Service Request – 1

The Service Request procedure is used by a UE or by the network to request the establishment of a secure connection to an AMF.

Execution of the Service Request procedure brings the UE from CM-IDLE state into CM-CONNECTED state. 

The Service Request procedure is also used both when the UE is in CM-IDLE and in CM-CONNECTED states to activate a User Plane connection for an established PDU Session.

• CM-IDLE: the phone is considered to be on standby, conserving battery life and waiting for user activity or incoming communication.
• CM-CONNECTED: the mobile device can transmit and receive data packets to and from the internet or other data services.

There are two variants of the Service Request procedure: 

• UE-triggered: the procedure is initiated by the UE, e.g., when the UE has up-link data to send. 
• Paging: the procedure is initiated by the network, e.g., to establish User Plane connection when down-link data have arrived and been buffered in a UPF, or when the UE is in CM-IDLE state and the network wants to send a NAS message to the UE.

Test 1 : UE-triggered

• Before running the test make sure your 5GC nodes are started and RAN nodes are stopped:

deactivate-gnb

deactivate-ue

• Launching both the UE and the gNB, execute each command on its own terminal:

activate-gnb

activate-ue

• Open another SSH terminal & run:

switch-idle

Check both terminals of the UE and gNB:

• UE Console

• gNB Console

• After the UE becomes in the IDLE state run the following command:

sudo tcpdump -i any -w ~/captures/ue_triggered_test.pcap

• Open another SSH terminal & run:

ping-ue

Hit Ctrl + C to stop the network capture in the first terminal and download the pcap file ue_triggered_test.pcap.

The UE-triggered call flow