I'm a programmer at my organization, but somehow got drafted into looking into some server stuff so forgive me of my ignorance:

They want to give our sales people secure access to our internal sites using their iPads. This must be secure (obviously) but also revocable from the company's side (if someone quits they can no longer access our network).

I see from http://support.apple.com/kb/HT1288 that the iPad supports "RSA SecurID", "CRYPTOCard", and "Kerberos" authentication methods. Will one of these do what we need? Are there any major differences between them?