Private network traffic

Description

Private network traffic refers to traffic that is sent to or received from a Next Generation Network (NGN) for processing according to an agreed set of rules specific to an enterprise or a community of closely related enterprises. In the context of the IP Multimedia CN Subsystem (IM CN), this type of traffic is normally confined within a single enterprise, but it can also exist between two different enterprises if not precluded by regulatory requirements. The concept was introduced in 3GPP Release 8 and has been maintained through subsequent releases with a significant wording change in Release 17 to align with NGN terminology.

The architecture supporting private network traffic involves the IM CN subsystem, which includes core network elements such as Call Session Control Functions (CSCFs), Home Subscriber Servers (HSSs), and Application Servers (ASs). These elements process private network traffic according to enterprise-specific rules, which may include routing policies, access control, and service invocation. The traffic is typically identified by specific identifiers or tags that allow the network to distinguish it from public traffic. For example, a Private User Identity or a specific service profile may be used to mark traffic as private.

How it works: When a user equipment (UE) initiates a session, the network determines whether the traffic is private based on subscription data and enterprise agreements. The CSCF, acting as the central control element, applies the agreed rules to route the traffic appropriately. This may involve dedicated bearers, specific QoS parameters, or even dedicated network slices. The rules are often stored in the HSS and enforced by the CSCF and other nodes. Private network traffic can be exchanged between UEs within the same enterprise or between UEs of different enterprises, provided that inter-enterprise agreements and regulatory constraints allow it.

Key components include the enterprise's own network infrastructure (e.g., a private IP network or a dedicated NGN), the 3GPP network elements that handle the traffic, and the interfaces between them. The IM CN subsystem provides the session control, while the transport layer (e.g., IP) carries the actual data. Security mechanisms such as IPsec and TLS may be used to protect private traffic. The concept is closely related to enterprise communications, closed user groups (CUGs), and network slicing, as private network traffic can be carried over dedicated slices.

In later releases, particularly from Release 17 onwards, the definition was updated to include traffic sent to or received from an NGN, reflecting the evolution towards 5G and the integration of NGN concepts. This change acknowledges that private network traffic may traverse not only the IM CN subsystem but also other NGN components. The term remains relevant for enterprises seeking secure, isolated communication services within a public land mobile network (PLMN).

Purpose & Motivation

Private network traffic exists to enable enterprises to use 3GPP networks for their internal communications while maintaining control over routing, security, and service quality. Before its introduction, enterprises relied on private branch exchanges (PBXs) or leased lines, which lacked mobility and integration with mobile networks. The IM CN subsystem provided a standardized way to deliver IP-based multimedia services, but public traffic handling did not cater to enterprise-specific rules. Private network traffic fills this gap by allowing enterprises to define and enforce their own policies within the operator's network.

The concept addresses the need for closed user groups and enterprise-specific services, such as corporate VPNs, internal conferencing, and unified communications. It also supports regulatory requirements by allowing traffic to be confined within national boundaries or specific enterprises. The evolution to include NGN reflects the convergence of fixed and mobile networks, enabling enterprises to extend their private networks across different access technologies.

By defining private network traffic, 3GPP provides a framework for operators to offer enterprise services that are secure, reliable, and customizable. This fosters new business models and revenue streams for operators while meeting the communication needs of enterprises.