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IP Allocation in NR

 

 

IP allocation in NR process is very similar to LTE IP Allocation process at high level. It is done by a pair of NAS signaling (PDU Session Establishment Request and PDU Session Establishment Accept) as it is done by a pair of NAS message (PDN Connectivity Request and Activate Default/Dedicated EPS Bearer Context Request) in LTE.

Major difference between NR IP address allocation and LTE IP allocation address would lie in how to configure QoS parameters.

 

Following is overall signaling procedure for IP allocation in 5G. For the details of these messages refer to 5GSM page.

 

Direction

Message

UE Timer

NW Timer

UE -> NW(SMF)

ULInformationTransfer + UL NAS Transport

  + PDU SESSION ESTABLISHMENT REQUEST

T3580 Start

 

UE <- NW(SMF)

DLInformationTransfer + DL NAS Transport

  + PDU SESSION ESTABLISHMENT ACCEPT

T3582 Stop

 

 

 

 

PDU Session Establishment Request

 

This is a sample message from the log provided by Amarisoft.

 

{
  message c1: ulInformationTransfer: {
    criticalExtensions ulInformationTransfer: {
      dedicatedNAS-Message '7E02FF096300027E006701001E2E0509C1FFFF93A17B001380000A00000
                                      200000100000C00000300000D00120581250403696D73'H
    }
  }
}

 


    Message: UL NAS transport

    Data:

    Protocol discriminator = 0x7e (5GS Mobility Management)
    Security header = 0x2 (Integrity protected and ciphered)
    Auth code = 0xff096300
    Sequence number = 0x02
    Protocol discriminator = 0x7e (5GS Mobility Management)
    Security header = 0x0 (Plain 5GS NAS message, not security protected)
    Message type = 0x67 (UL NAS transport)
    Payload container type = 1 (N1 SM information)
    Payload container:
      Protocol discriminator = 0x2e (5GS Session Management)
      PDU session identity = 5
      Procedure transaction identity = 9
      Message type = 0xc1 (PDU session establishment request)
      Integrity protection maximum data data:
        Maximum data rate per UE for user-plane integrity protection 
                                         for uplink = 0xff (Full data rate)
        Maximum data rate per UE for user-plane integrity protection 
                                         for downlink = 0xff (Full data rate)
      PDU session type = 0x3 (IPv4v6)
      SSC mode = 0x1 (1)
      Extended protocol configuration options:
        Ext = 1
        Configuration protocol = 0
        Protocol ID = 0x000a (IP address allocation via NAS signalling)
        Data =
        Protocol ID = 0x0002 (IM CN Subsystem Signaling Flag)
        Data =
        Protocol ID = 0x0001 (P-CSCF IPv6 Address Request)
        Data =
        Protocol ID = 0x000c (P-CSCF IPv4 Address Request)
        Data =
        Protocol ID = 0x0003 (DNS Server IPv6 Address Request)
        Data =
        Protocol ID = 0x000d (DNS Server IPv4 Address Request)
        Data =
    PDU session ID = 5
    Request type = 0x1 (initial request)
    DNN = "ims"

 

 

PDU Session Establishment Accept

 

{
  message c1: dlInformationTransfer: {
    rrc-TransactionIdentifier 0,
    criticalExtensions dlInformationTransfer: {
      dedicatedNAS-Message '7E0206FC019B027E0054431081C176589E9EBFCD7490B34CBFBFE56
                            B450981C176589E9EBFCD7446404791118261539040490100'H
    }
  }
}

 

    Protocol discriminator = 0x7e (5GS Mobility Management)
    Security header = 0x2 (Integrity protected and ciphered)
    Auth code = 0x66f143b0
    Sequence number = 0x03
    Protocol discriminator = 0x7e (5GS Mobility Management)
    Security header = 0x0 (Plain 5GS NAS message, not security protected)
    Message type = 0x68 (DL NAS transport)
    Payload container type = 1 (N1 SM information)
    Payload container:
      Protocol discriminator = 0x2e (5GS Session Management)
      PDU session identity = 5
      Procedure transaction identity = 9
      Message type = 0xc2 (PDU session establishment accept)
      Selected PDU session type = 0x3 (IPv4v6)
      Selected SSC mode = 0x1 (1)
      Authorized QoS rules:
        QoS rule 1:
          QoS rule identifier = 1
          Rule operation code = 1 (create new QoS rule)
          DQR = 1 (the QoS rule is the default QoS rule)
          Number of packet filters = 1
          Packet filter identifier = 15
            Packet filter direction = 3 (bidirectional)
            Match-all
          QoS rule precedence = 255
          QFI = 1
      Session AMBR:
        Session-AMBR for downlink = 3000000 kbps
        Session-AMBR for uplink = 1000000 kbps
      PDU address:
        PDU session type = 3 (IPv4v6)
        IPv6 = ::2001:468:3000:1
        IPv4 = 192.168.4.2
      Authorized QoS flow descriptions:
        QoS flow description 1:
          QFI = 1
          Operation code = 1 (create new QoS flow description)
          E = 1 (parameters list is included)
          Number of parameters = 1
          5QI = 5
      Extended protocol configuration options:
        Ext = 1
        Configuration protocol = 0
        Protocol ID = 0x000d (DNS Server IPv4 Address)
        Data = 8.8.8.8
        Protocol ID = 0x0003 (DNS Server IPv6 Address)
        Data = 2001:4860:4860:0:0:0:0:8888
        Protocol ID = 0x000c (P-CSCF IPv4 Address)
        Data = 192.168.4.1
        Protocol ID = 0x0001 (P-CSCF IPv6 Address)
        Data = 2001:468:3000:1:0:0:0:0
        Protocol ID = 0x0002 (IM CN Subsystem Signaling Flag)
        Data =
      DNN = "ims.mnc001.mcc001.gprs"
      PDU session ID = 5

 

 

 

Reference

 

[1] 3GPP SA2 architecture and functions for 5G mobile communication system

[2] 5G beyond radio access: a flatter sliced network

[3] End to End Network Slicing