Hi We can use the iframe in our web app and add tableau url.

have used tableau username and passwords in i frame.

If you are passing these in on the query string, you are approaching single sign on in a very insecure way. Doing what you're doing is very, very dangerous and I wouldn't use this technique if you value the security of your data.

Use Trusted Tickets instead. You can read about this mechanism here:

Trusted Authentication

http://onlinehelp.tableau.com/current/server/en-us/trusted_auth.htm

Thanks

sankar

Hi Murthy -

Users need a license if they use Tableau Server regardless of whether they are presented with a login screen call or not. There really isn't a "free ride" in this regard unless you buy a hardware based license which covers the whole machine vs. a certain number of users. 

That said, you can use SAML or Trusted Tickets for SSO. Both of these techniques are documented in our Help files.

Hope this helps!