Good article. An excerpt from a chord paper:

“We also present extensions to the Chord protocol that make it practical in actual systems. These extensions include support for concurrent joins, nodes leaving voluntarily and involuntarily, a high degree of fault tolerance, and minimizingthe network distance that a query travels.

The Chord protocol and its extensions have been implemented in the Chord system. The Chord system uses the Chord primitive to provide a peer-to-peer lookup service that allows applications to insert and update key/value pairs and lookup values for a given key. The implementation is efficient (a single Chord node can process over 10,000 lookups per second) and scales well with the number of nodes (a lookup in a network of 250 nodes travels on average 7 hops).”

Hop: “ In computer networks, a hop is an intermediate connection in a string of connections linking two devices.

Whenever a router or gateway is an intermediary device between two different and remote hosts, nodes or networks, it is known as a hop.”

PoSign - VCN, mutual. The one is the other.