The Transparent proxy model allows the Border Router to forward traffic on behalf of Wi-SUN nodes so that they appear as directly attached hosts on the upstream network, even though there is a routing hop between the upstream and the Wi-SUN devices. The Border Router just proxies neighbor discovery (ND) and related link-presence signaling and relays packets without address translation, so devices use their own IPv6 addresses end to end.

In this mode, the Border Router acts as a mediator, ensuring that external/upstream systems see Wi-SUN nodes as if they were directly attached, while transparently forwarding across the Wi-SUN hop.

Transparent proxy model

When to use

Choose Transparent proxy if:

  • The operator wants to reduce routing complexity in the external network.

  • Simplicity is more important than granular control of addressing.

  • The upstream network and applications are designed to handle direct communication with many individually addressable devices on the Wi-SUN network.

  • Only one Border Router is expected to serve the the same upstream L3 domain.

  • The expected network is small (e.g., ≤200 nodes) and unlikely to grow quickly.

Pros and cons

  • Pros

    • Simplifies integration by representing the entire network (upstream and Wi-SUN) uniformly.

    • Reduces complexity in external routing tables.

    • Can ease integration with legacy upstream services.

    • Individual devices are reachable on the upstream network without adding static routes or advertising additional prefixes.

  • Cons

    • Limits monitoring and management from the upstream side.

    • Adds reliance on the Border Router as a single proxy point, creating a potential bottleneck.

    • Less transparent for troubleshooting and end-to-end visibility.

Address assignment

This model can use the Border Router’s built-in DHCPv6 service, known as BR-local DHCPv6 or the DHCPv6 relay approach.

This is how BR-local DHCPv6 works (click to expand)

BR-local DHCPv6 refers to the Border Router’s built-in DHCPv6 service, which assigns IPv6 addresses directly to Wi-SUN nodes within its PAN. In this mode, the Border Router acts as the DHCPv6 server for the entire mesh, managing address allocation locally and independently of any upstream infrastructure.

The Border Router:

  • Assigns IPv6 addresses to all nodes in the Wi-SUN network.

  • Maintains its own address pool, typically derived from a static prefix or a delegated prefix obtained via DHCPv6-PD.

  • Handles all DHCPv6 requests locally — no relay or upstream coordination is required.

  • Operates autonomously, ensuring address assignment even if the upstream connection becomes unavailable.

For example, if the Border Router is assigned the prefix 2001:db8:100::/64:

  • It runs a local DHCPv6 service.

  • Wi-SUN nodes request addresses via DHCPv6.

  • The Border Router assigns addresses such as:

    • 2001:db8:100::10

    • 2001:db8:100::11

    • and so on.

All communication remains within this prefix, allowing the Border Router to manage and route all local traffic effectively.

The key advantages of this approach are:

  • Self-contained operation: No dependency on upstream DHCPv6 servers.

  • Faster provisioning: Address assignment happens locally.

  • Resilience: The network continues to operate even during temporary upstream outages.

  • Simplicity: Ideal for smaller or standalone Wi-SUN deployments.

This is how DHCPv6 relay works (click to expand)

DHCPv6 relay is a mechanism in which the Border Router forwards address assignment requests from Wi-SUN nodes to an upstream DHCPv6 server. Instead of managing addresses locally, the Border Router acts as a relay agent, integrating the Wi-SUN mesh into a centrally managed IPv6 network.

The Border Router:

  • Relays DHCPv6 requests from Wi-SUN nodes to an upstream DHCPv6 server, such as one in an enterprise or provider network.

  • Receives the responses from the upstream server and forwards them back to the requesting Wi-SUN nodes.

  • Does not maintain its own address pool; all addressing decisions are handled centrally by the upstream infrastructure.

  • Integrates the Wi-SUN mesh into a broader, centrally managed IPv6 network.

For example, if the upstream DHCPv6 server manages the prefix 2001:db8:100::/64:

  • The Border Router relays DHCPv6 messages from Wi-SUN nodes to the upstream server.

  • The upstream server allocates addresses under that prefix and returns them through the Border Router.

  • Each Wi-SUN node receives a globally unique IPv6 address, such as:

    • 2001:db8:100::10

    • 2001:db8:100::11

    • and so on.

All address management, lease control, and prefix distribution are handled upstream, ensuring consistent policy and coordination across multiple Border Routers.

The key advantages of this approach are:

  • Centralized management: A single DHCPv6 server can coordinate addressing across many Border Routers or sites.

  • Scalability: Simplifies large deployments by avoiding local address pools on each Border Router.

  • Consistency: Enables unified prefix planning and monitoring under enterprise or service provider policies.

  • Integration: Fits naturally into existing DHCPv6-managed infrastructure.

Considerations

Transparent proxy introduces trade-offs between simplicity and visibility:

  • Device management: In more complex network environments, this model may limit routing control and reduce visibility into which nodes are being accessed through the Border Router.

  • Protocol support: Ensure the proxy handles all required protocols (e.g., TCP, UDP, ICMP).

  • Performance and scale: The Border Router must maintain individual proxy entries to respond to all neighbor solicitation traffic and route the resulting traffic, which impacts scalability.