TPG packet core decommissioning caused emergency call issues

TPG Telecom’s planned decommissioning of its older 4G packet core network mid-last year caused some customers to lose the ability to make emergency calls, the regulator has found.

The telco earlier switched to a dual-mode core network capable of 4G and 5G services, and planned to decommission its older 4G packet core network in the early hours of August 15 last year.

The decommissioning work caused a “partial loss” of core components and led to some - but not all - customers losing the ability to make and receive calls for about 80 minutes - between 12.40am and 2am.

Due to the uneven impact of the incident, the inability of some users to be able to lodge emergency calls went undetected by TPG’s “automated processes and real-time monitoring” systems, according to an investigation [pdf] by the Australian Communications and Media Authority (ACMA).

ACMA said 147 emergency calls were attempted during the outage, including two calls from international users roaming on the TPG network.

Of these, 104 calls “camped on the Optus or Telstra network and thus the end users successfully accessed the emergency call service,” ACMA noted.

“The remaining 43 end users’ emergency calls were unsuccessful and were not carried to the relevant point of termination.”

According to documentation, “emergency ‘camp-on’ may occur when a caller is outside their own mobile carrier’s network coverage, but is within the coverage of another mobile carrier. 

“This allows a caller to make a Triple Zero call whenever in the range of a mobile network.”

Welfare checks hours later found 18 users did not require emergency assistance, while 24 others “were referred to the applicable law enforcement agency in their state” when unable to reach the triple zero, ACMA said.

TPG was formally warned by ACMA for not advising Telstra of the issues until 9.07am, almost eight hours after detecting the problems.

Telstra is the emergency calling service operator, answering all calls lodged with the service.

“It’s crucial that all telcos have their systems and processes in place to ensure any network outages impacting Triple Zero are identified and addressed as soon as possible,” ACMA member Samantha Yorke said in a statement.

“They must also take timely action to alert other key stakeholders in the Triple Zero ecosystem where a problem is being experienced.”

TPG Telecom said that the delay was caused by human error and that “all relevant personnel have now been trained on its processes”.