A server is a 1:N node that specializes in maintaining a common persistent store for a number of other nodes, its clients. That number may be 1. In other words, it may have only one client.
A server finding itself the only server to a group of nodes will normally seek to persuade other servers to support the group as well. The less reliable the servers, the larger the number of servers needed.
Storage may be either replicated or shared. If it is replicated, each of the M servers in the group will have identical content. If it is shared, then each server will carry a fraction of the content, with no overlap between servers.
It is expected that servers will often be organized as a separate p2p network that supports the user node-level p2p network, especially where the user-level network is large and long-lived.
It is likely that servers will commonly specialize as certification authorities, usually as one of a group which must jointly sign certificates, generally following a protocol which involves voting. Such specialized servers are consensus nodes.
Throughout this document, the term server will always mean an XLattice server as described in this section, except where otherwise qualified.