In order to prevent conflicts between any two endpoints, uniqueness is guaranteed by comparing the public keys of their agreed upon cipher set.
The binary value of each endpoint's public key is compared and they are placed in high-to-low sorted order.
To achieve this the two public keys can be visited bit by bit, the first key that at a given position has a 1 (higher) where the other has a 0 (lower) is the one that has higher order.
Based on this comparison the two are labeled as ODD (high) endpoint and an EVEN (low) endpoint.
This mechanism ensures that that both endpoints will mutually agree on their label consistently and without communication.