Self-managed SIP Transfer

Thank you for choosing TNBN as your SIP Provider

To self-manage and transfer your ISDN lines to TNBN SIPS please fill out your details below and we shall email you an application form to complete and return.

Helpful notes when switching to SIP from ISDN

With a timeline set for 2025, BT’s recent announcement that it intends to switch off the ISDN network may not seem like urgent news. After all, with just a few years to go, there’s plenty of time to organise the system that will replace your existing telephony.

But the secret to a successful SIP implementation is planning – and the more time you have to plan, the better your chances of a system that works quickly and efficiently from day one.

The time to start planning your SIP implementation is now. And thankfully, it’s easier than you might think.

What you need to do from start to finish – If you require help call TNBN on 0800 019 5562

When operating a self managed transfer from ISDN to SIP it will be your responsibility to ensure you have a SIP enabled PBX, or SIP Gateway on a non sip enabled PBX. Your telephone PBX maintenance company should be able to help you with this information. Make sure you have enough bandwidth on your broadband connection for voice (this is usually 100 kb per call) so that it will not slow down your speeds for data connections. Before TNBN ports your ISDN phone numbers into the cloud (including any DDI numbers) we shall send you the PBX configuration details, the broadband ports to open, and will provide you with a dummy SIP and a date for the initial porting from ISDN to SIP will follow in due course. You will need to speak to your broadband provider to open the specific firewall ports to enable SIP access. You will need to arrange with your PBX maintainers to connect your broadband circuit into your PBX or gateway and it would be a good idea to run trials with the dummy SIP (provided by TNBN) to ensure everything is working and running parallel with your current ISDN set up, before the actual port of your ISDN to SIP takes place. Once the commence date of the porting of our ISDN to SIP takes place you will need to arrange with your PBX maintenance company to be on site to programme the system with the converted ISDN to SIP numbers and any DDI numbers associated with the account. There may be some down time in service during this programming.

Quick guide transferring from ISDN to SIP

1. Check that your system and handsets support SIP and you have enough bandwidth for voice calls

If your telephone systems and handsets don’t support SIP, they’ll be rendered useless when ISDN is withdrawn.

In this situation, you can opt for a premises-based SIP PBX or alternatively, an ISDN-SIP gateway allows you to convert the ISDN interfaces on the PBX to a SIP interface. This can then be connected to any SIP provider over an IP connection. A gateway is a comparatively affordable option, available from as little as £800 – although this comes at the cost of some features.

Think about how many people in your organisation use the phone at anyone time. Typically a VOIP call uses 100kbps per call. Make sure you have enough bandwidth so that it doesn’t slow down your internet connection. Some internet providers can split some of your broadband speeds in two parts – one for voice and one for data.

2. Configuration details and broadband firewall ports to open to access TNBN SIP

We shall send you all the configuration details and broadband firewall ports to open via email when we receive your completed application form, and have set up your account.

3. Time frames switching from ISDN to SIP

As part of your planning for a migration to SIP, you’ll want to estimate likely costs and timescales.

For reference, the timescales for common migration methods are:

  • SIP trunk into a SIP-ready PBX and migrate phone numbers from BT (4 weeks)
  • SIP trunk into an ISDN-SIP gateway and migrate phone numbers from BT (6 weeks)
  • Implement a new hosted telephone system and migrate phone numbers from BT (4 weeks)
  • Replace the PBX, implement SIP trunks to it, and migrate phone numbers from BT (8 weeks)

4. Split your migration into two parts

Transitioning all your telecoms to a new system can be a huge undertaking, fraught with potential complications and issues. When you switch all your systems at once, a single failure could result in all inbound and outbound communications going offline.

To help, you can split your migration into two phases – inbound and outbound. This takes large amounts of risk out of the migration.

5. Run your new and old systems in parallel

Finally, it’s best to consider your migration as an on going process, not a moment of ‘switching’ from ISDN to SIP.

Ideally, you’ll run your old and new systems (ISDN and the dummy SIP) side-by-side for a short period of time. This creates redundancy, so your roll-out can be incremental and controlled at every stage.

To help you manage this TNBN will provide you will some dummy SIPS before the transfer of your ISDN to SIP takes place.

Of course, this is only possible if you make the transition well in advance of the ISDN switch off date, where your old systems will become inoperable.