Synapses

A synapse is a persistent, stateful, weighted connection between two NTL nodes. Synapses are the edges in the neural graph — they determine how signals flow through the network.

How Synapses Differ from Connections

Property	HTTP Connection	WebSocket	NTL Synapse
State	Stateless	Session state	Weighted, learning
Lifetime	Per-request	Session duration	Persistent, evolving
Direction	Client → Server	Bidirectional	Bidirectional
Adaptation	None	None	Strengthens/weakens with use
Memory	None	In-memory only	Persisted to the storage backend

The key difference: synapses learn. A synapse that frequently carries successful signals becomes stronger, meaning it gets priority for future signal propagation. A synapse that goes unused weakens and eventually prunes. This mirrors Hebbian learning in neuroscience — connections that fire together wire together.

Synapse Structure

struct Synapse {
    // Identity
    id: SynapseId,
    local_node: NodeId,
    remote_node: NodeId,

    // State
    weight: f32,                    // Current strength (0.0 - 1.0)
    state: SynapseState,           // Active, Weakening, Dormant, Pruned
    established_at: u64,           // Creation timestamp
    last_active: u64,              // Last signal timestamp

    // Statistics
    signals_transmitted: u64,      // Total signals sent
    signals_received: u64,         // Total signals received
    avg_latency_ns: u64,           // Average round-trip nanoseconds
    error_rate: f32,               // Failed signal ratio

    // Configuration
    transport: TransportBinding,   // Underlying transport (QUIC, TCP, etc.)
    max_weight: f32,               // Weight ceiling
    decay_rate: f32,               // Weight decay per interval
}

Synapse Lifecycle

  Discover → Handshake → Active → Strengthen/Weaken → Dormant → Prune
                            │                             │
                            └─────── Reactivate ──────────┘

1. Discovery

Nodes discover potential synapse partners through:

Bootstrap nodes — Well-known entry points that introduce new nodes to the network
Signal traces — Signals carry their path; receiving nodes can form synapses with upstream nodes
Discovery signals — Nodes broadcast capability announcements

2. Handshake

When two nodes decide to form a synapse, they perform a handshake:

Exchange node identities and capabilities
Negotiate transport binding (TCP only today — see Transport Bindings)
Exchange cryptographic material via the pluggable crypto module
Establish initial weight (typically 0.1)

3. Active State

An active synapse transmits signals bidirectionally. With each successful signal transmission:

Weight increases by a configurable delta
Latency statistics update
The synapse is marked as recently active

4. Strengthening

Weight increases when:

Signals are successfully transmitted and acknowledged
High-weight signals traverse the synapse
The remote node provides valuable responses (as determined by the application layer)

// Weight adjustment formula
new_weight = min(
    current_weight + (signal.weight * strengthen_factor),
    max_weight
)

5. Weakening

Weight decreases when:

Time passes without signal activity (decay)
Signals fail or time out
The remote node becomes unreliable

// Decay formula (applied periodically)
new_weight = current_weight * (1.0 - decay_rate)

6. Dormancy

When a synapse’s weight drops below the dormancy threshold (configurable, default 0.01), it enters a dormant state. Dormant synapses:

Stop actively transmitting signals
Retain their state in the storage backend
Can be reactivated if the remote node sends a signal

7. Pruning

After a configurable dormancy period (default: 7 days), dormant synapses are pruned — their state is archived and the connection resources are released.

Transport Bindings

Synapses are transport-agnostic. The actual bytes move over a configurable transport layer:

Transport	Use Case	Properties	Status
TCP	Everything, today	Reliable, widely supported	Implemented
QUIC	Intended default for internet	Multiplexed, encrypted, low latency	Design
Unix Socket	Same-machine nodes	Zero network overhead	Design
Bluetooth LE	Proximity mesh	Offline-capable, IoT	Design
Custom	Specialized	Application-defined	Design

The reference implementation is TCP-only, and performs no transport negotiation. ntl-net opens a TCP connection and runs a three-message authenticated handshake over it; there is no step at which transports are advertised or selected.QUIC is the intended default, for good reasons — multiplexing many signal streams over one connection, built-in encryption, and connection migration across network changes, all of which matter for mobile and intermittent links. None of it is written yet.[synapse.transport] is commented out of config.example.toml for this reason: preferred and fallback were read by nothing, and preferred = "quic" named a transport that does not exist. Tracking: openNTL/ntl#15.

Synapse Topology

The collection of all synapses in the network forms the synapse topology — a weighted, directed graph. This topology is:

Self-organizing — No central authority defines it
Adaptive — It reshapes based on actual signal patterns
Resilient — Node failures cause local topology adjustment, not global disruption
Observable — Nodes can inspect their local topology for monitoring and debugging

Local vs Global Topology

No single node knows the full network topology. Each node maintains knowledge of:

Its direct synapses (immediate connections)
Nearby topology (2-3 hops, learned through signal traces)
Bootstrap references (known stable nodes for re-entry)

This local-knowledge design is critical for scalability and privacy.

Configuration

Synapse behavior is configurable per-node:

[synapse]
initial_weight = 0.1
max_weight = 1.0
decay_rate = 0.01            # Weight decay per hour
dormancy_threshold = 0.01
prune_after_hours = 168      # 7 days
max_synapses = 1000          # Per-node connection limit

# Not read by anything yet, and `quic` is not implemented — see the warning
# under Transport Bindings above.
# [synapse.transport]
# preferred = "quic"
# fallback = "tcp"

Introduction

Core Concepts

Guides

Adapters

Security

Governance

How Synapses Differ from Connections

Synapse Structure

Synapse Lifecycle

1. Discovery

2. Handshake

3. Active State

4. Strengthening

5. Weakening

6. Dormancy

7. Pruning

Transport Bindings

Synapse Topology

Local vs Global Topology

Configuration

​How Synapses Differ from Connections

​Synapse Structure

​Synapse Lifecycle

​1. Discovery

​2. Handshake

​3. Active State

​4. Strengthening

​5. Weakening

​6. Dormancy

​7. Pruning

​Transport Bindings

​Synapse Topology

​Local vs Global Topology

​Configuration

How Synapses Differ from Connections

Synapse Structure

Synapse Lifecycle

1. Discovery

2. Handshake

3. Active State

4. Strengthening

5. Weakening

6. Dormancy

7. Pruning

Transport Bindings

Synapse Topology

Local vs Global Topology

Configuration