SINGAPORE - An unstable pair of mobile site switches - equipment responsible for routing signalling traffic - has been identified by M1 as the root cause of last Tuesday's five-hour outage.
In a statement yesterday, the telco said this caused intermittent connections between the switches and its customer database.
Many customers who tried to make voice calls could not be authenticated by M1's network, with unsuccessful attempts at authentication hogging network resources, leading to congestion at the customer database.
"The congestion cascaded to another network layer, tying up additional network resources and preventing customers from making or receiving calls," M1 said.
While the incident is still being investigated, M1 said it has "reconfigured" the equipment to eliminate congestion that may arise.
Chief executive Karen Kooi said the telco will be enhancing its software to manage "sudden and unexpected extreme traffic conditions".
"In addition, an independent expert will be appointed to review our network architecture and connectivity to further enhance network performance," Ms Kooi added.
She said M1 is continually upgrading its network, which has also become more sophisticated, inevitably increasing the level of complexity when troubleshooting.
M1 has invested $125 million to upgrade its mobile network, improving resilience to outages and reducing the number of dropped calls.
Text messaging and mobile data services were also affected intermittently during last week's outage, which lasted from 7am to 12.15pm.
Communications and Information Minister Yaacob Ibrahim said last week that he was "dismayed" to hear of the disruption, adding that customers had given feedback in past incidents that M1 could have done better in providing updates.
M1 said yesterday that it had updated customers through channels such as Facebook, its corporate website and its call centre hotline during the disruption.
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