+------------------------------------------+
 | +-----+   +------+   (```).     +------+ |   (````).    +-----+
 | | SUB |-->| EMU  |--(x-haul'.-->| EPC  |--->(  PDN ).-->| CDN |
 | +-----+   +------+   `__..''    +------+ |   `__...'    +-----+
 +------------------------------------------+
               4G Mobile Network Functions