Yes. A node can choose any other security model or existing security infrastructure to authenticate a user. This is very similar to local authentication or authorization where users can only access resources provided by a single node. However, in order to perform data exchanges with other nodes in the Network, a Network node must be capable of validating security tokens issued by NAAS. In many situations, a user may simply login at NAAS and then use the obtained security token to conduct data exchanges with other nodes. NAAS simplifies the authentication process and facilitates single sign-on (SSO) in the Exchange Network.