8.51 Target Identification

29.2743GPP3GPP Evolved Packet System (EPS)Evolved General Packet Radio Service (GPRS) Tunnelling Protocol for Control plane (GTPv2-C)Release 18Stage 3TS

8.51.1 General

The Target Identification information element is coded as depicted in Figure 8.51-1.

Bits

Octets

8

7

6

5

4

3

2

1

1

Type = 121 (decimal)

2 to 3

Length = n

4

Spare

Instance

5

Target Type

6 to (n+4)

Target ID

Figure 8.51-1: Target Identification

Target Type values are specified in Table 8.51-1.

Table 8.51-1: Target Type values and their meanings

Target Types

Values (Decimal)

RNC ID

0

Macro eNodeB ID

1

Cell Identifier

2

Home eNodeB ID

3

Extended Macro eNodeB ID

4

gNodeB ID

5

Macro ng-eNodeB ID

6

Extended ng-eNodeB ID

7

en-gNB ID

8

<spare>

9 to 255

8.51.2 RNC ID

The Target Type is RNC ID for SRNS relocation procedure, handover to UTRAN and RAN Information Relay towards UTRAN or GERAN operating in GERAN Iu mode, and 5G-SRVCC from NG-RAN to UTRAN procedure. In this case the "Target ID" field shall contain a non-transparent copy of the corresponding IEs (see clause 8.2.2) and be encoded as specified in Figure 8.51-1a below. The "Target RNC-ID" part of the "Target ID" parameter is specified in 3GPP TS 25.413 [33] and 3GPP TS 38.413 [84].

NOTE 1: The ASN.1 parameter "Target ID" is forwarded non-transparently in order to maintain backward compatibility.

NOTE 2: The preamble of the "Target RNC-ID" (numerical value of e.g. 0x20) shall not be included into octets 6 to (n+4). Also, the optional "iE-Extensions" parameter shall not be included into the GTP IE.

Bits

Octets

8

7

6

5

4

3

2

1

6

MCC digit 2

MCC digit 1

7

MNC digit 3

MCC digit 3

8

MNC digit 2

MNC digit 1

9 to 10

LAC

11

RAC (see NOTE 3)

12 to 13

RNC-ID

a to (a+1)

Extended RNC-ID (optional)

Figure 8.51-1a: Target ID for Type RNC ID

If only two digits are included in the MNC, then bits 5 to 8 of octet 7 (MNC digit 3) shall be coded as "1111".

The location area code (LAC) consists of 2 octets. Bit 8 of octet 9 is the most significant bit and bit 1 of octet 10 is the least significant bit. The coding of the location area code is the responsibility of each administration. Coding using full hexadecimal representation (binary, not ASCII encoding) shall be used.

During a 5G-SRVCC Handover, the AMF does not receive the target RAC in the "Target RNC-ID" part of the "Target ID" IE of the Handover Required message (see clause 9.3.1.25 of 3GPP TS 38.413 [84]). The AMF should set the RAC to a default value, e.g. hexadecimal value ‘FF’. The MME_SRVCC shall ignore the received RAC value.

The RNC-ID consists of 2 octets and contains 12 bits long value (see 3GPP TS 25.413 [7]). Bit 4 of octet 12 is the most significant bit and bit 1 of octet 13 is the least significant bit (bits 8 to 5 of octet 12 are set to 0). The coding of the RNC-ID is the responsibility of each administration. Coding using full hexadecimal representation (binary, not ASCII encoding) shall be used.

The Extended RNC-ID consists of 2 octets and contains 16 bits long value within the range 4096 to 65535. Bit 8 of octet a is the most significant bit and bit 1 of octet (a+1) is the least significant bit. The coding of the Extended RNC-ID is the responsibility of each administration. Coding using full hexadecimal representation (binary, not ASCII encoding) shall be used. If the optional Extended RNC-ID is included, then the receiver shall ignore the RNC-ID.

If the optional Extended RNC-ID is not included, then the length variable ‘n’ = 8 and the overall length of the IE is 13 octets. Otherwise, ‘n’ = 10 and the overall length of the IE is 15 octets.

NOTE 3: In the "TargetRNC-ID" ASN.1 type definition in 3GPP TS 25.413 [7] the "RAC" parameter is marked as optional. RAC is however always available at an SGSN/MME when it sends the RAC in e.g. a GTPv2 Forward Relocation Request message.

8.51.3 Macro eNodeB ID

The Target Type is Macro eNodeB ID for:

– handover to E-UTRAN Macro eNodeB;

– RAN Information Relay towards E-UTRAN; and

– a TNL address discovery response of a candidate en-gNB via the S1 interface or via inter-system signalling (see clauses 22.3.6.2 and 22.3.6.3 of 3GPP TS 36.300 [19]).

In this case the Target ID field shall be coded as depicted in Figure 8.51-2.

Bits

Octets

8

7

6

5

4

3

2

1

6

MCC digit 2

MCC digit 1

7

MNC digit 3

MCC digit 3

8

MNC digit 2

MNC digit 1

9

Spare

Macro eNodeB ID

10 to 11

Macro eNodeB ID

12 to 13

Tracking Area Code (TAC)

Figure 8.51-2: Target ID for Type Macro eNodeB

The Macro eNodeB ID consists of 20 bits. Bit 4 of Octet 9 is the most significant bit and bit 1 of Octet 11 is the least significant bit. The coding of the Macro eNodeB ID is the responsibility of each administration. Coding using full hexadecimal representation (binary, not ASCII encoding) shall be used.

8.51.4 Home eNodeB ID

The Target Type is Home eNodeB ID for handover to E-UTRAN Home eNodeB. In this case the coding of the Target ID field shall be coded as depicted in Figure 8.51-3.

Bits

Octets

8

7

6

5

4

3

2

1

6

MCC digit 2

MCC digit 1

7

MNC digit 3

MCC digit 3

8

MNC digit 2

MNC digit 1

9

Spare

Home eNodeB ID

10 to 12

Home eNodeB ID

13 to 14

Tracking Area Code (TAC)

Figure 8.51-3: Target ID for Type Home eNodeB

The Home eNodeB ID consists of 28 bits. See 3GPP TS 36.413 [10]. Bit 4 of Octet 9 is the most significant bit and bit 1 of Octet 12 is the least significant bit. The coding of the Home eNodeB ID is the responsibility of each administration. Coding using full hexadecimal representation (binary, not ASCII encoding) shall be used.

8.51.5 Extended Macro eNodeB ID

The Target Type is Extended Macro eNodeB ID for:

– handover to E-UTRAN Macro eNodeB;

– RAN Information Relay towards E-UTRAN; and

– a TNL address discovery response of a candidate en-gNB via the S1 interface or via inter-system signalling (see clauses 22.3.6.2 and 22.3.6.3 of 3GPP TS 36.300 [19]).

In this case the Target ID field shall be coded as depicted in Figure 8.51-4.

Bits

Octets

8

7

6

5

4

3

2

1

6

MCC digit 2

MCC digit 1

7

MNC digit 3

MCC digit 3

8

MNC digit 2

MNC digit 1

9

SMeNB

Spare

Extended Macro eNodeB ID

10 to 11

Extended Macro eNodeB ID

12 to 13

Tracking Area Code (TAC)

Figure 8.51-4: Target ID for Type Extended Macro eNodeB

The Extended Macro eNodeB ID consists of 21 bits. The coding of the Macro eNodeB ID is the responsibility of each administration. Coding using full hexadecimal representation (binary, not ASCII encoding) shall be used.

If the SMeNB flag is not set the Extended Macro eNodeB ID contains a Long Macro eNodeB ID with a length of 21 Bits. Bit 5 of Octet 9 is the most significant bit and bit 1 of Octet 11 is the least significant bit.

If the SMeNB flag is set the Extended Macro eNodeB ID contains a Short Macro eNodeB ID with a length of 18 Bits. Bits 5 to 3 of Octet 9 shall be set to 0 by the sender and shall be ignored by the receiver. Bit 2 of Octet 9 is the most significant bit and bit 1 of Octet 11 is the least significant bit.

8.51.6 Cell Identifier

The Target Type is Cell Identifier for E-UTRAN handover to GERAN and RAN Information Relay towards GERAN. In this case the coding of the Target ID field shall be same as the Octets 3 to 10 of the Cell Identifier IEI in 3GPP TS 48.018 [34].

8.51.7 gNodeB ID

The Target Type is gNodeB ID for an EPS to 5GS handover to a target gNodeB. In this case the coding of the Target ID field shall be coded as depicted in Figure 8.51.7-1.

Bits

Octets

8

7

6

5

4

3

2

1

6

MCC digit 2

MCC digit 1

7

MNC digit 3

MCC digit 3

8

MNC digit 2

MNC digit 1

9

Spare

gNodeB ID Length

10 to 13

gNodeB ID

14 to 16

5GS Tracking Area Code (TAC)

Figure 8.51.7-1: Target ID for Type gNode ID

The gNodeB ID Length field, in bits 1 to 6 of octet 9, indicates the length of the gNodeB ID in number of bits.

The gNodeB ID consists of 22 to 32 bits. The coding of the gNodeB ID is the responsibility of each administration. Coding using full hexadecimal representation (binary, not ASCII encoding) shall be used. Bit 1 of Octet 13 is the least significant bit. The most significant bit is determined as follows:

– if the gNodeB ID Length is 32, bit 8 of octet 10 is the most significant bit;

– if the gNodeB ID Length is 24, bit 8 of octet 11 is the most significant bit; all the bits of octet 10 shall be set to 0 by the sender and ignored by the receiver;

– if the gNodeB ID Length is between 22 and 31, other than 24, the most significant bit is the bit determined by the operation "gNodeB ID Length modulo 8", of octet 10 if the length is greater than 24, or of octet 11 if the length is smaller than 24. All the bits from bit 8 of octet 10 down to the most significant bit (excluded) shall be set to 0 by the sender and ignored by the receiver.

The 5GS TAC consists of 3 octets. Bit 8 of Octet 14 is the most significant bit and bit 1 of octet 16 the least significant bit. The coding of the tracking area code is the responsibility of each administration. Coding using full hexadecimal representation (binary, not ASCII encoding) shall be used.

8.51.8 Macro ng-eNodeB ID

The Target Type is Macro ng-eNodeB ID for an EPS to 5GS handover to a target Macro ng-eNodeB. In this case the coding of the Target ID field shall be coded as depicted in Figure 8.51.8-1.

Bits

Octets

8

7

6

5

4

3

2

1

6

MCC digit 2

MCC digit 1

7

MNC digit 3

MCC digit 3

8

MNC digit 2

MNC digit 1

9

Spare

Macro eNodeB ID

10 to 11

Macro ng-eNodeB ID

12 to 14

5GS Tracking Area Code (TAC)

Figure 8.51.8-1: Target ID for Type Macro ng-eNodeB

Octets 6 to 11 shall be encoded as specified for the Macro eNodeB (see Figure 8.51-2).

The 5GS TAC consists of 3 octets. Bit 8 of Octet 12 is the most significant bit and bit 1 of octet 14 the least significant bit. The coding of the tracking area code is the responsibility of each administration. Coding using full hexadecimal representation (binary, not ASCII encoding) shall be used.

8.51.9 Extended Macro ng-eNodeB ID

The Target Type is Extended Macro ng-eNodeB ID for an EPS to 5GS handover to a target Extended Macro ng-eNodeB. In this case the coding of the Target ID field shall be coded as depicted in Figure 8.51.9-1.

Bits

Octets

8

7

6

5

4

3

2

1

6

MCC digit 2

MCC digit 1

7

MNC digit 3

MCC digit 3

8

MNC digit 2

MNC digit 1

9

SMeNB

Spare

Extended Macro eNodeB ID

10 to 11

Extended Macro ng-eNodeB ID

12 to 14

5GS Tracking Area Code (TAC)

Figure 8.51.9-1: Target ID for Type Extended Macro ng-eNodeB

Octets 6 to 11 shall be encoded as specified for the Extended Macro eNodeB (see Figure 8.51-4).

The 5GS TAC consists of 3 octets. Bit 8 of Octet 12 is the most significant bit and bit 1 of octet 14 the least significant bit. The coding of the tracking area code is the responsibility of each administration. Coding using full hexadecimal representation (binary, not ASCII encoding) shall be used.

8.51.10 en-gNB ID

The Target Type is an en-gNB ID for:

– a TNL address discovery request of a candidate en-gNB via the S1 interface or via inter-system signalling (see clauses 22.3.6.2 and 22.3.6.3 of 3GPP TS 36.300 [19]).

In this case, the Target ID field shall be coded as depicted in Figure 8.51.10-1.

Bits

Octets

8

7

6

5

4

3

2

1

6

MCC digit 2

MCC digit 1

7

MNC digit 3

MCC digit 3

8

MNC digit 2

MNC digit 1

9

5TAC

ETAC

en-gNB ID Length

10 to 13

en-gNB ID

p to (p+1)

Tracking Area Code (TAC)

q to (q+2)

5GS Tracking Area Code (TAC)

Figure 8.51.10-1: Target ID for Type en-gNB ID

The en-gNB ID Length field, in bits 1 to 6 of octet 9, indicates the length of the en-gNB ID in number of bits.

Bits 7 and 8 of octet 9 shall be encoded as follows:

– Bit 7 – ETAC: when set to "1", octets p to (p+1) shall be present and encode a TAC (EPS); otherwise, octets p to (p+1) shall be absent.

– Bit 8 – 5TAC: when set to "1", octets q to (q+2) shall be present and encode a 5GS TAC; otherwise, octets q to (q+2) shall be absent.

The en-gNB ID consists of 22 to 32 bits. The en-gNB ID shall be coded as the gNodeB ID field of the gNodeB ID in clause 8.51.7.

When present, the TAC shall consist of 2 octets and shall be coded as the TAC field of the Macro eNodeB ID in clause 8.51.3.

When present, the 5GS TAC shall consist of 3 octets and shall be coded as the 5GS TAC field of the gNodeB ID in ubclause 8.51.7.