Visited Policy and Charging Enforcement Function

Description

The V-PCEF is a critical network function within the 3GPP Policy and Charging Control (PCC) architecture, specifically for roaming scenarios. It resides in the Visited Public Land Mobile Network (VPLMN), which is the network a subscriber is physically connected to while outside the geographical coverage of their Home Public Land Mobile Network (HPLMN). The V-PCEF's primary role is to enforce dynamic policy and charging rules on the user plane traffic for a roaming subscriber. It is typically co-located with the Gateway GPRS Support Node (GGSN) in a GPRS core or the Packet Data Network Gateway (PGW) in an Evolved Packet Core (EPC). The V-PCEF interfaces with the Home PCRF (H-PCRF) via the S9 roaming interface, which is a Diameter-based protocol. Through this interface, the H-PCRF provides the V-PCEF with Policy and Charging Control (PCC) rules that are derived from the subscriber's profile and service data. These PCC rules contain instructions for gating (allowing/blocking traffic), QoS parameters (like guaranteed bit rate and allocation/retention priority), and charging information (such as charging keys and metering methods). The V-PCEF then installs these rules and applies them to the appropriate IP-CAN (IP Connectivity Access Network) bearer. It performs functions like packet inspection, filtering, and marking to ensure the traffic receives the contracted QoS. It also generates charging data records (CDRs) based on the applied rules and forwards them to the appropriate charging system in the VPLMN. This enforcement ensures that a roaming user's service experience and billing are consistent with their home network subscription, even when they are being served by a foreign operator's infrastructure.

Purpose & Motivation

The V-PCEF was introduced to address the complexities of applying consistent policy and charging control for subscribers roaming between different mobile network operators. Prior to its standardization, roaming scenarios posed significant challenges for enforcing the home operator's service policies (like QoS for specific applications) and accurate charging in the visited network. The visited network lacked the context of the subscriber's home subscription profile. The V-PCEF, as part of the PCC architecture, solves this by establishing a standardized control interface (S9) between the home and visited networks. This allows the home operator to retain control over the policy decisions (made by the H-PCRF) while delegating the enforcement of those decisions to a trusted function within the visited network. This separation of control and enforcement across administrative domains enables advanced, dynamic service provisioning for roamers, supports inter-operator QoS agreements, and facilitates accurate and transparent charging, which is fundamental for commercial roaming agreements. It ensures that services like IMS-based voice or video, which have strict QoS requirements, work seamlessly for a roaming user as they do at home.

Key Features

• Enforces PCC rules from the Home PCRF on roaming user traffic
• Located at the gateway (GGSN/PGW) in the Visited PLMN
• Interfaces with the H-PCRF via the Diameter-based S9 reference point
• Applies gating, QoS marking, and bandwidth management per PCC rules
• Generates charging data records (CDRs) for roaming usage
• Supports dynamic policy control for service data flows (SDFs)

Evolution Across Releases

Defining Specifications