Research on the introduction of e-mail shows that some employees get more influence and other employees get less influence than before. Mention some common uses of such encryption techniques. The same key can be used for letters to a certain recipients from different senders. Transfer of symmetric encryption keys, identification, digital signatures, digital seals. Describe which units communicate which objects in the two sub-layers of X.400.
Higher layers communicate with higher layers indirectly through the lower layers.
Mention also a functionality which can make name servers more efficient by reducing the number of necessary interconnections. Name servers can call each other and can cache the answers they get, so that a new question for the same domain name can be answered more rapidly.