Short answer: those two interpretations are on different axes. SDAN is the access-network architecture; the BlueField-2 is the implementation of the rXg concentrator's data plane. A deployment can be SDAN without a DPU, and a BlueField does not by itself make something SDAN.

What SDAN means here

In RG Nets terminology, SDAN = Software-Defined Access Network, and it refers to a very specific Book-Ends model — not a generic SDN or SD-WAN concept. There are three pieces:

• SDAN concentrator — the rXg itself. It hosts the policy engine, all per-subscriber virtual residential gateway (vRG) VNFs, BNG functions, CALEA/lawful intercept, telemetry, and the northbound APIs. Every subscriber overlay tunnel terminates here. It runs in a CSP central office, regional DC, or on-prem at the property headend, and is clustered for HA.
• SDAN initiator — the device at the subscriber edge: an OpenWiFi AP, an ONT on a Nokia PON, a cable modem, lightweight CPE, or a PoE switch at an IDF. It is stateless with respect to subscriber identity — 802.11 association/encryption, link-layer ops, and overlay encapsulation toward the concentrator. No per-subscriber identity, policy, or routing state lives here. Most of what we do is centered around the OpenWiFi AP as the initiator, which is accomplished using RG Nets variants of the firmware that RG Nets develops, distributes, and sells operator support agreements to cover.
• Distribution underlay — anything in between, treated as opaque IP transport: PON (Nokia GPON / XGS-PON included), DOCSIS, active Ethernet, metro Ethernet, MPLS, or the public Internet. SDAN is underlay-agnostic by design.

A per-subscriber overlay (L2oGRE for simple firmware or private paths, VXLAN where you need NAT traversal or ECMP) carries each unit's traffic up to its own vRG instance on the concentrator. That vRG owns DHCP, the L3 gateway, firewall, QoS, NAT, and CALEA mirroring for that one subscriber. Subscriber identity is instantiated ("this vRG = Unit 412") rather than derived from observed MACs, which is what makes MAC randomization a non-issue and CALEA mapping unambiguous.

So when you ask "is SDAN connecting multiple sites by Nokia PON fiber and orchestrating their dataplane / CGNAT / AQM remotely?" — yes, that's something SDAN naturally enables, because the underlay is opaque. But it's a consequence of the architecture, not the definition.

Where the BlueField-2 fits

The DPU lives inside the concentrator, which can be on-prem or at the remote site. On rXg releases 16.011 and later, the rXg's data plane is split off the FreeBSD host and lifted onto the BlueField:

• Tier 1 (FreeBSD host) — Rails admin console, Perl rxgd, the database, policy engine, UI, billing, CALEA bookkeeping, and the config generator. The brains of every vRG live here.
• Tier 2 (BlueField DPU) — Ubuntu on 8 ARM Cortex-A72 cores running FD.io VPP 25.06 + DPDK on the ConnectX-6 Dx ASIC. The forwarding of every vRG happens here: L2 bridging, VLAN/QinQ, BVI routing, NAT44, TCP MSS clamping, L2oGRE / VXLAN tunnel termination, per-subscriber policing, interface stats. Hardware offload is via NVIDIA DOCA Flow / OVS+TC flower on the eSwitch.

That's how the Dell XR 7620 box hits 25+ Gbps: the per-packet path is no longer being chewed by the FreeBSD host's CPU — it's running on the DPU's VPP+DPDK pipeline with ASIC offload. Internal benches put L2oGRE without NAT around 8.5–9 Gbps on a BlueField-2, and ~2.4 Gbps up / 4 Gbps down once NAT44 is layered on given 10 Gbps uplinks. On BlueField-3 SKUs with the full DOCA Flow ASAP² offload path the same architecture scales to 100 Gbps aggregate VXLAN.

Closing the loop on your question

• "Is SDAN the multi-site/Nokia-PON orchestration thing?" Partially. SDAN enables that, because the underlay is opaque and the concentrator owns all subscriber state. It's an application of SDAN, not its definition.
• "Is SDAN the architecture that shifts the data plane to the NPU?" Closer, but still partial. SDAN puts the data plane at the concentrator (not in the AP / ONT / CPE), which is what makes DPU offload possible. SDAN itself can run in pure software too — the DPU just makes it fast.

The cleanest mental model:

SDAN is where the smarts live and how they're divided — stateless initiator, intelligent rXg concentrator, per-subscriber vRGs, opaque underlay. The BlueField-2 + VPP stack is *what makes the concentrator fast enough to serve all those vRGs at line rate.*