The CapLocationHeaders feature adds proprietary SIP headers to outbound INVITE requests to allow CAP charging of the session.

The OC-Charging-GT header contains the location of the subscriber to allow roaming to be correctly charged.

The OC-IM-TDP header contains the location of the SCP that IM-SSF should send charging requests to.

The OC-Replication-Information header contains instructions on how the IM-SSF should handle session tracking and replication.

Feature cheat sheet

Feature Script Name

CapLocationHeaders

MMTel or SCC

Both

Call-Type

Orig or Term

Session Plan

mmtel-orig, scc-tads-only

Execution Points

SipAccess_SubscriberCheck

Network Operator Config

Yes

Subscriber Config

No

POJO or SBB

POJO

Feature FSMs

None

Feature Parameters

None

SAS Support

Yes

RA Entity Links

None

Network Operator Data

The CapLocationHeaders feature depends on configuration in the CapChargingConfigProfileTable to specify how to generate the OC-Charging-GT header.

It also reads the RefreshPeriod in the SessionRefresh configuration profile table to determine the refresh period to include on the OC-Replication-Information header when replication is enabled.

CapChargingConfigProfileTable

Configuration is stored on a profile table called CapChargingConfigProfileTable.

Data is scoped according to a Sentinel selection key.

Attribute Name Type Default Description
ChargingGTFormatString

String

null

The format template to use when creating Charging GTs. It must be a digit string except for tokens ('{iso}', '{mcc}', '{mnc}) which are substituted in.

UnknownLocationChargingGT

String

null

The Charging GT to use when one could not be generated because the user’s location could not be determined.

OnlyChargeTerminatingCallsIfInternationalRoaming

boolean

false

When true, terminating calls will only be charged if the served user is roaming outside of their home country.

Session Input Variables

Variable name Type Comments

ChargeMode

Enum

The feature will only run if the charge mode is CAP.

SentinelSelectionKey

SentinelSelectionKey

Affects which profiles are loaded from each configuration table.

CallType

Enum

Affects whether CAP headers are added and what values are used for them.

RoamingStatus

Enum

If the call is terminating and not roaming, no headers are added.

VLRNumber

AddressString

If the call is CS terminating then the VLRNumber is used for the OC-Charging-GT.

VMSCAddress

AddressString

If the call is CS terminating and there is no VLRNumber available then the VMSCAddress is used for the OC-Charging-GT.

OcImTdpHeader

String

The value to use for the OC-IM-TDP header.

IsoCountryCode

String

The ISO country code that the subscriber is registered with. It is used for formatting the OC-Charging-GT header.

PaniMccMncs

List<MccMnc>

The MCCs and MNCs that the subscriber is registered with. They are used for formatting the OC-Charging-GT header.

SessionUACLegReplicationTrigger

Enum

Used to determine if replication should be indicated as enabled on the OC-Replication-Information header.

SessionUASLegReplicationTrigger

Enum

Used to determine if replication should be indicated as enabled on the OC-Replication-Information header.

Statistics

CapLocationHeaders statistics are tracked by the sentinel.volte.sip SBB and can be found under the following parameter set in REM:
SLEE-Usage → sentinel.volte.sip service → sentinel.volte.sip SBB → feature → CapLocationHeaders
or with rhino-stats:
"SLEE-Usage.Services.ServiceID[name=sentinel.volte.sip,vendor=OpenCloud,version=3.1.0].SbbID[name=sentinel.volte.sip,vendor=OpenCloud,version=3.1.0].feature.CapLocationHeaders"

Statistic

Type

Description

Started

Counter

Incremented when the feature is invoked.

FailedToStart

Counter

Incremented when Sentinel VoLTE encounters an error while attempting to start the feature.

IssuedWarning

Counter

Incremented when a non-fatal problem is encountered and the feature issues a warning.

FailedDuringExecution

Counter

Incremented when a fatal problem is encountered and the feature cannot execute correctly.

TimedOut

Counter

Incremented when the feature takes too long to complete and Sentinel VoLTE aborts execution.

CapLocationHeadersNotRequired

Counter

Incremented when the feature determines that no CAP location headers need to be added.

UsedVlrNumber

Counter

Incremented when the VLR number is used for the OC-Charging-GT header.

UsedVmscNumber

Counter

Incremented when the VMSC address is used for the OC-Charging-GT header.

NoVlrOrVmscNumberFound

Counter

Incremented when no VLR number and no VMSC address could be found.

UsedGeneratedChargingGT

Counter

Incremented when a generated Charging GT is used for the OC-Charging-GT header.

UsedUnknownLocationChargingGT

Counter

Incremented when the unknown location Charging GT is used for the OC-Charging-GT header.

SetOCIMTDP

Counter

Incremented when an OC-IM-TDP header is set on an outgoing request.

SetOCChargingGT

Counter

Incremented when an OC-Charging-GT header is set on an outgoing request.

SetOCReplicationInformation

Counter

Incremented when an OC-Replication-Information header is set on an outgoing request.

Installation

CapLocationHeaders is a GSM only feature and as such will only be deployed if GSM mode is selected in the installer.

Behaviour

The behaviour varies depending on whether the call is terminating or not.

Originating Behaviour

The feature attempts to generate a Charging GT using the ChargingGTFormatString and sets the OC-Charging-GT with this. If this fails, the feature uses the UnknownLocationChargingGT for the OC-Charging-GT header.

The feature sets the OC-IM-TDP header to the value stored in session state by the FetchIMCSI feature.

The feature sets the OC-Replication-Information as described below in the Replication Information section.

Terminating Behaviour

If the subscriber is not roaming the feature will check the OnlyChargeTerminatingCallsIfInternationalRoaming configuration value to determine whether it should do anything.

If the call is forked then the following occurs for each outgoing forked leg.

If the outgoing leg is CS then the feature attempts to set the OC-Charging-GT to the VLR Number retrieved by FetchMSRN. If there is no VLR Number in session state, the feature attempts to set the OC-Charging-GT to the VMSC address. If that is not present in session state either then the feature returns.

If the outgoing leg is PS then the feature attempts to generate a Charging GT using the ChargingGTFormatString and sets the OC-Charging-GT with this. If this fails, the feature uses the UnknownLocationChargingGT for the OC-Charging-GT header.

The feature sets the OC-IM-TDP header to the value stored in session state by the FetchIMCSI feature.

The feature sets the OC-Replication-Information as described below in the Replication Information section.

Generating Charging GTs

The feature uses the CAP Charging Component to generate Charging GTs based on location data.

Replication Information

The feature includes an OC-Replication-Information header on the request towards the IM-SSF which indicates whether replication behaviour is required.

The header value is determined based on the values of the SessionUASLegReplicationTrigger and SessionUACLegReplicationTrigger session input fields. If either of the fields indicated DISABLED then the the header value will be set to disabled, otherwise it will be set ot enabled.

When the header value is set to enabled, a refreshPeriod parameter will be added as well. This parameter is used to determine the TTL value the IM-SSF should use for session ownership records when doing session tracking. It is set equal to the value of the RefreshPeriod field in the SessionRefresh configuration profile table.

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Sentinel VoLTE Version 3.1.0