ISDN shutdown & the migration to SIP

News /

There has been much deliberation in the industry as to when BT might switch off the PSTN and ISDN networks but there has never been a date set until now.

BT Group CEO Gavin Patterson has set a date of 2025 to switch off ISDN services from its Public Switched Telephone Network (PSTN). BT Group are set to no longer accept any new orders or amendments to services pertaining to any ISDN product as of 2020 with the final termination set for 2025.

Thinking of switching your business telecommunications from ISDN to SIP Trunking?

What is PSTN?

The public switched telephone network (PSTN) is the aggregate of the world's circuit-switched telephone networks that are operated by national, regional, or local telecoms operators, providing infrastructure and services for public telecommunication. Analogue voice data is sent over a circuit-switched phone line made up of copper wires which is owned and operated by your phone provider.

What is ISDN?

Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the traditional circuits of the public switched telephone network. Put simply your standard telephone line is used to send voice and data over the same line. This is why you can make phone calls on a home telephone and plug your broadband router in to access the internet using the same port.

Why is BT switching to IP?

BT introduced ISDN nationwide in 1986 and since then connectivity has advanced greatly. The recent investment and nationwide roll out of superfast fibre Internet and new Ethernet products provides a viable alternative. In fact BT have not installed any new ISDN lines in central London since 2014, which goes to show that many businesses have already moved on. But switching over 3 million active ISDN users is no small task which is why they have given businesses so much notice.

What are the alternatives?

The recent investment in the UK communications network has made the new fibre infrastructure widely available and affordable to small businesses. This means IP based solutions such as VoIP and SIP are the top alternatives for businesses.

What is SIP?

SIP (Session Initiation Protocol) provides you with a phone line which is carried over your fibre Internet connection removing the need for an ISDN phone line. SIP lines used to have reliability problems due to inadequate underlying broadband connections. These issues have now been fixed due to the recent connectivity improvements and Service Level Agreements now offered by providers.

What is VoIP?

VoIP is a cloud based telephony solution which moves your whole phone system online so all your calls are sent over your Internet connection. This digital cloud based phone system offers a wide range of additional features such as call recording, receiving voicemails via email, call queuing and unified communications – being able to access the system on multiple devices such as a mobile, tablet and desktop.

Top 5 benefits of SIP and VoIP

  • Huge savings – Up to a 78% reduction in costs compared to ISDN due to cheaper calls and no more expensive line rental.
  • Greater flexibility – Move anywhere in the UK and simply plug back into the network with no need to change numbers.
  • Faster installation – No more waiting for an engineer to install physical lines means you get connected faster.
  • Higher resiliency – Multiple fibre lines can be installed providing an automatic backup and failover so you’re always connected.
  • Advanced features – Increased control, integration and analytics offers a huge range of new and advanced features.

In summary ISDN phone lines are no longer a viable option for many businesses, simply because they don’t meet the critical business requirements of flexibility whilst saving on costs.

So, what should you think about doing?

SIP Trunking is the service getting the press and is also the service that’s rapidly replacing ISDN lines. Simply put SIP is an IP based telephony service. This means you can combine voice and data services to make your business’ telecoms more economically efficient.

It’s not a small project for any business, no matter what size, to replace a fully built voice infrastructure. A good supplier, of which TTNC is one, should help you plan the process that will transcend your company to the premier league of phone networking.

Let’s look at the migration process step-by-step

Understanding what you have and planning is key. Your voice networking infrastructure will run over a standard IP network and should be treated in the same way as any other network deployment or project. Migrating from ISDN to SIP Trunking follows a similar method to a larger IP network deployment, just with the addition of a few phone specifics too.

1. Planning is key

  • How many phone numbers or extensions (DDIs) are there? You’ll need to think about where they are directed to: for example, are you forwarding your Freephone or local phone numbers to your main receptionist or an automated phone line (IVR)? Are you forwarding certain calls to specific departments or members of staff (Hunt Groups)?
  • How are your inbound calls handled? Do you use call queues, IVRs? Does your business provide customers with information through recordings? If departments or individual users within your business can divert calls to other locations or numbers, how does the company configure this?
  • Do you have voicemail? If so, how do you access the system?
  • Do you know the extensions of every user in your voice networking system? This information will simplify the migration process.

When TTNC carry out this process for a customer we get to know how all calls are handled throughout the business and per department. This is done by completing an end to end audit for each type of call that you handle. This will be recorded and presented in an end to end call flow diagram. The information retrieved will aid the decision making process for any potential new equipment requirements and act as a firm foundation for a testing plan.

2. Current phone line issues

Once your existing phone network has been documented and diagrams of your call handling management produced the next step is to identify the opportunities and changes that can be made to help your business, which only SIP can offer.

Your company, like many others, could have processes for call flows that were implemented many years ago (decades in some cases!). This puts businesses at a disadvantage because features, services and functionality won’t reflect the current telecoms features and options that are available.

Tell us what your current communication issues are and we can advise on how SIP Trunking will help overcome these problems.

3. Test

Testing is critical and will find the route of all your failures. Create, agree and document a testing plan. This needs to include the processes your business take to verify the correct management of call handling.

4. Hands on

Now you have identified your needs, it is time to meet those demands by choosing the most cost effective and beneficial equipment and services. Your call-routing requirements and scales of flexibility will determine this. You might like to consider the below:

  • Do you have good bandwidth? SIP Trunks need decent bandwidth so to see the true benefits you will need a good reliable Internet connection
  • Is the use of an SBC (session border controller) possible? If not, you’ll need a SIP aware firewall. An SBC is hardware that controls how calls are initiated, conducted and terminated.
  • Does your business use an in-house IP-based phone system? If the answer is no then you can either upgrade or implement a SIP gateway. If you do have an IP phone system you’ll be above to choose between existing analogue handsets (with adaptors) and new feature rich IP Phones.
  • Does your company separate voice and data traffic? If not you should implement a separate set od switches and cabling for SIP equipment (if it isn’t possible then implement VLANS to split the traffic)

5. Setting up

Now that your business has identified the phone network requirements, created a testing plan and has acquired the new technology, the next step is to install and configure so that it works with your new SIP service.

Now it’s testing time. Assign some test numbers to your SIP line and run it through your testing plan. Testing your flexibility is essential; try simulating some failures through the system to make sure a suitable DR (disaster recovery) plan is in place.

6. The porting

Once everything is up and running with no problems, you can go through with the migration from ISDN to SIP safely and without any downtime whatsoever

TTNC, or your SIP supplier, will need to provide some information in the form of a porting request for all of your business phone numbers. Ensuring the required information is correct and submitted is an essential task if you want to avoid the porting request being rejected. This process can take a few weeks so we recommend that you don’t cancel your ISDN phone line just yet; it will help you avoid problems before the process is complete.

7. Cut the cord

You can now release your ISDN phone line. Call your ISDN provide requesting them to cancel your account and shut down any associated equipment. Now you will be able to take advantage of a more cost-effective, future proof and feature rich solution. You can also save up to 50% on line rental and around 25% on your outbound call costs too.

8. Conclusion

In conclusion the ISDN shutdown should be seen as an opportunity and not a reason to panic. The pain and panic of transition can be taken away by having conversations with providers to plan your transition. You have the opportunity to benefit now so why wait until 2020?

Further Information

Explore TTNC's SIP Trunk service as you plan on migrating from ISDN:

Alternatively, you could look at replacing your ISDN lines with VoIP Users, a product developed with simplicity in mind. Assign unique VoIP Users for even greater flexibility:

Or call a Specialist: +44 20 3151 1000