Telstra in mobile-to-SIP brownout

Telstra is experiencing another outage/brownout, this time reportedly impacting calls from mobile phones to lines handled by session initiation protocol (SIP).

The Australian Network Operators Group's mailing list contains several reports of calls not making it into SIP networks.

Telstra's 'fessed up to something problematic on its networks, as the Tweets below show.

Mainly affecting VIC and TAS with some impact elsewhere. We're investigating as a priority.

— Telstra (@Telstra) March 22, 2016

Carriers dispute the Twitter details: we hear that calls aren't making it to Western Australia either.

There's no word on the nature of the outage/brownout, but El Reg understands that carriers require a gateway to shift calls from the mobile network to SIP networks. If that is indeed the only problem Australia's dominant carrier has today, those gateways appear an obvious source of the issue. Failure on a scale that can take down big slabs of cities bespeaks more than isolated failure: a carrier as (usually) careful as Telstra will have redundant units in place or the ability to fail over between facilites. For a big outage to occur suggests operator error that's impacted a fleet of devices or their interdependencies.

Network design and service choices by customers may also be to blame as there's no reason not to build failover from SIP to the public switched telephone network (PSTN). We'll update this story as and when Telstra releases information.

If the carrier has cocked up again, it's heaping misery upon misery after last week experiencing an outage on its mobile network and February's nationwide outage. Telstra compensated customers for those outages with free download days on which it did not count downloads towards users' quotas. ®