How to Choose a SIP Trunking Provider

With the growth of the SIP trunking market, many providers claim to offer the best services. However, how do you find the right SIP trunking service provider for your needs?

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Try doing a Google search on ‘SIP trunking’, and you will get nearly 1.5 million results. A bewildering number of vendors all claim to be the best SIP provider, which can make it difficult for you to cut through all the fluff and find someone who can help you realize the benefits of SIP trunking.

All SIP services and providers are not created equal, so you must look for the following key attributes from a would-be provider:

  • Quality – Running your voice traffic on a data network helps you save money, but when you do so, you must make sure that your voice traffic gets priority. This will ensure that your voice service is always clear and it does not sound like you have a bad connection. Good SIP trunking providers can tag voice packets with quality of service (QoS) markers to give them priority treatment over other forms of data on your network.
  • Security – SIP is a new form of traffic that will need to run on your data network – one that your network may not recognize. Firewall updates or the deployment of a SIP-aware gateway or session border controller is required for most Internet-based deployments. For greater security, a private IP-VPN network service can completely protect your traffic from Internet-based threats. Your SIP trunking provider should guide you through your options and recommend the best solution.
  • Experience – SIP trunking is an innovative service, but it is still not widely used in Canada. Ensure that your provider has experience in deploying SIP trunking and can help you use it to super-power your unified communications (UC) infrastructure. A provider that has knowledge of how UC and SIP trunking work together can be a great asset.
  • Network – SIP trunking connects your private voice network to the public phone network via a SIP-enabled connection. A SIP trunking provider that owns and operates both voice and IP data networks can route calls with fewer handoffs or points of interconnection. This can ensure you get high-quality service that is easy to manage and support.

Your SIP trunking provider should make your implementation as low-risk and efficient as possible. Their project plan should allow you to focus on your core business while they focus on testing, project management and simplifying your complex networks.

What qualities do you want from a SIP trunking provider? Feel free to share your comments and questions below. 


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  1. Choose a provider with a world class network, maturity in the market place, a robust solid QOS offering, national coverage backed with a strong security methodology and you will be fine.

    Choosing a provider with an Asterisk Platform in the Cloud and no QOS or Security features will not be a wise choice.

    John Leonardelli / 11 years ago
  2. A very good point made by Mr Leonardelli. Folks need to remember that you get what you pay for, and often open source offerings without features like security and QoS can cause headaches and service issues down the road. Thanks for the comment.

    Grant Bykowy / 11 years ago
  3. Try to find a definition for “SIP Trunk”. The term SIP trunk or even the word trunk does not appear in the IETF’s current working definition of SIP or RFC 3261. Even the most accomplished in the field have not been able to come up with a definition that seems to fit the bill. Jonathan Rosenberg proposed in his 2008 IETF draft the following:
    “ A SIP trunk is a virtual sip entity on a server (UAS, UAC or
    proxy) constrained by a predefined set of polices and rules that
    determine how to process requests.”
    Then in the immediately subsequent paragraph:
    “The behavior of the trunk is conditioned on a contract – an agreement
    between the client and the server, that so long as requests are
    formatted based on the nature of the contract, the request will
    receive the specified treatment.”
    I’m not sure if both parts were intended to form his proposed definition but either way the draft was not ratified. Two years later he offered four other possible definitions in an interview with Unified Communications magazine so elusive is the definition of “SIP Trunk”

    I’m thinkin this has got to be leading to some confusion folks! The author points out that everyone and his brother’s got SIP trunks,.. SIP trunks,.. SIP trunks come an get yer SIPtrunks!
    Based on Rosenberg’s first paragraph I just have to create a “virtual sip entity” on a server and bingo I got a SIP trunk. There is an entire industry based on connecting to this “virtual sip entity” over whatever you happen to have. I have sometimes heard of the requirement described as “a good internet connection”. I use Google voice all the time over my broadband connection. It works well most of the time but occasionally I will hear hav t top at my ister or offee. Why? Because there is no CoS capability on my home gear and even if there was my residential ISP connection doesn’t support QoS anyway. If there is any upstream congestion in my ISP’s network they will drop packets of my inbound voice just like they will drop anything else to alleviate the temporary congestion condition unless you have an agreement with them not to (QoS). Yea it’s great for chatting with your wife while she’s on her errands but would you really deploy this in a business environment?

    Ask your SIP trunk provider if the transport mechanism from your premise to the point of “drop off” to the PSTN and vice versa is provisioned with a quality of service. Unless the answer is yes don’t bother.

    Dave Kincaid / 11 years ago
    • Excellent point raised by Mr Kincaid – the term ‘SIP Trunk’ is not clear in terms of a single comprehensive definition. Even Rosenberg, the ‘grandaddy of SIP’, after taking pains to define it, came up with four different use cases in which a SIP Trunk is used. Since it seems so difficult to cover all technical uses of a SIP Trunk in a single definition, I prefer to rely more on the practical definition – something that business people use day in and day out, and something that defines what it does for you in practical terms. There are many, but here’s a good one IMO:

      Session Initiation Protocol (SIP) trunking is the use of voice over IP (VoIP) to facilitate the connection of a private branch exchange (PBX) to the PSTN via the Internet. In effect, the Internet replaces the conventional telephone trunk, allowing an enterprise to communicate with fixed and mobile telephone subscribers worldwide. SIP is the signaling protocol as defined in IETF RFC 3261, and the trunk allows for multiple concurrent sessions to be established between the user and the PSTN.

      Thanks for the post!

      Grant Bykowy / 11 years ago