CDSSO extends single sign-on beyond a single domain. Basic single sign-on uses HTTP cookies within a single DNS domain. In basic single sign-on, the OpenSSO Enterprise server and all policy agent-protected resources reside in the same DNS domain. When a user successfully authenticates to an OpenSSO Enterprise server, an SSO token, represented by an HTTP cookie, is set to the user's browser with the OpenSSO Enterprise DNS domain as the cookie domain. From this point until the session terminates or expires, the browser always presents the SSO token to any server or policy agent in the same DNS domain based on the HTTP protocol. This allows OpenSSO Enterprise and the policy agents to reexamine the validity of the user session and identity, and then enforce security policies without re-authentication. But basic single sign-on cannot be used in environments where OpenSSO Enterprise and its policy agents reside in different DNS domains.
For example, OpenSSO Enterprise and some policy agents may reside in www.domain1.com while some other policy agents reside in www.domain2.com. During authentication to OpenSSO Enterprise, the SSO token is set to the browser with domain1.com as the cookie domain. However, when the browser accesses the resources protected by policy agents in domain2.com, the browser does not present the SSO token to the policy agents. For the policy agents, no SSO token means the user is not authenticated. The policy agents force the user to authenticate. The OpenSSO Enterprise in the appropriate DNS domain sees that the browser does have a valid session SSO token. OpenSSO Enterprise redirects the browser back to the original requested resource in www.domain2.com creating a redirection loop.
To overcome this problem, you can configure the CDSSO feature in the OpenSSO Enterprise server in its policy agents. CDSSO is a mechanism for passing SSO tokens to policy agents protecting resources present in different DNS domains. CDSSO makes it possible for users to authenticate once against OpenSSO Enterprise server in a primary DNS domain, and then access resources protected by the policy agents present in other DNS domains without having to re-authenticate. CDSSO is an OpenSSO Enterprise proprietary mechanism to support single sign-on across multiple domains. Alternatively, you can use standards-based Federation protocols to achieve single sign-on across multiple domains.