The phones! They were one of the basic utilities of the 20th century, and were just about as reliable as death and taxes. Even when then power grid went down, you still had a fair shot of getting a phone call through thanks to the reliability of the Plain Old Telephone Service.

Today, we eschew the simplicity of copper and mechanical switches for the supreme bandwidth and capability of high-speed cellular connectivity. With that, we accept that the additional complexity comes with a risk of complicated failures that bring everything tumbling down. Australia’s largest telecommunications provider found that out to its peril just a few short months ago.

Networked Failures

Generally, we expect our telecommunications networks to be supremely reliable. There is no moment of the day when someone doesn’t need to make a call, particularly in emergencies, and the wheels of industry and commerce depend on constant connectivity these days. Tolerance for failure is generally very thin. Despite this, and the efforts of engineers to maintain uptime at as many nines as possible, Telstra fell badly short on July 8th, 2026. The company had a nationwide outage that affected 8.8 million people, leaving them unable to make calls or connect to the network at all.

The cause of the outage would prove to be particularly embarrassing. Telstra owns and operates a highly advanced cellular network, offering 4G and 5G service across the nation’s cities and much of its outback areas. The company may outwardly appear to be a shining beacon of modern connectivity, but there was something dank lurking in the company’s server closets. Namely, three aging network time servers that had the capacity to bring the whole system to its knees.

The NTP server in question is old enough to still rock a vacuum fluorescent display, something you don’t see on a lot of modern network hardware. Credit: Microsemi

The culprit? A Microchip Technologies SSU 2000 NTP server. The model dates back to the early 2000s. Twenty four years later, Telstra still relied upon three of the units to provide network time protocol (NTP) services across its network. The servers were generally perfectly adequate in this role on any given day. That was, until the Melbourne server had a wobble.

A technician was working in the early morning to replace a backup power feed in the chassis housing the server. This caused the server to be rebooted at 3:38 AM, which normally would not be a problem. However, at some point in the last two decades or so, the server had gone through a configuration change. While it was originally intended to be a Stratum 3 NTP server, getting its time reference from a Stratum 2 unit, that process had failed at some point. It had been reconfigured instead to use its internal GPS card to gain time directly from the satellite network instead. Unfortunately, the server was also remarkably old, and suffered from a well-documented GPS date rollover bug, such that when it rebooted, it reported the time as 2006 rather than 2026.

Victoria’s V/Line train services were unable to run, as the Telstra network outage made communication across the system impossible. Credit: Thomas Hobley, CC BY-SA 4.0

The problem that stemmed from this was because time is critical to authentication. An endless cascade of devices downstream of the NTP server picked up the wrong time, and started using it to sign digital certificates and the like. This immediately caused other systems on the network to reject the spurious traffic with certificates that were 20 years out of date. The impact was swift and vast—Telstra was quickly facing a nationwide outage affecting millions of customers.

The issue was first detected at 4:20 AM. The naughty server was isolated by 7:11 AM, but it would take until 10:30 AM to identify all the network components which had received erroneous time data. It took several hours further—until 4 PM—to properly quell the NTP issues. In the meantime, a significant portion of the country had seen its phones offline all day, and entire rail networks had ground to a halt as their Telstra-based communications systems went completely offline.

Later submissions to a government inquiry would reveal Telstra had received two reminders to patch the GPS card, in 2020 and 2022. The vendor itself had issued warnings about the GPS rollover bug as early as November 2000. A decision not to fix the bug had been taken as recently as January 2026, because the undocumented change to have the server rely on GPS time was unknown, and thus the update was considered unnecessary. Simply patching the system would have prevented the issue from ever occurring in the first place.

When the outage became apparent, Telstra notified the Triple Zero Custodian, a body founded in 2025 to oversee the integrity of the emergency service. Credit: Telstra submission to government inquiry

The issue once again brought telecommunications availability in Australia to the forefront of the conversation. Repeat outages across Australian mobile networks have led to particular concerns about the ability for people to reach emergency services by calling Triple Zero from mobile handsets. The latest failure on Telstra’s behalf has led the local telecommunications industry to issue new guidance to the public on what to do when a call to Triple Zero doesn’t go through.

Modern handsets are designed to switch to a different cellular network in the case an emergency call can’t be connected—a process called emergency camp-on. However, this process takes time, and the caller will often hear silence on the line while the phone is attempting to connect. The new advice is that callers should hang up and try again straight away if their first call to Triple Zero doesn’t connect within a few seconds. On the second call, though, the phone should be given up to a minute to find another network to get the call through.

In the case of this outage, camp-on functionality worked—some 3,200 Triple Zero calls were passed to Optus and TPG networks when Telstra’s failed. However, there were some ongoing issues that saw a further 604 Triple Zero calls fail over the period to 2 PM the next day.

Overall, Telstra’s failure was a major one. It’s rare for a major network to go down so completely and over such a wide geographical area. The fact that it happened because of an undocumented change to an ancient network appliance is all the more embarrassing. It will drive home the message that documenting even seemingly minor changes is important, with the lesson likely to be told in the halls of the Australian telco for some decades to come.