10 Contents of messages

03.793GPPStage 2Support of Optimal Routeing phase 1TS

This clause specifies the changes to the content of each message shown in clauses 5, 6 and 9, including those messages which are already specified for GSM Phase 2 but which require changes for Optimal Routeing. It should be read as a ‘delta’ on the corresponding clause of GSM 03.18; those information elements which are the same for SOR as for the basic call without OR are not specified in this clause.

In the tables which follow, information elements are shown as mandatory (M) or conditional (C). A mandatory information element shall always be present. A conditional information element shall be present if certain conditions are fulfilled; if those conditions are not fulfilled it shall be absent.

10.1 Messages on the B interface (MSC-VLR)

10.1.1 Send Info For Outgoing Call

This message is specified in GSM 03.18 [6].

10.1.2 Send Info For Outgoing Call negative response

This message is specified in GSM 03.18 [6].

10.1.3 Send Info For Incoming Call

This message is specified in GSM 03.18 [6].

10.1.4 Send Info For Incoming Call ack

This message is specified in GSM 03.18 [6]. The following additional information elements are required:

Information element name

Required

Description

OR indicator

C

Indicates whether the call has been routed directly from a GMSC not in the same PLMN as the HLR. Shall be present if it was received in the Provide Roaming Number, otherwise shall be absent.

GMSC address

C

E.164 address of the GMSC. Shall be present if it was received in the Provide Roaming Number, otherwise shall be absent.

Call reference number

C

Call reference number used by the GMSC for this call. Shall be present if it was received in the Provide Roaming Number, otherwise shall be absent.

Originating CSI

C

Originating CAMEL subscription information. Shall be present if the B subscriber has subscribed to originating CAMEL service and VMSCB supports CAMEL; otherwise shall be absent.

10.1.5 Send Info For Incoming Call negative response

This message is specified in GSM 03.18 [6].

10.1.6 Complete Call

This message is specified in GSM 03.18 [6]. The following additional information elements are required:

Information element name

Required

Description

OR indicator

C

Indicates whether the call has been routed directly from a GMSC not in the same PLMN as the HLR. Shall be present if it was received in the Provide Roaming Number, otherwise shall be absent.

GMSC address

C

E.164 address of the GMSC. Shall be present if it was received in the Provide Roaming Number, otherwise shall be absent.

10.1.7 Process Call Waiting

This message is specified in GSM 03.18 [6]. The following additional information elements are required:

Information element name

Required

Description

OR indicator

C

Indicates whether the call has been routed directly from a GMSC not in the same PLMN as the HLR. Shall be present if it was received in the Provide Roaming Number, otherwise shall be absent.

GMSC address

C

E.164 address of the GMSC. Shall be present if it was received in the Provide Roaming Number, otherwise shall be absent.

10.2 Messages on the C interface (MSC-HLR)

10.2.1 Send Routeing Info

This message is specified in GSM 03.18 [6]. The following additional information elements are required:

Information element name

Required

Description

Interrogation type

M

Indicates the type of interrogation: basic(for routeing information for an MT call) or forwarding (when the GMSC has been asked to resume call handling for OR of late call forwarding).

OR interrogation indicator

C

Indicates that the interrogation is from a GMSC not in the same PLMN as the HLR. Shall be present if the interrogation is from a GMSC not in the same PLMN as the HLR, otherwise shall be absent.

OR capability

C

Indicates the phase of OR which the GMSC supports. Shall be present if the GMSC supports OR, otherwise shall be absent.

GMSC address

M

E.164 address of the GMSC.

Call reference number

C

Call reference number used by the GMSC for this call. Shall be present if the interrogation type=basic call, otherwise shall be absent.

Forwarding reason

C

Indicates the reason for forwarding (on busy, on no subscriber reply, or on mobile subscriber not reachable). Shall be present if the Interrogation type=forwarding, otherwise shall be absent.

Basic service group

C

Basic service group which applies for this call. Shall be present if the Interrogation type=forwarding, otherwise shall be absent.

10.2.2 Send Routeing Info ack

This message is specified in GSM 03.18 [6]. Two new information elements are required, and the condition for the presence of one existing information element is changed, as shown in the following table.

Information element name

Required

Description

Forwarding interrogation required

C

Indicates that the GMSC shall interrogate the HLR for routeing information for late call forwarding. Shall be present if the SRI ack contains an MSRN and GMSC has to interrogate the HLR for routeing information for late call forwarding, otherwise shall be absent.

VMSC address

C

E.164 address of the VMSC in whose area the B subscriber is currently registered. Shall be present in the Send Routeing Info ack if the OR interrogation indicator in the Send Routeing Info was present and the HLR supports optimal routeing of basic mobile-to-mobile calls and the HLR has not determined that the call is to be forwarded, otherwise shall be absent.

Roaming number

C

E.164 address required to route the call to the VMSC of the B party. Shall be present in the Send Routeing Info ack which is sent in response to a Send Routeing Info with Interrogation type=basic if the HLR has determined that the charging requirements for optimal routeing are not contravened and that the call is not to be forwarded, otherwise shall be absent.

10.2.3 Send Routeing Info negative response

This message is specified in GSM 03.18 [6]. The negative response information element can take the following values in addition to those specified in GSM 03.18 [6]:

– OR not allowed

– Busy subscriber

– No subscriber reply

10.3 Messages on the D interface (VLR-HLR)

10.3.1 Provide Roaming Number

This message is specified in GSM 03.18 [6]. The following additional information elements are required:

Information element name

Required

Description

GMSC address

C

E.164 address of the GMSC. Shall be present if it was received by the HLR in the Send Routeing Info, otherwise shall be absent.

Call reference number

C

Call reference number used by the GMSC for this call. Shall be present if it was received by the HLR in the Send Routeing Info, otherwise shall be absent.

OR interrogation indicator

C

Indicates that the HLR received the corresponding Send Routeing Info from a GMSC not in the same PLMN as the HLR. Shall be present if the HLR received the Send Routeing Info from a GMSC not in the same PLMN as the HLR, otherwise shall be absent.

10.3.2 Provide Roaming Number ack

This message is specified in GSM 03.18 [6].

10.3.3 Provide Roaming Number negative response

This message is specified in GSM 03.18 [6].

10.3.4 Provide Subscriber Information

This message is specified in GSM 03.18 [6].

10.3.5 Provide Subscriber Information ack

This message is specified in GSM 03.18 [6].

10.4 Messages on the E interface (MSC-MSC)

10.4.1 Resume Call Handling

The following information elements are required:

Information element name

Required

Description

Call reference number

M

Call reference number used by the GMSC for this call.

Forwarding reason

M

Indicates the reason for forwarding (on busy, on no subscriber reply, or on mobile subscriber not reachable).

Basic service group

M

Basic service group which applies for this call.

IMSI

M

IMSI of the B subscriber.

Forwarded-to number

M

E.164 number of the C subscriber.

Notification to calling party

M

Indication of whether the calling party is to be notified that the call has been forwarded.

Forwarded-to subaddress

C

Subaddress of the C subscriber (see GSM 03.03 [4]). Shall be present if a forwarded-to subaddress is stored in the VLR in association with the forwarded-to number; otherwise shall be absent.

CUG interlock

C

For the definition of this IE, see GSM 03.85 [9]. Shall be present if the VLR has determined that the forwarded call is to be treated as a CUG call in accordance with the rules in GSM 03.85 [9], otherwise shall be absent.

CUG outgoing access

C

For the definition of this IE, see GSM 03.85 [9]. Shall be present if the VLR has determined that the forwarded call is to be treated as a CUG call with outgoing access in accordance with the rules in GSM 03.85 [9], otherwise shall be absent.

Originating CSI

C

Originating CAMEL subscription information excluding triggering criteria. Shall be present if the B subscriber has subscribed to originating CAMEL service and VMSCB supports CAMEL and the triggering criteria are satisfied for the forwarding leg; otherwise shall be absent.

10.4.2 Resume Call Handling ack

This message contains no information elements.

10.4.3 Resume Call Handling negative response

The negative response information element can take the following values:

– OR not allowed

– Forwarding failed

Annex A (informative):
Handling of an IAM at an MSC

An MSC which receives an IAM from an originating exchange may react in three different ways:

– It acts as a transit exchange, i.e. it relays the IAM to a destination exchange determined by analysis of the called party address, and thereafter relays other ISUP signalling between the originating and destination exchange until the connection is released. This behaviour is not specific to GSM;

– It acts as a terminating exchange, i.e. it attempts to connect the call to an MS currently registered in the service area of the MSC;

– It acts as a GMSC, i.e. it interrogates an HLR for information to route the call. If the HLR returns routeing information, the MSC uses the routeing information from the HLR to construct an IAM, which it sends to a destination exchange determined by analysis of the routeing information from the HLR.

The method which the MSC uses to determine how to handle the IAM is described in GSM 03.18 [6]. However, the number analysis required to derive the address of an HLR in a different PLMN from the MSC is much more extensive than that required to derive the address of an HLR in the same PLMN as the MSC – the MSC needs to be able to recognise the combination of country code and national destination code for every subscriber of every PLMN to which calls are to be optimally routed.

A PLMN operator may decide to implement the ability to recognise a called party address as belonging to a GSM PLMN which is not the PLMN of the MSC in only a subset of the MSCs in his PLMN. Other MSCs will route international calls to one of the MSCs which have the capability for extra number analysis.

When a GMSC has interrogated an HLR and received an MSRN, the GMSC may need to route the call to the HPLMN of the called subscriber. If the call is routed through an MSC which has the capability to analyse an address to derive an HLR address, a method must be provided to prevent the transit MSC from performing a further interrogation of the HLR, using the MSRN as an MSISDN. The method used to prevent this further interrogation is a matter for the PLMN operator.

Annex B (informative):
Change Request History

SMG#

TDoc

SPEC

VERS

NEW_VERS

PHASE

SUBJECT

s21

050/97

03.79

2.0.0

5.0.0

2+

Support of Optimal Routing phase 1 (stage 2)

s22

373/97

03.79

5.0.0

5.1.0

2+

Editorial alignment of interrogation types

s22

373/97

03.79

5.0.0

5.1.0

2+

Conditional parameters in Send Routing Info ack message

s24

97-913

03.79

5.1.0

5.2.0

R96

Concentration of description of core call handling functions in 03.18, Changes to ease the documentation of new services

s25

98-0086

03.79

5.2.0

5.3.0

R96

Correction to CAMEL phase 1 for forwarded calls

s27

98-0768

03.79

5.3.0

5.4.0

R96

Optionality for support of OR of basic mobile-mobile calls

s27

6.0.0

Release 1997 version

S29

N2-99590

03.79

6.0.0

6.1.0

R97

Notification of Call Forwarding to the gsmSCF

CN05

N2-99B49

03.79

6.1.0

6.2.0

R97

Handling of Release during forwarding interrogation of the HLR

CN05

N2-99B28

03.79

6.1.0

6.2.0

R97

Removal of TDP Criteria from Resume Call Handling

CN05

N2-99C83

03.79

6.1.0

6.2.0

R97

Notification of Call Forwarding to the gsmSCF before activating call forwarding process

CN07

N2B000167

03.79

6.2.0

6.3.0

R97

Correction of CF Notification

Annex B (informative):
Enhancements for later phases

This annex includes information on enhancements to SOR which are intended for inclusion in a later phase; its purpose is to act as an aide memoire for the rapporteur of the stage 2 for later phases.