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Sip and bite switch12/7/2023 Message type = 0xcb (PDU session modification command)ĭQR = 0 (the QoS rule is not the default QoS rule) This is similar to Activate dedicated EPS bearer context request In other words, you may implement the service in such a way that both IMS signaling and voice data go through the single data pipe). This process is initiated by NW via PDU session modification command ( NOTE : Even though this step is done in most of the real network implementation for IMS service, it is not mandatory in protocol point of view. For setting up the data only traffic (not IMS signaling), usually NW sets up another data pipe (QoS flow) dedicated for the data traffic. Once IMS registration is done and the user trigger IMS call, it would reach a certain point where another data pipe for IMS data traffic (i.e, Voice traffic). PDU session modification command (Log shared by Amarisoft) Protocol ID = 0x0001 (P-CSCF IPv6 Address) Protocol ID = 0x000c (P-CSCF IPv4 Address) Protocol ID = 0x0003 (DNS Server IPv6 Address) Protocol ID = 0x000d (DNS Server IPv4 Address) ![]() Operation code = 1 (create new QoS flow description) Packet filter direction = 3 (bidirectional) Rule operation code = 1 (create new QoS rule)ĭQR = 1 (the QoS rule is the default QoS rule) Message type = 0xc2 ( PDU session establishment accept) This is similar to Activate default EPS bearer context Once network recieves the PDU session establishment request message from UE, Network informs the UE of the requested information (P-CSCF) and creates a QoS pipe that is necessary for the traffic. PDU session establishment accept (Log shared by Amarisoft). Protocol ID = 0x000d (DNS Server IPv4 Address Request) Protocol ID = 0x0003 (DNS Server IPv6 Address Request) Protocol ID = 0x000c (P-CSCF IPv4 Address Request) Protocol ID = 0x0001 (P-CSCF IPv6 Address Request) Protocol ID = 0x0002 (IM CN Subsystem Signaling Flag) Protocol ID = 0x000a (IP address allocation via NAS signalling) Maximum data rate per UE for user-plane integrity protection for downlink Maximum data rate per UE for user-plane integrity protection for uplink Message type = 0xc1 ( PDU session establishment request) Protocol discriminator = 0x2e (5GS Session Management) Payload container type = 1 (N1 SM information) ![]() Security header = 0x0 (Plain 5GS NAS message, not security protected) Security header = 0x2 (Integrity protected and ciphered) Protocol discriminator = 0x7e (5GS Mobility Management) If you are familiar with VoLTE process, you would notice that the role of this message is similar to PDN Connectivity Request in VoLTE. I would like you to note that this message is requesting a PDU setup with DNN="ims" and requesting the IP address for P-CSCF. This is the message from UE that initiate setting up the configuration which are required to do IMS registration. PDU session establishment request (Log shared by Amarisoft) So it may not be set when the voice call is expected purely through VoNR NOTE : S1 mode capability at step 3 indicates whether UE support EPS Fallback or not. ![]() UE should notify the IMS related capabilities ( IMS-Parameters) Usage setting = voice centric, GMM capability S1 mode = true I would only put those steps related to VoNR.Īll the necessary UAC condition should be met for allowing IMS call. I wouldn't put all the details of NR signaling procedure here. You would see a little bit of differences in terms of signaling message name comparing to VoLTE setup, but those differences are due to signaling difference between LTE and NR, not specifically due to IMS side difference. ![]() In this page, I would mostly focus on the differences in VoNR.įollowing is the overall call flow of NR. So if you are already familiar with VoLTE, you would catch up VoNR very quickly and most of the contents listed in my IMS notes would applies to VoNR as well. Even in terms of 3GPP, the details of VoNR procedure is described in 23.228 which is mainly for IMS for LTE and 5G specific details are provided as an appendix The main difference is that the IMS is established by and go through 5G Core network in VoNR whereas it is established by and go through 4G core network. They are all based on Voice call over IMS.
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