It seemed that once we have IMS in place we can add the VoWifi service for free. Of course, there is hardly ever anything for free. As we have is in the VoWifi Overview there are quite a few things we need to take into account. In IMS we have to be more sensitive when it comes to routing, forking, location services etc. In the access network we have to make sure that the communication is secure enough and that we can trigger an access transfer when needed. In this post we’ll go through the security part of it and describe the basic flows.
It is not that difficult to get lost among all the security frameworks, protocols and procedures we have implemented in ePDG. In order to establish an IPSec tunnel we have to use IKEv2 for encryption and then some form of EAP for authentication and then we can start with ESP encryption.
So let’s start with a short dictionary: