SP Logout, redirecting to the IDP

[Steven Carmody]

On 1/14/15 11:04 AM, Cantor, Scott wrote:
>> Is there any chance that the SP, when it does this redirect, could add
>> an attribute to the redirect url telling the IDP the entityID value of
>> the SP which is doing the redirect to the Logout endpoint ?
>
> No, because I'm not going to duplicate what SAML already supports. You're
> not obligated to implement single logout fully in the IdP, but if you want
> to do logout, that's the way you're meant to pass the message.
>

so... what does an App do to cause an SP to send a SAML Logout msg to an 
IDP, rather than just a redirect ?