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    What is SIP Trunking and How Does it Work?

    Find out what SIP Trunking is, SIP Trunk definition and common terms, and the differences between SIP vs VoIP vs PRI. This guide will provide a complete understanding of how SIP Trunking works and if you should choose SIP for your business.

    SIP Trunks

    Communications technology is transforming. Where companies would have once only had the choice of a traditional phone system for their communication needs, digital transformation has brought with it a host of enhanced options including, Cloud PBX, VoIP phone services, cloud contact center platforms, and SIP Trunking.

    These technologies have found new meaning in recent years – especially in the wake of the COVID-19 crisis.

    “With the nature of the office transforming significantly during the pandemic, the need for a more flexible communications solution is top of the agenda for many businesses around the globe,”  Jonah Fink, CEO of net2phone, observes. “Evidence suggests people are actively seeking out employers that provide the flexibility of a hybrid work environment. Providers can expect to see continued interest in services throughout 2022.”

    What is SIP Trunking?

    Before we get into a deeper explanation of SIP Trunking, it would probably be a clever idea to establish a definition for the term.

    What is SIP Trunking

    SIP Trunking refers to a virtual telephone line which connects a business telecoms system to the public phone network. Compared to an ISDN connection, SIP Trunking is established via a data network. SIP Trunking is often used independently, as an alternative to ISDN, although it’s not unusual for the two systems to be combined to offer a hybrid solution.

    What is SIP?

    SIP, or Session Initiation Protocol is a method of data transmission used to set up connections between different devices including computers, desktop phones, mobile phones, video conferencing units, and file servers. It governs the establishment, termination, and time during phone calls as unique sessions. 

    How Does SIP Trunking Work?

    By acting as the virtual equivalent of an analogue telephone line, SIP trunks allow a communications provider to connect multiple channels to a PBX, thus allowing the operator to make and receive voice calls over the internet.

    Essentially, the physical phone handsets, headsets, or other communication hardware in an office environment or contact center communicate with an on-premises PBX. The call is then routed through the SIP trunk/s and then connected to the internet to make Voice over IP web calls possible.

    How does SIP Trunking work

    Main SIP Trunking Features

    SIP Trunking allows your business to enjoy flexible, reliable, and secure voice services with enterprise grade features, including:

    • Unlimited calling 
    • Virtual phone numbers (DIDs)
    • Hybrid SIP and Hosted environment support
    • Enhanced quality of service (QoS) for voice communications
    • Increased security
    • Compatibility with most IP-PBXs and gateways

    What Is The Difference Between SIP Trunking and VoIP?

    SIP Trunking and VoIP operate in tandem to make web calls possible. They both refer to internet telephony but you shouldn’t directly compare SIP to VoIP.

    VoIP, meaning Voice over Internet Protocol or Voice over IP, is a technology that enables the transmission of voice and other communications media such as text and video over an internet connection. SIP is one of those protocols.

    The main difference between VoIP and SIP is that VoIP is a method of transferring voice and/or video data over the internet, while SIP provides the protocol necessary to initiate, manage, and end those calling sessions.

    So, you can see how SIP trunks and VoIP work together to facilitate such communication features as:

    • Voice calls
    • Video conferencing
    • Audio conferencing
    • Messaging

    SIP Trunking vs. PRI

    PRI (Primary Rate Interface) and SIP (Session Initiating Protocol) are two methods accustomed to connect your business to a telephone network.

    PRI uses a T-1 transmission technology to make calls. It has been widely accustomed to support voice communications for over 40 years. A PRI circuit includes 23 voice channels to support 23 concurrent calls and one data channel to support call-related functionality like display while SIP Trunking uses an internet connection to make calls.

    The main difference between PRI vs SIP is that PRI uses a traditional phone line while SIP uses the internet to make calls. Comparing PRI vs SIP Trunking, PRI can be argued to provide a better voice call quality due to the dedicated physical lines but it is less flexible, doesn't offer failover to mobile phones, and is more expensive to install and upgrade. 

    Should You Choose SIP For Your Business?

    Because of the greater scalability, cost savings, flexibility and other benefits afforded by SIP Trunking, larger businesses with over 50 employees tend to choose it compared to other VoIP options.

    SIP Trunking, depending on the PBX capabilities, can offer all the features and benefits a business would get with a hosted PBX, with additional efficiency and quality thanks to the removal of primary interfaces. Because phone lines can be shared across multiple locations, and audio and video are consolidated into a single line, the cost savings associated with SIP Trunking can also be significant.

    The deciding factor when choosing between SIP Trunking and hosted PBX should be the size of the business. Smaller businesses will nearly always be better off with hosted PBX, as it provides all of the functionality of VoIP at little cost, both at the startup phase, and then later when it comes to maintaining the system. SIP Trunking, on the other hand, is better for larger businesses with more employees with existing PBX in place.

    How to Choose the Best SIP Trunking Provider?

    When deciding on a SIP Trunking provider to handle the communication needs of your business, you want to make sure you are dealing with a company which understands the world of unified communications inside and out.

    Your business’ ability to communicate with its audience is one of the most important parts of the operation, so you need to be confident the team providing your comms is a dedicated specialist which lives and breathes unified communications.

    SIP Trunking FAQs

    How much does SIP Trunking cost?

    You may need to purchase a SIP-ISDN Gateway, and you’ll make an upfront payment to your SIP trunk provider to establish the connection and a monthly fee to maintain it. Beyond this, the call and operational charges should actually save you money.

    Is SIP Trunking dependable?

    As long as the equipment is well maintained, you have a solid internet connection, and the platform is operated by an experienced unified communications provider then, short of a power cut or internet service disruption, you should not experience any significant interruptions with SIP Trunking.

    Is there a phone number limit using SIP trunking?

    You are only limited by the number of trunks you can accommodate. It is easy to calculate how many SIP trunks you need. Each trunk has capacity for approximately 20 channels. Therefore, if, for example, your contact center needs to be making up to 100 calls simultaneously, you will need five trunks in total.

    How to Switch to SIP trunking?

    Get in touch with one of the friendly unified communications experts here at net2phone and we’ll be happy to talk though the process with you.