What an amazing era for evolving telecommunications that we are in right now.  We have evolutionary technology such as Unified Communications, Video, mobility and so on.  And, when you break it down, SIP trunking is that key foundational technology that can make a difference in successful rollouts of new communication applications and services.  We’ve have all heard how SIP trunking can save money, simplify networks and pave the way to Unified Communications for everyone. You may even be sold, sight unseen, and ready to sign on the dotted line. But before you take an axe to your dependable PRI trunks—and we’re not saying you shouldn’t—here are five things to think about BEFORE you do.
 

1. Who will provide your SIP trunking services?

You’ve got choices here. Lots of them. Chances are very good that your existing voice service provider—the one who’s been leasing you PRI trunks all these years—also provides SIP trunking services. In addition, there are dozens of Internet Telephony Service Providers (or ITSPs) and pure-play SIP trunking providers to consider. And don’t forget your broadband data service provider, who may also provide SIP trunking services. There are a healthy number of competitors which makes this a buyer’s market, so compare your options before making a decision….but make sure you read the rest of this blog J
 

2. How much will it cost?

As with PRI trunks, calculating the true cost of SIP communications can be complex. SIP trunks are usually leased per month based on a fixed amount of bandwidth that may include a maximum number of concurrent calls, X number of “free” long-distance minutes and other factors. But what about internationals calls and long-distance calls that exceed your monthly plan? To get a true view of total cost, compare your monthly voice usage today with the SIP trunking plan of tomorrow—you might be surprised to find that some plans are more costly than they first seem.
 

3. Will you lose the phone numbers you have today?

You better not…unless you don’t want customers to call.  Number portability is a requirement in many countries, but if you need to add new phone numbers you might find yourself limited by the numbers that you can choose. For example, not every SIP trunking provider has access to local numbers in every region—a nice feature of SIP that allows you to set up a virtual, local presence in lieu of an impersonal (and more costly) toll-free numbers.  So make sure you understand what the SIP providers can offer you for phones numbers –  a good number can help achieve your local presence marketing identity.
 

4. What happens if your SIP trunk goes down?

Even a service with 99.9% reliability can goes down. Factor in network issues, equipment failures and Mother Nature, and your business needs to have a plan in place in the event that the SIP trunking service is cut off. One option is to choose a SIP trunking provider with a redundant architecture that greatly reduces the risk of failure. Another is to build your own redundancy model by choosing a backup SIP trunking service in a different geography or, more commonly, holding on to a few PRI trunks for connectivity to the good, old and reliable PSTN.
 

5. How will SIP trunking impact call quality?

Ideally, SIP trunking should provide equal or better quality of service than the PSTN, which is a pretty high bar to clear considering how, well, clear most landline connections are today. One of the ways that SIP trunking service providers control voice quality is through call admission control: admitting only as many calls as the network can handle at a given time, so that a sudden spike in demand doesn’t impact the performance of calls in progress. Another method of call quality control involves the use of codecs—basically, a coder/decoder that translates audio packets into a high bandwidth (for higher quality) or low bandwidth (for higher volume) protocol. There’s a wide degree of variety in how SIP trunking service providers ensure call quality in their own networks, so be prepared to ask them about call admission control and codec support up front.
 
In addition, nearly all SIP trunking service providers will provide some kind of service level agreement (or SLA) to their customers outlining what they can expect in terms of network uptime, call completion rates, MOS Scores for call quality, etc. Again, these vary from company to company, so read the fine print.
 

And finally…

I have left out what may be the most important consideration of all: the session border controller (or SBC). In fairness, that one consideration really deserves its own blog, because SBCs can impact the security, quality and reliability of SIP trunking services in a variety of ways, from routing to interoperability to scalability. I’ll have to save that topic for a (near) future blog. Until then, “keep on a trunkin’”.