Systems

Internal subsystems that make up the Consul runtime. The agent and server share most of these; a handful are server-only.

System	Role	Server-only?
Agent runtime	The central Agent struct, HTTP/DNS, local state, anti-entropy	No
Server and Raft	Raft consensus, FSM, MemDB state store, RPC endpoints, leader loops	Yes
DNS interface	DNS server that answers service and node queries	No (runs on agents)
xDS server	Translates proxy snapshots into Envoy resources via delta-xDS	No (runs on agents)
Proxy config (proxycfg)	Builds per-proxy ConfigSnapshots from the catalog, intentions, and config entries	No
Connect CA	Root CA + leaf certificate issuance for service mesh identity	Mostly server (CA) + cache on agents
Cluster peering	Newer cross-cluster connectivity model (alternative to WAN federation)	Yes (control plane)
Gossip and federation	Serf-based LAN/WAN gossip, federation state replication	Both
Auto-config and auto-encrypt	Bootstrap protocols that distribute initial config and TLS to client agents	Server issues, agents consume
V2 resource framework	Generic resource/controller machinery powering catalog v2, multicluster, etc.	Yes (server hosts the resource service)
Streaming and materialized views	gRPC streaming subscribe + materialized-view caches	Server publishes; agents subscribe

For user-visible capabilities, see Features. For the public Go modules and protobuf packages, see Packages.