Data Charging Data Record (CDR) Format

Offline Charging for PGW-C

OmniPGW by Omnitouch Network Services

Overview
CDR File Format
CDR Fields
CDR Events
File Structure
Configuration
CDR Generation Flow
Field Details
Examples
Integration

Overview

The Data CDR (Charging Data Record) format provides offline charging capabilities for the Packet Gateway Control Plane (PGW-C). CDRs are generated to record bearer session events, data usage, and subscriber information for billing and analytics purposes.

This common format is compatible with SGW-C CDRs, ensuring consistency in charging records across the EPC infrastructure.

Key Features

CSV-based format - Simple, human-readable comma-separated values
Event-based recording - Captures bearer start, update, and end events
Volume metering - Records uplink and downlink data usage
Automatic rotation - Configurable file rotation based on time intervals
3GPP compliant - Follows 3GPP TS 32.251 (PS domain charging) and TS 32.298 (CDR encoding)

Use Cases

Use Case	Description
Offline Charging	Generate CDRs for postpaid billing
Analytics	Analyze subscriber usage patterns
Audit Trail	Track all bearer session events
Capacity Planning	Monitor network resource utilization
Troubleshooting	Debug session and bearer issues

CDR File Format

File Naming Convention

<epoch_timestamp>

Example:

1726598022

The filename is the Unix epoch timestamp (in seconds) of when the file was created.

File Location

Default directory:

PGW-C: /var/log/pgw_c/cdrs/

Configurable via cdr_directory parameter in config/runtime.exs.

File Header

Each CDR file begins with a multi-line header containing metadata:

# Data CDR File:
# File Start Time: HH:MM:SS (unix_timestamp)
# File End Time: HH:MM:SS (unix_timestamp)
# Gateway Name: <gateway_name>
# epoch,imsi,event,charging_id,msisdn,ue_imei,timezone_raw,plmn,tac,eci,sgw_ip,ue_ip,pgw_ip,apn,qci,octets_in,octets_out

Header Fields:

File Start Time - When the CDR file was created (human-readable and Unix timestamp)
File End Time - When the file rotation will occur (human-readable and Unix timestamp)
Gateway Name - Identifier for the PGW-C instance (configured via pgw_name parameter)
Column Headers - CSV field names for the data records

CDR Fields

Field Summary

Position	Field Name	Type	Description
0	epoch	integer	Event timestamp (Unix epoch seconds)
1	imsi	string	International Mobile Subscriber Identity
2	event	string	CDR event type (e.g., "default_bearer_start")
3	charging_id	integer	Unique charging identifier for the bearer
4	msisdn	string	Mobile Station ISDN Number (phone number)
5	ue_imei	string	International Mobile Equipment Identity
6	timezone_raw	string	UE timezone (reserved, currently empty)
7	plmn	integer	Public Land Mobile Network identifier
8	tac	integer	Tracking Area Code
9	eci	integer	E-UTRAN Cell Identifier
10	sgw_ip	string	SGW-C S5/S8 control plane IP address
11	ue_ip	string	UE IP address (IPv4\|IPv6 format)
12	pgw_ip	string	PGW-C S5/S8 control plane IP address
13	apn	string	Access Point Name
14	qci	integer	QoS Class Identifier
15	octets_in	integer	Downlink data volume (bytes)
16	octets_out	integer	Uplink data volume (bytes)

CDR Events

Event Types

CDRs are generated for three types of events:

Event Type	Format	Description	When Generated
Bearer Start	`<type>_bearer_start`	Bearer establishment	Create Session Response sent
Bearer Update	`<type>_bearer_update`	Usage reporting during session	Periodic usage reports from user plane
Bearer End	`<type>_bearer_end`	Bearer termination	Delete Session Request/Response

Bearer Types:

default - Default bearer (one per PDN connection)
dedicated - Dedicated bearer (zero or more per PDN connection)

Event Examples

default_bearer_start      - Default bearer established
default_bearer_update     - Default bearer usage update
default_bearer_end        - Default bearer terminated
dedicated_bearer_start    - Dedicated bearer established
dedicated_bearer_update   - Dedicated bearer usage update
dedicated_bearer_end      - Dedicated bearer terminated

File Structure

Example CDR File

# Data CDR File:
# File Start Time: 18:53:42 (1726598022)
# File End Time: 19:53:42 (1726601622)
# Gateway Name: sgw-c-prod-01
# epoch,imsi,event,charging_id,msisdn,ue_imei,timezone_raw,plmn,tac,eci,sgw_ip,ue_ip,pgw_ip,apn,qci,octets_in,octets_out
1726598022,310260123456789,default_bearer_start,12345,15551234567,123456789012345,,349552,1234,5678,10.0.0.15,172.16.1.100|2001:db8::1,10.0.0.20,internet,9,0,0
1726598322,310260123456789,default_bearer_update,12345,15551234567,123456789012345,,349552,1234,5678,10.0.0.15,172.16.1.100|2001:db8::1,10.0.0.20,internet,9,1048576,524288
1726598622,310260123456789,default_bearer_update,12345,15551234567,123456789012345,,349552,1234,5678,10.0.0.15,172.16.1.100|2001:db8::1,10.0.0.20,internet,9,5242880,2097152
1726598922,310260123456789,default_bearer_end,12345,15551234567,123456789012345,,349552,1234,5678,10.0.0.15,172.16.1.100|2001:db8::1,10.0.0.20,internet,9,10485760,5242880

File Rotation

CDR files are automatically rotated based on the configured duration:

Rotation Process:

Close current CDR file
Create new file with current timestamp
Write header to new file
Continue recording CDRs to new file

Configuration

Configuration Parameters

PGW-C CDR generation is configured in config/runtime.exs:

Parameter	Type	Description	Default	Recommended
`pgw_name`	string	PGW instance identifier (appears in CDR headers)	"omni-pgw01"	Use hostname or instance ID
`cdr_file_duration`	integer	File rotation interval (ms)	3600000	3600000 (1 hour)
`cdr_directory`	string	CDR output directory path	"/tmp/pgw_c"	`/var/log/pgw_c/cdrs`
`usage_report_interval`	integer	URR reporting interval (ms) - how often PGW-U sends usage reports	60000	60000 (1 minute)

Configuration Examples

Minimal Configuration (config/runtime.exs):

config :pgw_c,
  # CDR file configuration
  pgw_name: "omni-pgw01",
  cdr_file_duration: 3_600_000,           # 1 hour
  cdr_directory: "/var/log/pgw_c/cdrs",

  # URR configuration (triggers usage reports from PGW-U)
  usage_report_interval: 60_000           # 60 seconds

Production:

config :pgw_c,
  pgw_name: "pgw-c-prod-01",
  cdr_file_duration: 3_600_000,           # 1 hour rotation
  cdr_directory: "/var/log/pgw_c/cdrs",
  usage_report_interval: 60_000           # 1 minute updates

Development:

config :pgw_c,
  pgw_name: "pgw-c-dev",
  cdr_file_duration: 300_000,             # 5 minute rotation for testing
  cdr_directory: "/tmp/pgw_c_cdrs",
  usage_report_interval: 30_000           # 30 second updates for faster testing

High-Volume:

config :pgw_c,
  pgw_name: "pgw-c-prod-heavy",
  cdr_file_duration: 1_800_000,           # 30 minute rotation
  cdr_directory: "/mnt/fast-storage/cdrs",
  usage_report_interval: 300_000          # 5 minute updates (reduce overhead)

URR (Usage Reporting Rules)

PGW-C uses PFCP URRs (Usage Reporting Rules) to trigger usage reports from PGW-U. When a URR threshold is reached or time expires, PGW-U sends a Session Report Request containing usage data, which triggers CDR generation.

How URR Configuration Works:

usage_report_interval (in ms) is converted to seconds for PFCP time threshold
PGW-C creates URR with time threshold during session establishment
PGW-U sends periodic usage reports at configured interval
Each usage report triggers a bearer_update CDR event
Final usage report (on session deletion) triggers bearer_end CDR event

Example: usage_report_interval: 60_000 means:

PGW-U reports usage every 60 seconds
CDR update events generated every 60 seconds
Granular usage tracking for billing

URR Type Definition:

# lib/core/session/types.ex
defmodule PGW_C.Session.Types.URR do
  typedstruct do
    field :urr_id, non_neg_integer()
    field :measurement_method, :duration | nil
    field :reporting_triggers, :time_threshold | nil
    field :time_threshold, non_neg_integer() | nil  # seconds
  end
end

See PFCP Interface Documentation for URR PFCP details and lib/core/session/impl/procedures.ex:468 for URR creation during session establishment.

CDR Generation Flow

Bearer Lifecycle CDR Events

PGW-C CDR Generation:

CDR Generation Events

1. Bearer Start:

When: Create Session Response is sent
Purpose: Records bearer establishment with zero usage
octets_in: 0
octets_out: 0

2. Bearer Update:

When: PFCP Session Report Request received from PGW-U (URR usage report)
Purpose: Records incremental data usage
octets_in: Cumulative downlink bytes since bearer start
octets_out: Cumulative uplink bytes since bearer start
Trigger: URR time threshold expires (configured via usage_report_interval)

3. Bearer End:

When: PFCP Session Deletion Response received from PGW-U (with final usage report)
Purpose: Records final data usage before session termination
octets_in: Final total downlink bytes
octets_out: Final total uplink bytes

Field Details

1. epoch (Timestamp)

Type: Unix epoch timestamp (seconds)

Description: The time when the CDR event occurred

Example:

1726598022  → 2025-09-17 18:53:42 UTC

2. imsi (Subscriber Identity)

Type: String (up to 15 digits)

Format: MCCMNC + MSIN

Description: International Mobile Subscriber Identity uniquely identifying the subscriber

Example:

310260123456789
  └─┬─┘└─┬─┘└────┬────┘
   MCC  MNC     MSIN
   (310)(260) (123456789)

Source: UE context, received in Create Session Request

3. event (CDR Event Type)

Type: String

Format: <bearer_type>_bearer_<event>

Values:

default_bearer_start
default_bearer_update
default_bearer_end
dedicated_bearer_start
dedicated_bearer_update
dedicated_bearer_end

Determination:

If EBI (EPS Bearer ID) equals LBI (Linked Bearer ID): default
If EBI does not equal LBI: dedicated

Source: Bearer context (EBI vs LBI comparison)

4. charging_id (Charging Identifier)

Type: Unsigned 32-bit integer

Description: Unique identifier for charging correlation across network elements

Example:

Source: Assigned by PGW-C, received in Create Session Response

Usage:

Correlates charging events across SGW and PGW
Used in Diameter Gy/Gz charging interfaces
Unique per bearer

5. msisdn (Phone Number)

Type: String (E.164 format)

Description: Mobile Station ISDN Number (subscriber's phone number)

Format: Country code + national number

Example:

15551234567
 └┬┘└───┬───┘
  CC  National
  (1) (5551234567)

Source: UE context, typically from HSS via MME

6. ue_imei (Equipment Identity)

Type: String (15 digits)

Format: TAC (8) + SNR (6) + Spare (1)

Description: International Mobile Equipment Identity (device identifier)

Example:

123456789012345
└───┬───┘└─┬─┘└┘
   TAC   SNR S

Source: UE context, received from MME

7. timezone_raw (UE Timezone)

Type: String (currently reserved/empty)

Description: Reserved field for UE timezone information

Current Status: Not populated (empty field in CSV)

Future Use: May include timezone offset and daylight saving time flag

Example:

,  (empty field)

8. plmn (Network Identifier)

Type: Integer (legacy format)

Description: Public Land Mobile Network identifier encoded as little-endian hex

Encoding Process:

MCC: 505, MNC: 57
  ↓
"50557"
  ↓
Swap pairs: "055570"
  ↓
Hex to decimal: 0x055570 = 349552

Example:

349552  → MCC: 505, MNC: 57

Source: UE location information from MME

Note: This is a legacy encoding format for backward compatibility

9. tac (Tracking Area Code)

Type: Unsigned 16-bit integer

Description: Tracking Area Code identifies the tracking area where the UE is located

Range: 0 - 65535

Example:

Source: UE location information, received from MME in Create Session Request

Usage:

Identifies mobility management area
Used for paging and location updates
Part of TAI (Tracking Area Identity)

10. eci (E-UTRAN Cell Identifier)

Type: Unsigned 28-bit integer

Description: E-UTRAN Cell Identifier uniquely identifies the cell serving the UE

Format: eNodeB ID (20 bits) + Cell ID (8 bits)

Range: 0 - 268,435,455

Example:

Source: UE location information from MME

Usage:

Identifies specific cell tower and sector
Used for handover and mobility management
Granular location information

11. sgw_ip (SGW Control Plane IP)

Type: String (IPv4 or IPv6 address)

Description: SGW-C's S5/S8 control plane IP address (F-TEID)

Format: Dotted decimal (IPv4) or colon-hex (IPv6)

Example:

10.0.0.15       (IPv4)
2001:db8::15    (IPv6)

Source: Local configuration, assigned to S5/S8 interface

12. ue_ip (UE IP Address)

Type: String (IPv4|IPv6 format)

Description: IP address assigned to the UE for the PDN connection

Format: <ipv4>|<ipv6>

Examples:

172.16.1.100|                      (IPv4 only)
|2001:db8::1                       (IPv6 only)
172.16.1.100|2001:db8::1          (Dual-stack)

Source: PDN Address Allocation (PAA) from PGW-C

Notes:

Empty IPv4: No IPv4 address allocated
Empty IPv6: No IPv6 address allocated
Both present: Dual-stack PDN connection

13. pgw_ip (PGW Control Plane IP)

Type: String (IPv4 or IPv6 address)

Description: PGW-C's S5/S8 control plane IP address (remote F-TEID)

Format: Dotted decimal (IPv4) or colon-hex (IPv6)

Example:

10.0.0.20       (IPv4)
2001:db8::20    (IPv6)

Source: Received in Create Session Response from PGW-C

14. apn (Access Point Name)

Type: String (up to 100 characters)

Description: Access Point Name identifying the external network (PDN)

Format: DNS-like label format

Examples:

internet
ims
mms
enterprise.corporate

Source: Received in Create Session Request from MME

Usage:

Determines which external network to connect to
Drives policy and charging rules
May determine IP address pool

15. qci (QoS Class Identifier)

Type: Unsigned 8-bit integer

Description: QoS Class Identifier defines the bearer's quality of service

Range: 1 - 9 (standardized), 128-254 (operator-specific)

Standardized QCI Values:

QCI	Resource Type	Priority	Packet Delay	Packet Loss	Example Service
1	GBR	2	100 ms	10^-2	Conversational Voice
2	GBR	4	150 ms	10^-3	Conversational Video
3	GBR	3	50 ms	10^-3	Real-time Gaming
4	GBR	5	300 ms	10^-6	Non-conversational Video
5	Non-GBR	1	100 ms	10^-6	IMS Signaling
6	Non-GBR	6	300 ms	10^-6	Video (buffered)
7	Non-GBR	7	100 ms	10^-3	Voice, Video, Gaming
8	Non-GBR	8	300 ms	10^-6	Video (buffered)
9	Non-GBR	9	300 ms	10^-6	Default Bearer

Example:

9  → Default bearer (best effort)

Source: Bearer QoS parameters from PGW-C

16. octets_in (Downlink Volume)

Type: Unsigned 64-bit integer

Description: Number of bytes transmitted in the downlink direction (network → UE)

Units: Bytes

Example:

1048576  → 1 MB downlink

Source: PFCP Volume Measurement from PGW-U (via URR usage reports)

Notes:

Cumulative for update events
Final total for end events
Always 0 for start events
Reports triggered by URR time threshold (configured via usage_report_interval)

17. octets_out (Uplink Volume)

Type: Unsigned 64-bit integer

Description: Number of bytes transmitted in the uplink direction (UE → network)

Units: Bytes

Example:

524288  → 512 KB uplink

Source: PFCP Volume Measurement from PGW-U (via URR usage reports)

Notes:

Cumulative for update events
Final total for end events
Always 0 for start events
Reports triggered by URR time threshold (configured via usage_report_interval)

Examples

Example 1: Basic Session with Single Update

Timeline:

Bearer established
5 minutes later: Usage update (10 MB down, 5 MB up)
Session terminated

CDR Output:

# Data CDR File:
# File Start Time: 10:00:00 (1726570800)
# File End Time: 11:00:00 (1726574400)
# Gateway Name: pgw-c-01
# epoch,imsi,event,charging_id,msisdn,ue_imei,timezone_raw,plmn,tac,eci,sgw_ip,ue_ip,pgw_ip,apn,qci,octets_in,octets_out
1726570800,310260111111111,default_bearer_start,10001,15551111111,111111111111111,,349552,1000,2000,10.0.0.20,172.16.1.1|,10.0.0.20,internet,9,0,0
1726571100,310260111111111,default_bearer_update,10001,15551111111,111111111111111,,349552,1000,2000,10.0.0.20,172.16.1.1|,10.0.0.20,internet,9,10485760,5242880
1726571400,310260111111111,default_bearer_end,10001,15551111111,111111111111111,,349552,1000,2000,10.0.0.20,172.16.1.1|,10.0.0.20,internet,9,10485760,5242880

Example 2: Dual-Stack Session with Multiple Updates

Timeline:

Dual-stack bearer established (IPv4 + IPv6)
Multiple usage updates
Session terminated

CDR Output:

1726570800,310260222222222,default_bearer_start,10002,15552222222,222222222222222,,349552,1001,2001,10.0.0.20,172.16.1.2|2001:db8::2,10.0.0.20,internet,9,0,0
1726571100,310260222222222,default_bearer_update,10002,15552222222,222222222222222,,349552,1001,2001,10.0.0.20,172.16.1.2|2001:db8::2,10.0.0.20,internet,9,2097152,1048576
1726571400,310260222222222,default_bearer_update,10002,15552222222,222222222222222,,349552,1001,2001,10.0.0.20,172.16.1.2|2001:db8::2,10.0.0.20,internet,9,8388608,4194304
1726571700,310260222222222,default_bearer_update,10002,15552222222,222222222222222,,349552,1001,2001,10.0.0.20,172.16.1.2|2001:db8::2,10.0.0.20,internet,9,20971520,10485760
1726572000,310260222222222,default_bearer_end,10002,15552222222,222222222222222,,349552,1001,2001,10.0.0.20,172.16.1.2|2001:db8::2,10.0.0.20,internet,9,31457280,15728640

Example 3: Session with Dedicated Bearer

Timeline:

Default bearer established (QCI 9)
Dedicated bearer created for video (QCI 6)
Usage updates for both bearers
Dedicated bearer deleted
Default bearer terminated

CDR Output:

1726570800,310260333333333,default_bearer_start,10003,15553333333,333333333333333,,1258248,1002,2002,10.0.0.20,172.16.1.3|,10.0.0.20,internet,9,0,0
1726571100,310260333333333,dedicated_bearer_start,10004,15553333333,333333333333333,,1258248,1002,2002,10.0.0.20,172.16.1.3|,10.0.0.20,internet,6,0,0
1726571400,310260333333333,default_bearer_update,10003,15553333333,333333333333333,,1258248,1002,2002,10.0.0.20,172.16.1.3|,10.0.0.20,internet,9,5242880,2097152
1726571400,310260333333333,dedicated_bearer_update,10004,15553333333,333333333333333,,1258248,1002,2002,10.0.0.20,172.16.1.3|,10.0.0.20,internet,6,104857600,1048576
1726571700,310260333333333,dedicated_bearer_end,10004,15553333333,333333333333333,,1258248,1002,2002,10.0.0.20,172.16.1.3|,10.0.0.20,internet,6,209715200,2097152
1726572000,310260333333333,default_bearer_end,10003,15553333333,333333333333333,,1258248,1002,2002,10.0.0.20,172.16.1.3|,10.0.0.20,internet,9,10485760,4194304

Analysis:

Default bearer (10003) carries background traffic (10 MB down, 4 MB up)
Dedicated bearer (10004) carries video traffic (200 MB down, 2 MB up)
Different QCI values (9 vs 6) reflect different QoS treatment

Integration

CDR Processing Pipeline

CDR Collection Methods

1. File-based Collection:

# Monitor CDR directory (PGW-C)
inotifywait -m /var/log/pgw_c/cdrs/ -e close_write | while read path action file; do
    # File rotation completed, process CDR
    process_cdr "$path$file"
done

2. Real-time Streaming:

# Tail and stream to processing pipeline
tail -F /var/log/pgw_c/cdrs/* | process_cdr_stream

Session Management - Session lifecycle and CDR triggers
PFCP Interface - Usage reporting from PGW-U via URRs
Monitoring Guide - CDR generation metrics and alerting
Configuration Guide - CDR and URR configuration parameters
Diameter Gx Interface - Policy control for QCI values in CDRs
Diameter Gy Interface - Online charging integration

3GPP References

TS 32.251 - Packet Switched (PS) domain charging
TS 29.274 - 3GPP Evolved Packet System (EPS); GTP-C protocol
TS 29.244 - Interface between CP and UP nodes (PFCP) - URR support
TS 32.298 - CDR encoding

CDR Format - Offline Charging Records for PGW-C

Developed by Omnitouch Network Services

Documentation Version: 1.0 Last Updated: 2025-12-28

Table of Contents​

Overview​

Key Features​

Use Cases​

CDR File Format​

File Naming Convention​

File Location​

File Header​

CDR Fields​

Field Summary​

CDR Events​

Event Types​

Event Examples​

File Structure​

Example CDR File​

File Rotation​

Configuration​

Configuration Parameters​

Configuration Examples​

URR (Usage Reporting Rules)​

CDR Generation Flow​

Bearer Lifecycle CDR Events​

CDR Generation Events​

Field Details​

1. epoch (Timestamp)​

2. imsi (Subscriber Identity)​

3. event (CDR Event Type)​

4. charging_id (Charging Identifier)​

5. msisdn (Phone Number)​

6. ue_imei (Equipment Identity)​

7. timezone_raw (UE Timezone)​

8. plmn (Network Identifier)​

9. tac (Tracking Area Code)​

10. eci (E-UTRAN Cell Identifier)​

11. sgw_ip (SGW Control Plane IP)​

12. ue_ip (UE IP Address)​

13. pgw_ip (PGW Control Plane IP)​

14. apn (Access Point Name)​

15. qci (QoS Class Identifier)​

16. octets_in (Downlink Volume)​

17. octets_out (Uplink Volume)​

Examples​

Example 1: Basic Session with Single Update​

Example 2: Dual-Stack Session with Multiple Updates​

Example 3: Session with Dedicated Bearer​

Integration​

CDR Processing Pipeline​

CDR Collection Methods​

Related Documentation​

3GPP References​

Table of Contents

Overview

Key Features

Use Cases

CDR File Format

File Naming Convention

File Location

File Header

CDR Fields

Field Summary

CDR Events

Event Types

Event Examples

File Structure

Example CDR File

File Rotation

Configuration

Configuration Parameters

Configuration Examples

URR (Usage Reporting Rules)

CDR Generation Flow

Bearer Lifecycle CDR Events

CDR Generation Events

Field Details

1. epoch (Timestamp)

2. imsi (Subscriber Identity)

3. event (CDR Event Type)

4. charging_id (Charging Identifier)

5. msisdn (Phone Number)

6. ue_imei (Equipment Identity)

7. timezone_raw (UE Timezone)

8. plmn (Network Identifier)

9. tac (Tracking Area Code)

10. eci (E-UTRAN Cell Identifier)

11. sgw_ip (SGW Control Plane IP)

12. ue_ip (UE IP Address)

13. pgw_ip (PGW Control Plane IP)

14. apn (Access Point Name)

15. qci (QoS Class Identifier)

16. octets_in (Downlink Volume)

17. octets_out (Uplink Volume)

Examples

Example 1: Basic Session with Single Update

Example 2: Dual-Stack Session with Multiple Updates

Example 3: Session with Dedicated Bearer

Integration

CDR Processing Pipeline

CDR Collection Methods

Related Documentation

3GPP References