How it Works

The SMF supports the following 3GPP timers:

GTP Retransmission Timer

The SMF or PGW-C starts the timer denoted in the T3-RESPONSE. The timer is invoked when a signalling message, for which a reply is expected, is sent. A signalling message or the triggered message may be lost if a response is not received before the T3-RESPONSE timer expires.

After the T3-RESPONSE timer expires, the message corresponding to the T3-RESPONSE timer is then retransmitted if the total number of retry attempts is less than N3REQUESTS.

5G N1N2 Reattempt Timer

If AMF rejects the N1N2 MessageTransfer with cause code as "Temporary reject registration ongoing" or "Temporary reject handover ongoing", then the SMF starts the timer for reattempting N1N2 MessageTransfer.

After the timer expires, the message corresponding to N1N2 MessageTransfer is reattempted based on the configured retry attempts.