Description
The Serving Network Name (SNN) is a critical identifier in the 5G System (5GS) defined in 3GPP Release 15 and beyond. It serves as a human-readable and machine-processable name for the network currently serving a User Equipment (UE). The primary purpose of the SNN is to provide an unambiguous identifier for the serving network during authentication and security key derivation procedures, ensuring that security contexts are bound to the correct network.
Architecturally, the SNN is constructed and used by the core network, specifically the Authentication Server Function (AUSF) and the UE. It is derived from the core network identifiers. For a public network, the SNN is typically constructed as "5G:mnc<MNC>.mcc<MCC>.3gppnetwork.org", where MNC and MCC are the Mobile Network Code and Mobile Country Code from the PLMN ID. For a Non-Public Network (NPN), the SNN may additionally include a Network Identifier (NID), formatted as "5G:mnc<MNC>.mcc<MCC>.nid<NID>.3gppnetwork.org". This structure ensures global uniqueness.
During the 5G Authentication and Key Agreement (5G-AKA) or Extensible Authentication Protocol (EAP)-based procedures, the SNN is sent from the network to the UE. The UE and the AUSF both use this SNN as an input parameter (along with other values like the Subscription Permanent Identifier (SUPI)) into the key derivation functions. This binds the generated security keys (like K_AUSF, K_SEAF) specifically to this serving network name. This mechanism prevents key reuse across different networks and enhances security, particularly in scenarios involving network slicing or roaming, by ensuring a cryptographic separation between different serving network contexts.
Purpose & Motivation
The SNN was introduced with 5G in Release 15 to address specific security and identification requirements that were not fully met by previous mechanisms like the Serving Network (SN) identity used in EPS. In 4G EPS, the network identity was implicitly derived from the PLMN ID but wasn't always explicitly and consistently formatted as a named parameter in all security procedures. 5G's enhanced security architecture demanded a more robust and explicit method.
Its creation was motivated by the need for stronger network authentication, support for new network deployment models like Non-Public Networks (NPNs), and the foundational requirements for network slicing. By having a standardized, structured name, the 5G system can more securely anchor the authentication process. It solves the problem of ensuring that the keys generated during authentication are uniquely tied to the specific network (or network slice instance) the UE is accessing, which is crucial for preventing security context confusion, especially in complex multi-operator, multi-slice, or private network environments.
Classification
Release Timeline
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (8 CRs across 4 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the formal definition and standardized format for the Serving Network Name (SNN) were introduced for primary authentication. The SNN, a UTF-8 string of maximum 1020 octets, is structured as "5G:mnc<MNC>.mcc<MCC>.3gppnetwork.org" for PLMNs, with a specific syntax to ensure a three-digit MNC. It is used within the AT_KDF_INPUT attribute during EAP-AKA' authentication, enabling the UE to perform an SNN check as part of network authentication.
In Release 16, the SNN (Serving Network Name) function was formally extended to support SNPNs (Standalone Non-Public Networks), defining a new SNN-SNPN-ID format that includes the Network Identifier (NID) appended after the PLMN ID. This introduced a distinct coding structure, using a colon delimiter, to differentiate between public PLMN and private SNPN network identifiers within the SNN string. The release also included corrections and clarifications to the SNN reference and its application in authentication procedures.
In Release 17, the SNN (Serving Network Name) function was enhanced to explicitly support SNPN (Standalone Non-Public Network) operations, including verification procedures when an AAA-Server is used for primary authentication and authorization. Furthermore, the specification extended the description of the SNN to cover its application in NSWO (Non-Seamless WLAN Offload) scenarios. These updates formalized the SNN format for SNPNs, which includes both the PLMN ID and a Network Identifier (NID), as defined in the ABNF syntax.
In Release 18, the primary update for the Serving Network Name (SNN) function was a correction related to its application in 5G Non-Seamless WLAN Offload (NSWO). This built upon the previous Release 17 work which had extended the SNN description specifically for NSWO operations. The SNN itself, used in authentication key derivation and network verification, maintains its defined format consisting of a service code and a network identifier for either a PLMN or an SNPN.
- Correction for SNN related to 5G NSWO TS 24.501CR5125
Explore further
Broader topics and technologies where SNN plays a role.
Defining Specifications
3GPP specifications that define or reference SNN, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 24.501 vj50 | 5G NAS Protocols Specification | Rel-19 |
| TS 24.890 vg00 | 5G NAS Protocol for 5GS Stage 3 | Rel-16 |
