Redirect User without asking for IdP.

[Peter Schober]

* Saurabh Tyagi <saurabh.tyagi at thepsi.com> [2013-07-15 13:08]:
> If I write some kind of parameter(Idp's EntityId) in URL while
> accessing the application which is behind sp.

You either have to do IdP discovery (i.e., asking the subject) or make
up things that allow you to "sidestep" discovery. (While possible I'd
steer clear of automating selection of the IdP based on the HTTP User
Agent's IP address, as the subject may want to select another IdP.)

The latter usually involves giving specially crafted links (or
resources at your server) to the institution, which will always
initiate a session with that institution's IDP, e.g. using the
requireSessionWith content setting.
https://wiki.shibboleth.net/confluence/display/SHIB2/NativeSPContentSettings

Such constructs are sometimes called "WAYFless URLs" since accessing
those does not (visibly) invoke a WAYF ("Where Are You From", what is
now standardized as "IdP discovery") service.

Much of that depends on how sessions are initiated, wheather active or
lazy protection is being used, etc.

> Can I access that parameter at Embedded Discovery Service  side?

If you already know the IdP's entityID you don't need the EDS. You
just pass it to your SP's Login handler.
-peter