I found an answer to this. Thought, I will share my findings.
GTPP supports some messages which are not imminent in Diamete/Radius to make the Billing infrastructure much more robust and efficient.
Such as Node Alive Request/Response & Redirection Request/Resp .
Node Alive req/resp basically to allow a quicker reconnect capability and its usage will have a reduced load effect on the network, particularly when there are many network nodes doing billing updates. It may also be used to inform when a new network node has become available for service. The usage of this message allows a longer interval to be configured for the Echo req/resp.
Redirection req/resp allows CDR traffic is to be redirected to another CGF due to the sending CGF node is
about to stop service (for maintenance etc).
