After helping a variety of customers move to SIP trunks, there are a few speed bumps that seem to come up regularly. In general, SIP trunking is a mature technology and we’ve had great success with customers both large and small. That said, SIP trunks are not always easy to implement so it is best to be prepared.
6 things to look out for
1. SIP trunks are not all created equal. While the basic SIP standard is universal, the specific architecture and requirements vary from carrier to carrier and even between different offerings from the same carrier. You have to do your homework here and dig into the specifics. Be careful during contract negotiations, carriers will tend to underplay the complexities of the setup so you have to take it upon yourself to ask questions.
2. SIP trunks don’t exist in a vacuum. In order to make them work, there are several moving parts to consider. The configuration of the SIP trunk, the circuit that is delivering it to you, the network on your premise that it is traversing, and your VoIP phone system must all work in concert.
3. How is the trunk being delivered? There are many options here and each has implications for your configuration. Is there a dedicated point to point circuit (MPLS or Ethernet)? If the SIP trunk is coming from your internet provider are they both sharing the same circuit possibly with a separate interface? Is the trunk being delivered over the open internet?
4. To SBC or not SBC, that is the question. It is best practice to have a Session Border Controller (SBC) to delineate where your network meets the carriers network. This may sound simple but once again there are many variables: Who is providing the SBC? Do I want a dedicated appliance, a multifunction router, or SBC software on a virtual server? Should the SBC sit in front, behind or beside the firewall?
5. Don’t overlook planning for your network. With all of the variables involved in how a SIP trunk is delivered and how it talks to your VoIP phone system, take time to plan out your network configuration and IP scheme before you implement. Make sure your carrier, your network support team, and your VoIP system support team all agree on the architecture before you begin.
6. Watch out for firewalls, load balancers and WAN optimization appliances. If the SIP trunk traverses any of these make sure it is part of the network design and you have experts on their configuration available. If you can avoid traversing them, your life will be much easier.
I hope you found this helpful. Please reach out if you have any questions or leave me a message in the comments below. Thanks for reading!