Unique session shibboleth and CAS

[Peter Schober]

* samir el otmani <elotmani.samir at gmail.com> [2015-01-15 16:59]:
> what about the SP session , it's keeped even if the IDP ask always
> the CAS .

I don't know what exactly you're asking.
I also don't know anything about CAS.
If the SP is assumed to be a SAML SP, e.g. the Shibboleth SP software,
then yes, the SP will establish a session (referenced in the web
browser as an HTTP Cookie) after processing the SAML assertion
recieved from the IDP. That session has a certain lifetime and an
inactivity timeout. The SP does /not/ send the web browser to the IDP
on every single interaction, as this would severely disrupt any kind
of usage of the web resource.
So the SP has a session, and the applicaton protected by the SP
probably has one too.

I don't see how this relates to your choice remoting authentication
from your Shib IDP to your CAS IDP.

Does this help?
https://wiki.shibboleth.net/confluence/display/SHIB2/FederatedSessionManagement

-peter