Manage High Bandwidth LTE Network With User Plane IMSI Filtering

Our approach is to search for specific user data within network traffic. In GTP-based networks users are identified by IMSI/MSISDN. This is a unique identifier that represents every user in the network. The main issue with using IMSI/MSISDN is that user plane traffic does not contain that information; it exists only in the control plane, or signaling traffic. Therefore, this creates the need for a correlation mechanism between the user plane and control plane. The Cubro EXA24160 addresses this problem with its powerful CPU-based architecture and ability to analyze and decode protocols. These features enable the EXA24160 to correlate and identify all traffic of specific users.

A prerequisite for performing efficient IMSI filtering is an aggregation layer that is capable of load balancing on the inner IP of a  GTP tunnel. Once this is achieved, any given user session will always be forwarded to the same output of the aggregation layer. This deterministic output is even more important when it comes to scalability and the only way to guarantee that IMSI filtering will work properly is to have this function in place. In the scenario below the EXA G5+ unit is load balancing GTP-U traffic to multiple IMSI filtering units. Simultaneously, it is broadcasting the GTP-C to all units. As previously mentioned this is necessary because the GTP-C is needed to identify the correct packets from the user traffic.

The IMSI filtering unit will search for the GTP-C packets of the desired targets and will correlate the user traffic accordingly. Finally, the correlated traffic  will be forwarded to the required output.