RLPx Peer Selection Proposal

This is a proposal about how we to select peers using the discovery protocol. It is not implemented yet.

In this strategy the maximum number of active peers is N * 2, where N is configurable and should typically be 5 <= N <= 8.

Finding peers to dial

The 512 bit (256 bit) space is divided into N ranges. The dialer maintains N slots, one for each range.

In order to find peers, it performs a node lookup with a random target in reach range corresponding to an empty slot. The results of the lookup are then dialed. If dialing does not succeed for any node, another random lookup is performed in that range. Dialed addresses should be cached for some amount of time to avoid re-dialing unreachable nodes pointlessly.

Handling incoming connections

Again, the 512 bit (256 bit) space is divided into N ranges. The listener maintains N buckets, one for each range.

For an incoming connection, after the remote identity has been verified in the handshake, the listener should keep the new peer if the corresponding bucket is empty or if the total number of inbound peers is less than N.

When the number of inbound peers reaches N, the new connection replaces a random existing connection from any bucket with more than one entry.