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Network Architecture

TARPN uses a mesh network topology where each node connects to multiple neighbors via dedicated point-to-point radio links.

Network Topology

        ┌───────┐           ┌───────┐
        │Node A │───────────│Node B │
        └───┬───┘           └───┬───┘
            │                   │
            │     ┌───────┐     │
            └─────│Node C │─────┘
                  └───┬───┘
                      │
                  ┌───┴───┐
                  │Node D │
                  └───────┘

Each link is a dedicated simplex (one frequency) or half-duplex connection between exactly two nodes.

Protocol Stack

Layer Protocol Description
Application BBS, Chat, Telnet User services
Session NET/ROM Node routing and session management
Transport AX.25 / IL2P Packet framing, FEC
Physical FM Radio VHF/UHF modulation

Routing

TARPN nodes use NET/ROM (Network Routing) protocol implemented by LinBPQ:

  • Automatic route discovery - Nodes broadcast routing tables
  • Quality-based routing - Links scored by reliability
  • Multi-hop forwarding - Packets routed through network
  • Alias addressing - Human-readable node names

The primary link type. Each radio port connects to exactly one neighbor.

[Node A Radio 1] ──── frequency 1 ────> [Node B Radio 2]
                <──── frequency 1 ─────

Configuration:

  • Simplex frequency per link
  • 9600 baud recommended (1200 baud minimum)
  • IL2P protocol for FEC

Connect distant nodes over the Internet:

[Node A] ──── Internet ────> [Node B]

Not Recommended

Internet links bypass the amateur radio purpose of TARPN. Use sparingly for critical backbone connections only.

Node Types

Full Node

  • 2-4 radio ports
  • Part of the mesh backbone
  • Routes traffic for other nodes

Leaf Node

  • 1-2 radio ports
  • Connects to the network but doesn't route
  • End-user access point

Gateway Node

  • Provides Internet connectivity (email, etc.)
  • Connects to external services
  • Usually also a full node

Quality Metrics

LinBPQ assigns quality scores to each link:

Quality Description
255 Perfect (direct connection)
203 Excellent radio link
150 Good radio link
100 Marginal link
< 100 Poor link

Quality is used for routing decisions - higher quality paths preferred.

Traffic Flow

Local Traffic

[User] ──> [Local Node] ──> [Application]

Remote Traffic

[User] ──> [Node A] ──> [Node B] ──> [Node C] ──> [Application]

The network automatically routes packets through the optimal path.

Services

BBS (Bulletin Board System)

  • Personal mailboxes
  • Bulletin boards
  • Message forwarding between nodes

Chat

  • Real-time keyboard-to-keyboard
  • Group chat rooms
  • Available via TARPN-HOME web interface

Telnet

  • Remote node access
  • Command line interface
  • Diagnostic tools

Network Coordination

NC Packet (North Carolina)

The original TARPN network, coordinated through ncpacket.net.

Frequency Coordination

  • Coordinate with neighbors to avoid interference
  • See Frequencies for allocation guide

Linking Guidelines

  • Only link to neighbors you can reliably reach
  • Maintain links you commit to
  • See Network Rules for policies