title: Single Sign On across multiple domains
body: <p>Our company has multiple domains set up with one website hosted on each of the domains. At this time, each domain has its own authentication which is done via cookies. </p>
  
  <p>When someone logged on to one domain needs to access anything from the other, the user needs to log in again using different credentials on the other website, located on the other domain. </p>
  
  <p>I was thinking of moving towards single sign on (SSO), so that this hassle can be eliminated. I would appreciate any ideas on how this could be achieved, as I do not have any experience in this regard.</p>
  
  <p>Thanks.</p>
  
  <p><strong>Edit:</strong>
  The websites are mix of internet (external) and intranet (internal-used within the company) sites.</p>