Summary
T-Mobile US suffered a major network outage where a large number of subscribers could not send or receive voice or text messaging due to an outage in Nokia-Siemens' Home Location Register (HLR) as a result of an overload condition. This was the second incident that NSN has with their HLR that could prove to be costly.
Analysis
Home Location Register (HLR) is a very critical network element in a mobile network where all subscriber information, location, and status resides. It provides subscriber profile, location, services, on/off status and other features. A mobile switch typically consults with the HLR for authentication of the user before allowing the user to make a call or send a text message as well as determining where the subscriber is when a call or a text message is delivered. When HLR is out, the subscribers are out of luck.
Last Tuesday, as part of network consolidation and upgrade, NSN's HLR in T-Mobile US did not manage to handle the overload condition smoothly and crashed and resulted in having 5% of their subscribers without service for many hours. This was not the first incident for NSN. A very similar outage took place in T-Mobile Germany in April that left a black eye.
Since telecom contracts come with penalties, it could not have come at a worse time for NSN. T-Mobile is probably going to demand significant penalties as a result of this outage and NSN has to be an extra effort in assuring that their product is carrier grade and can handle large traffic in a transition mode.
