question to user auth and session handling

[tabanaku]

ello,

we want to buy and integrate a vBulletin Forum in our webpage. I didnt find out exactly if vBulletin is supporting our tech requests:

- is there a standard way to implement a module / addon which we program to auth a user (because we have a existing userdatabase)

- can vBulletin handle allready existing Sessions (from main page / main directory) or is its forcing a new session? (especially if a user log in)

If I am using / writing a hack for vBulletin, e. g. a hack for auth the user, is it normally possible to update vBulletin if a patch comes? or must I merge all patches manually to my enhancements?

thank you very much!

regards,

Markus