7.5.10 Closed User Group (CUG)

29.1633GPPInterworking between the IP Multimedia (IM) Core Network (CN) subsystem and Circuit Switched (CS) networksTS

7.5.10.0 General

The protocol specification of the Closed User Group supplementary service is described in 3GPP TS 24.654 [101].

7.5.10.1 Interworking at the I-MGCF

If the I-MGCF supports the interworking of CUG supplementary service, the I-MGCF shall map between the SIP and ISUP messages in accordance with table 7.5.10.1.1.

Table 7.5.10.1.1: Mapping of SIP messages to ISUP messages

SIP Message

ISUP Message

INVITE request containing a XML cug body with CUG XML schema

IAM containing the Closed user group interlock code Parameter and the closed user group call indicator of the Optional Forward Call Indicator Parameter

If the MGCF supports the interworking of CUG supplementary service, the I-MGCF shall interwork the CUG XML schema with the ISUP Closed user group interlock code parameter and the Closed user group call indicator of the optional forward call indicator parameter in accordance with tables 7.5.10.1.2 and 7.5.10.1.3.

Table 7.5.10.1.2: Mapping of the SIP XML CUG Element to the ISUP closed usergroup interlock code parameter

CUG XML Element

Source component value

ISUP Closed user group interlock code Parameter

derived value of parameter field

networkIndicator

networkIdentityType = 4 hexbinary coded digits (NOTE)

"Network Identity"

Octet 1 & Octet 2 including 4 binary coded digits derived from XML Network Identity

cugInterlockBinaryCode

sixteenbitType = 16 bit coded value

"Binary Code"

Octet 3 & Octet 4 including a 16 bit Binary Code derived from the XML Binary Code

NOTE: ISUP Closed user group interlock code Parameter Octet 1 contains "Network Identity" (NI) digits 1 & 2 and Octet 2 contains "Network Identity" digits 3 & 4.The networkidentityType is filled with "Octet1 & Octet 2" = "NI digit 1, NI digit 2, NI digit 3, NI digit 4". Example: Digit 1=0, Digit 2=4, Digit 3=9, Digit 4=0 so the networkidentityType is encoded with "0490".

Table 7.5.10.1.3: Mapping of the SIP XML CUG Element to the ISUP closed user group call indicator included in the optional Forward Call Indicator Parameter

CUG XML Element

Source component value

ISUP "Optional Forward Call Indicator" Parameter

derived value of parameter field

cugCommunicationIndicator

Type=00

"closed user group call" indicator

non-CUG call

Type=01

spare

Type=10

closed user group call, outgoing access allowed

Type=11

closed user group call, outgoing access not allowed

If the I-MGCF supports the interworking of CUG supplementary service, then if an INVITE request with the MIME including a cug XML element is received and the terminating network is not supporting CUG, the I-MGCF shall behave as shown in table 7.5.10.1.4.

Table 7.5.10.1.4: Action at the I-MGCF with a PSTN/ISDN network without CUG capability

cugCommunicationIndicator in INVITE request

Action at the I-MGCF

Type=11 (CUG without outgoing access)

Release the communication with 403

Type=10 (CUG with outgoing access)

Treat the communication as an ordinary call (NOTE)

Non-CUG

Treat the communication as an ordinary call

NOTE: The cugCommunicationIndicator shall not be mapped or if appropriate the CUG call indicator of the optional forward call indicator shall be set to non-CUG call.

7.5.10.2 Interworking at the O-MGCF

If the MGCF supports the interworking of CUG supplementary service, the O-MGCF shall map between the SIP and ISUP messages in accordance with table 7.5.10.2.1

Table 7.5.10.2.1: Mapping of ISUP messages to SIP messages

ISUP Message

SIP Message

IAM containing the Closed user group interlock code Parameter and the closed user group call indicator of the Optional Forward Call Indicator Parameter

INVITE request containing a XML cug body with CUG XML schema

If the MGCF supports the interworking of CUG supplementary service, the MGCF shall interwork the CUG XML schema with the ISUP Closed user group interlock code parameter and the Closed user group call indicator of the optional forward call indicator parameter in accordance with tables 7.5.10.2.2 and table 7.5.10.2.3.

Table 7.5.10.2.2: Mapping of the ISUP closed usergroup interloccode to SIP XML CUG element

ISUP Closed user group interlock code Parameter

Source component value

CUG XML Element

derived value of parameter field

"Network Identity"

Octet 1 & Octet 2 including 4 binary coded digits

networkIndicator

networkIdentityType = 4 hexbinary coded digits derived from Network Identity (NOTE)

"Binary Code"

Octet 3 & Octet 4 including a 16 bit Binary Code

cugInterlockBinaryCode

sixteenbitType = 16 bit coded value derived from Binary Code

NOTE: ISUP Closed user group interlock code Parameter Octet 1 contains "Network Identity" (NI) digits 1 & 2 and Octet 2 contains "Network Identity" digits 3 & 4.The networkidentityType shall be filled with "Octet1 & Octet 2" = "NI digit 1, NI digit 2, NI digit 3, NI digit 4". Example: Digit 1=0, Digit 2=4, Digit 3=9, Digit 4=0 so the networkidentityType is encoded with "0490".

Table 7.5.10.2.3: Mapping of the ISUP Closed user group call indicator to SIP XML CUG element

ISUP Optional Forward Call Indicator Parameter

Source component value

CUG XML Element

derived value of parameter field

closed user group call indicator

non-CUG call

cugCommunicationIndicator

Type=00

spare

Type=01

closed user group call, outgoing access allowed

Type=10

closed user group call, outgoing access not allowed

Type=11

If the MGCF supports the interworking of CUG supplementary service, but the IMS is not supporting CUG, the procedures described in ITU Q.735.1 [42] shall apply if an INVITE request with the MIME body including a cug XML element is sent and the O-MGCF supports CUG supplementary service.