SessionInitiationCommonQueryParameters

entityID 

URI

The IdP to request authentication from.

target 

absolute URL

The URL to return the user to after authenticating. If unspecified, the homeURL attribute for the application is used.

acsIndex 

string

The index value of the <md:AssertionConsumerService> element to instruct the IdP to use in returning an assertion to the SP

authnContextClassRef 

whitespace-delimited URIs

Requests that particular authentication context classes be used by the IdP.