Internal
Phone Services are provisioned by the administrator, and the IP phone receives its list of configured services from its configuration file that is downloaded through TFTP during the registration cycle. The Services, Messages, and Directories URLs specified in the phone URL enterprise parameters are not used. Any valid Java MIDlet services that are provisioned will be installed and available to run. This is the default setting. With this setting, IP phones no longer need to contact the IP Phone Service first to receive their list of configured services. Instead they can directly proceed to access the desired service.
External URL
Phone Services are not provisioned in the configuration file obtained via TFTP. The phone uses only the Phone Services URLs specified in the Phone URL enterprise parameters. Java MIDlets will not run because they must be provisioned internally to install and execute. This behavior is identical to pre-7.0 releases of Unified CM.
Both
Any Phone Services provisioned in the configuration file will appear first, followed by any services dynamically retrieved via the corresponding URL when the Services, Messages, or Directories button is pressed on the IP phone. Any Java MIDlets provisioned in the configuration file will be installed and available to run.
With Services Provisioning set to Internal, the phone will receive its subscribed phone services from the phone's configuration file and store these (and their corresponding service URLs) in flash. This allows the phone to access the service URLs directly on a web server without first querying the Cisco CallManager IP Phone Service. With Services Provisioning set to Internal, the Corporate and Personal Directories default services also have an extra level of redundancy built into the phones. When these services are selected, the phone will attempt to send an HTTP message with the proper URL string to the Unified CM with which it is currently registered. Therefore, the Unified CM Group configuration of the phone's device pool provides redundancy for these services. What this means is that when the phone registers with secondary CM server provided in the CM group, then at the same time it also gets subscribed phone services from the phone's configuration file and store these (and their corresponding service URLs) in flash and keep continuing to work.
Regards
Deepak
