Telenor on Thursday handed in a report to the Norwegian Post and Telecommunications Authority where the company informs of the breakdown that affected the mobile network in Norway on Friday 10 June. The report also accounts for measures implemented to prevent similar errors from reoccurring.
“This is the most extensive breakdown that Telenor has experienced since the mobile network was established in 1993 and the demand for information is huge. We have now composed a report, which will answer the questions posed by the authorities. We will also continue the dialogue with the authorities to ensure that everybody get he answers they need,” said CEO of Telenor Norway, Ragnar Kårhus
Restart created interruptions
Telenor’s report shows that the error occurred in connection with a restart and software upgrade on a centrally located server for mobile broadband. The server was restarted because of interruptions that affected some customers.
Right after the restart problems were detected in large parts of the national mobile traffic. Telenor’s surveillance systems showed that the traffic between servers in the mobile network increased far beyond normal levels. This internal traffic between servers is called signalling traffic. The increased signalling traffic continued to increase to the extent that the servers no longer managed to connect calls and SMSes to recipients.
“When looking for faults we had indications that the controlled restart of the server for mobile broadband could have triggered the problems, but it was not clear how this could affect the voice traffic. It is not normal that a restart creates such heavy signalling traffic between network servers, which we experienced Friday. The signalling traffic also created disturbances in several network units and it therefore became difficult and time consuming to localize the cause of the breakdown and have it corrected,” said Ragnar Kårhus.
The network back to normal around midnight
Comprehensive fault correction attempts were immediately implemented several places in the network. During the search, and attempts at correction, technicians found that a particular voice server was especially overloaded. The server in question was disconnected and then reconfigured. The situation then gradually improved in the entire mobile network. It was then decided to conduct the same procedure for all voice servers in the network. After this work was finalised around midnight on Friday, the situation returned to normal.
Telenor now believes that the signalling traffic increased far more than normal after the reconfiguration, due to the fact that the signalling level in the network was already high. Telenor has already implemented a number of measures to protect against similar events in the future.
“Primarily, we have increased the capacity in the network. In addition, we have established protective mechanisms that come into force if abnormal increases in signalling traffic occur. Along with several other measures, this has reduced the likelihood that we will be facing the same kind of situation that we experienced on June 10,” said Ragnar Kårhus.
Telenor will also conduct a complete analysis of the design of the mobile network, and will also have the network structure evaluated by externals.
Chief Communication Officer Telenor Norway,
Tel: +47 911 55 381,
Tel: + 47 952 09 037,