/mcpDirectory integration To enable users to search contacts and dial from the directory, integrate Cisco Unified CM with the organization's LDAP directory. Although Unified CM allows the creation of local user contacts, LDAP directory integration is required when using Cisco Jabber because it provides a single location for directory management and enables users to authenticate to Cisco Unified CM and Cisco Jabber by using their LDAP directory credentials. Cisco Unified CM pulls user and contact information from LDAP directories and synchronizes user parameters – name, surname, username, telephone number, and SIP URI – when changes occur. The IM and Presence Service pulls user and contact information from Cisco Unified CM. Classes of service Classes of service define which users can access which services, such as allowing only emergency and local calls from lobby phones while allowing unrestricted calls from executive phones. The complexity of the dial plan is directly related to the number of differentiated classes of service it supports. To define classes of service, configure partitions and calling search spaces in Cisco Unified CM. The number of classes of services supported by a dial plan depends on the granularity and complexity of the classes. For more information about classes of service and details on enterprise dial plan design, see the Cisco Collaboration SRND Dial Plan chapter. Multi-Cluster Deployment Considerations Consider deploying more than one Cisco Unified CM cluster (and Unified CM IM&P cluster) if you have any of the following requirements: • Administrative separation — This includes the need to keep users from different parts of the organization on separate infrastructures, or the requirement to have different departments operate different parts of the communications infrastructure. • Geographic footprint — Technical limitations such as excessive propagation delay might prohibit endpoint registrations (for example, endpoints in Asia registering to an enterprise call control hosted in the US). In a multi-cluster deployment, interconnect all the individual Unified CM clusters through SIP trunks. To avoid session traversal through individual clusters, deploy a full mesh of SIP trunks. With four or more clusters, deploy Cisco Unified CM Session Management Edition to centralize the dial plan and trunking and to avoid the complexity of a full-mesh SIP trunk topology. In multi-cluster deployments, use Global Dial Plan Replication (GDPR) to replicate dial plan information between clusters. GDPR can advertise a +E.164 number, one enterprise significant number (ESN), and up to five alpha- numeric URIs per directory number. An ESN is the abbreviated inter-site dialing equivalent of a directory number. The information advertised and learned through GDPR enables deterministic intercluster routing for these dialing habits: • +E.164 dialing based on the advertised +E.164 numbers • Enterprise abbreviated inter-site dialing based on the advertised ESNs • Alpha-numeric URI dialing based on the advertised URIs • PSTN dialing based on normalization to +E.164