EPC: GTP-U echo request/reply (not implemented)
The GTP-U user plane echo request/reply is a not implemented feature.
The GTP-U echo request/reply mechanism is primarily used for path management purposes between the EPC nodes and the eNodeBs.
The GTP-U ping a simple application layer feature. If a node receives a GTP-U echo request, it will respond with a GTP-U echo reply message. If a peer does not respond after a specified number of echo requests, the peer is declared down and all subscriber sessions with the peer are brought down.