe a link between two communications endpoints.

The first major point to be aware of is that not all SIP Trunking Providers are identical, as they package (and price) their services quite differently, and the entire technology is just new enough that there is not yet a general industry standard. That means that each SIP provider will have their own technical methodology, their own standard and optional services, and their own ideas of what your business can benefit from. When talking to SIP Trunking Providers be prepared to answer 3 main questions, which we expand on below.

Maximum Number of Concurrent Calls?

The maximum number includes the number of incoming and outgoing concurrent calls that you need to support. This number could be limited by the PBX (phone switch) you have installed at your place of business, but it's more likely to be soft-capped by the size of your business in general. If you are currently utilizing PSTN T1 voice lines then the amount of money you save will be moderate if you need only 20 simultaneous calls, but it will be much greater if you need to support 25 for example. That's because your typical dedicated PSTN T1 voice line supports exactly 23 simultaneous calls, break that hard limit, and you are paying for a second T1 line, doubling your base expense. SIP trunking doesn't have that "quantum leap" effect, you pay for exactly the number of connections you need, no more or less, and you can expand the cap as your business grows.

Sidenote: Many modern PBXs have powerful features that might cause you to underestimate the number of phone lines you need. For example, the FindMe/FollowMe feature of your PBX might take an incoming call and simultaneously forward it to your cellphone, home phone, and off-site business phone, using four connections (one incoming and three outgoing) at the same time. Obviously, if this should happen to multiple workers at once (say, the boss sends out a voice blast to his entire department at once), the effect can be profound.

Total Incoming Phone Numbers Needed?

Incoming phone numbers can be very useful to a business of any size, for example, do you want each employee to have their own phone number? Or do you want to separate sales promotions by phone number so you can easily judge which are the most productive? Keep in mind that many companies only offer incoming phone lines that are locally available, for example, you can only call into them from a specific city. This can be both a boon and a bane, for while your customers can only reach you from their homes on your local city line, if you purchase a line localized to another city, you can give your customers there the impression that you have a presence in their cities.

IP Ready or Standard PBX?

If you've already upgraded to an IP-PBX, a SIP trunking service can connect directly to your PBX, provided the two are interoperable; remember that there are not a lot of industry standards in this area as of yet. Each IP-PBX manufacturer and SIP provider has their own mostly-unique take on the technology, so be prepared to give your IP-PBX's make and model number to the provider to verify interoperability (some examples are Asterisk, 3CX, Cisco Callmanager, Allworks & Shoretel).

If you're still using a legacy PBX, it is still an option. However, many of the features, particularly of the Unified Communications variety, won't work. You'll still get to make free phone calls and some of the Web-based features of your service, but you'll probably want to upgrade to an IP-PBX and IP phones as your current equipment needs replacing.

Other Questions to Consider

How Much Bandwidth Do I Need?

This answer starts with knowing the answer to the above questions. SIP calls use your Internet connection, so you need to add your current maximum Internet bandwidth use (you can find out with a quick call to your ISP), plus enough to support the maximum number of simultaneous calls you have to support. There are quite a few factors that go into how much bandwidth each call will require, but you can generally estimate 92 Kbps each and be very safe. If you have a high call volume business, you might want to ask your ISP if they have a service that can dynamically allocate bandwidth, but either way, if you don't already have a lot of excess bandwidth going unused, you can expect to need to upgrade your bandwidth when making teh switch over.

SIP Trunking Provider Requirements?

There is tremendous variety in service providers today. Some may offer you an Internet connection, acting as both ISP and SIP provider. Some provide expansive call-quality and/or equipment-reliability guarantees. Some give you powerful diagnostic tools to help you address any call-quality issues on your own. You probably won't find it all under one roof, so deciding what your dealbreakers are ahead of time is critical.

Do You Need Fax Services?

IP telephony in general has one major weakness: faxes. Every service provider has their own solution to this dilemma, ranging from "don't use them" to very elaborate Integrated Access Devices (IADs) that they install on your premises with analog ports that can support fax machines. In many cases, it's actually wise to keep a single traditional PSTN line in order to run faxes and make emergency calls if for some reason your power goes out or your Internet connection is otherwise unavailable. Alternatively, consider moving to an Online Fax Service and say goodbye to that old fax machine!

Related Articles for Further Reading

The following provides links to SIP trunking related articles that may be of interest.

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