Network

Nexus OS inverts the traditional network architecture. In Linux, the TCP/IP stack runs inside the kernel — a 30-million-line attack surface where a malformed packet can crash the entire system.

In Nexus: the kernel delivers the mail; it does not read the letter.

Architecture

┌──────────────────────────────────────────────┐
│  Application (curl, browser, etc.)           │
├──────────────────────────────────────────────┤
│  POSIX Shim (socket, connect, send)          │  Membrane
│  or Native ION Channel API                   │
├──────────────────────────────────────────────┤
│  LwIP TCP/IP Stack (Grafted)                 │  Userland
│  or UTCP Sovereign Transport                 │
├──────────────────────────────────────────────┤
│  Per-Process ION Rings (proc_rx, proc_tx)    │  Zero-Copy
├──────────────────────────────────────────────┤
│  NetSwitch (L2 Demux)                        │  Kernel
├──────────────────────────────────────────────┤
│  VirtIO-Net Driver (HAL)                     │  Raw Frames
└──────────────────────────────────────────────┘

Components

• Network Membrane — The userland network stack (grafted LwIP + POSIX shim)
• UTCP — Sovereign transport protocol for Nexus-to-Nexus traffic
• Libertaria Wire Frame — The Libertaria protocol stack wire format

The NetSwitch

The NetSwitch is the only networking code that runs inside the kernel. It is a simple L2 packet demultiplexer:

1. The VirtIO-Net driver delivers a raw Ethernet frame
2. The NetSwitch reads the EtherType field (2 bytes)
3. Based on the EtherType, it places the frame on the correct ION Ring:

EtherType	Destination	Protocol
0x0800	Membrane fiber	IPv4 (LwIP)
0x86DD	Membrane fiber	IPv6 (LwIP)
0x88B5	UTCP fiber	Sovereign transport
0x4C57	LWF fiber	Libertaria Wire Frame

The NetSwitch does not parse headers, compute checksums, or manage connections. It reads two bytes and routes.

Why This Matters

Isolation: If a network-facing application (curl, a web server, an MQTT client) crashes due to a malformed packet, only that application's fiber dies. The kernel continues running. The NetSwitch continues routing. Other applications are unaffected.

Security: The TCP/IP stack is outside the kernel's trust boundary. A vulnerability in LwIP cannot escalate to kernel privileges because LwIP runs in a userland fiber with a restricted capability set.

Sovereignty: For internal Nexus-to-Nexus traffic, UTCP provides identity-centric transport that doesn't depend on IP addresses, DNS, or any legacy infrastructure. Nodes know each other by cryptographic identity (CellID), not by IP.