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5 ways SIP trunking beats ISDN connectivity

7th June 2021
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With the UK Superfast Fibre Rollout and PSTN Network switch-off drawing closer, many businesses using ISDN lines are finding themselves in need of an alternative. SIP trunking has become the popular replacement for soon-defunct ISDN networks. What many don’t know are the many ways SIP trunking offers better functionality than the ISDN services it’s replacing. 

It’s estimated up to 2 million UK business rely on ISDN (Integrated Services Digital Network) lines. Since being introduced to the UK market in 1985, ISDN2 and ISDN30 lines have provided businesses with affordable telephone and internet connectivity at a scale that fits their usage requirements. 

However, as was announced by BT in 2015, the UK’s PSTN (Public Switched Telephone Network) will be permanently switched off in 2025. The UK’s analogue telecoms infrastructure will be replaced by a state-of-the-art, superfast national fibre network. This industry redefining shake-up means, amongst other things, that every ISDN line in the country will become non-functional.

This presents the 2 million UK businesses relying on ISDN2 or ISDN30 connections with a question; what’s the best replacement for ISDN?

At Immervox, we’ve found that SIP (Session Initiation Protocol) trunking has been the most popular choice. Not only does it provide a cost-effective replacement for your old ISN infrastructure, but it offers improved functionality and, when all is said and done, a superior and more reliable connection.

If your business is still relying on ISDN2 or ISDN30 lines, and you’ve yet to decide on how you’re to replace them, here is our list of 5 ways SIP trunking is a better connectivity solution than ISDN. 

SIP vs ISDN: What’s the difference?

Before we break down where SIP trunking surpasses ISDN, let’s take a brief look at the two and where they differ.

ISDN solutions transmit voice and data over a traditional copper network. It offered many advantages over the commonplace analogue PSTN lines which preceded it, including:

  • Multiple number provision (DDI) 
  • Support for channel bonding.
  • A guaranteed data transfer rate.

SIP trunking utilises IP networks to transmit voice and data. It can be used in conjunction with your businesses existing IP gateway or IP phone system/PBX. Unlike ISDN, SIP trunking requires no additional infrastructure or cabling.

What SIP does better than ISDN

So now you understand what SIP and ISDN are and what makes them different, here are our top 5 ways that SIP trunking surpasses ISDN lines.

Reason 1: SIP is more cost-effective than ISDN

Because it runs over IP, call costs with SIP trunking are significantly reduced. With the right usage and call plan, this can mean significant savings on your monthly comms spend. SIP also doesn’t require PRI lines, which adds additional long term savings.

Another reason SIP trunking is a cheaper solution than ISDN is the savings on hardware and services. SIP trunking requires no additional hardware or network infrastructure to install, provided your existing broadband connecting is reliable. This removes maintenance and upkeep expenses from your telecoms and data bill. 

The final reason SIP is a more cost-effective ROI than ISDN is that, because SIP runs over your fibre broadband IP cables, you can run voice and data over the same lines. This makes managing your communications and connectivity expenses much easier. Rather than managing telecoms and broadband separately, with SIP they can be streamlined into a single monthly package. 

Reason 2: SIP trunking supports failover and disaster recovery

Because your SIP infrastructure isn’t tied to a single physical phone network, calls can easily be rerouted. Businesses that employ a SIP trunking solution can easily redirect customer can client calls to a backup-site or phone extension in the event of main premises downtime. 

It’s because of this flexibility that SIP trunking is a much better solution for business continuity. The ease at which a failover and call rerouting can be initiated means that SIP can be an important and reliable component of your organisations’ disaster recovery plan. 

Because ISDN lines are built on and configured exclusively to your on-premise network infrastructure, ISDN doesn’t provide the same security. Whereas SIP can easily be utilised as a safeguard against the impact of major events, it isn’t possible to create an effective failover procedure for ISDN networks without extensive time and financial investment.

Reason 3: SIP offers extensive flexibility, scalability, and configuration

Scaling or configuring an ISDN network is costly, time-consuming, and far too complex to consider doing on a by-the-user or by-the-extension basis. Because ISDN networks are so heavily dependent on physical hardware infrastructure, any changes to them usually require an on-site visit from an engineer or technician. 

Because SIP is firmware and software-based, configuration can be carried out remotely. Many SIP services include browser-based configuration. Adding or removing extensions can be done in a few clicks, with no manual set-up necessary beyond connecting the new terminal and headset to your internal network. 

Reason 4: SIP trunking is a WFH and Remote-friendly solution

During the height of the 2020 Coronavirus pandemic, 60% of UK adults were working remotely from home. 26% of those surveyed planned to continue working fully or partially from home even after lockdown restrictions are eased.

Remote teams and a hybrid office/WFH culture are predicted to be the norm as we moved forward into the 21st century. Any infrastructure solution your business employs must take this into account, and facilitating obstacle-free WFH for your employees should be part of your communications strategy.

SIP trunking offers many functions ISDN doesn’t which make it ideal for the remote-inclusive future. For example, automatic call routing to mobile phones when employees are out of the office. Missed calls can be incredibly damaging to your organisations’ reputation, and when your staff are geographically spread due to remote working the risk of poor customer service increases dramatically. 

The functionality of SIP trunking mitigates these risks. It offers easy-to-implement solutions to remote and WFH problems that ISDN simply cannot. 

Reason 5: Rapid deployment and number porting makes SIP ideal for temporary sites and mobile business

ISDN installations typically take around six weeks, provided there aren’t complications. A SIP trunk, on the other hand, can be installed in around 48 hours. This rapid deployment makes it ideal for temporary sites (such as building sites or portable cabins). Set up is also incredibly simple, as SIP trunks require no additional cabling to be laid or construction work to install (gone are the days of having to knock a hole in the wall every time you needed another 3-4 terminals connected).

Many businesses that work across temporary sites also have staff who work on the move. If you have a nomadic workforce SIP trunking is ideal. Because SIP numbers aren’t geographically dependent, if you move premises or relocate across the country it’s quick and easy to port your UK number to your new location. Because ISDN connections are on fixed lines it isn’t possible to transfer and port numbers in this way.

SIP trunking: bringing enterprise-grade connectivity to your business after the ISDN withdrawal

As we said at the beginning of this article, ISDN2 and ISDN30 lines in the UK are going to be disconnected by 2025 (perhaps sooner, depending on your location). 

If your business is still using ISDN lines, the Uk-wide upgrade to a national superfast fibre network means that you’re going to have to replace them. This is the largest change to the UK’s national telecoms infrastructure in close to 30 years, it’s not something that any business can ignore.

SIP trunking continues to be the most popular choice for our customers who are proactively implementing the connectivity and communications infrastructure they’ll need to rely on post ISDN switch-off. We hope this piece has given you some insight into why SIP trunking has been so warmly adopted by Immervox customers across the UK. 

If you think SIP trunking is the right ISDN replacement for your business, or if you think it isn’t and want to know about further alternatives, give the team a call. We’re always available to discuss your current business infrastructure and how we can work with you to adapt it for life after the PSTN switch off.

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