Configuration Update

Configuration Update is a network-initiated 5GMM procedure used by the AMF to update UE-related configuration after registration. Typical information includes network name, time zone, allowed NSSAI, rejected NSSAI, configured NSSAI, and other parameters that can change while the UE remains registered.

• Signaling Sequence
• Message Structure
  • Example : Configuration Update Command
  • Example : Configuration Update Complete

Signaling Sequence

The AMF sends Configuration Update Command to provide new configuration information. Depending on the indication in the command, the UE may return Configuration Update Complete.

Message Structure

The Configuration Update Command is usually NAS protected after the security context is established. It may include multiple optional IEs. Therefore the exact message size and content vary depending on what information the network wants to update.

Example : Configuration Update Command

The following example is based on an Amarisoft MME log where the network updates display name and time information after registration. The whole decoded NAS message is shown below.

04:09:34.281 [NAS] DL 0064 5GMM: Configuration update command
        Protocol discriminator = 0x7e (5GS Mobility Management)
        Security header = 0x2 (Integrity protected and ciphered)
        Auth code = 0x4eb28fa3
        Sequence number = 0x03
        Protocol discriminator = 0x7e (5GS Mobility Management)
        Security header = 0x0 (Plain 5GS NAS message, not security protected)
        Message type = 0x54 (Configuration update command)
        Full name for network:
          Length = 16
          Data = 81 c1 76 58 9e 9e bf cd 74 90 b3 4c bf bf e5 6b
        Short name for network:
          Length = 9
          Data = 81 c1 76 58 9e 9e bf cd 74
        Local time zone = 64
        Universal time and local time zone:
          Data = 12 11 71 90 90 43 40
        Network daylight saving time:
          Length = 1
          Data = 00
                

Example : Configuration Update Complete

The checked Amarisoft MME log did not include Configuration Update Complete because acknowledgement was not required in that example. The following constructed example shows the entire message when the UE is required to acknowledge the command.

[NAS] UL 5GMM: Configuration update complete
        Protocol discriminator = 0x7e (5GS Mobility Management)
        Security header = 0x2 (Integrity protected and ciphered)
        Auth code = example
        Sequence number = example
        Protocol discriminator = 0x7e (5GS Mobility Management)
        Security header = 0x0 (Plain 5GS NAS message, not security protected)
        Message type = 0x55 (Configuration update complete)