IP Connectivity Access Network

Description

The IP Connectivity Access Network (IPCAN) is a core architectural concept within 3GPP specifications that models the collection of network functions and transport resources responsible for providing IP connectivity to a user. It is not a single physical network but a logical abstraction encompassing the entire path from the User Equipment (UE) to the gateway that interfaces with external Packet Data Networks (PDNs), such as the internet or IMS. The IPCAN includes the radio access network (e.g., E-UTRAN, UTRAN, GERAN, NG-RAN), the core network gateways (e.g., P-GW in EPC, UPF in 5GC), and the interconnecting transport network. Its primary role is to establish one or more IP-CAN bearers—logical channels with specific QoS characteristics—to carry user plane IP traffic.

Architecturally, the IPCAN is central to the Policy and Charging Control (PCC) framework. The PCRF (Policy and Charging Rules Function) uses the IP-CAN session as a management context. An IP-CAN session represents the association between a UE and a specific PDN, identified by an APN (Access Point Name). Within this session, one or more IP-CAN bearers are established. The PCRF provides policy rules (PCC rules) to the PCEF (Policy and Charging Enforcement Function), typically residing in the P-GW, which then installs these rules to govern the IP-CAN bearers. This governance includes gating (allowing/blocking packets), QoS control (setting bearer characteristics like QCI, ARP, GBR), and charging control (metering traffic and generating charging data records).

The operation of IPCAN is dynamic. When a UE attaches to the network and requests a PDN connection, an IP-CAN session is established. The PCEF may initiate a PCRF interaction to obtain initial PCC rules. Throughout the session, events like UE mobility, service requests, or network-triggered modifications can cause the PCRF to push updated rules, leading to the modification, establishment, or termination of IP-CAN bearers. This allows for service-aware network resource allocation. For example, a voice over LTE (VoLTE) call triggers the establishment of a dedicated bearer with a guaranteed bit rate (GBR), while background email sync uses a default non-GBR bearer. The IPCAN concept thus decouples service logic (handled by the PCRF/AF) from connectivity management, enabling flexible service delivery.

Purpose & Motivation

IPCAN was introduced to provide a standardized, technology-agnostic model for IP connectivity management within 3GPP's all-IP core network architecture, which began with the Evolved Packet Core (EPC) in Release 8. Prior to EPC, 3GPP networks (GPRS, UMTS) managed packet data contexts, but the approach was more tightly coupled to specific access technologies and lacked a unified policy control framework. The shift towards an all-IP network for all services, including voice (via IMS), necessitated a more robust, flexible, and policy-driven method to establish and control IP data paths.

The creation of the IPCAN concept solved several key problems. First, it provided a common abstraction layer for policy and charging control, allowing the PCRF to apply rules consistently whether the UE was connected via LTE, HSPA, or later, non-3GPP access like WiFi. This was essential for fixed-mobile convergence and seamless service experience. Second, it formalized the relationship between a user's service session (e.g., an IMS voice call) and the underlying transport bearer, enabling dynamic QoS enforcement based on real-time service requirements. This was a significant advancement over static QoS provisioning. Finally, by defining the IP-CAN session and bearer model, it created a clean architecture for charging systems to correlate usage with specific services and policies, supporting complex charging models like sponsored data or zero-rating.

Key Features

• Abstracts the end-to-end IP connectivity path from UE to PDN Gateway
• Forms the management context for Policy and Charging Control (PCC) rules
• Supports establishment, modification, and termination of IP-CAN bearers with specific QoS
• Enables access-agnostic policy enforcement across 3GPP and non-3GPP accesses
• Provides the framework for service-aware charging and accounting
• Facilitates mobility management and session continuity for IP flows

Evolution Across Releases

Defining Specifications