Online Charging System (OCS) Integration

Comprehensive guide to OmniTAS integration with Online Charging Systems via Diameter Ro interface, including real-time credit control, AVP extraction, and FreeSWITCH variable mapping.

Architecture Overview
What Controls Whether a Call Is Charged
Credit Control Flow
AVP Parsing and Variable Mapping
Configuration
FreeSWITCH Integration
Answer & Hangup Notifications
Diameter Messages
Metrics
Troubleshooting
Reference
- FreeSWITCH Channel Variables
- AVP Codes Reference

Architecture Overview

OmniTAS implements the Diameter Ro interface per 3GPP TS 32.299 for real-time online charging. The system authorizes calls by requesting credit from an OCS before call setup, monitors credit during the call, and reports final usage on termination.

Key Components

Credit-Control-Request (CCR):

CCR-Initial (Type 1): Sent before call setup to request initial credit authorization
CCR-Update (Type 2): Sent during active calls for re-authorization or interim updates
CCR-Terminate (Type 3): Sent on call termination with final usage reporting

Credit-Control-Answer (CCA):

Contains granted service units (time quota in seconds)
Includes vendor-specific AVPs with additional charging data
Provides routing information, charged party details, and service identifiers

What Controls Whether a Call Is Charged

A call produces Diameter CCRs only if all three of the following conditions hold. They are evaluated when OmniTAS builds the Mobile Originating (MO) dialplan for the call:

Online charging is enabled — online_charging.enabled is true. When false, OmniTAS authorizes every call locally and never contacts the OCS.
The call is Mobile Originating (MO) — only the MO leg is charged. Mobile Terminating (MT) calls are never charged: the MT path does not perform OCS authorization, so no credit-control session is created for it.
The destination is not exempt — the dialled number does not match any pattern in skipped_regex (e.g. emergency numbers, service codes).

If all three hold, OmniTAS sends a CCR-Initial and opens a credit-control session keyed by the SIP Call-ID. From that point, CCR-Update and CCR-Terminate are driven by answer/hangup events (see Answer & Hangup Notifications) and are only generated for call legs that have an open session. MT legs, bridged B-legs, and exempt calls therefore never produce CCRs.

Note: Reaching the OCS does not guarantee the call connects. A successful authorization with zero granted units bars the call — see Credit Exhaustion and Call Barring. Barring happens after a CCR is sent; it is distinct from the conditions above, which decide whether a CCR is sent at all.

Credit Control Flow

Call Authorization Sequence

Credit Exhaustion and Call Barring

Call barring at setup. If the OCS returns a successful CCA (Result-Code 2001) but with zero granted units — or an explicit denial such as 4012 (DIAMETER_CREDIT_LIMIT_REACHED) or 4010 (DIAMETER_END_USER_SERVICE_DENIED) — OmniTAS treats the call as having no credit and bars it with hangup cause OUTGOING_CALL_BARRED. The subscriber never connects. This is the expected outcome for an unprovisioned or out-of-credit subscriber.

Mid-call exhaustion. If credit is granted at setup but later runs out (a periodic CCR-Update returns zero units or a credit-limit error), OmniTAS terminates the in-progress call. With credit_exhaustion_announcement configured it transfers the caller to an announcement before hangup; otherwise it hangs up directly.

CCR-Terminate fires at the exhaustion moment, before any cleanup. When the balance is exhausted, OmniTAS sends the CCR-Terminate immediately (charged answer→exhaustion), then plays the out-of-credit announcement or hangs up. This is deliberate: the time the subscriber spends listening to the "you're out of balance" prompt is not chargeable, so the CDR must end when credit ran out — not when the user hangs up from the recording. The session terminates at that point, so the eventual FreeSWITCH hangup for the call finds no session and sends nothing (idempotent — no second CCR-T). This holds whether cleanup is a transfer-to-announcement or a direct hangup, so it does not depend on the FreeSWITCH hangup cause.

OmniTAS supports multiple mechanisms for handling credit exhaustion, with automatic integration between scheduled hangups and credit exhaustion announcements.

Scheduled Hangup with Dynamic Rescheduling

When schedule_hangup_auth is enabled, OmniTAS schedules a FreeSWITCH timer that automatically terminates calls when granted credit expires. This timer is dynamically rescheduled every time new credit is granted via CCR-Update responses.

How it works:

Buffer Logic:

OmniTAS sends CCR-Update messages before the granted credit expires to ensure continuous service. The buffer time is configurable via ccr_update_buffer_seconds (default: 2 seconds).

Example timeline:

T+0s: Call answered, OCS grants 10s, timer scheduled for T+10s
T+8s: CCR-U sent (10s - 2s buffer)
T+8.1s: OCS grants 10s, timer rescheduled to T+18.1s (10s from now)
T+16.1s: CCR-U sent
T+16.2s: OCS grants 10s, timer rescheduled to T+26.2s
Call continues as long as OCS keeps granting credit

Logs to watch:

[OCS HANGUP RESCHEDULE] Found UUID <uuid> for call <id> - rescheduling timer to 10s from now
[SCHED TRANSFER] Scheduling transfer to credit_exhausted dialplan for <uuid> in 10s
[OCS HANGUP RESCHEDULE] Successfully rescheduled timer for call <id> (UUID: <uuid>)

Integration: schedule_hangup_auth + credit_exhaustion_announcement

When both features are enabled, OmniTAS automatically uses scheduled transfers instead of direct hangups, allowing the caller to hear an announcement before call termination.

Without announcement configured:

config :tas, :online_charging,
  schedule_hangup_auth: true,
  credit_exhaustion_announcement: nil

→ Uses sched_hangup - direct hangup when credit expires

With announcement configured:

config :tas, :online_charging,
  schedule_hangup_auth: true,
  credit_exhaustion_announcement: "${base_dir}/sounds/en/us/callie/misc/8000/credit_exhausted.wav"

→ Uses sched_transfer - transfers to credit_exhausted dialplan which plays announcement then hangs up

How the transfer works:

OmniTAS sets tas_call_reason=credit_exhausted channel variable
Schedules transfer to credit_exhausted extension in ims_as dialplan context
When timer fires:
- FreeSWITCH transfers A-leg to credit_exhausted dialplan
- Bridge breaks automatically, B-leg receives BYE
- Dialplan plays announcement to A-leg
- Call terminates after announcement

Benefits:

Caller hears professional announcement instead of abrupt disconnect
B-leg (called party) doesn't hear announcement
CCR-T still sent with actual usage
Announcement path: Must be relative to FreeSWITCH base directory (use ${base_dir} variable)

Immediate Credit Exhaustion During CCR-Update

If the OCS denies credit or returns zero seconds during a CCR-Update, OmniTAS immediately triggers credit exhaustion handling, overriding any scheduled timer.

OCS Response Scenarios:

Handled Error Codes:

OCS Response	Action	Logs
`{:ok, 0}` (Zero seconds)	Immediate credit exhaustion hangup	`Credit exhausted (zero seconds allocated) - triggering immediate hangup`
`{:error, 4012}` (CREDIT_LIMIT_REACHED)	Immediate credit exhaustion hangup	`Credit exhausted (4012 CREDIT_LIMIT_REACHED) - triggering immediate hangup`
`{:error, 4010}` (END_USER_SERVICE_DENIED)	Immediate credit exhaustion hangup	`Service denied (4010 END_USER_SERVICE_DENIED) - triggering immediate hangup`
`{:error, reason}` (Other errors)	Stop periodic CCR job, scheduled timer fires	`Periodic CCR failed with error <reason> - Stopping job`
`{:ok, N}` where N > 0	Reschedule timer to +N seconds	`Periodic CCA allocated Ns, will send next CCR-U in (N-buffer)s`

Priority: Immediate credit exhaustion handling wins over scheduled timer. If OCS denies credit at T+8s but timer was scheduled for T+10s, the immediate hangup at T+8s occurs and the scheduled timer becomes irrelevant.

Example timeline with mid-call credit denial:

T+0s:   Call answered
T+0.1s: OCS grants 10s → Timer scheduled for T+10.1s
T+8s:   CCR-U sent (buffer = 2s)
T+8.1s: OCS returns 0 seconds → Immediate transfer to credit_exhausted dialplan
T+8.2s: Announcement plays to caller
T+10s:  Call terminated (scheduled timer irrelevant)

Logs for immediate credit exhaustion:

[warning] Credit exhausted (zero seconds allocated) - triggering immediate hangup
[warning] Hanging up call <id> (UUID: <uuid>) due to credit exhaustion
[info] Credit exhaustion announcement config: "${base_dir}/sounds/..."
[info] Playing announcement before hangup: ...
[info] Setting tas_call_reason=credit_exhausted for <uuid>
[info] Transferring to credit exhausted dialplan: uuid_transfer <uuid> credit_exhausted XML ims_as

Summary: Credit Exhaustion Mechanisms

OmniTAS provides two complementary mechanisms:

Scheduled Timer (schedule_hangup_auth):
- Automatic hangup/transfer when granted credit expires
- Dynamically rescheduled on each CCR-U response
- Uses buffer logic to send CCR-U before expiration
- Integrates with announcement feature
Immediate Exhaustion Handling:
- Triggered when OCS denies credit during CCR-U
- Overrides scheduled timer
- Supports announcement playback
- Handles specific Diameter error codes

Both mechanisms respect the credit_exhaustion_announcement configuration and will play the configured audio before terminating calls when configured.

AVP Parsing and Variable Mapping

Overview

OmniTAS automatically extracts Attribute-Value Pairs (AVPs) from Credit-Control-Answer messages and makes them available to FreeSWITCH as channel variables. This enables dialplan logic to use OCS-provided data for routing decisions, billing purposes, or call treatment.

Supported AVP Types:

Simple values (UTF8String, Unsigned32, Integer32)
Grouped AVPs with nested structures
Vendor-specific AVPs (e.g., 3GPP Service-Information)

Variable Naming Convention: AVPs are flattened into dot-notation channel variables with the prefix CCA:

CCA.<AVP-Name>.<Nested-AVP-Name>.<Value-AVP-Name> = "value"

Common AVP Mappings

Service-Information AVP (3GPP)

The Service-Information grouped AVP (AVP Code 873, Vendor-ID 10415) contains IMS-specific charging details:

Example OCS Response:

Service-Information
  ├── IMS-Information
  │     ├── Carrier-Select-Routing-Information: "1408"
  │     └── Node-Functionality: 6
  └── Alternate-Charged-Party-Address: "NickTest"

Resulting FreeSWITCH Variables:

CCA.Service-Information.Carrier-Select-Routing-Information = "1408"
CCA.Service-Information.Alternate-Charged-Party-Address = "NickTest"

Accessing in Dialplan: Variables use dot notation and hyphens as shown above:

<action application="log" data="INFO Carrier: ${CCA.Service-Information.Carrier-Select-Routing-Information}"/>

Viewing with uuid_dump: In FreeSWITCH console or ESL, variables appear with the variable_ prefix:

variable_CCA.Service-Information.Carrier-Select-Routing-Information: 1408
variable_CCA.Service-Information.Alternate-Charged-Party-Address: NickTest

Note: FreeSWITCH preserves dots and hyphens in variable names. The variables work in all dialplan contexts and applications.

Granted-Service-Unit AVP

Time quotas are extracted and made available:

OCS Response:

Granted-Service-Unit
  └── CC-Time: 600

Variable:

allocated_time = 600

AVP Processing Logic

Processing Rules:

Grouped AVPs add a level to the variable name hierarchy but have no value themselves
Simple AVPs are mapped to variables with their full dotted path
Vendor-Specific AVPs are processed identically to standard AVPs
Unknown AVPs are safely skipped without errors

Example: Multi-Level Nesting

OCS CCA Structure:

Service-Information (Grouped)
  ├── IMS-Information (Grouped)
  │     ├── Node-Functionality: 6
  │     ├── Role-Of-Node: 1
  │     ├── Calling-Party-Address: "tel:+313380000000670"
  │     └── Time-Stamps (Grouped)
  │           ├── SIP-Request-Timestamp: "2026-01-24T22:40:18Z"
  │           └── SIP-Response-Timestamp: "2026-01-24T22:40:18Z"
  └── IN-Information (Grouped)
        └── Real-Called-Number: "24724741234"

FreeSWITCH Variables Created:

CCA.Service-Information.IMS-Information.Node-Functionality = "6"
CCA.Service-Information.IMS-Information.Role-Of-Node = "1"
CCA.Service-Information.IMS-Information.Calling-Party-Address = "tel:+313380000000670"
CCA.Service-Information.IMS-Information.Time-Stamps.SIP-Request-Timestamp = "2026-01-24T22:40:18Z"
CCA.Service-Information.IMS-Information.Time-Stamps.SIP-Response-Timestamp = "2026-01-24T22:40:18Z"
CCA.Service-Information.IN-Information.Real-Called-Number = "24724741234"

Configuration

Online Charging Parameters

Parameter	Type	Required	Default	Description
`enabled`	Boolean	No	`false`	Master switch for online charging. When `false`, all calls bypass OCS authorization (no CCRs are sent). See What Controls Whether a Call Is Charged.
`requested_units_seconds`	Integer	No	`0`	Talk time (seconds) requested per reservation in the `Requested-Service-Unit` of CCR-Initial/Update. *`0` (default) sends an empty* RSU (the AVP is present but carries no `CC-Time`), letting the OCS choose the grant — this matches the Nokia TAS against the Viti CGRateS, which ignores requested units and computes its own grant. Set a positive** value to reserve a specific `CC-Time` per RFC 4006 for a standards OCS that rates on the request.
`report_and_reserve`	Boolean	No	`false`	3GPP SCUR usage reporting, matching the Nokia TAS. When `true`, every CCR-Update and CCR-Terminate carries a `Used-Service-Unit` reporting the `CC-Time` consumed since the last report (incremental), plus a `3GPP-Reporting-Reason`: `RATING_CONDITION_CHANGE (6)` on the answer update, `QUOTA_EXHAUSTED (3)` on periodic updates, `FINAL (2)` on terminate. The OCS debits each increment and settles the unused tail of the last grant on terminate. When `false`, only CCR-T reports usage (cumulative from answer, no reason). The sum of incremental `CC-Time` over a call equals the answered duration.
`service_identifier`	Integer	No	`1`	Stable, provisioned `Service-Identifier` (AVP 439) sent in every CCR. The OCS keys rating on `{Service-Context-Id + Service-Identifier}`, so this must be a fixed value, not random.
`periodic_ccr_time_seconds`	Integer	No	`10`	Fallback interval in seconds between CCR-Update messages when the OCS does not return a usable grant. In normal operation the next CCR-U is timed dynamically from the granted credit (`allocated_time - ccr_update_buffer_seconds`).
`ccr_update_buffer_seconds`	Integer	No	`2`	Safety buffer in seconds before granted credit expires. OmniTAS sends the next CCR-U at `(allocated_time - buffer)` so credit is extended before it runs out. Recommended: 2-5 seconds.
`schedule_hangup_auth`	Boolean	No	`false`	Enable automatic call hangup/transfer when granted credit expires. When `true`, OmniTAS schedules a FreeSWITCH timer based on `allocated_time` from each CCA and reschedules it on every CCR-U response. Works with `credit_exhaustion_announcement`.
`credit_exhaustion_announcement`	String	No	`nil`	Audio file path for the credit-exhaustion announcement. When configured with `schedule_hangup_auth`, uses a scheduled transfer to play the announcement before hangup. When configured alone, plays the announcement on immediate credit exhaustion only. Path must use the FreeSWITCH variable form: `"${base_dir}/sounds/..."`. Set to `nil` for direct hangup without announcement.
`skipped_regex`	List[String]	No	`[]`	List of regex patterns matched against the destination number. Matching destinations bypass OCS entirely (no session, no CCRs). Useful for emergency numbers and service codes (e.g., `"^911$"`, `"^000$"`).

Diameter Connection Parameters

Parameter	Type	Required	Default	Description
`origin_host`	String	Yes	-	OmniTAS Diameter Identity (FQDN). Must be unique across your Diameter network. Example: `"tas01.epc.mnc123.mcc456.3gppnetwork.org"`.
`origin_realm`	String	Yes	-	OmniTAS Diameter Realm. Used for routing decisions. Example: `"epc.mnc123.mcc456.3gppnetwork.org"`.
`destination_realm`	String	Yes	-	OCS Diameter Realm. Requests are routed to peers in this realm.
`destination_host`	String	No	`nil`	Specific OCS Diameter Identity. When `nil`, routing based on `destination_realm` only. Use when direct routing to specific OCS instance required.

Configuration Example

config :tas, :online_charging,
  # Master switch
  enabled: true,

  # 0 = empty RSU, let the OCS decide the grant (matches Nokia TAS / CGRateS).
  # Set a positive value only for a standards OCS that rates on the requested units.
  requested_units_seconds: 0,

  # Stable provisioned service identifier
  service_identifier: 1,

  # Fallback re-auth interval (normal timing is dynamic from the grant)
  periodic_ccr_time_seconds: 10,

  # Re-authorize 2s before granted credit expires
  ccr_update_buffer_seconds: 2,

  # Schedule hangup based on granted credit
  schedule_hangup_auth: true,

  # Play announcement before credit exhaustion hangup
  credit_exhaustion_announcement: "ivr/ivr-account_balance_low.wav",

  # Skip OCS for emergency calls and voicemail
  skipped_regex: [
    "^911$",      # Emergency (US)
    "^000$",      # Emergency (AU)
    "^\*86$"     # Voicemail access
  ]

config :tas, :diameter,
  # Service identity
  origin_host: "tas01.epc.mnc001.mcc001.3gppnetwork.org",
  origin_realm: "epc.mnc001.mcc001.3gppnetwork.org",

  # OCS routing
  destination_realm: "epc.mnc001.mcc001.3gppnetwork.org",
  destination_host: nil  # Realm-based routing

How it works:

When a call is received:

Destination number is checked against skipped_regex patterns
If matched, call bypasses OCS (useful for emergency services)
If not matched, CCR-Initial sent to OCS at destination_realm
CCA response is parsed for granted units and AVPs
AVPs are mapped to FreeSWITCH variables (see AVP Mapping)
Call proceeds with allocated_time and AVP data available
CCR-Update sent every periodic_ccr_time_seconds during call
If schedule_hangup_auth enabled, automatic hangup when credit expires
CCR-Terminate sent on call completion

Use cases:

Basic OCS: Enable with defaults for standard credit control
High-value calls: Reduce periodic_ccr_time_seconds to 30s for frequent re-auth
Prepaid service: Enable schedule_hangup_auth and set credit_exhaustion_announcement
Emergency compliance: Add emergency numbers to skipped_regex to ensure always connected

FreeSWITCH Integration

Accessing AVP Variables in Dialplan

AVP data extracted from CCA messages is available as channel variables in FreeSWITCH dialplan:

<extension name="Route_with_OCS_Data">
  <condition field="destination_number" expression="^(.+)$">

    <!-- Access carrier routing info from OCS -->
    <action application="log"
            data="INFO Carrier Code: ${CCA.Service-Information.Carrier-Select-Routing-Information}"/>

    <!-- Access charged party from OCS -->
    <action application="log"
            data="INFO Charged Party: ${CCA.Service-Information.Alternate-Charged-Party-Address}"/>

    <!-- Access granted time -->
    <action application="log"
            data="INFO Allocated Time: ${allocated_time} seconds"/>

    <!-- Route based on carrier code -->
    <action application="set"
            data="carrier_code=${CCA.Service-Information.Carrier-Select-Routing-Information}"/>
    <action application="bridge"
            data="sofia/external/$1@carrier-${carrier_code}.sip.example.com"/>

  </condition>
</extension>

Variable Availability

Timing:

Variables are set before FreeSWITCH call setup
Available throughout entire call duration
Persist across call transfers and updates

Scope:

Channel-scoped (specific to individual call leg)
Not inherited by bridged/transferred legs
Safe to use in all dialplan applications

Example Use Cases

1. Carrier Selection Based on OCS Data

Use OCS-provided carrier code to route calls:

<extension name="Carrier_Selection">
  <condition field="${CCA.Service-Information.Carrier-Select-Routing-Information}" expression="^(.+)$">
    <action application="bridge"
            data="sofia/external/${destination_number}@carrier-$1.example.com"/>
  </condition>

  <!-- Fallback if no carrier specified -->
  <condition field="${CCA.Service-Information.Carrier-Select-Routing-Information}" expression="^$">
    <action application="bridge"
            data="sofia/external/${destination_number}@default-carrier.example.com"/>
  </condition>
</extension>

How it works: OCS returns carrier code "1408" in Service-Information AVP. FreeSWITCH routes call to carrier-1408.example.com gateway based on this data.

2. Alternate Billing Party

Route billing to a different party based on OCS response:

<extension name="Alternate_Billing">
  <condition field="${CCA.Service-Information.Alternate-Charged-Party-Address}" expression="^(.+)$">

    <!-- Log billing party for CDRs -->
    <action application="set"
            data="billed_party=$1"/>
    <action application="export"
            data="billed_party=$1"/>

    <!-- Include in SIP headers -->
    <action application="set"
            data="sip_h_X-Billed-Party=$1"/>

    <action application="bridge"
            data="sofia/external/${destination_number}@trunk.example.com"/>
  </condition>
</extension>

How it works: OCS specifies alternate charged party (e.g., corporate account). OmniTAS extracts "NickTest" from AVP and makes it available to dialplan for CDR recording and SIP header insertion.

3. Time-Limited Calls with Warnings

Provide warnings before credit expires:

<extension name="Credit_Warnings">
  <condition field="destination_number" expression="^(.+)$">

    <!-- Schedule warning 30 seconds before hangup -->
    <action application="set"
            data="warning_time=${expr(${allocated_time} - 30)}"/>

    <action application="sched_hangup"
            data="+${allocated_time} ALLOTTED_TIMEOUT"/>

    <action application="sched_broadcast"
            data="+${warning_time} playback::ivr/ivr-account_balance_low.wav"/>

    <action application="bridge"
            data="sofia/external/$1@trunk.example.com"/>
  </condition>
</extension>

How it works: Uses allocated_time from OCS to schedule automatic hangup and plays warning announcement 30 seconds before disconnection.

Answer & Hangup Notifications

After the CCR-Initial authorizes a call, OmniTAS still needs to know when the call is answered (to begin metering and send the CCR-Update) and when it ends (to send the CCR-Terminate). These events are sourced from FreeSWITCH over the Event Socket Layer (ESL).

How it works:

OmniTAS holds a persistent inbound ESL connection to the local FreeSWITCH and subscribes to CHANNEL_ANSWER and CHANNEL_HANGUP_COMPLETE.
On CHANNEL_ANSWER, it reads the SIP Call-ID and the real answer timestamp and sends the CCR-Update that starts metering.
On CHANNEL_HANGUP_COMPLETE, it reads the SIP Call-ID and the FreeSWITCH hangup cause and sends the CCR-Terminate with the final used time.
Events are matched to a credit-control session by SIP Call-ID. Events for call legs without a session (MT legs, bridged B-legs, exempt calls) are ignored — this is what keeps non-charged calls from producing CCRs.
Duplicate answer is idempotent. Both legs of a bridged call fire CHANNEL_ANSWER and can resolve to the same Call-ID; only the first sends a CCR-Update and starts the periodic sender, the rest are ignored (otherwise you get duplicate CCR-Us and double periodic senders).
A transfer ends the charged session. A BLIND_TRANSFER/ATTENDED_TRANSFER hangup is treated as a normal hangup → CCR-Terminate (the charged caller has left the call, or the call was transferred to the out-of-credit announcement). Once a session has terminated, any later hangup for the same Call-ID finds no session and sends nothing.

The CallEventListener always runs (a real deployment always has the co-located FreeSWITCH; it is skipped only under test_mode). It is not gated by a separate switch — whether a CCR is sent is decided per event by online_charging.enabled. With charging off the listener still receives and logs CHANNEL_ANSWER/CHANNEL_HANGUP_COMPLETE at debug but sends no CCR. (Earlier releases had a separate esl_notifications toggle; it was removed because it had to agree with online_charging.enabled and silently broke charging — only CCR-Initial, no CCR-U/CCR-T — when charging was on but the toggle was absent.)

Deprecated: `/call_event` HTTP endpoint

Earlier releases detected answer/hangup via FreeSWITCH dialplan curl hooks that POSTed to a /call_event HTTP endpoint on OmniTAS. This mechanism is deprecated. The dialplan hooks have been removed and ESL is now the notification source.

The /call_event endpoint still exists and returns 200 OK so that any lingering dialplan references do not error, but it performs no charging action. Operators upgrading from an older release should ensure their dialplans no longer rely on it.

Diameter Messages

CCR-Initial (Request Type 1)

Sent before call setup to request authorization and initial credit allocation.

Key AVPs Sent:

AVP	Code	Type	Description
Session-Id	263	UTF8String	Session identifier, constant for the whole credit-control session (CCR-I/U/T share it). Derived deterministically from the SIP Call-ID.
Auth-Application-Id	258	Unsigned32	Value `4` for Diameter Credit Control Application per RFC 4006
Service-Context-Id	461	UTF8String	`"000.000.12.32260@3gpp.org"` for IMS charging per TS 32.299
CC-Request-Type	416	Enumerated	Value `1` (INITIAL_REQUEST)
CC-Request-Number	415	Unsigned32	Sequence number — `0` for INITIAL_REQUEST, then `1`, `2`, … for subsequent requests in the session per RFC 4006 §8.2
Service-Identifier	439	Unsigned32	Stable provisioned service identifier (`service_identifier` config)
Subscription-Id	443	Grouped	Subscriber MSISDN or IMSI
Requested-Service-Unit	437	Grouped	Reservation request — `CC-Time` = `requested_units_seconds`
Service-Information	873	Grouped	IMS-specific call details (calling/called party, Role-Of-Node, timestamps)

Example CCR-I:

Session-Id: "tas01.example.org;1463927445;1744753804"
Auth-Application-Id: 4
CC-Request-Type: 1 (INITIAL_REQUEST)
CC-Request-Number: 0
Subscription-Id:
  - Subscription-ID-Type: 0 (END_USER_E164)
    Subscription-ID-Data: "313380000000670"
Multiple-Services-Credit-Control:
  - Service-Identifier: 1
    Requested-Service-Unit:
      - CC-Time: 300 (requested reservation)
Service-Information:
  - IMS-Information:
      - Role-Of-Node: 0 (ORIGINATING_ROLE)
      - Node-Functionality: 6 (AS)
      - Calling-Party-Address: "tel:+313380000000670"
      - Called-Party-Address: "tel:+24724741234"

The Requested-Service-Unit carries a real reservation (not zero). The OCS decides the actual grant and returns it in the CCA's Granted-Service-Unit.

CCA (Credit-Control-Answer)

Response from OCS with authorization decision and granted credit.

Key AVPs Received:

AVP	Code	Type	Description
Result-Code	268	Unsigned32	`2001` for success. See Result Codes for error values.
Granted-Service-Unit	431	Grouped	Allocated credit (time in seconds)
Service-Information	873	Grouped	Additional charging data (carrier info, charged party, etc.)

Example CCA with AVPs:

Session-Id: "tas01.example.org;1769294418268;8a078232"
Result-Code: 2001 (DIAMETER_SUCCESS)
CC-Request-Type: 1
CC-Request-Number: 1
Granted-Service-Unit:
  - CC-Time: 600 (10 minutes granted)
Service-Information:
  - IMS-Information:
      - Carrier-Select-Routing-Information: "1408"
  - Alternate-Charged-Party-Address: "NickTest"

Resulting Variables:

allocated_time = 600
CCA.Service-Information.Carrier-Select-Routing-Information = "1408"
CCA.Service-Information.Alternate-Charged-Party-Address = "NickTest"

CCR-Update (Request Type 2)

Sent during active calls for periodic re-authorization or interim usage reporting.

When Sent:

On call answer (CHANNEL_ANSWER from ESL) — CC-Request-Number = 1, with the real answer time in the SIP-Response-Timestamp
Periodically during the active call, timed dynamically as allocated_time - ccr_update_buffer_seconds from each grant (falling back to periodic_ccr_time_seconds)

Key Differences from CCR-I:

CC-Request-Type: 2 (UPDATE_REQUEST)
CC-Request-Number: 1 on answer, then increments on each periodic re-auth
Requested-Service-Unit: the next reservation (requested_units_seconds)
Same constant Session-Id as the CCR-Initial

Consumed time is reported in the CCR-Terminate (Used-Service-Unit), not in interim CCR-Updates. Interim updates extend the reservation; final usage is settled at termination.

CCR-Terminate (Request Type 3)

Sent on call hangup (CHANNEL_HANGUP_COMPLETE from ESL) with final usage reporting.

Key AVPs:

CC-Request-Type: 3 (TERMINATION_REQUEST)
CC-Request-Number: next in sequence (e.g. 2)
Used-Service-Unit: total consumed talk time (CC-Time, seconds since answer)
Termination-Cause: 1 (DIAMETER_LOGOUT) per RFC 6733 §8.15
Cause-Code (AVP 861, IMS-Information): 0 for a normally answered-and-released call, 2 for an unsuccessful session setup, per TS 32.299

Result Codes

Code	Name	Description	OmniTAS Action
2001	DIAMETER_SUCCESS	Request approved	Parse AVPs, setup call
4010	DIAMETER_END_USER_SERVICE_DENIED	Service denied for subscriber	Reject call with `CALL_REJECTED`
4012	DIAMETER_CREDIT_LIMIT_REACHED	Insufficient credit	Reject call with `OUTGOING_CALL_BARRED`
5003	DIAMETER_AUTHORIZATION_REJECTED	OCS policy denied	Reject call with `CALL_REJECTED`
5xxx	Permanent failures	OCS configuration or system error	Reject call, log error

Reference: RFC 6733 §7.1 and 3GPP TS 32.299

Metrics

See doc/metrics.md for the full metric catalogue. The metrics below are the ones relevant to online charging.

Diameter Request / Response Metrics

CCRs are split by request type via the command label so CCR-Initial (setup), CCR-Update (interim re-auth) and CCR-Terminate (teardown) can be tracked independently — a spike in failed interim updates is then visible on its own.

Metric: diameter_requests_total (Counter) — Diameter requests sent Metric: diameter_responses_total (Counter) — Diameter responses received Metric: diameter_response_duration_milliseconds (Histogram) — request round-trip time

Labels:

application - ro (online charging) or sh (subscriber data)
command - ccr_i, ccr_u, ccr_t (Ro) or udr (Sh)
result_code - (responses only) Diameter Result-Code: 2001, 4012, etc.; 0 = timeout / unparseable reply
result - (duration only) success, nocredit, error

Example queries:

# CCR rate by request type
sum by (command) (rate(diameter_requests_total{application="ro"}[5m]))

# CCR error rate, per request type (anything that is not 2001)
sum by (command) (rate(diameter_responses_total{application="ro", result_code!="2001"}[5m]))

# Credit limit rejections (4012)
rate(diameter_responses_total{application="ro", result_code="4012"}[5m])

# 95th percentile CCR latency by request type
histogram_quantile(0.95,
  sum by (le, command) (rate(diameter_response_duration_milliseconds_bucket{application="ro"}[5m]))
)

Credit-Control Quota Metrics

Metric: ro_charging_quota_seconds Type: Histogram Description: Quota (in seconds) observed on each CCR, for verifying charging correctness Labels:

request_type - ccr_i, ccr_u, ccr_t
kind - requested (CC-Time in Requested-Service-Unit), granted (Granted-Service-Unit, 0 = no credit), used (Used-Service-Unit on terminate)

Example queries:

# Median granted quota at call setup
histogram_quantile(0.5, rate(ro_charging_quota_seconds_bucket{request_type="ccr_i", kind="granted"}[5m]))

# No-credit grants (zero-second allocations) per second
rate(ro_charging_quota_seconds_bucket{kind="granted", le="0"}[5m])

# Total used seconds reported on termination per second (sanity-check against billed minutes)
rate(ro_charging_quota_seconds_sum{kind="used"}[5m])

OCS Authorization & Event Metrics

Metric: ocs_authorization_attempts_total (Counter) Labels: result (success, nocredit, timeout, error), skipped (true if bypassed via regex, else false)

Metric: online_charging_events_total (Counter) — lifecycle events Labels: event_type (authorize, answer, reauth, hangup, credit_exhaustion_hangup, hangup_rescheduled), result (success, nocredit, timeout, error, triggered)

Example queries:

# Authorization success rate (excluding skipped)
sum(rate(ocs_authorization_attempts_total{result="success", skipped="false"}[5m]))
  / sum(rate(ocs_authorization_attempts_total{skipped="false"}[5m]))

# Calls released mid-call due to credit exhaustion
rate(online_charging_events_total{event_type="credit_exhaustion_hangup"}[5m])

Troubleshooting

AVP Variables Not Available in FreeSWITCH

Symptoms:

FreeSWITCH dialplan cannot access ${CCA.Service-Information.*} variables
Variables show as empty or undefined

Possible causes:

OCS not returning Service-Information AVPs in CCA
AVP parsing failed due to unexpected structure
Variables not exported to FreeSWITCH channel

Resolution:

Verify OCS Response Contains AVPs

Check OmniTAS logs for CCA message:

[debug] Credit Control Answer: {:diameter_packet, ...}
[debug] Parsed AVP variables: %{
  "CCA.Service-Information.Carrier-Select-Routing-Information" => "1408",
  "CCA.Service-Information.Alternate-Charged-Party-Address" => "NickTest"
}

If "Parsed AVP variables" is empty %{}, OCS is not returning the expected AVPs.

Check for AVP Parsing Errors

Look for warnings in logs:
```
[warning] got back another type of reply: {...}
```
This indicates AVP structure doesn't match expected format. Check Diameter packet structure.

Verify FreeSWITCH Variable Export

In FreeSWITCH console or ESL:

freeswitch> uuid_dump <call-uuid>

Look for variables with the variable_ prefix and CCA. in the name:

variable_CCA.Service-Information.Carrier-Select-Routing-Information: 1408
variable_CCA.Service-Information.Alternate-Charged-Party-Address: NickTest
variable_CCA.Auth-Application-Id: 4
variable_CCA.Result-Code: 2001

Note: FreeSWITCH preserves dots and hyphens in variable names. They work correctly in dialplan:

<action application="log" data="Carrier: ${CCA.Service-Information.Carrier-Select-Routing-Information}"/>

Call Rejected with "unhandled" Error

Symptoms:

Logs show: [warning] Could not authorize call: :unhandled
Valid CCA responses (Result-Code 2001) are rejected
Calls fail despite OCS approving them

Possible causes:

CCA message structure doesn't match expected pattern
Vendor-specific AVPs in unexpected positions
AVP position index mismatch

Resolution:

This was a known issue fixed in recent releases. Ensure you're running current version.

Previous behavior: Pattern matching required:

Granted-Service-Unit AVP at position 7 exactly
Empty vendor-specific AVP list []

Current behavior: Pattern matching accepts:

Granted-Service-Unit AVP at any position
Non-empty vendor-specific AVP lists

If issue persists:

Capture CCA packet structure from logs
Check if AVPs are in expected Diameter format
Verify Result-Code is 2001

OCS Timeout on All Requests

Symptoms:

All CCR requests timeout
Logs show: [debug] Got back response for authorize: {:error, :timeout}
No CCA received within 5 seconds

Possible causes:

Network connectivity to OCS/DRA
Firewall blocking Diameter port (3868)
Incorrect destination_realm or destination_host
OCS not responding to requests

Resolution:

Verify Network Connectivity

Test TCP connection to OCS:
```
telnet ocs.example.com 3868
```
Should connect successfully. If connection refused or timeout, check firewall rules.

Check Diameter Configuration

Verify destination_realm matches OCS configuration:

config :tas, :diameter,
  destination_realm: "epc.mnc001.mcc001.3gppnetwork.org"  # Must match OCS realm

Review OCS Logs

Check OCS for incoming CCR messages. If OCS receives requests but doesn't respond:
- Verify OmniTAS origin_host is recognized by OCS
- Check OCS peer configuration allows connections from OmniTAS
- Verify Service-Context-Id and Application-Id match OCS expectations

Credit Exhaustion Not Hanging Up Calls

Symptoms:

Calls continue beyond granted credit time
No automatic hangup when allocated_time expires
schedule_hangup_auth enabled but not working

Possible causes:

FreeSWITCH scheduled hangup not configured
schedule_hangup_auth is false
Call state not tracked properly

Resolution:

Verify Configuration

Ensure schedule_hangup_auth is enabled:

config :tas, :online_charging,
  schedule_hangup_auth: true

Check FreeSWITCH ESL Connection

Verify OmniTAS can send commands to FreeSWITCH:
```
[debug] Schedule Hangup Response: {:ok, "+OK"}
```
If error or no response, check FreeSWITCH Event Socket configuration.
Monitor Call State

Check that call UUID is tracked in call state:
```
[debug] Setting Scheduled Hangup for call in 600 seconds
```
If UUID not found, call state tracking may have issues.

Skipped Regex Not Bypassing OCS

Symptoms:

Emergency calls (911, 000) still go through OCS authorization
Numbers matching skipped_regex patterns are not bypassed
Delays on emergency calls

Possible causes:

Regex pattern syntax error
Destination number format mismatch
Regex not properly escaped

Resolution:

Verify Regex Patterns

Test regex compilation:
```
Regex.compile("^911$")  # Should return {:ok, ~r/^911$/}
```
Common mistakes:
- Missing anchors: Use ^911$ not 911
- Escaping: Use \* for literal asterisk, not \*
Check Number Format

Verify destination number format matches pattern:
```
[debug] Checking if dialled number "911" matches skipped regex...
```
If number is formatted as "+1911" but pattern is "^911$", it won't match.

Example Patterns

config :tas, :online_charging,
  skipped_regex: [
    "^911$",           # US Emergency
    "^000$",           # AU Emergency
    "^112$",           # International Emergency
    "^\*86$",         # Voicemail (escaped asterisk)
    "^1?800\d{7}$"    # Toll-free numbers
  ]

Reference

3GPP Specifications

Specification	Title	Relevant Sections
TS 32.299	Diameter charging applications	§6.3 (Ro interface), §7.2 (AVP definitions)
TS 32.240	Charging architecture and principles	§5 (Online charging)
TS 29.229	Cx and Dx interfaces	Service-Information AVP usage in IMS

IETF RFCs

RFC	Title	Relevant Sections
RFC 6733	Diameter Base Protocol	§3 (Protocol overview), §7 (Error handling)
RFC 4006	Diameter Credit-Control Application	§8 (Credit-Control messages)

AVP Codes Reference

Vendor-ID 0 = IETF base (RFC 6733 / RFC 4006); Vendor-ID 10415 = 3GPP (TS 32.299).

Complete CCR structure (voice call)

Every AVP OmniTAS includes in a call Credit-Control-Request, with grouping shown:

Credit-Control-Request (Command 272, App 4)
├─ Session-Id (263)
├─ Origin-Host (264)
├─ Origin-Realm (296)
├─ Destination-Realm (283)
├─ Destination-Host (293)                       [only if configured]
├─ Auth-Application-Id (258)            = 4
├─ Service-Context-Id (461)             = 000.000.12.32260@3gpp.org
├─ CC-Request-Type (416)
├─ CC-Request-Number (415)
├─ Event-Timestamp (55)
├─ User-Name (1)                                [only if username set]
├─ Termination-Cause (295)                      [CCR-T only]
├─ Subscription-Id (443)
│   ├─ Subscription-Id-Type (450)       = 0 (END_USER_E164)
│   └─ Subscription-Id-Data (444)       = subscriber MSISDN
├─ Multiple-Services-Credit-Control (456)
│   ├─ Service-Identifier (439)
│   ├─ Requested-Service-Unit (437)             [CCR-I, CCR-U]
│   │   └─ CC-Time (420)
│   └─ Used-Service-Unit (446)                  [CCR-T]
│       └─ CC-Time (420)
└─ Service-Information (873, v10415)
    ├─ IN-Information                            [operator extension]
    │   └─ Real-Called-Number
    └─ IMS-Information (876, v10415)
        ├─ Role-Of-Node (829)           = 0 (ORIGINATING_ROLE)
        ├─ Node-Functionality (862)     = 6 (AS)
        ├─ User-Session-Id (830)        = SIP Call-ID
        ├─ Calling-Party-Address (831)
        ├─ Called-Party-Address (832)
        ├─ Requested-Party-Address (1251)
        ├─ Time-Stamps (833)
        │   ├─ SIP-Request-Timestamp (834)
        │   ├─ SIP-Request-Timestamp-Fraction (2301)
        │   ├─ SIP-Response-Timestamp (835)               [once answered]
        │   └─ SIP-Response-Timestamp-Fraction (2302)     [once answered]
        └─ Cause-Code (861)                       [CCR-T]

AVPs sent by OmniTAS (CCR)

The In column shows which request types carry the AVP: I = CCR-Initial, U = CCR-Update, T = CCR-Terminate.

AVP	Code	Vendor	Type	In	Value / Source
Session-Id	263	0	UTF8String	I U T	Constant per call (derived from SIP Call-ID); identical across I/U/T
Origin-Host	264	0	DiameterIdentity	I U T	OmniTAS Diameter identity (`origin_host`.`origin_realm`)
Origin-Realm	296	0	DiameterIdentity	I U T	`origin_realm`
Destination-Realm	283	0	DiameterIdentity	I U T	OCS realm
Destination-Host	293	0	DiameterIdentity	I U T	Only present if a specific OCS host is configured
Auth-Application-Id	258	0	Unsigned32	I U T	`4` (Diameter Credit Control Application)
Service-Context-Id	461	0	UTF8String	I U T	`000.000.12.32260@3gpp.org`
CC-Request-Type	416	0	Enumerated	I U T	`1`=Initial, `2`=Update, `3`=Terminate
CC-Request-Number	415	0	Unsigned32	I U T	`0` for Initial, then `1`, `2`, …
Event-Timestamp	55	0	Time	I U T	Time the request was generated
User-Name	1	0	UTF8String	I U T	Optional; only if a username/IMSI is supplied
Termination-Cause	295	0	Enumerated	T	`1` (DIAMETER_LOGOUT)
Subscription-Id	443	0	Grouped	I U T	Subscriber identity (see children)
→ Subscription-Id-Type	450	0	Enumerated	I U T	`0` (END_USER_E164)
→ Subscription-Id-Data	444	0	UTF8String	I U T	Subscriber MSISDN
Multiple-Services-Credit-Control	456	0	Grouped	I U T	Credit-control container (see children)
→ Service-Identifier	439	0	Unsigned32	I U T	`service_identifier` (stable, provisioned)
→ Requested-Service-Unit	437	0	Grouped	I U	Reservation request
→ → CC-Time	420	0	Unsigned32	I U	`requested_units_seconds`
→ Used-Service-Unit	446	0	Grouped	T	Final consumption
→ → CC-Time	420	0	Unsigned32	T	Consumed seconds since answer
Service-Information	873	10415	Grouped	I U T	3GPP service container
→ IN-Information	—	10415	Grouped	I U T	Operator extension carrying the real dialled number
→ → Real-Called-Number	—	10415	UTF8String	I U T	Dialled (called) number
→ IMS-Information	876	10415	Grouped	I U T	IMS charging details
→ → Role-Of-Node	829	10415	Enumerated	I U T	`0` (ORIGINATING_ROLE) — MO is the charged leg
→ → Node-Functionality	862	10415	Enumerated	I U T	`6` (AS)
→ → User-Session-Id	830	10415	UTF8String	I U T	SIP Call-ID (OCS correlation key)
→ → Calling-Party-Address	831	10415	UTF8String	I U T	`tel:+<calling MSISDN>`
→ → Called-Party-Address	832	10415	UTF8String	I U T	`tel:+<called number>`
→ → Requested-Party-Address	1251	10415	UTF8String	I U T	`tel:+<called number>`
→ → Time-Stamps	833	10415	Grouped	I U T	SIP request/response times
→ → → SIP-Request-Timestamp	834	10415	Time	I U T	INVITE time (whole seconds)
→ → → SIP-Request-Timestamp-Fraction	2301	10415	Unsigned32	I U T	INVITE time (milliseconds)
→ → → SIP-Response-Timestamp	835	10415	Time	U T	Answer (200 OK) time — only once answered
→ → → SIP-Response-Timestamp-Fraction	2302	10415	Unsigned32	U T	Answer time (milliseconds) — only once answered
→ → Cause-Code	861	10415	Integer32	T	`0` normal release / `2` unsuccessful setup

Codes shown as — are operator/vendor extensions carried under Service-Information; they have no 3GPP-assigned code and are defined in the OmniTAS Diameter dictionary.

AVPs received from the OCS (CCA)

AVP	Code	Vendor	Type	Description
Result-Code	268	0	Unsigned32	`2001` = success; see Result Codes
Granted-Service-Unit	431	0	Grouped	Allocated credit
→ CC-Time	420	0	Unsigned32	Granted seconds (`allocated_time`). `0` ⇒ no credit ⇒ bar/hangup
Service-Information	873	10415	Grouped	Optional charging data returned by the OCS
→ Carrier-Select-Routing-Information	2023	10415	UTF8String	Carrier routing code (mapped to a FreeSWITCH variable)
→ Alternate-Charged-Party-Address	1280	10415	UTF8String	Billing party identifier (mapped to a FreeSWITCH variable)

All Service-Information sub-AVPs returned in the CCA are flattened into FreeSWITCH channel variables — see AVP Parsing and Variable Mapping and FreeSWITCH Channel Variables.

FreeSWITCH Channel Variables

All extracted AVP data is available as FreeSWITCH channel variables:

Variable Name	Source	Example Value	Description
`${allocated_time}`	Granted-Service-Unit / CC-Time	`600`	Allocated time in seconds
`${CCA.Session-Id}`	Session-Id AVP	`omni-as01.epc...;1769299669873;325e2f2e`	Diameter session identifier
`${CCA.Result-Code}`	Result-Code AVP	`2001`	CCA result (2001 = success)
`${CCA.Auth-Application-Id}`	Auth-Application-Id AVP	`4`	Diameter application (4 = CC)
`${CCA.CC-Request-Type}`	CC-Request-Type AVP	`1`	Request type (1=Initial)
`${CCA.CC-Request-Number}`	CC-Request-Number AVP	`1`	Sequence number
`${CCA.CC-Time}`	CC-Time AVP (if present)	`600`	Granted time quota
`${CCA.Origin-Host}`	Origin-Host AVP	`ocs01.epc.mnc001.mcc001.3gppnetwork.org`	OCS host identifier
`${CCA.Origin-Realm}`	Origin-Realm AVP	`epc.mnc001.mcc001.3gppnetwork.org`	OCS realm
`${CCA.Service-Information.Carrier-Select-Routing-Information}`	Service-Information → Carrier-Select-Routing-Information	`1408`	Carrier routing code from OCS
`${CCA.Service-Information.Alternate-Charged-Party-Address}`	Service-Information → Alternate-Charged-Party-Address	`NickTest`	Alternate billing party

Variable Format:

All CCA AVPs use the prefix CCA.
Nested AVPs use dot notation: CCA.Parent.Child
Dots and hyphens are preserved in variable names
In uuid_dump, variables appear with variable_ prefix

Example uuid_dump output:

variable_allocated_time: 600
variable_CCA.Service-Information.Carrier-Select-Routing-Information: 1408
variable_CCA.Service-Information.Alternate-Charged-Party-Address: NickTest
variable_CCA.Result-Code: 2001

Table of Contents​

Architecture Overview​

Key Components​

What Controls Whether a Call Is Charged​

Credit Control Flow​

Call Authorization Sequence​

Credit Exhaustion and Call Barring​

Scheduled Hangup with Dynamic Rescheduling​

Integration: schedule_hangup_auth + credit_exhaustion_announcement​

Immediate Credit Exhaustion During CCR-Update​

Summary: Credit Exhaustion Mechanisms​

AVP Parsing and Variable Mapping​

Overview​

Common AVP Mappings​

Service-Information AVP (3GPP)​

Granted-Service-Unit AVP​

AVP Processing Logic​

Example: Multi-Level Nesting​

Configuration​

Online Charging Parameters​

Diameter Connection Parameters​

Configuration Example​

FreeSWITCH Integration​

Accessing AVP Variables in Dialplan​

Variable Availability​

Example Use Cases​

1. Carrier Selection Based on OCS Data​

2. Alternate Billing Party​

3. Time-Limited Calls with Warnings​

Answer & Hangup Notifications​

Deprecated: /call_event HTTP endpoint​

Diameter Messages​

CCR-Initial (Request Type 1)​

CCA (Credit-Control-Answer)​

CCR-Update (Request Type 2)​

CCR-Terminate (Request Type 3)​

Result Codes​

Metrics​

Diameter Request / Response Metrics​

Credit-Control Quota Metrics​

OCS Authorization & Event Metrics​

Troubleshooting​

AVP Variables Not Available in FreeSWITCH​

Call Rejected with "unhandled" Error​

OCS Timeout on All Requests​

Credit Exhaustion Not Hanging Up Calls​

Skipped Regex Not Bypassing OCS​

Reference​

3GPP Specifications​

IETF RFCs​

AVP Codes Reference​

Complete CCR structure (voice call)​

AVPs sent by OmniTAS (CCR)​

AVPs received from the OCS (CCA)​

FreeSWITCH Channel Variables​

Table of Contents

Architecture Overview

Key Components

What Controls Whether a Call Is Charged

Credit Control Flow

Call Authorization Sequence

Credit Exhaustion and Call Barring

Scheduled Hangup with Dynamic Rescheduling

Integration: schedule_hangup_auth + credit_exhaustion_announcement

Immediate Credit Exhaustion During CCR-Update

Summary: Credit Exhaustion Mechanisms

AVP Parsing and Variable Mapping

Overview

Common AVP Mappings

Service-Information AVP (3GPP)

Granted-Service-Unit AVP

AVP Processing Logic

Example: Multi-Level Nesting

Configuration

Online Charging Parameters

Diameter Connection Parameters

Configuration Example

FreeSWITCH Integration

Accessing AVP Variables in Dialplan

Variable Availability

Example Use Cases

1. Carrier Selection Based on OCS Data

2. Alternate Billing Party

3. Time-Limited Calls with Warnings

Answer & Hangup Notifications

Deprecated: `/call_event` HTTP endpoint

Diameter Messages

CCR-Initial (Request Type 1)

CCA (Credit-Control-Answer)

CCR-Update (Request Type 2)

CCR-Terminate (Request Type 3)

Result Codes

Metrics

Diameter Request / Response Metrics

Credit-Control Quota Metrics

OCS Authorization & Event Metrics

Troubleshooting

AVP Variables Not Available in FreeSWITCH

Call Rejected with "unhandled" Error

OCS Timeout on All Requests

Credit Exhaustion Not Hanging Up Calls

Skipped Regex Not Bypassing OCS

Reference

3GPP Specifications

IETF RFCs

AVP Codes Reference

Complete CCR structure (voice call)

AVPs sent by OmniTAS (CCR)

AVPs received from the OCS (CCA)

FreeSWITCH Channel Variables