Telstra Nationwide Outage: What We Know About the Network Meltdown

Telstra's chief financial officer has fronted the media, saying Wednesday's nationwide outage was caused by malfunctioning "nodes" that manage time synchronisation within some of the network data centres.

However, Australia's biggest telco says it has no idea what caused the timer issues.

The outage has affected potentially millions of Australians by impacting payment systems and public transport services.

Here's what we know.

When did the outage happen?

The Telstra outage happened on Wednesday morning, with outage monitoring site Downdetector.com showing a large spike in reports beginning about 4:30am AEST.

The number of reports made to the website doubled from 308 to 776 between 5:27am and 5:42am, before hitting a peak at 6:42am when more than 7,000 people lodged issues with Telstra's services.

These numbers have since fallen significantly.

Mobile signal was the most commonly reported issue (49 per cent), followed by mobile internet (42 per cent).

How many people have been affected?

Potentially millions of Australians across the country.

Telstra's chief financial officer (CFO) Michael Ackland said in a press conference that he was not sure of the exact numbers, but believed it was in the thousands.

"It could be tens of thousands, but I think it's more likely in the thousands," Mr Ackland said.

The outage was not focused on a particular state, with Telstra customers all across the country expressing their frustration.

But not all the telco's customers were affected, with some reporting on social media and to the ABC that they were still able to make calls, send text messages, access the internet, or have full access.

What caused the Telstra outage?

We don't know the root cause of the outage.

However, Mr Ackland said the issue likely involved "nodes" in Sydney and Melbourne data centres that help synchronise network systems.

The nodes serve a function by keeping time across Telstra's entire mobile network, meaning that disruption to that service is replicated throughout the system.

"You can imagine that lots of computer systems have to synchronise time," he said.

"It's one of the ways that you authenticate what's going on in the network. And the time synchronisation in those nodes wasn't working as it should. We don't know why yet."

Mr Ackland added that the telco had been able to restore some of the nodes within the affected data centre servers, but that it would take time for them to sync up with the wider network, and that there was still "further restoration to occur".

Telstra said there was no evidence of a cyberattack or malicious activity and that it would continue investigating all possible causes.

Why can't I make calls or use mobile data?

That's probably because your phone plan is with Telstra or other mobile providers that operate on Telstra's network, including Boost, Aldi, Tangerine, Belong and Everyday Mobile.

Telstra recommends trying the following steps to reconnect to the network (these may not work for everyone):

Restart your device: Turn your phone off, wait a few seconds, and then turn it back on

Airplane/flight mode: Go to your airplane mode, turn it on for roughly about three seconds, and then turn it off (try this method as a back-up)

When will the Telstra outage be fixed?

We're not sure how long it will take to rectify the outage completely.

But in a statement released around 10am AEST, Telstra said it had "just under 90 per cent of calls and data now flowing successfully across the network".

"Our teams are working as quickly as possible to restore remaining services and get all customers back online," it read.

Mr Ackland said Telstra's immediate priority was to restore services, before it considered customer compensation.

"Our focus at the moment is absolutely on getting things up and running, and we will deal with our customers post the event," he said.

The domino effect

The implications of the outage have been widespread, affecting Triple Zero (000) calls, regional train services and payment systems.

The outage has also led to delays in Hobart's magistrates court.

ABC News journalist Sophie Jaggers said lawyers told the court this morning that they have been unable to contact their clients to remind them of their court appearances due to the outage.

So far, two cases have had to be stood down due to these communication issues.