Duplicate Message

The message sequence number is a monotonically increasing number that is unique among messages originating from a peer. No two messages from the same peer have the same sequence number.

However, messages from different peers can have the same sequence number, so this number alone cannot be used to uniquely identify a message. A peer id is unique, so the unique message ID is the concatenation of the message author id and sequence number fields.

Maintaining a list of all message IDs seen by the peer is not scalable. A timed cached is used to detect duplicate messages seen in the last the 10 minutes.