Data Network Name

Description

The Data Network Name (DNN) is a fundamental identifier in the 5G System (5GS) and Evolved Packet System (EPS). It is a string (e.g., "internet", "ims") that uniquely identifies a Packet Data Network (PDN) or Data Network (DN) external to the 3GPP network. When a UE establishes a Protocol Data Unit (PDU) Session in 5GS or a PDN Connection in EPS, it must specify a DNN. This DNN is a key parameter used by the network to select the appropriate User Plane Function (UPF) in 5GS or Packet Data Network Gateway (PGW) in EPS that provides connectivity to that external network.

Architecturally, the DNN is used in conjunction with other identifiers like the Single Network Slice Selection Assistance Information (S-NSSAI). Upon receiving a PDU Session Establishment Request with a DNN, the Access and Mobility Management Function (AMF) interacts with the Session Management Function (SMF). The SMF uses the DNN, along with subscription data from the Unified Data Management (UDM) and policies from the Policy Control Function (PCF), to select a specific UPF instance. The DNN determines the external network's point of interconnection and influences the session's QoS characteristics, charging policies, and security requirements.

The DNN's role extends beyond simple gateway selection. It is integral to policy and charging control. The PCF may apply different policy and charging control (PCC) rules based on the DNN. For example, traffic destined for the DNN "internet" might have one set of QoS rules, while traffic for a DNN associated with a low-latency enterprise service would have another. The DNN is also used in network exposure; when a third-party application function (AF) requests specific traffic handling, it often references the DNN. Furthermore, the DNN is a critical parameter for network slicing, as a slice can be configured to support only specific DNNs, enabling service-specific network partitions.

Purpose & Motivation

The DNN was introduced to fulfill the same essential purpose as the Access Point Name (APN) in earlier systems but within the new service-based architecture of 5GS. It solves the problem of unambiguously identifying the external data network to which a user's session should be connected. This is a fundamental requirement for routing user plane traffic correctly and applying appropriate network policies.

In the context of 5G's support for diverse services (eMBB, URLLC, mMTC), the DNN provides a clear handle for the network to differentiate between service types. For instance, a UE might use one DNN for regular internet browsing and a different DNN for accessing a mission-critical industrial IoT service, even though both sessions might be served by the same UE. This allows for simultaneous connectivity to multiple data networks with independent policy treatment.

The evolution from APN to DNN reflects architectural simplification and alignment with IP networking principles. While APN had a structure that included network and operator identifiers, the DNN is a more straightforward label. Its purpose is deeply integrated with 5G's core tenets: network slicing, where a DNN may be mapped to a specific slice instance; service-based architecture, where the DNN is a common parameter across Nsmf, Npcf, and other service-based interfaces; and support for edge computing, where a DNN can point to a local area data network (LADN). It addresses the limitations of the older APN model by being more flexible and better suited for automated management and orchestration in cloud-native 5G cores.