Home Network Prefix

Description

The Home Network Prefix (HNP) is a critical identifier in IP mobility management protocols, specifically defined within the 3GPP context for Dual-Stack Mobile IPv6 (DSMIPv6) and Proxy Mobile IPv6 (PMIPv6). Conceptually, it is an IPv6 prefix (or an IPv4 address/prefix in dual-stack scenarios) that is permanently associated with a mobile node (MN) and anchored at its home agent (HA) in DSMIPv6 or at the local mobility anchor (LMA) in PMIPv6. This prefix defines the MN's 'home network' in the IP routing sense. The MN configulates one or more home addresses (HoAs) from this prefix, which remain constant regardless of the MN's current point of attachment to the network.

In operation, when an MN roams to a visited network, it acquires a care-of address (CoA) from the local access router. In DSMIPv6, the MN itself registers this CoA with its HA using a Binding Update message, creating a binding between its stable HoA (derived from the HNP) and its current CoA. The HA then intercepts packets destined for the MN's HoA and tunnels them to the MN's CoA. In PMIPv6, which is a network-based protocol, the mobility access gateway (MAG) in the visited network performs the registration with the LMA on behalf of the MN. The LMA, which hosts the HNP, ensures packets are routed to the MAG serving the MN. The HNP is thus the topological anchor point for the MN's IP session, enabling seamless IP continuity.

The allocation of the HNP is a core function of the home network. It is typically assigned during the MN's initial attachment or subscription provisioning. The HNP is stored in the MN's subscription profile in the AAA (Authentication, Authorization, and Accounting) infrastructure. During network access authentication, the AAA server can communicate the assigned HNP to the network entity acting as the mobility anchor (HA or LMA). The HNP's scope is global, meaning it is routable within the Internet, allowing correspondent nodes to communicate with the MN using its home address without any awareness of its mobility.

Purpose & Motivation

The HNP concept was developed to solve the fundamental problem of session continuity for mobile devices in IP networks. The original Internet architecture assumed endpoints were stationary; a host's IP address also indicated its topological location. Mobility breaks this assumption, as moving to a new network typically requires a new IP address, breaking existing TCP connections and application sessions. Mobile IP protocols (MIPv6, DSMIPv6) were created to decouple a node's identifier (its home address) from its locator (its care-of address).

The HNP provides the stable identifier basis for this decoupling. It allows a mobile node to have a persistent 'home' on the Internet represented by its home address, derived from the HNP. This solves the problem of reachability and session persistence. The motivation for standardizing HNP within 3GPP was to provide a unified, IP-based mobility solution for 3GPP and non-3GPP access networks (like Wi-Fi) as defined in the Evolved Packet Core (EPC). It enables features like seamless handovers between 3GPP and trusted non-3GPP access without breaking IP-based services like VoIP or video streaming. Prior approaches relied on link-layer mobility or application-layer solutions, which were often inefficient or not universally applicable.

Key Features

• Serves as the stable routing prefix for a mobile node's home address
• Anchored at the home agent (DSMIPv6) or local mobility anchor (PMIPv6)
• Enables IP session continuity across different access networks
• Globally routable, allowing direct communication from correspondent nodes
• Assigned from the mobile node's home operator address space
• Supports both IPv6 prefixes and IPv4 address/prefixes in dual-stack operation

Evolution Across Releases

Defining Specifications