SIP providers offer many services

What does it mean to be a provider of SIP services?

SIP trunking

The term “SIP Provider” means different things depending on who is using it. It has its roots in “SIP Trunking”, which is a service provided to businesses that allows them to connect their in-house IP PBX systems to the outside world - the public switched telephone network or PSTN.

Without SIP Trunking, devices within a PBX can only talk to other devices on the same network. The Internet Telephony Service Provider (ITSP) gives their clients a pipe or a “trunk”, which makes the connection to the PSTN, thereby exponentially increasing the reach and usefulness of their PBXs. One example of a SIP trunking service is our own, OnSIP trunking.

This is the most common definition of an SIP provider today. However, there are now lots of new entrants to the field offering innovative services making use of the SIP protocol as a backbone. These nimble ITSPs are able to build on the traditional SIP trunk service and create entirely new business models; these new “SIP Providers” are changing the face of the VoIP industry.

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Hosted SIP (PBX)

While a SIP trunk only caters to firms who already have their own IP PBX system built and are ready to hook up to the PSTN, the latest breed of SIP providers don’t require their clients to have anything other than phones. These ITSPs have their own PBXs hosted on their servers and allow businesses to make use of them, delivering VoIP services at extremely low prices. 'Hosted PBX' services come with built-in connections to the PSTN network, eliminating their clients' need to purchase trunking separately.

There are also many SIP services which are targeted towards private individuals such as and These offerings allow people to get their own SIP accounts for free. offers a PSTN connection while getonsip is currently SIP only, meaning you can only make calls to SIP addresses.

Additional Benefits for Hosted SIP customers

We offer SIP hosting, which puts the full benefits of the technology within the reach of firms who have no SIP infrastructure of their own. Along with the ability to make VoIP calls, businesses can get SIP accounts to distribute to their employees, which allows anyone using a SIP device to call them for free as long as they know the SIP address associated with that account.

A SIP address looks just like an email ID. By default, the domain of the email - the part just before the “.com” will belong to the ITSP providing the service. When we host your VoIP communications, your SIP address will look something like “” However, we also give you the ability to change the SIP address domain to match the corporate email ID which your employees use.

This page expands on an earlier blog post by Rob, 'What is a SIP service Provider?'

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