Your Guide to the End of ISDN

The impact is plain and simple: Australian businesses will need to switch over to Voice over Internet Protocol (VoIP). Specifically, if a business still wants to make and receive calls directly from a 10-digit phone number, they will also require SIP Trunking to be set up.1

disconnected services

On the 30th of September 2019, Integrated Service Digital Network (ISDN) disconnections will commence. While businesses using these services have received early warnings from their carrier as to disconnections time frames, the replacement of these services can take some time, requiring both telco and business project effort, and should not be left to the last minute or risk loss of service. By the end of 2022, ISDN will no longer exist in Australia.2

The NBN has recently announced that they will start to remove the ISDN lines from the ground for Fibre to the Node, Fibre to the Building and Fibre to the Premises, and it is speculated that they will also remove it for Fibre to the Curb.3

  • Services affected will include Telstra Home/landline phone services (except some Telstra Velocity lines).
  • Home and landline phone services from all other phone companies, where the service is provided over Telstra’s copper phone lines.
  • All ADSL, ADSL2 and ADSL2+ internet services from all providers.
  • Telstra BigPond cable internet services.
  • Optus cable internet and cable phone services.
  • Some Special Services.4

Telstra has already ceased the sale of its ISDN2, ISDN2 Enhanced, ISDN10/20/30, DDS Fastway, Megalink and Frame Relay products.

What is ISDN?

ISDN is a digital network technology that carries voice conversations and data services digitally over the public switched telephone network. ISDN, a standard in its time, was responsible in the 1990s for transforming use of the internet and teleconferencing; eventually leading to the development of faster, cheaper DSL and cable modem internet services. 5


ISDN Alternatives

Businesses replacing their ISDN lines may need new internet connections if they do not already have them in place. For many businesses, an NBN business grade broadband connection to the internet will be adequate for normal internet browsing, access to hosted applications or use by organisations as a redundant or backup internet link.

These fibre or copper cable services are asymmetric in nature (fast download, slower upload speeds i.e. 60Mbps/3Mbps) and offer a fixed IP address to help prevent impacts from network congestion (being contended), commonly experienced in residential grade internet services due to peak local usage levels.6

Where businesses and organisations require the enabling of fast data streams at all times, uncontended regardless of usage, then a dedicated symmetric business fibre broadband connection to the internet may be required (equal upload and download speeds i.e. 500Mbps/500Mbps). This is especially important for supporting cloud telephony and online collaboration leveraging VoIP and SIP services for larger organisations.

Read more about VOIP and SIP below.

SIP Trunk as a Service: Updating Your Phone Service

VoIP means making or receiving phone calls over the internet or internal networks. Session Initiated Protocol (SIP), on the other hand, is an application layer protocol used to establish, modify and terminate multimedia sessions such as VoIP calls.

The replacement for ISDN already exists and it’s cheaper than ISDN, SIP is the future of business voice. SIP does require the following prerequisites; a data carriage service (internet link), an Internet Protocol Private Branch Exchange (IP PBX) that can be locally or cloud hosted and SIP handsets.

A SIP Trunk (digital equivalent of a traditional ISDN phone line) enables the company or organisation end point’s PBX to send and receive PSTN (traditional hard wired, circuit switched analogue call access to the rest of world) calls via the Internet. A SIP Trunk needs to connect to an IP PBX enabling multiple users to share lines. Getting the assistance of a Data#3 subsidiary, Discovery Technology, will help simplify this process.

SIP Trunk

There are a number of advantages with a SIP service, you can keep the same phone number or number ranges, no matter where you are located i.e. the numbers are portable. There are no more fixed line rentals. You get call package options with competitive rates e.g. free local, national calls, mobile, international. You can add a failover PBX to increase your redundancy if your primary PBX is unavailable for whatever reason. You can use your existing data connection for carriage of the service.

SIP is very scalable, as software defines the number of voice channels (SIP channels / lines), changes can be made easily and quickly to ramp up or down the size of the service.


Migrating to a SIP Trunk Service?

You will need to determine how many SIP trunks are required (usually one per site) and for each trunk how many SIP channels. The channels are charged monthly per channel and available for 24 and 36 month terms.

The organisation will likely have existing phone numbers that they require porting to the new SIP service. They are normally referred to as single numbers or 100 number ranges. Single numbers can be ported in about two weeks and 100 number ranges take five to six weeks to port. There is a porting charge applicable and all numbers and 100 number ranges attract a monthly charge for their rental.

SIP Trunk Calling Plans

SIP trunk calling plans are charged per month. They differ based on the term (24 or 36 months) and call services on offer (local calls, STD/national calls, mobile calls usually expressed as 1000 minutes of calls. These can be aggregated and used by all users i.e. Four (4) channels would provide 4,000 minutes of included mobile calls per month). An A-Z overseas country rate card can be provided if the business intends to allow international dialling. With base calling packages, mobile calls are usually charged per minute. Any premium numbers i.e.1300 service desk number, are just forwarded to one of the new ported extensions and do not need to be migrated as such.

SIP Channels

Once the company has determined the number of concurrent phone calls they expect, inbound and outbound, use this number to set the number of SIP Channels. However, remember to check if they intend to run any services i.e. internal conference call facilities that require external callers to join them via a PSTN line. Ask what the upper number of internal and external participants would be. Consider adding the number of expected external conference callers to the total number of SIP Channels.

There have been cases where all external conference call participants have joined the call, but the internal conference call organiser cannot join the call because all SIP Channels are in use. If the company plans to use Cisco Webex Calling then no additional allowance for SIP Channels allowance needs to be made into a conference call as these are all coordinated inside the Webex Calling service accessed via the internet.

Telecommunications companies do not often allow businesses to break up 100 number ranges to consolidate them. If a business migrating from ISDN to SIP is also downsizing and only requires 3 of their 5 100 number ranges then they would have to change their extensions to only use those numbers included within the 3 100 number ranges they have elected to keep.

The SIP Trunk provider will normally expose the caller ID (number) to an external device being called unless managed otherwise in the hosted SIP / IP PBX service i.e. WebEx Calling.


Services that will not be switched off

Some existing phone lines

The copper network within nbn™ Fixed Wireless and Sky Muster™ Satellite areas will not be switched off. Premises within these areas will have the choice to keep their existing landline phone service over the copper network active, or switch over to a VoIP service on the nbn™ access network through a preferred phone and internet provider – connecting your new phone via the nbn™ supplied equipment3. Your phone and internet provider can assist with your phone and internet services. Check your address to see what technology you will receive at your premises.

Other fibre providers or private networks

If your phone or internet is already provided over another fibre network, such as a network provided by your building owner, private enterprise network, health or education network, or a cable network that’s not owned by Telstra or Optus (such as TransACT – excluding ACT customers being migrated to the nbn™ access network, OptiComm, Pivit, etc.), they should continue operating unless your provider advises otherwise3.


If you’re subscribed to Foxtel pay TV over satellite or Telstra Cable, it will not be switched off as part of the nbn™ access network rollout. If you access any Foxtel services via the internet (through an Xbox, PC, tablet, smartphone, smart TV, etc.), ask your phone and internet provider if your connection will be in line with Foxtel’s minimum requirements3.

Frequently Asked Questions

Contact a Cloud Calling Specialist

We work with organisations across Australia to assess their readiness to move to cloud calling and collaboration, consult and assist with cloud calling migrations, and ensure the network can handle the new solution.

Contact a specialist at Data#3, to learn more about how you can prepare for the end of the ISDN, or to learn more about Cisco’s cloud calling solution.

1. Sims, C (2019). How will the ISDN shutdown in Australia impact your business? [Online] Available at: https://www.ccna.com.au/blog/how-will-the-isdn-shutdown-in-australia-impact-your-business/
2. Jenkin, M (2019). Telstra begins ISDN shutdown this year. [Online] Available at: https://www.crn.com.au/news/telstra-begins-isdn-shutdown-this-year-519494
3. NBN (2019). Services that will be switched off. [Online] Available at: https://www.nbnco.com.au/learn/device-compatibility/services-that-will-be-switched-off
4. NBN (2019). Special Services that may be [Online] Available at: https://www.nbnco.com.au/business/special-services/affected-special-services
5. What is my IP address (2019). What is ISDN? [Online] Available at: https://whatismyipaddress.com/isdn
6. Choi, J (2019). Difference between business and consumer NBN plans [Online] Available at: https://www.finder.com.au/difference-business-and-consumer-nbn-plans
7. Telaustralia (2019). What is a 100 Number Direct In Dial Range (DID Range). [Online] Available at: https://telaustralia.com.au/faq/what-is-a-100-number-direct-in-dial-range-did-range
8. Telstra (2019). Key differences between SIP & VOIP 2019 [Online] Available at: https://www.telstraglobal.com/insights/blogs/blog/key-differences-between-sip-voip
9. WhatIs.com [Online]. What is IP PBX (private branch exchange) [Online] Available at: https://searchunifiedcommunications.techtarget.com/definition/IP-PBX

Tags: Cisco, Cisco Collaboration Suite, Cisco Webex, Collaboration, Mobility, Networking



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