What Is SIP Trunking?

The technology industry loves its acronyms, and in the world of voice communication you’ll encounter many, like VoIP, PABX, and ISDN. One that you’ll frequently find when talking about IP-based phone systems is SIP, in particular SIP trunking. So what exactly is SIP trunking and what does it do?

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SIP stands for Session Initiation Protocol. What this does is to provide a protocol that is used to initiate and terminate voice calls when using a VoIP wholesale network. SIP trunking is an extension of this that allows a private exchange (PABX) to send and receive calls over the internet rather than using the more traditional route of an ISDN line.

Why Do You Need SIP Trunking?

If you have an existing phone system using a PABX and attached to the public phone network via ISDN, you might be wondering if SIP trunking is relevant to you. The problem is that ISDN is a technology that is on its way out. BT will be switching off ISDN services in 2025 as it updates its network to one based on IP standards.

This means businesses will have to switch to SIP trunking. So when you are looking to update your telecoms and are asking what is VoIP termination, you also need to look seriously at SIP trunking in order to future-proof your investment. It can be part of a Unified Communications strategy too.

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SIP Trunking Advantages

The big advantage SIP trunking has over ISDN is that it’s cheaper. ISDN is a dedicated line that you have to rent, whereas SIP uses an internet connection. This means line rental is cheaper and you will save on call costs too. If you have multiple sites, you may even be able to get free calls between them.

Another advantage of this is scalability. ISDN lines support only a limited number of voice calls before you need to add another connection at more cost. Using VoIP is much more flexible, making it easier to add new calling capacity as your business grows or to cope with seasonal peaks in demand.

If your business relies heavily on telecoms, then SIP trunking is good for business continuity too, because in the event of a problem you can easily relocate to a new location. Provided there’s a suitable internet connection, you can be up and running again quickly.