_idp_session with idp

[MA Lanxin]

Hello,

I have a questiona about session at IdP side.

According to the page
https://wiki.shibboleth.net/confluence/display/SHIB2/IdPCookieUsage

Once a user has been authenticated they will have a long-lived session with the IdP which is tracked by a cookie named _idp_session. This cookie contains only information necessary for identifying the user's IdP session. This cookie is created a "session" cookie.

My question is:
Does the session(_idp_session) with IDP use tomcat session or http session?
Can we see the seesionID? If yes, How can we get the session ID?

Thanks a lot,

REgards,
Lanxin