Packet.NetRom 0.35.0

Packet.NetRom

NET/ROM L3 routing, L4 circuits, and the INP3 time-routing overlay for the Packet.NET stack.

Packet.NetRom is the NET/ROM networking layer: the L3 routing table (NODES broadcasts + the multiplicative per-hop quality model), the L4 virtual-circuit state machine (CircuitManager / NetRomCircuit), the L3 forwarding decision for transit nodes, and the INP3 time-routing overlay (L3RTT link timing, RIF/RIP). It runs above an AX.25 interlink - the wire types are codecs over NetRomPacket, and the routing/transport types are host-free (no AX.25 or node-host dependency), so you wire them to a transport yourself. Part of Packet.NET, a .NET amateur-radio / AX.25 packet stack, built on Packet.Core and Packet.Ax25.

Install

dotnet add package Packet.NetRom

Quick start

Parse a NODES broadcast you heard from a neighbour and learn its routes into a routing table - the read-only ingest path a node uses to build its view of the network:

using Packet.Core;
using Packet.NetRom.Routing;
using Packet.NetRom.Wire;

var me   = new Callsign("Q0PDN");      // our own node callsign
var nbr  = new Callsign("N0CALL");     // the neighbour whose broadcast we heard

// Build a node's own NODES broadcast, then parse it (here we round-trip the builder;
// in production you'd parse the info field of a received PID-0xCF UI frame).
byte[][] frames = NodesBroadcastBuilder.Build(
    senderAlias: "NODE",
    entries: [ new(new Callsign("AA1AA"), "BBS", new Callsign("AA1AA"), Quality: 200) ]);

if (NodesBroadcast.TryParse(frames[0], out var broadcast))
{
    var table = new NetRomRoutingTable();
    table.Ingest(originator: nbr, myCall: me, portId: "vhf", broadcast: broadcast);

    NetRomRoutingSnapshot view = table.Snapshot();
    foreach (var dest in view.Destinations)
        Console.WriteLine($"{dest.Alias} ({dest.Destination}) via {dest.BestRoute?.Neighbour} q={dest.BestRoute?.Quality}");
}

Call table.Sweep() at the broadcast interval to age routes out, BuildAdvertisement(obsoleteMinimum) to originate your own NODES, and MarkNeighbourDown(new NeighbourKey(portId, neighbour)) for immediate link-down failover (or MarkPortDown(portId) when a whole port goes away). For L4 circuits, mint one with CircuitManager.OpenCircuit(remoteNode), wire its SendPacket sink to your interlink, then Connect / Send / Disconnect.

Key types

• NetRomRoutingTable - the learned L3 routing table: ingests NODES broadcasts, derives per-hop qualities, keeps best routes per destination with obsolescence decay, hands out immutable snapshots.
• NetRomRoutingSnapshot / NetRomDestination / NetRomRoute - the immutable read-only routing view (with ResolveDestination for connect <alias>).
• NeighbourKey - a neighbour is the (port, callsign) pair, not the callsign: one station audible on two ports is two adjacencies, each with its own path quality, its own routes and its own link. NetRomRoute carries the port; NetRomRoutingSnapshot gives you NeighbourFor(key), NeighboursOf(callsign) and BestNeighbourFor(callsign). See docs/netrom-multiport-neighbours.md.
• CircuitManager - owns the L4 circuit table: mints circuits, demultiplexes inbound datagrams, accepts/refuses inbound connects, drives retransmit timers.
• NetRomCircuit - one end of an L4 virtual circuit: sliding-window transport with negotiated window, choke flow control, NAK retransmit, and 236-byte fragment/reassembly.
• NetRomForwarding - the pure L3 forwarding decision for a transit node (TTL decrement, loop guard, best/per-flow next-hop selection).
• Inp3Engine - the host-free INP3 link-timing engine: L3RTT probing, SNTT smoothing, neighbour-down detection.
• NetRomPacket / NodesBroadcast / Inp3Rif - the wire codecs (total parsing - malformed bytes return false, never throw).

See also

• Source & issues
• Packet.Ax25 - the AX.25 interlink NET/ROM datagrams ride over (PID 0xCF)
• Packet.Core - Callsign and the shared primitives

AGPL-3.0-licensed. Part of the Packet.NET stack.