SIP trunking is taking the business world by storm. According to researcher, Infonetics, in North America, 45% of businesses are already using SIP trunking with an increase to 67% predicted by the end of this year. We get the chance to chat with people every day who are excited about the possibilities that SIP trucking offers, but who are generally unfamiliar with how it works or what to expect. We thought it would be useful to explain some of the fundamental aspects of SIP trunking without a lot of industry jargon or unexplained acronyms.

What is SIP Trunking?

SIP stands for Session Initiation Protocol.  SIP trunking is a method of sending voice and other unified communications services over the internet. It works with an IP-enabled PBX (private branch exchange). SIP trunking replaces traditional telephone lines or PRIs (Primary Rate Interface).

Before SIP became a popular and reliable method of transmitting voice signals, telephone calls were carried over the Public Switched Telephone Network (PSTN). The PSTN is the network of the copper phone lines we traditionally associate with the “telephone.” The PSTN is a circuit switched network, which requires a physical connection between two points to complete a call.

SIP trunks are virtual phone lines that enable users to make and receive phone calls over the internet to anyone in the world with a phone number. SIP trunks utilize a packet switch network, in which voice calls are broken down into digital packets and sent across a network to the final destination.

SIP Channels

Each SIP trunk supports SIP channels. A SIP channel is equivalent to one incoming or outgoing call. A SIP trunk can hold an unlimited number of channels, so users only need one SIP trunk no matter how many concurrent calls they expect. The number of channels required depends on how many calls the business will make at any one time.

The Difference Between SIP and VoIP (Voice over Internet Protocol)

Although SIP and VoIP are often used interchangeably, they are not the same thing.  VoIP stands for Voice Over Internet Protocol.  It is a broad term that covers any phone calls made over the Internet. It includes a group of protocol technologies of which SIP is an example.  SIP is one of the specific protocols that enable VoIP.


Voice Codecs

Codecs convert audio voice signals into compressed digital form for transmission over the internet. When the signal reaches its destination on the network, the codec converts it to an uncompressed audio signal for replay. It’s what makes VoIP possible. Different codecs have different levels of compression. The two most popular for SIP trunking are G.711 and G.729. G.711 provides an uncompressed high-quality voice, while G.729 is compressed so that it uses less bandwidth at the sacrifice of quality.

Carrier Tiers and Call Quality

Great audio quality is essential for any business communication system. The best solutions offer voice quality that is indistinguishable from traditional landlines, but it is important to be diligent about the grade of the carrier network used by your SIP provider.  Only Tier-1 carriers connect directly to the backbone of the internet for the highest possible call quality and reliability.

Router Setting: Quality of Service (QoS)

Quality of Service (QoS) is a router setting that tells the network to prioritize voice calls over other data traffic.  Small delays in the signal reaching the network, or a bit of data loss isn’t something that users consuming data will notice, but it can wreak havoc with voice calls. Enabling QoS ensures that audio quality will remain high even while data-intensive activities, like downloading large files or streaming content, happen in the background.

Why Choose SIP?

There are many benefits of SIP for your business. One of the most important is the reduced communications costs. In many cases, unlimited local and long-distance calls to most of North America are bundled in with the monthly fee for each SIP channel.  What’s more, many SIP providers allow you to provision channels on-demand, meaning that you get, and pay for, only the number of channels that you need now and can easily grow at any time.

Additional benefits include built-in business continuity features, network consolidation, and Unified Communication features like video, presence, application integration, and instant messaging.

You don’t need to be a networking or telecommunications expert to take advantage of SIP for your business. We do recommend choosing a strong partner that will help walk you through the implementation process and support you as the needs of your business change over time. If you have additional questions about how SIP might work for you, we’re happy to help.


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