If you have worked in broadband for a while you will have called the subscriber-edge box both a BRAS and a BNG, and wondered whether anyone means something different by the two. For practical purposes they are the same network function — the gateway where broadband subscribers terminate and become routed internet users. BRAS (Broadband Remote Access Server) is the older name; BNG (Broadband Network Gateway) is the term the industry standardised on as the role grew. This note sets out where each came from, what is genuinely the same, and what a modern BNG does that the original BRAS did not.
Where BRAS came from
The BRAS is a creature of the DSL era. Subscribers dialled up a PPPoE session over ADSL, the session ran from the DSLAM across the access network to the BRAS, and the BRAS did the things a subscriber edge has always done: authenticate the session (usually against RADIUS), hand out an address, apply a rate limit, and account for the traffic. "Remote access server" is the lineage — it is the broadband descendant of the dial-up RAS. For years "BRAS" was simply what the box was called.
How the role became the BNG
Two things stretched the term past breaking point. First, access changed: fibre (FTTP) and Ethernet aggregation brought IPoE alongside PPPoE, dual-stack IPv6 became a requirement rather than a nice-to-have, and wholesale models pushed sessions over L2TP to a remote LNS. Second, the edge absorbed more roles: carrier-grade routing, per-service VRFs, integrated CGNAT, and richer QoS. The box was no longer just a "remote access server"; it was the gateway between the broadband access network and the IP/MPLS core. The industry settled on Broadband Network Gateway for that larger role, and BNG is now the standard term. A vendor still writing "vBRAS" (a virtual BRAS) means the same thing as a vBNG.
What is the same
Strip away the terminology and the core job is unchanged from the BRAS:
- Terminate the subscriber session — PPPoE, IPoE, or an L2TP tunnel from a wholesale LAC.
- Authenticate and authorise the line, typically against RADIUS.
- Assign addressing — an IPv4 address and, now, an IPv6 prefix.
- Enforce policy — per-subscriber rate limits and service plans.
- Account for the traffic, with interim updates and a stop record.
Anyone who ran a BRAS recognises every one of these on a BNG. The session model, the RADIUS exchange and the accounting are continuous with the DSL era.
What the BNG added
The differences are what the role grew to include:
| Classic BRAS | Modern BNG | |
|---|---|---|
| Access | PPPoE over DSL | PPPoE, IPoE, L2TP LNS; dual-stack as one session |
| Addressing | IPv4, often single-stack | IPv4 and IPv6 (WAN + delegated prefix) |
| Routing | Static or a simple IGP toward the core | Full provider edge — see below |
| Carrier NAT | A separate box | Integrated CGNAT (NAT44) |
| Platform | Purpose-built chassis | Chassis or software on x86 (a vBNG) |
The routing change is the biggest. A modern BNG is a converged provider edge (PE) and BNG: it is a first-class router in the core, not just a subscriber terminator bolted on behind one. In Netavo BNG that means BGP with VPNv4/VPNv6, a selectable IGP (IS-IS or OSPF), MPLS L3VPN and EVPN, per-service VRFs and ECMP — all on the same box that terminates the subscribers. Collapsing the PE and the BNG into one system removes a hop, a box and a licence from the edge.
The BNG also left the chassis
The other shift is that the BNG no longer has to be dedicated hardware. A software BNG — a vBNG — runs the same role on standard x86-64 servers, with the data plane accelerated in software (DPDK or AF_XDP) rather than on a forwarding ASIC. That is a change of platform, not of function: it is still the BRAS's job, done on commodity compute. (See what is a vBNG for that side of the story.)
Where Netavo BNG fits
Netavo BNG is a carrier-grade software BNG — the function a BRAS provided, modernised and run on standard x86-64 servers. It terminates PPPoE, IPoE and L2TP LNS subscribers (up to 100,000 concurrent sessions), is a converged PE/BNG with BGP/VPNv4/VPNv6, IS-IS or OSPF, MPLS L3VPN and EVPN, and includes integrated CGNAT (NAT44). The data plane keeps forwarding from shared-memory state even while the control plane restarts or upgrades. If your network notes still say "BRAS", this is the box they mean — one generation on.
FAQ
Is a BRAS the same as a BNG?
Yes. They name the same subscriber-edge function. BRAS (Broadband Remote Access Server) is the older, DSL-era term; BNG (Broadband Network Gateway) is the term the industry standardised on as the role grew to include IPoE, IPv6, carrier-grade routing and integrated services. A "virtual BRAS" (vBRAS) and a vBNG mean the same thing.
Why did the industry move from "BRAS" to "BNG"?
Because the box outgrew the name. The original BRAS terminated PPPoE over DSL. As access moved to fibre and IPoE, IPv6 became mandatory, wholesale pushed sessions to an L2TP LNS, and the edge absorbed carrier routing and integrated CGNAT, "remote access server" no longer described it. "Broadband Network Gateway" names that larger role.
Does a BNG do routing that a BRAS did not?
Yes. A modern BNG is a converged provider edge: Netavo BNG runs BGP with VPNv4/VPNv6, a selectable IGP (IS-IS or OSPF), MPLS L3VPN and EVPN, per-service VRFs and ECMP on the same box that terminates subscribers, so it is a first-class router in the core rather than a terminator sitting behind one.
Is Netavo BNG a BRAS?
It is the modern form of one. Netavo BNG performs the same subscriber-edge function a BRAS did — session termination, RADIUS authentication, addressing, policy and accounting — on standard x86-64 servers, and adds the IPoE, IPv6, converged routing and integrated CGNAT that define a BNG.