how we can retrieve SessionId in classMethod ??

Hello Dean White...

Can you please tell me like how we can retrieve SuperSessionID in classMethod ??

Now i want to use SuperSessionID instead of SessionID,  outside the package. 

Also one confirmation that "SessionID keeps same in entire message flow or it varies ?? i heard that SessionID may change in diff instances."

please explain me which ID keep unique (SessionID or SuperSessionID)  ??

I want to filter the message base upon that only...