Cisco Unified Personal Communicator release 8.5(2) can use DNS SRV lookup to automatically find the IM and Presence server in the client's Active Directory domain. Automatic discovery of a user’s home node is achieved through a combination of DNS lookup and the login redirect feature on IM and Presence. For more information about the redirect feature, see Cisco Unified Personal Communicator sign-in and redirect.
The DNS SRV records details about a particular service on a network. A DNS administrator can map many hosts to the same service name. It is also possible for a DNS administrator to provide load balancing by enabling the round robin option on their DNS server. This ensures that a different server is returned each time an SRV request is made.
A prerequisite of
Cisco Unified Personal Communicator being able to perform DNS SRV lookups is that an administrator adds a DNS SRV record for the service name _cuplogin in the DNS server based on the IM and Presence server domain name.
The example below assumes the service name to be _cuplogin and the IM and Presence server domain name to be company.com. In this case, the SRV record defined within the DNS server catering to the domain company.com would be _cuplogin._tcp.company.com. This is an example of a DNS SRV query.
_cuplogin._tcp.company.com SRV service location:
srv hostname =cupserver.company.com
internet address =10.53.56.57
Cisco Unified Personal Communicator does not use the port mapped in the SRV record. Port 8443 is the default port used.
The DNS SRV record on
Cisco Unified Personal Communicator is populated automatically by
Cisco Unified Personal Communicator based on the service name and the domain name (connection specific suffix if not Active Directory domain) used by the user upon login.
For example, if the user and IM and Presence node have the same domain name, <company>.com, the IM and Presence node address is cupserver.company.com. The administrator defines the SRV record as _cuplogin._tcp.company.com within the enterprise resolving to cupserver.company.com.
Cisco Unified Personal Communicator release 8.5(2) automatically populates the SRV record _cuplogin._tcp.company.com to perform an SRV lookup. If the user logs into a domain different from the IM and Presence domain, you must follow the steps in Location of registry key.
When using the DNS SRV feature,
Cisco Unified Personal Communicator release 8.5(2) and later uses the following logic:
Cisco Unified Personal Communicator looks up the IM and Presence node address within its local cache. Note that the local cache only exists if the user logged into IM and Presence successfully at least once.
If the IM and Presence node address can not be retrieved from the local cache, the local registry is checked. The registry may contain either a host address or a domain hint.
If the local registry does not have an address,
Cisco Unified Personal Communicator does a DNS SRV query. If the DNS SRV query fails, a DNS A query is performed.
After a successful login,
Cisco Unified Personal Communicator ensures that the IM and Presence node address is used for subsequent logins. If a user’s home node is different IM and Presence node, the original IM and Presence node is capable of redirecting
Cisco Unified Personal Communicator to the uses’s home IM and Presence node. Successful login will result in
Cisco Unified Personal Communicator updating the local cache with the new node address so that redirect only happens once.
Steps 2 through 4 above only apply to first-time logins and rare cases.