NATn

NATn is a term used in networking to describe a theoretical extension of Network Address Translation that generalizes NAT into a multi-stage, scalable translation framework. In NATn, address translation occurs across a chain of levels, allowing n distinct stages of mapping between internal private addresses and public-facing address space. The concept aims to provide finer control, improved scalability, and clearer policy enforcement in large, multi-tenant or globally distributed networks.

Architecture and components typically envisioned for NATn include NATn gateways (NATnG), a translation policy controller, and a set of translation engines. Each level maintains its own binding table that maps internal addresses and ports to intermediate or final public identifiers. A pool of public or semi-public addresses is allocated for use at the final level, while intermediate levels can apply domain- or tenant-specific mappings. The system may also integrate with centralized management to define per-tenant or per-service translation rules.

Operation generally envisions packets traversing from level 0 through level n, with each stage applying a translation step while preserving session state. NATn supports static and dynamic mappings, port preservation where possible, and timeouts for idle flows. It can incorporate policy-based routing to direct flows to specific NATn gateways and can accommodate protocol-aware handling for common transport protocols.

Use cases often cited include large data centers, multi-tenant cloud networks, mobile backhaul, and service provider backbones facing IPv4 scarcity. Benefits cited are scalability, granular auditing, and flexible policy enforcement; drawbacks include added complexity and potential performance overhead, along with compatibility considerations for end-to-end encryption and some protocols. NATn remains a conceptual framework rather than an official standard, with related discussions in NAT64 and large-scale NAT contexts.