Glossary - thunderlytics.net

Metrics

Centrality (Betweenness): Betweenness centrality measures how often a node appears on the shortest path between two other nodes in the network. Nodes with high betweenness are critical routing hubs.
Centrality (Closeness): Closeness centrality measures how close a node is to all other nodes, calculated as the inverse of the average shortest path length.
Centrality (Harmonic): Harmonic centrality is similar to closeness centrality but uses the harmonic mean of distances. More robust for real-world networks with disconnected components.
Centrality (Pagerank): PageRank measures the importance of a node based on the quality of its connections, not just the quantity. Originally designed by Google for ranking web pages.
Centrality (Eigenvector): Eigenvector centrality assigns scores based on the principle that connections to high-scoring nodes contribute more to a node's score.
Centrality (Katz): Katz centrality extends eigenvector centrality by considering not just direct connections but also indirect paths of any length, with a decay factor.
THY Score: The Thunderlytics composite score combines multiple centrality metrics into a single ranking, weighing betweenness, harmonic, and other measures.
THY Score (Micro Nodes): A THY-Score variant optimized for micro nodes with fewer channels. Adjusts weighting to surface smaller nodes important within their local neighborhood.

Open: A node has at least one open channel (no on-chain close recorded). A channel is open while its funding output is still unspent. This is the broadest level — includes everything currently announced in gossip, regardless of routing health.
Valid: Open nodes and channels with non-null capacity. Used as the base for component detection, snapshots, and graph metric computation. Removes only structural noise, not routing problems.
Healthy: Valid plus active: nodes whose state is HEALTHY or ACTIVE and channels currently considered active. The homepage hero, globe, top rankings and capacity totals all use this subset, so the numbers reflect the operational network rather than the full gossip table.

Healthy: Both directions are enabled, both routing policies are valid, and the channel is present in gossip. Payments can flow in either direction.
Active: Open and routable, but with one direction disabled. Payments may flow in only one direction.
Zombie: The channel is announced in gossip but has no valid routing policy on either side. It is not used for payment routing.
Disabled: Both directions have set the disabled flag. No payments can flow through this channel.
Gone: The channel has disappeared from the gossip network. Usually a precursor to a close that has not yet been confirmed on-chain.
Closed: The funding output has been spent on-chain. The channel is permanently closed.

Healthy: Active, reachable on at least one announced address, and located in the network's main connected component.
Active: Has at least one active channel but is either unreachable or sits outside the main connected component.
Inactive: Still announced in gossip with open channels, but none of its channels are currently active (zombie, disabled, etc.).
Gone: Disappeared from the gossip network — its last open channel either closed or has not been re-announced.

Base Fee: A fixed fee charged for every payment routed through the channel, regardless of amount. Expressed in millisatoshis (msat).
Fee Rate (PPM): A proportional fee charged as a fraction of the payment amount, expressed in parts per million (PPM).
HTLC Limits: The minimum and maximum payment sizes this node will forward through the channel. Both expressed in millisatoshis.
Time Lock Delta: The number of Bitcoin blocks by which the timelock of incoming HTLCs is extended. A safety margin for on-chain dispute resolution.

Connected Component: A group of nodes where every node can reach every other node through a sequence of channels.
Graph Diameter: The longest shortest path between any two nodes in the connected network. Represents worst-case hop count.
Pareto Distribution: Shows how concentrated the network's capacity is among nodes. Helps assess centralization risk.
Clearnet: Nodes reachable via standard IPv4 or IPv6 internet connections. Faster but exposes IP address.
Tor: Nodes reachable only via the Tor anonymity network (.onion addresses). Better privacy but higher latency.