Definition: S8 Home Routing (S8HR) and N9 Home Routing (N9HR) are mechanisms used in mobile networks to handle data traffic when a user is roaming, ensuring that the subscriber’s home operator retains control over services, security, and billing.

Homerouting (S8HR, N9HR) explained

S8 Home Routing (S8HR) originates from 4G LTE architecture. In this model, when a user roams onto a visited network, their data traffic is tunnelled back to the home network through the S8 interface, which connects the visited network’s Serving Gateway (SGW) to the home network’s Packet Data Network Gateway (PGW). Even though the user is physically connected to a foreign network, all their internet traffic is routed through their home operator. This allows the home network to enforce policies, apply charging rules, and maintain consistent service behaviour. The downside is that routing traffic over long distances can increase latency and reduce efficiency compared to handling data locally.

N9 Home Routing (N9HR) is the 5G equivalent of S8HR, adapted to the 5G core (5GC) architecture. Instead of SGW and PGW, 5G uses User Plane Functions (UPFs), and the N9 interface connects the visited network’s UPF to the home network’s UPF. Like S8HR, all user data is sent back to the home network, ensuring centralized control over traffic, security, and charging. N9HR supports advanced 5G capabilities such as network slicing and service-based architecture, making it more flexible and scalable than its 4G predecessor.

In both cases, the key idea is home routing: user traffic is always processed by the home network, regardless of location. While this approach ensures consistency and control, it may introduce higher latency compared to alternatives like local breakout, where data is handled within the visited network. In summary, S8HR and N9HR represent similar concepts across 4G and 5G, with N9HR being the modernized version aligned with 5G architecture.