On traditional PSTN telephone networks, businesses would purchase bundles of lines, known as trunks, from their service provider in order to give them access to the phone network. The concept of trunking has stuck even as we move towards VoIP systems, and effectively SIP trunking does the same job, providing access for a business system to the service provider’s network.
The difference is that unlike the physical cable connection used by a traditional trunk connection, a SIP trunk is a purely virtual link provided over the internet. So what are the benefits of this technology to your business?
With older telephone systems there were numerous things to think about. ISDN lines, basic rate interfaces, primary rate interfaces, PSTN gateways and more. A SIP trunk does away with all of these, simplifying the process of connecting and reducing costs. If your business operates over multiple sites you can use a single SIP trunk connection to serve all of them with no need for multiple connections.
There is no longer a requirement to have separate connections for voice and data traffic. As the business expands, it’s also much easier to scale up the system without the need to install additional lines or equipment.
Adopting SIP means that you are effectively outsourcing your link to the PSTN to your service provider rather than having it directly linked to your PABX. This has a number of advantages. First, calls are carried via the internet to a point close to their destination before transferring to the PSTN, thus again cutting costs. Second, you may no longer need a PABX in-house at all, allowing you to move the whole operation to the cloud.
There will, of course, be some initial costs, including switching to an IP-PBX whether in-house or in the cloud, and supplying desktop access in the form of IP phones or soft phones.
Businesses are increasingly shifting to more flexible working models, allowing staff to work from home, or to hot desk. In addition, modern business requires a flexible approach that recognises people may be out of the office for much of the time.
Until recently, these remote workers may have accessed networks via a VPN. While this is good for data connections, it has some drawbacks when it comes to using VoIP telecoms. SIP trunking allows the use of remote connectivity apps. These mean that remote users can access enterprise PABX functions easily whether they are at home, in a hotel or in a branch office, or anywhere they have access to the internet.
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Moving to IP to cut call costs by using a reputable provider such as IDT means you get a connection that can handle far more traffic than a traditional phone system. However, it is important to ensure that the quality of service (QoS) on offer is acceptable.
If you are relying on the same network to process both voice and data traffic, QoS settings need to take account of the fact that voice is very sensitive to delays and will need to take priority over other traffic in most circumstances.
This is often achieved using a Multiprotocol Label Switching (MPLS) network that allows flexibility in the way in which traffic is routed. This allows effective management of bandwidth. These capabilities are handled at the network level so again it’s necessary to have a SIP-capable firewall in order to handle the traffic and allow the service to be used securely. Contrary to popular views, it is not the internet that presents a bottleneck to VoIP traffic but the company’s own network or its immediate connection to the ISP.
Any service that relies on the use of the internet is bound to raise concerns over how secure it is. Again, the importance of using a SIP-aware firewall is key to defending against unauthorised activity.
What’s known as a SIP proxy can be used for filtering and verification as well as routing. It can also control which ports traffic is allowed to use. For added security, you can add encryption too. It’s also essential to have effective authentication of the connection to the service provider. Some PBXs can provide this, otherwise it will need to be handled by the firewall. Existing enterprise firewalls may not be able to handle SIP traffic. An upgrade or switch to a SIP-ready solution may, therefore, be required and this is something else to be factored into costs.
A final concern is the resilience of the network. Relying on an internet connection for your calls means that if you lose the internet you lose voice too. A SIP-capable PBX or firewall should be able to provide redundancy by switching traffic to an alternative carrier in the event of problems.