Directory synchronization is a method of managing user accounts when using a third-party cloud-based application and directory solution. Directory synchronization allows the user accounts in the local directory, such as Active Directory, to be automatically synchronized with the user accounts in the cloud directory, such as Azure Active Directory. This way, the users can use the same credentials to access both the local and the cloud resources, and the administrators can manage the user accounts from a single point. Option A, cloud directory, is not a method, but a type of directory service that is hosted in the cloud. Option C, assurance framework, is not related to user account management, but to the evaluation and verification of security controls. Option D, Lightweight Directory Access Protocol (LDAP), is a protocol for accessing and querying directory services, not a method for managing user accounts.

The reverse address resolution protocol (RARP) sends out a packet including a MAC address and a request to be informed of the IP address that should be assigned to that MAC.
Diskless workstations do not have a full operating system but have just enough code to know how to boot up and broadcast for an IP address, and they may have a pointer to the server that holds the operating system. The diskless workstation knows its hardware address, so it broadcasts this information so that a listening server can assign it the correct
IP address.
As with ARP, Reverse Address Resolution Protocol (RARP) frames go to all systems on the subnet, but only the RARP server responds. Once the RARP server receives this request, it looks in its table to see which IP address matches the broadcast hardware address. The server then sends a message that contains its IP address back to the requesting computer. The system now has an IP address and can function on the network.
The Bootstrap Protocol (BOOTP) was created after RARP to enhance the functionality that
RARP provides for diskless workstations. The diskless workstation can receive its IP address, the name server address for future name resolutions, and the default gateway address from the BOOTP server. BOOTP usually provides more functionality to diskless workstations than does RARP.
The evolution of this protocol has unfolded as follows: RARP evolved into BOOTP, which evolved into DHCP.
The following are incorrect answers:
NAT is a tool that is used for masking true IP addresses by employing internal addresses.
ARP does the opposite of RARP, it finds the MAC address that maps with an existing IP address.
Data Link layer The Data Link layer is not a protocol; it is represented at layer 2 of the OSI model. In the TCP/IP model, the Data Link and Physical layers are combined into the
Network Access layer, which is sometimes called the Link layer or the Network Interface layer.
Reference(s) used for this question:
Harris, Shon (2012-10-25). CISSP All-in-One Exam Guide, 6th Edition,
Telecommunications and Network Security, Page 584-585 and also 598. For Kindle users see Kindle Locations 12348-12357. McGraw-Hill.
and
KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten
Domains of Computer Security, John Wiley & Sons, 2001, Chapter 3: Telecommunications and Network Security (page 87).