Timers in 5G AMF (Access and Mobility Management Function)

Article by Abhijeet Kumar

In 5G networks, the AMF (Access and Mobility Management Function) manages access and mobility of User Equipment (UE). Timers ensure that registration, deregistration, authentication, and paging are handled efficiently.

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T3522 Timer

• Purpose: Manages the deregistration procedure between the AMF and the UE.
• Technical Details: It starts when the AMF sends a?Deregistration Request?message to the UE and stops when the AMF receives a?Deregistration Accept?message from the UE.

If the timer expires, the AMF resends the Deregistration Request message.

N3522 Counter

• Purpose: Specify the maximum number of retries for sending the Deregistration Request message.
• Technical Details: If the AMF does not receive a Deregistration Accept message, it retries up to?N3522?times.

.?T3550 Timer

• Purpose: Manages the initial registration or mobility registration update procedure.
• Technical Details: Starts when the AMF sends a?Registration Accept?message. It stops when the AMF receives a?Registration Complete?message from the UE.

If the timer expires, the AMF resends the Registration Accept message

.?N3550 Counter

• Purpose: Specify the maximum number of retries for sending the Registration Accept message.
• Technical Details: If the AMF does not receive a Registration Complete message, it retries up to?N3550?times.

T3560 Timer

• Purpose: Manages the authentication or security mode command procedure.
• Technical Details: Starts when the AMF sends an?Authentication Request?or?Security Mode Command?message. It stops when the AMF receives an?authentication response?or?security mode complete?message. If the timer expires, the AMF resends the Authentication Request or Security Mode Command message.

N3560 Counter

• Purpose: Specifies the maximum number of retries for sending the Authentication Request or Security Mode Command message.
• Technical Details: If the AMF does not receive a response, it retries up to?N3560?times.

T3570 Timer

• Purpose: Manages the identity request procedure.
• Technical Details: Starts when the AMF sends an?Identity Request?message. Stops when the AMF receives an?Identity Response?message. If the timer expires, the AMF resends the Identity Request message.

N3570 Counter

• Purpose: Specifies the maximum number of retries for sending the Identity Request message.
• Technical Details: If the AMF does not receive an Identity Response, it retries up to?N3570?times.

T3512 Timer

• Purpose: Manages the periodic registration update procedure.
• Technical Details: Starts when the UE transitions from?CM-CONNECTED?to?CM-IDLE?state. When the timer expires, the UE initiates a periodic registration update.

.?T3502 Timer

• Purpose: Manages the reinitiation of registration requests in case of registration failure.
• Technical Details: Starts when a registration request fails. When the timer expires, the UE reinitiates the registration request.

T3513 Timer

• Purpose: Manages the paging procedure.
• Technical Details: Starts when the AMF sends a?Paging Request?message. Stops when the AMF receives a?Service Request?or?Registration Request?message. If the timer expires, the AMF resends the Paging Request message.

N3513 Counter

• Purpose: Specifies the maximum number of retries for sending the Paging Request message.
• Technical Details: If the AMF does not receive a response, it retries up to?N3513?times.

T3555 Timer

• Purpose: Manages the configuration update procedure.
• Technical Details: Starts when the AMF sends a?Configuration Update Command?message. Stops when the AMF receives a?Configuration Update Complete?message. If the timer expires, the AMF resends the Configuration Update Command message.

N3555 Counter

• Purpose: Specifies the maximum number of retries for sending the Configuration Update Command message.
• Technical Details: If the AMF does not receive a response, it retries up to?N3555?times.

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