4G/LTE - Attach Type

  

 

 

 

Attach Type

 

The Attach Type indicates the purpose of the attach and as in most of other procedure, the attach type is also determined by a kind of mutual agreement between UE and Network. It means that UE indicates the attatch type I want to get and Network finaly determines available attach type and informs it to UE as in following procedure.

There are three different types of attach as listed below.

  • EPS attach : indicate the attach for EPS services only)
  • Combined EPS/IMSI attach  : indicate the attach for both EPS and non-EPS services
  • EPS emergency attach : indicate the attach for emergency bearer services

Direction

Message

UE --> NW

RRC : RRC Connection Setup Complete + NAS : Attach Request + ESM : PDN Connectivity Request

UE <-- NW

RRC : RRC Connection Reconfiguration + NAS : Attach Accept + NAS : Activate Default EPS Bearer Context Req

 

 

Attach Request

 

NAS EPS Mobility Management Message Type: Attach request (0x41)

 0... .... = Type of security context flag (TSC): Native security context (for KSIasme)

 .100 .... = NAS key set identifier:  (4)

 .... 0... = Spare bit(s): 0x00

 .... .010 = EPS attach type: Combined EPS/IMSI attach (2)

 EPS mobile identity

     Length: 11

     .... 0... = odd/even indic: 0

     .... .110 = Type of identity: GUTI (6)

     Mobile Country Code (MCC): Unknown (1)

     Mobile Network Code (MNC): Unknown (01)

     MME Group ID: 32769

     MME Code: 0

     M-TMSI: 0x00000001

 UE network capability

     Length: 4

     1... .... = EEA0: Supported

     .1.. .... = 128-EEA1: Supported

     ..1. .... = 128-EEA2: Supported

     ...0 .... = 128-EEA3: Not Supported

     .... 0... = EEA4: Not Supported

     .... .0.. = EEA5: Not Supported

     .... ..0. = EEA6: Not Supported

     .... ...0 = EEA7: Not Supported

     0... .... = EIA0: Not Supported

     .1.. .... = 128-EIA1: Supported

     ..1. .... = 128-EIA2: Supported

     ...0 .... = 128-EIA3: Not Supported

     .... 0... = EIA4: Not Supported

     .... .0.. = EIA5: Not Supported

     .... ..0. = EIA6: Not Supported

     .... ...0 = EIA7: Not Supported

     1... .... = UEA0: Supported

     .1.. .... = UEA1: Supported

     ..0. .... = UEA2: Not Supported

     ...0 .... = UEA3: Not Supported

     .... 0... = UEA4: Not Supported

     .... .0.. = UEA5: Not Supported

     .... ..0. = UEA6: Not Supported

     .... ...0 = UEA7: Not Supported

     0... .... = UCS2 support (UCS2): The UE has a preference for the default alphabet

     .1.. .... = UMTS integrity algorithm UIA1: Supported

     ..0. .... = UMTS integrity algorithm UIA2: Not Supported

     ...0 .... = UMTS integrity algorithm UIA3: Not Supported

     .... 0... = UMTS integrity algorithm UIA4: Not Supported

     .... .0.. = UMTS integrity algorithm UIA5: Not Supported

     .... ..0. = UMTS integrity algorithm UIA6: Not Supported

     .... ...0 = UMTS integrity algorithm UIA7: Not Supported

 

 

Attach Accept

 

NAS EPS Mobility Management Message Type: Attach accept (0x42)

0000 .... = Spare half octet: 0

.... 0... = Spare bit(s): 0x00

.... .010 = Attach result: Combined EPS/IMSI attach (2)

GPRS Timer - T3412 value

    GPRS Timer: timer is deactivated

        111. .... = Unit: value indicates that the timer is deactivated (7)

        ...0 0000 = Timer value: 0

Tracking area identity list - TAI list

    Length: 6

    0... .... = Spare bit(s): 0x00

    .00. .... = Type of list: list of TACs belonging to one PLMN,

                              with non-consecutive TAC values (0)

    ...0 0000 = Number of elements: 0 [+1 = 1 element(s)]

    Mobile Country Code (MCC): Unknown (1)

    Mobile Network Code (MNC): Unknown (01)

    Tracking area code(TAC): 0x0001