Different sessions across controllers?

I’m seeing something odd or perhaps not, I really don’t know as I can’t
seem to find any information on this problem. When accessing the
various controlers in my application, I seem to get different session
objects, i.e., the object IDs are different. So, data that I put into
my session in controller A is not present when controller B accesses the
session (as it is a different object). However, on subsequent requests
through controller A, the session is the same and my data is present.
Is there something special you have to do to maintain the same session
between application controllers? I’ve found tons of information on
shutting off the sessions on a per-controller basis, but nothing on
this. Help!