This topic describes how Unified Communications mobile and remote access works.
The figure illustrates the Unified Communications mobile and remote access service discovery on the public network for a Cisco Jabber client in phone-only mode.
The service discovery occurs as follows:
- Cisco Jabber sends a DNS SRV lookup for _cisco-uds._tcp.hq.cisco.com to a public DNS server.
- The public enterprise DNS server that manages hq.cisco.com does not have such an SRV and the lookup fails. Cisco Jabber sends another DNS SRV record lookup for _collab-edge._tls.hq.cisco.com. This time the lookup is successful and the FQDN of the Cisco Expressway Edge server is provided to the Cisco Jabber client in the DNS response.
- The Cisco Jabber client starts the mobile and remote access negotiation with the Cisco Expressway Edge server.
- A certificate is presented to Cisco Jabber and may need to be manually trusted by the user if it is not signed by a CA server that the client PC already trusts. A TLS handshake is exchanged to establish a secure connection.
- When the connection between Cisco Jabber and Cisco Expressway Edge is established, Cisco Jabber tries to register to the services that are enabled on Cisco Expressway Core, which in this case is Cisco Unified Communications Manager.
- Cisco Expressway Core makes a DNS SRV record lookup for _cisco-uds._tcp. _cisco-uds._tcp.hq.cisco.com to the internal DNS server.
- The registration request from Cisco Jabber is then sent to Cisco Unified Communications Manager by the Cisco Expressway Series devices.
Cisco Expressway Edge acts as a proxy for Cisco Jabber. Cisco Expressway Edge passes messages that it receives from Cisco Jabber to Cisco Expressway Core over the firewall traversal connection. Cisco Expressway Core then sends the request to Cisco Unified Communications Manager.