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Manage High Bandwidth LTE Network With User Plane IMSI Filtering

The Challenge

It is too expensive to monitor the entire network traffic due to the increased volume. However, monitoring is required for troubleshooting and providing a better user experience. Managing high bandwidth LTE network is possible with user plane IMSI filtering. But monitoring the user plane in LTE networks involves two problems - traffic growth/volume and legal issues.

The technical Solution from Cubro

This is the subscriber-triggered user plane monitoring solution. The EXA platform can filter on the S1U interface on the inner IP address of the GTP tunnel. This is done completely in hardware so there are no performance limitations regarding the load on the device; even multiple 100 Gbit streams of network traffic and several 1000 filters can be handled on a single unit. This IP address is dynamic, however, and can change in each PDP context message. This IP address is typically managed by the network itself; it isn’t easy for even the operator to identify it. In this case the Cubro Probe offers the right solution to the problem. Using the Cubro Probe it is possible to decode all signalling traffic on the network and build a dynamic correlation list of IMSI to user IP. This list can be used in a third party application to construct filters based on IMSIs.

How Does The Subscriber-Triggered User Plane Monitoring Solution Work?

This drawing shows an actual implementation. The traffic arrives at an EXA32100 where it is separated into user plane and signalling plane. One copy of the signalling is sent to the monitoring systems and the other stream is sent to the Cubro Probe. The Cubro Probe extracts the metadata and builds the correlated IMSI - IP Table. This table is handled by a standard server. The operator’s customer portal triggers the approval from the subscriber via a ReST API. After this approval from the subscriber, the server configures the rules on the EXA32100. At this moment the monitoring system starts receiving the user plane data generated by this subscriber. After a configurable time frame the approval is recalled automatically in order to cease the forwarding of the subscriber’s user plane traffic.

how user plane monitoring works

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