Reliability Contest: ISDN vs VOIP

28th September 2016

Fife Chamber member 9 Dots Consulting wanted to share their latest blog with their fellow members!

We have now reached a point in the UK where over 50% of businesses are using IP-based telecom solutions rather than the traditional BT digital network known as ISDN, and with the announcement of the ISDN switch-off by Openreach at the start of the year, the move to VOIP is now an inevitability for British businesses. With increased functionality and savings upwards of 60%, it would appear to be a no-brainer, but for businesses we are talking to, one of the concerns holding them back is the perceived lack of reliability and quality of these technologies. For the vast majority of businesses, the availability and quality of their telecoms is an absolute priority. The question I hear most often is ‘If I move to VOIP, what happens if my broadband goes down?’ or “We tried VoIP in the past and had lots of call quality issues.” This article looks to cover the key points, dispel the myths, and clarify the actual reliability of ISDN vs VOIP.

Call quality

ISDN has been around since 1986 and is seen as the standard bearer for high-quality, resilient business telephony. VoIP as a technology, although perceived as ‘new’ has actually been around since 1995 and really came to the fore with the launch of Skype in 2003. In simple terms VoIP is a voice or video call carried over your internet connection. As a result, the quality of the call is typically down to the quality of the connection to the internet. To say VoIP has call quality issues, is like saying a Ferrari has driving issues when driving it on a single track dirt road full of potholes. Take it on a race track and it will be brilliant. This is the case when VOIP is carried over a decent broadband connection.

The key to a great call on VoIP is to ensure it is carried over a resilient, business-grade broadband connection separated from your existing broadband network and that the routers, switches, cables and phones are all up to the task. To take this one step further, our Ethernet broadband products provide a Quality of Service (QoS) guarantee for call quality on our connections, allowing you to carry voice and data over the same connection with no call quality issues whatsoever.


‘But what if my broadband goes down? My broadband goes down all the time.’ As data usage has increased we have seen a dramatic increase in the number of calls regarding broadband issues. More often than not, there is absolutely no issue with the broadband, businesses have simply outgrown their existing connection which isn’t always easy to see until the connection starts to fail. As a business grows in people it’s easy to see the office filling up making it very obvious when there is simply no more room for another desk and it’s time for a bigger premises, but this is not easy to see on your broadband if it’s not pro-actively monitored. The reality is VoIP actually requires very little bandwidth, and the perception that the broadband ‘goes down a lot’ is usually because the business has outgrown their current service and it’s time to upgrade. The key is getting the right type of connection that is fit for your business needs. The key to a reliable broadband connection is to make sure you have enough bandwidth for the demands of your users, and to ensure you have the appropriate Service Level Agreements (SLAs) in place on the broadband product you have. Standard Openreach fix times on ISDN are ‘Aim to fix by the end of the next working day’ with a 6-hour fix 24/7 at a premium. Our Ethernet broadband products come with a 5-hour 24/7 SLA so if used for VOIP, are actually MORE reliable than your ISDN.

Disaster Recovery

The third leg to the ISDN vs SIP reliability stool is what happens in case of an outage, either in the short or long-term. Most businesses will have a business continuity plan for these situations, but are often quite limited with regard to the telecoms. Issues range from a line fault, as covered above, a power cut, or something more serious such as a fire, theft, flood or water damage. This is where the power of SIP really comes into its own.

If there is a line fault on ISDN services calls can of course be diverted however the issue first needs to be recognized and then your service provider needs to be contacted in order to initiate the divert. SIP has an ‘auto-failover’ solution built in so that if a call is not reaching its intended destination through the primary connection, calls are automatically diverted to a secondary broadband connection. This can be a back-up broadband connection in your current office, or for bigger ‘disasters’ calls can be automatically diverted to another office.

For businesses who use Direct Dial In’s (DDI’s) in their business, one of the biggest drawbacks of ISDN is that in the event of an outage the whole DDI range can only be diverted to one number. Imagine if all direct calls to all your staff members could only be answered by 1 mobile or 1 phone line. A major benefit of SIP is that it allows each individual DDI to be diverted to a different number so that calls can be diverted to your employee’s home line or mobile and can be built in to automatically happen should the worst happen.

In summary, IP-based voice solutions can be a terrible experience if delivered incorrectly or over the wrong broadband connection, however get this right and the reliability and DR features far outweigh those of traditional ISDN. There are many factors holding businesses back from making the switch from ISDN to IP-based solutions, but reliability certainly shouldn’t be one of them and the team at 9dots would be delighted to help you.

For more information or to read some of 9 Dots other blogs visit:

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