The switchover is coming: How to prepare for your migration to SIP

Blog by: Phil Curwood, Chief Technology Officer, Adept4 - 06-Feb-2019

ISDN networks will soon be no more. BT has announced their gradual phasing out, and by 2025 all organisations will be required to migrate over to IP networks. Generally, this means SIP trunking.

The benefits are there for the taking. SIP trunking allows voice and data to be transmitted over secure internet connections as opposed to fixed telephony lines – and, in turn, it enables massive improvements in terms of flexibility, scalability and cost. By shifting the migration pathBT has set out a clear plan for the transition. Next year, organisations will no longer be able to buy new analogue/ISDN lines, or order extra ISDN lines for expansion. Then, by 2025, the company plans to have migrated all organisation to the IP network.

In practice, this means that if you have any plans for upgrading or replacing your telephony system, then you mustthink in terms of an upgrade to SIP. And if you’re happily working with the analogue system you have in place, you should prepare yourself for both a potentialdrop in quality (since investment in ISDN is dramatically decreasing), and a migration within the next six years.

How to plan for said migration? Here are the key steps you need to cover.


Any technology migration project is the ideal opportunity to consider your business needs and plans for the future, and how your technology procurement can best enable them. As such, you should begin by assessing your current network infrastructure and capacity, evaluating whether or not it meets your needs today – and whether or not it is likely to meet your needs in the future.

Specifically, you should examine the available bandwidth on your existing data connectivity, your current call-flow, and your more general plans for business growth and expansion. The answers to these questions will help you to understand where your ISDN system might be lacking, and what your requirements are likely to be in the months and years ahead. Any good SIP provider should be able to consult with you throughout this process, and also advise on the scope of the ultimate migration.


SIP trunking requires far less in the way of hardware and physical infrastructure than ISDN networks, which should make for a far smoother and less disruptive installation than you have been used to with previous telephony upgrades. Depending on the scale of your operations, you might be able to migrate your entire telephony system to SIP trunking in a single step, or a phased transition might be a better approach. Regardless, downtime should not be necessary; installation, tests and checks should all be able to take place in a controlled fashion, alongside normal operations.

Because they merge voice and data, SIP-based communications systems can integrate with business applications such as videoconferencing and CRM tools, so this integration should also be planned for an carried out as part of the deployment process. 


Testing is an absolutely critical, yet sometimes a neglected aspect of any technology deployment. It should take place in a controlled environment alongside your core business operations for minimal disruption, and it should cover any and all of the third-party applications you might be integrating with your SIP trunking solution, as outlined above.

Go live

The final stage of your SIP migration can then take place, and provided that your planning and testing stages have been carried out thoroughly, this might only take a matter of hours. The full benefits of SIP trunking will then be available to you, from cheaper phone calls with no need for expensive ISDN line rental, to dramatically improved resilience and disaster recovery in the face of network failure.


Topics: SIP trunking, Telephony, Voice, Connectivity

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