CDR

Call Detail Record

Management →
Introduced in R99 Also in: Core Network, Management

CDR is the structured data record generated by a network element to document a service event, such as a call or data session, and serves as the fundamental unit for billing, charging, and traffic analysis in 3GPP networks.

Category
Management
Introduced
R99
Where
Services › Codecs
Also touches
2 segments
Specifications
50 specs
CDR Description Purpose Detected Changes Specifications

Description

A Call Detail Record (CDR) is a standardized, machine-readable log entry that captures the essential parameters of a service usage event within a 3GPP network. It is not a single, monolithic record but a family of record types defined for different services (e.g., MOC, MTC, SMS-MO, SMS-MT, GPRS) and generated by various network functions. The core network elements responsible for session and bearer management, such as the MSC Server for circuit-switched calls, the SGSN and GGSN for GPRS, or the MME, SGW, and PGW in the EPC, are the primary CDR generators. These nodes collect relevant information in real-time during the service instance and format it according to strict specifications defined in 3GPP TS 32.250 and related documents.

The architecture of CDR generation and handling involves several key components. The Charging Trigger Function (CTF), embedded within the network element (e.g., MSC, PGW), detects chargeable events and assembles the relevant charging information into a Charging Data Record. This CDR is then forwarded via a standardized interface (like Ga or Rf) to a Charging Data Function (CDF) in offline charging, or to an Online Charging System (OCS) in real-time scenarios. The CDR itself contains numerous fields, including but not limited to: the served party identifiers (MSISDN, IMSI), serving network identity, date and timestamps for session start and stop, duration, data volumes (uplink/downlink), QoS parameters applied, and identifiers for the specific service used. For roaming scenarios, the CDR will also contain Visited and Home PLMN identifiers.

Its role extends far beyond simple billing. CDRs are the primary source for post-processing systems that perform billing mediation, fraud detection, interconnect settlement with other operators, and detailed traffic analysis. The format and content of CDRs have evolved significantly from simple circuit-switched call logs to complex records encompassing IMS sessions, VoLTE calls, and massive IoT data transactions. The standardization ensures interoperability between network equipment from different vendors and between operators for roaming settlements. The processing of CDRs involves collection, correlation (e.g., matching a start record with its corresponding stop record), formatting for specific billing systems, and secure archival, forming the backbone of the operator's business support system (BSS).

Purpose & Motivation

The CDR exists to provide an accurate, auditable, and standardized record of service usage, which is indispensable for commercial telecommunications operations. Its primary purpose is to enable billing and charging, transforming network resource consumption into billable events for subscribers (postpaid) or for real-time credit control (prepaid). Without CDRs, operators would have no objective mechanism to charge for services, making commercial mobile networks financially unviable. It solves the fundamental problem of metering network usage in a multi-vendor, multi-operator environment.

Historically, the concept predates 3GPP, originating in fixed-line telephony (as referenced by ITU-T). In early mobile networks, the need became even more critical due to mobility, roaming, and a wider array of services beyond simple voice calls. The limitations of proprietary, non-standardized logging mechanisms were significant barriers to interoperability, especially for roaming where the home operator must bill its subscriber based on records generated by a visited foreign network. The 3GPP standardization of CDR formats, generation rules, and transfer protocols provided this essential common language.

Furthermore, CDRs address operational and business intelligence problems beyond pure billing. They provide the raw data for traffic engineering, network planning, fraud management (by detecting unusual calling patterns), and regulatory compliance (e.g., lawful interception logging). The evolution of CDRs to include detailed QoS parameters, location information, and service-specific attributes allows operators to implement sophisticated tariff plans, service quality guarantees, and new business models, making them a cornerstone of both network management and business operations.

Detected Changes Across Releases

from 3GPP Change Requests

Specific changes extracted from the „Change history“ tables of 3GPP specifications (74 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.

Rel-15 13 changes

In Release 15, key enhancements for the CDR function included the introduction of a new Charging Function record type (CHF-CDR) to support 5G charging, along with the addition of specific parameters for WLAN-based ProSe direct discovery and SMS charging information within the CHF CDR. The release also added the DataVolumeOctets field to the generic CDR part and introduced corrections and clarifications for various existing CDR parameters, such as the NetworkFunctionID and PDU Session level triggers. Furthermore, support for new 5G Technical Specifications was added to the CDR header description.

  • Add CDR parameter for WLAN-based ProSe direct discovery TS 32.298CR0654
  • Introduction of CHF-CDR TS 32.298CR0667
  • Addition of DataVolumeOctets in generic CDR part TS 32.298CR0668
  • Introduce new Charging Function record type TS 32.298CR0669
  • Addition of SMS Charging to CHF CDR TS 32.298CR0680
  • Addition of SMS info to CHF CDR TS 32.298CR0682

+ 7 more changes

Rel-16 21 changes

In Release 16, key enhancements to the CDR function focused on the CHF (Charging Function) to support new network capabilities. These included adding specific parameters for I-SMF triggers, the exposure function northbound API, IPv6 multi-homing with multi-homed PDU addresses, and the QHT (likely a QoS or quota parameter). The release also involved numerous corrections and clarifications for parameters related to SMS, RATType, AMF fields, and overall consistency to ensure accurate billing records.

  • Adding I-SMF related SMFTrigger in CHF CDR TS 32.298CR0780
  • Addition of CHF CDR for exposure function northbound API TS 32.298CR0786
  • Correction of BGCF CDR description TS 32.260CR0397
  • Correction of BGCF CDR description TS 32.298CR0723
  • Incomplete indicator missing in CDR TS 32.298CR0795
  • Correcting backwards compatibility on CHF CDR TS 32.298CR0817

+ 15 more changes

Rel-17 16 changes

In Release 17, the CDR function was expanded to support new 5G capabilities, including the generation of records for ProSe (Proximity Services) and Edge Computing. Enhancements were also made to the CHF (Charging Function) CDR to incorporate charging information for Cellular IoT (CIoT) and to add definitions for Edge Computing. Furthermore, specific identifiers like the PSCell ID were introduced into the SGW CDR, and support for IMS Charging was added within the CHF CDR framework.

  • Updating CDR handling for converged charging TS 32.260CR0417
  • Introduction of CDR generation and handling for 5G ProSe converged charging TS 32.277CR0042
  • Introduction of Detailed message format for converged charging TS 32.277CR0045
  • Add CDR file format for Edge Computing charging TS 32.297CR0039
  • CHF CDR enhancements to support of GERAN and UTRAN TS 32.298CR0875
  • Add charging information related to CIoT in CHF CDR TS 32.298CR0890

+ 10 more changes

Rel-18 13 changes

In Release 18, the CDR function was enhanced to support new charging scenarios, specifically for Time-Sensitive Networking (TSN) and 5G satellite access and backhaul. The release also introduced the addition of an invocation timestamp to CDRs for improved time tracking and made various corrections and clarifications to CDR syntax and definitions across different charging systems.

  • Rel-18 CR 32.298 Add TSN specific charging information to CDR TS 32.298CR0978
  • Add the support of 5G satellite access charging to CHF CDR TS 32.298CR0986
  • Add 5G satellite backhaul charging to CHF CDR TS 32.298CR0987
  • Rel-18 CR 32.260 Addition of invocation timestamp in CDR TS 32.260CR0435
  • Rel-18 CR 32.298 Addition of invocation timestamp in CHF CDR TS 32.298CR0960
  • Rel-18 CR 32.270 Clarification on MMS CHF CDR TS 32.270CR0037

+ 7 more changes

Rel-19 11 changes

In Release 19, the CDR function was extended to support new charging scenarios, including converged charging for Ranging and Sidelink Positioning procedures and for 5G Location Services (LCS). The release also introduced specific CDR parameters and detailed message formats for these new services, as well as for layer 3 multi-hop ProSe UE-to-Network relay communication. Additionally, charging information was added for UE-satellite-UE scenarios, and references for CAPIF CDRs were included.

  • Add CDR generation and handling for converged charging of Ranging and Sidelink Positioning TS 32.271CR0023
  • Introduction of Detailed message format for Ranging and Sidelink Positioning converged charging TS 32.271CR0027
  • Extend basic priciples, CDR generation and handling for 5G LCS converged charging TS 32.271CR0030
  • Add charging information to CDR for Ranging and Sidelink Positioning TS 32.298CR1022
  • Add layer 3 multi-hop ProSe UE-to-Network relay communication related CDR parameters TS 32.298CR1033
  • Extend CHF-CDR for 5G LCS converged charging TS 32.298CR1034

+ 5 more changes

Explore further

Broader topics and technologies where CDR plays a role.

Topics
OAM (Operations & Maintenance)EPC (Evolved Packet Core)IMS & Voice (VoLTE, VoNR)Roaming & InterconnectMEC (Edge Computing)LTE / LTE-Advanced
Technologies
LTE

Defining Specifications

3GPP specifications that define or reference CDR, with the latest known release. Sourced from the 3GPP document catalog — see methodology.

SpecificationTitleRelease
TR 21.905 vj00 3GPP Technical Terms and Definitions Rel-19
TS 22.115 vj00 Service Aspects; Charging and Billing Rel-19
TS 22.121 v1400 Virtual Home Environment Requirements Rel-5
TS 22.234 vd10 3GPP-WLAN Interworking Index Specification Rel-13
TR 22.950 vj00 Feasibility Study on Priority Service Rel-19
TR 22.976 v1200 Release 2000 Services Overview Rel-2
TS 23.039 v1400 SMSC to SME Interface Protocols Rel-5
TS 23.060 vj00 GPRS Service Description Stage 2 Rel-19
TS 23.125 v1700 Flow Based Charging Architecture Rel-7
TS 23.140 v1600 MMS Non-Realtime Service Definition Rel-6
TS 23.167 vj11 IMS Emergency Sessions Rel-19
TS 23.218 vj00 IMS Call Model Specification Rel-19
TS 23.222 vj80 Common API Framework for 3GPP Northbound APIs Rel-19
TS 23.228 vj50 IMS Stage-2 Service Description Rel-19
TS 23.682 vj30 3GPP TS 23682: MTC Architecture Enhancements Rel-19
TS 23.815 v1500 IMS Charging Implications Rel-5
TS 23.851 v1600 Network Sharing Architecture for 3G Systems Rel-6
TR 23.923 v1300 Mobile IP+ Feasibility Study for UMTS/GPRS Rel-4
TS 24.229 vj50 IMS call control protocol based on SIP and SDP Rel-19
TS 24.802 vc10 IMS II-NNI Traversal Scenario Determination Study Rel-12
TS 26.891 vg00 Media Distribution Services in 5G System Rel-16
TS 28.203 vi10 Charging management Rel-18
TS 28.204 vi11 Charging management Rel-18
TR 28.816 vh00 Charging for 5G Cellular IoT Rel-17
TR 28.843 vi10 Technical Report on Charging Aspects for Vertical Scenarios Rel-18
TS 28.849 vj10 CAPIF Phase2 Charging Study Rel-19
TS 29.333 vj00 MRFC-MRFP Mp Interface Protocol Rel-19
TS 29.421 v810 IMS Interworking with External IP Networks Rel-8
TS 32.240 vj40 Charging Management Architecture & Principles Rel-19
TS 32.250 vj00 Circuit Switched Offline Charging Rel-19
TS 32.251 vj00 PS Domain Charging Management Rel-19
TS 32.252 vc00 3GPP WLAN Interworking Charging Rel-12
TS 32.260 vj10 IMS Charging Management Rel-19
TS 32.270 vj00 MMS Charging Management Specification Rel-19
TS 32.271 vj20 3GPP LCS Charging Management Spec Rel-19
TS 32.272 vj00 Charging for Push-to-Talk over Cellular (PoC) Rel-19
TS 32.273 vj00 MBMS Charging Management Rel-19
TS 32.277 vj20 Charging Management for Proximity Services (ProSe) Rel-19
TS 32.278 vj00 Monitoring Events Offline Charging Specification Rel-19
TS 32.295 vj00 3GPP Charging: CDR Transfer via GTP' Protocol Rel-19
TS 32.296 vj00 Online Charging System (OCS) Architecture Rel-19
TS 32.297 vj00 Charging Data Record File Transfer Rel-19
TS 32.298 vj30 Charging Data Record (CDR) Parameter Specification Rel-19
TS 32.299 vj00 Diameter Charging Applications for 3GPP Rel-19
TS 32.808 v1800 Common User Profile Storage Framework Rel-8
TS 32.825 va00 Study on Rc Reference Point for ABMF Rel-10
TR 32.846 vh00 Charging for ProSe in 5GS Rel-17
TS 32.850 ve00 IMS Charging Correlation Methods Study Rel-14
TS 32.869 vf00 Diameter Overload Control for Charging Interfaces Rel-15
TS 33.849 ve00 3GPP Privacy Principles and Guidelines Rel-14