When using Cisco Expressway for XMPP federation, which platform handles the connection to the remote federation server?

Cisco IM and Presence Server manages internal XMPP sessions and presence subscriptions but does not directly connect to remote federation servers when Expressway is used.

Cisco Unified Communications Manager Publisher performs call control and directory services and plays no role in XMPP federation connectivity.

Cisco Expressway-C handles the internal traversal leg and connects to the IM and Presence Server, but the external connection to the remote federation server is the responsibility of Expressway-E.

Cisco Expressway-E is deployed in the DMZ and serves as the XMPP federation proxy, directly handling all inbound and outbound XMPP federation connections to remote servers outside the organization. It terminates the external TLS connection and relays XMPP traffic inward to Expressway-C and ultimately to the IM and Presence Server.