3.3.5.1.2 Parameter Marshaling

A resource IP/STS that sends a wsignin1.0 request message to a security token service in a different security realm MUST set the wtrealm parameter, as specified in Common Syntax for Request Messages (section 2.2.1). A WS resource that sends a wsignin1.0 request message to a security token service in the same security realm cannot use the wtrealm parameter. It MAY use the wreply parameter to distinguish itself from other WS resources in the security realm.<74>