Hi Jian,
Yes, this is a "requirement"
System Requirements for Single Sign On
The following single sign on system requirements exist for Cisco Unified Communications Manager:
•
Cisco Unified Communications Manager release 8.5(1) on each server in the cluster
The feature requires the following third-party applications:
•Microsoft Windows Server 2003 or Microsoft Windows Server 2008
•Microsoft Active Directory
•ForgeRock Open Access Manager (OpenAM) version 9.0
The single sign on feature uses Active Directory and OpenAM in combination to provide single sign on access to client applications.
These third party products must meet the following configuration requirements:
•Active Directory must be deployed in a Windows domain-based network configuration, not just as an LDAP server.
•The OpenAM server must be accessible on the network to all client systems and the Active Directory server.
•The Active Directory (Domain Controller) server, Windows clients, Cisco Unified Communications Manager, and OpenAM must be in the same domain.
•DNS must be enabled in the domain.
•No third-party products may be installed on the Cisco Unified Communications Manager server.
•The clocks of all the entities participating in SSO must be synchronized
http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/admin/8_5_1/ccmfeat/fssso.html#wp1419898
Cheers!
Rob
