IMSI filtering and subscribers visibility

How to offload the GTP User Plane traffic which does not belong to a list of subscribers?


Mobile data traffic continues to grow at an exponential rate, driven by mobile video and OTT services. Also if 5G is going to be deployed in many Telecom Operators networks, existing LTE mobile networks still have a high burden to carry, and it will continue to grow.

Monitoring this high volume traffic is a problem for the operators: they need it for troubleshooting and also for granting the best user experience to their customers, but the data traffic is growing at so high speed that they are not able to cope with it. 

In particular, for troubleshooting issues, sometime the information which are available in the GTP control plane is not enough: this is the case for example of a customer where the connection works perfectly, but OTT services, like skype, whatsapp, video, …, have some issues. 

In this case Telecom Operators need to analyse the User Plane traffic too: but they should do only for those subscribers who have the problems, otherwise they will kill probe processing capabilities. How to do that? The solution is to filter the User Plane traffic and forward it to the probes only for the subscribers who need that, and who belong to a specific list.

To identify uniquely the subscriber, the IMSI code may be used: IMSI is a unique number rigidly tied to the subscriber SIM card, and the operator can easily refer to its subscriber data base to identify such code.

This way the monitoring tools load will be highly reduced, and also privacy and legal issues will be solved.


The solution which Microtel Innovation provides is robust, and do not require any difficult operator tasks: our Aster GTP Packet Brokers may filter the GTP User Plane traffic based on IMSI White and Black lists, by correlating GTP Control and User plane data. 

One specific Use Case is related to do User Plane troubleshooting, and in the same time to grant the compliance with the privacy regulations: some Operators, due to GDPR rules, have put in place a strict process which prevent them from forwarding subscribers User Plane traffic to the Monitoring Probes, without subscribers’ approval. User Plane traffic analysis can be done only if and when the subscriber authorizes such activity.

Using Microtel Innovation Aster GTP Packet Brokers, this is a very easy task to implement. While all Control Plane traffic is send to the monitoring tools for generic troubleshooting purposes, the following process can be used for the User Plane data:

  • Customer approval is required before sending the User Plane data to the tools, for troubleshooting or any other agreed purpose 
  • Through the Operator’s customer portal such approval is registered in the Operator’s data base
  • At this point, the customer IMSI may be added to the Aster GTP Packet Broker White List: just few clicks on our seamless and easy to use Graphical User Interface, and this is done
  • From now on, the Aster GTP Packet Broker send the customer user data to the tools
  • It will stop when the IMSI is removed from the Aster White List.

Fig1: How to make GDPR and user data analysis coexist: an existing implementation