Replay protection prevents an attacker from replaying a license request message and potentially causing a denial-of-service (DoS) attack against the client (A denial-of-service attack is an attempt by attackers to prevent legitimate users of a service from using that service.). For example, a replay attack using the rollback counter could be used to “trick” the License Server into thinking that the DRM client is rolling back its state, causing a suspension of the account.
To learn more about replay protection, see AbstractRequestMessage.getMessageId()
the Adobe Access API Reference.