Iups Interface Link

Description

The IupsLink (Iups Interface Link) is a managed object class defined within the 3GPP Generic Network Resources Network Resource Model (NRM), referenced as GenericNetworkResourcesNRMDefs::ManagedFunction. It models a communication link on the Iups interface, which is the interface between a Home NodeB Gateway (HNB-GW) and the core network's Serving GPRS Support Node (SGSN) in 3GPP femtocell architectures. The Iups interface is essentially the Iu-PS interface as seen from the HNB-GW, carrying packet-switched user data and control signalling for Home NodeB subscribers.

In the 3GPP Home NodeB architecture, the HNB-GW acts as a concentrator and protocol proxy between many HNBs and the core network. The Iups interface connects the HNB-GW to the SGSN, reusing the standard Iu-PS protocol stack (RANAP over SCTP for control, and GTP-U over UDP/IP for user plane). The IupsLink managed object represents the logical link that carries this traffic. By modeling it as a ManagedFunction, the standard treats the link as a manageable entity with its own state, attributes, and relationships, rather than as an anonymous transport connection.

The ManagedFunction class is a fundamental building block in the 3GPP NRM. It represents a functional entity that can be managed, and it can contain other managed objects (such as termination points) as children. By defining IupsLink as a ManagedFunction, the standard allows the management system to treat each Iups link as a distinct managed element. This is important in HNB-GW deployments where a single gateway may have multiple Iups links to different SGSNs or to different core network pools, each requiring independent monitoring and configuration.

The IupsLink is specified in 3GPP TS 28.703, which defines the Generic Network Resources IRP NRM, and TS 32.636, which provides the corresponding solution set. The IRP framework ensures that the IupsLink can be managed through standardized operations regardless of the underlying management protocol (CORBA, XML, REST, etc.). Attributes of the IupsLink would typically include an identifier, operational state, administrative state, and references to the parent HNB-GW managed element and to the remote SGSN.

From an operational perspective, the IupsLink enables operators to monitor the health and performance of the connection between the HNB-GW and the core network. Failures on this link can affect all HNBs served by the gateway, making it a critical point for fault management. The object also supports capacity planning and load balancing, as operators can track utilization per link. Introduced in Release 10, the IupsLink has been carried forward through Release 19 without substantive changes to its definition, reflecting the stability of the Iu-PS architecture and its management model.

Purpose & Motivation

The IupsLink exists to provide a standardized, manageable representation of the link between a Home NodeB Gateway and the core network's packet-switched domain (SGSN). In early femtocell deployments, the HNB-GW's connections to the core network were often managed as simple transport links, without a standardized information model. This made it difficult for operators to integrate multi-vendor HNB-GWs into their management systems and to correlate faults across the access and core domains. The IupsLink solves this by defining a ManagedFunction object that represents the link as a first-class managed entity.

Historically, the Iu-PS interface was defined for macro cellular networks, connecting the Radio Network Controller (RNC) to the SGSN. When the Home NodeB architecture was introduced, the HNB-GW took on the role of the RNC for femtocells, and the interface to the SGSN was named Iups. The Generic Network Resources IRP, introduced in Release 10, provided the modeling framework. By defining IupsLink as a ManagedFunction, the standard ensures that the link can be managed using the same principles as other network functions, enabling consistent fault, configuration, and performance management.

The IupsLink also supports the broader goal of network convergence and automation. As operators move toward Self-Organizing Networks (SON) and network slicing, having standardized managed objects for core-facing links is essential for end-to-end service assurance. The IupsLink provides the anchor point for monitoring the performance of the packet-switched connection serving femtocell users.