This blog is by Teemu Mäkinen at Nokia Networks. Twitter: @teemujmakinen
This is a true story: A routine maintenance task goes wrong, causing a network element to fail. This disconnects hundreds of thousands of mobile broadband subscribers. The affected smartphones react by simultaneously and persistently trying to reconnect to the network. The result is a signaling storm that overwhelms the network, causing a wider crash that leaves people without service for hours.
In such a situation, one of the most vulnerable network elements is the Home Subscriber Server (HSS) which supports the LTE network’s Mobility Management Entities (MMEs) by performing subscriber authentication and authorization. As thousands of smartphones ask to reconnect to the network, the HSS is faced with a sudden and dramatic increase in workload.
The scenario described above happened to one of our European customers in early 2014. The outage was caused by the operator's engineers working on another vendor’s MME and affected almost 150,000 subscribers, lasting several hours at one of the busiest times of the day. The Nokia HSS saw a 13-fold signaling traffic increase, yet still managed to stay in service throughout the network outage. And when the operator’s engineers intervened manually to reduce the overload, the HSS went back to normal operation automatically by itself, helping the operator recover from the situation more quickly than would have been possible otherwise.
The HSS is central to our Subscriber Data Management (SDM) solution that consolidates subscriber profile and service data from across the network into one database. Our SDM is widely recognized as a highly robust solution. Current Analysis agrees, describing it recently as the “market-leading SDM implementation that offers high capacity with strong LTE traction”.
Maintaining business continuity and minimizing the risk of downtime are at the heart of our SDM philosophy as our new infographic shows. A good example of the solution’s built-in robustness is its innovative Intelligent Throttling and Prioritization feature. Using Quality of Service (QoS) data, the capability achieves even greater tolerance to signaling storms by selectively dropping non-essential data packets rather than ignoring packets at random. This helps maintain a manageable traffic load by, for example, ensuring that a smartphone’s attachment request is completed. Unlike random packet dropping, this eliminates the risk of a device disconnecting prematurely and then repeatedly trying to reconnect, which would only create even more signaling in the network.
It is clever features like these that have attracted over 100 LTE operators to adopt the Nokia SDM solution. Our SDM currently serves 3.8+ billion subscribers and some 185 2G/3G/LTE operators. Typically, once people get hooked on LTE, they want it on all the time. Nokia SDM aims to keep it that way.
We have more to share on SDM here.
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