most straightforward implementation it does not scale well breaking down the process into tiers allows asynchronous signaling to be used where it optimizes scalability and performance in the first tier of the process fig1 tier 1 steps 1 and 2 a user or subscriber uses the web browser to access a url in which an interface to primary directory is implemented the user requests changes to the service e g changes the 3des encryption key for a vpn tunnel the requested change causes a change in a data entry within the primary directory e g the 3deskey data entry associated with the user 39 s tunnel and through the replication protocol it gets relatively instantaneously replicated in the secondary directory this step creates an illusion of a successful physical implementation of the service change onto the ip network although service changes have not yet been implemented that is the data in the primary directory which models the service settings e g new 3deskey and the actual service settings on the ip network e g the 3deskey stored within the router are out of sync tier 1 is a synchronous process next the data changes which arise from a user 39 s ip service setting changes fig1 tier 2 step 3 are implemented in another secondary directory which is an integral part of das the difference between das as a secondary ldap directory and a standard secondary ldap directory is that das maintains old data as well as new data simultaneously a typical secondary directory immediately overwrites the old data with the new data upon a replication request from the primary ldap server after appropriate filtering of data changes and retrieving additional data from the ldap primary directory associated with the physical devices impacted by the service change das sends.