The N11 timer configuration is invoked when AMF rejects the N1N2 message transfer with the "Temporary reject registration ongoing" or "Temporary reject handover ongoing" cause code. Then, SMF considers the timer and reattempts the message transfer. When the timer expires, the transfer is reattempted based on the configured retry count.

To configure an N11 timer, use the following sample configuration:

config 
   profile failure-handling failure_handling_name 
      interface [ gtpc | N11 ] message message_type 
         cause-code [ temp-reject-register | temp-reject-handover ]   
            action [ retry { timeout timeout_duration | 
            max-retry retry_count } | clear | terminate ] 
            end 

NOTES:

• profile failure-handling failure_handling_name —Enter the name of the profile for failure handling.

• interface [ gtpc | N11 ] —Configure the interface over which the message transfer must happen.

• message message_type —Configure the message type to be transferred over the interface. The N11 interface supports the message type as N1N2Transfer.

• cause-code [ temp-reject-register | temp-reject-handover ] —Configure the HTTP cause code. You can configure multiple cause code values for a message.

• action [ retry | clear | terminate ] —Configure the action to perform when the message transfer is not successful.

• action [ retry { max-retry retry_count | timeout timeout_duration } —Specify the number of times the message transfer must be reattempted and the time interval between the consecutive attempts.

The GTP timer configuration is implemented when a signaling message or triggered message, for which a reply is expected, is lost as it did not get a response before the T3-RESPONSE timer expired. After the T3-RESPONSE timer expires, the message corresponding to the T3-RESPONSE timer is retransmitted if the total number of retry attempts is less than the N3‑REQUESTS times.

To configure a GTP timer, use the following sample configuration:

config 
   instance instance-id gr_instance_id 
      endpoint gtp 
         retransmission { max-retry retry_count | timeout timeout_duration }  
         end 

NOTES:

• endpoint gtp —Enter the GTP retransmission configuration.

• max-retry retry_count —Specify the number of times the signalling message request to SMF must be reattempted. The accepted range is 0–5. Default range is 3. When the retry_count is set to "0", the retransmission feature is disabled.

• timeout timeout_duration —Configure the interval of time (in milliseconds) after which the GTP retransmission request is reattempted. The accepted range is 0–10. Default range is 2. When the timeout_duration is set to "0", the retransmission feature is disabled.

This section provides the call flows for this feature.

This feature has the following limitation:

• Back-off timer triggering is not supported while clearing 4G PDN sessions as the 3GPP 29.274 specification does not support back-off timer IE in Delete Bearer Request message.

Note	The preceding limitation is applicable only to the non-roaming scenarios.

To define values for the back-off and jitter timers in DNN profile, use the following sample configuration:

config 
   profile dnn dnn_profile_name 
      timeout backoff backoff_timer_value 
      timeout jitter jitter_timer_value 
      end 

NOTES:

• timeout backoff backoff_timer_value : Specify the back-off timer value, in seconds. backoff_timer_value must be an integer in the range of 0-576000.

  The back-off timer is the maximum allowed duration used during IP exhaustion and N4 path failure cases.

• timeout jitter jitter_timer_value : Specify a jitter value to introduce randomness in the back-off timer value. jitter_timer_value must be an integer in the range of 0-1000.

  The jitter allows spreading the different backoff timers to the UE devices so that they all wait at different times before the next reconnection attempt.

  This configuration helps to prevent a session storm after the back-off timer expiry.

The following is an example configuration used during N4 path failure scenarios.

config 
   profile dnn test 
      timeout backoff 200 jitter 50 
      end 

Use the following sample configuration to enable the back-off timer at the GTP-C and N1 message levels.

config 
   profile access access_profile_name 
      gtpc message-handling create-session-response condition ip-exhaust action backoff cause cause_code_value 
      n1 message-handling pdu-session-release condition n4-pathfail action backoff cause cause_code_value 
      n1 message-handling pdu-session-establishment condition ip-exhaust action backoff cause cause_code_value 
      n1 message-handling pdu-modify condition self-protection action backoff cause cause_code_value 
      n1 message-handling pdu-establishment condition self-protection action backoff cause cause_code_value 
      end 

NOTES:

• gtpc message-handling create-session-response condition ip-exhaust action backoff cause cause_code_value : Use this command to enable a back-off timer at the GTP-C interface level for the Create Session Response (CSR) message. That is, the CSR message includes the Back-off Timer IE and its cause code during the exhaustion of IP address.

• n1 message-handling pdu-session-release condition n4-pathfail action backoff cause cause_code_value : Use this command to enable a back-off timer at the N1 interface level for the PDU Session Release message. That is, the PDU Session Release message includes the Back-off Timer IE and its cause code when the N4 path failure occurs.

• n1 message-handling pdu-session-establishment condition ip-exhaust action backoff cause cause_code_value : Use this command to enable a back-off timer at the N1 interface level for the PDU Session Establishment message. That is, the PDU Session Establishment message includes the Back-off Timer IE and its cause code during the exhaustion of IP address.

• n1 message-handling pdu-modify condition self-protection action backoff cause cause_code_value : Use this command to enable a back-off timer at the N1 interface level for PDU session modification message during the self-protection state. That is, the PDU session modification message includes the Back-off Timer IE and its cause code during the exhaustion of IP address.

• n1 message-handling pdu-establishment condition self-protection action backoff cause cause_code_value : Use this command to enable a back-off timer at the N1 interface level for PDU session establishment message during the self-protection state. That is, the PDU session establishment message includes the Back-off Timer IE and its cause code during the exhaustion of IP address.

The following is an example configuration used during the 4G attach and the exhaustion of IP addresses.

config 
   profile access access1 
      gtpc message-handling create-session-response condition ip-exhaust action backoff cause 73 
      end 

In this scenario, the attach fails and the CSR is sent with Back-off Timer IE and cause 73.

The following is an example configuration used during the 5G attach and the exhaustion of IP addresses.

config 
   profile access access1 
      n1 message-handling pdu-establishment condition ip-exhaust action backoff cause 26 
      end 

In this scenario, the attach fails and the PDU Session Establishment is sent with Back-off Timer and cause code value set to 26.

The following is an example configuration used during the 5G attach and the N4 path failure scenario.

config 
   profile access access1 
      n1 message-handling pdu-session-release condition n4-pathfail action backoff cause 26 
      end 

In this scenario, clear subscriber is triggered internally and PDU Session Release command is sent with Back-off Timer IE and cause 26.

This section describes how to verify the back-off timer configuration.

Use the show running-config command to verify the feature configuration.

The following is an example output of the show running-config profile access access1 command.

[unknown] smf# show running-config profile access access1
profile access access1
n1 message-handling pdu-establishment condition ip-exhaust action backoff cause 26
n1 message-handling pdu-release condition n4-pathfail action backoff cause 26
n26 idft enable timeout 15
n2 idft enable timeout 15
gtpc gtpc-failure-profile gtp1
gtpc message-handling create-session-response condition ip-exhaust action backoff cause 76
exit

The following is an example output of the show running-config profile dnn intershat command.

[unknown] smf# show running-config profile dnn intershat
profile dnn intershat
network-element-profiles chf chf1
network-element-profiles amf amf1
network-element-profiles pcf pcf1
network-element-profiles udm udm1
timeout backoff 500 jitter 100
charging-profile chgprf1
virtual-mac b6:6d:47:47:47:47
ssc-mode 2 allowed [ 3 ]
session type IPV4 allowed [ IPV6 IPV4V6 ]
upf apn intershat
dcnr true
exit