Transport. The Layer 4 Transport layer supports the TCP and UDP protocols in the OSI Reference Model. This layer creates an end-to-end transportation between peer hosts. The transmission can be connectionless and unreliable such as UDP, or connection-oriented and ensure error-free delivery such as TCP.
The following answers are incorrect: Network. The Network layer moves information between hosts that are not physically connected. It deals with routing of information. IP is a protocol that is used in Network Layer. TCP and UDP do not reside at the Layer 3 Network Layer in the OSI Reference Model.
Presentation. The Presentation Layer is concerned with the formatting of data into a standard presentation such as ASCII. TCP and UDP do not reside at the Layer 6 Presentation Layer in the OSI Reference Model.
Application. The Application Layer is a service for applications and Operating Systems data transmission, for example HTTP, FTP and SMTP. TCP and UDP do not reside at the Layer 7 Application Layer in the OSI Reference Model.
The following reference(s) were/was used to create this question:
ISC2 OIG, 2007 p. 411 Shon Harris AIO v.3 p. 424

Section: Security Operation Adimnistration
Explanation/Reference:
The security perimeter is the imaginary line that separates the trusted components of the kernel and the Trusted Computing Base (TCB) from those elements that are not trusted. The reference monitor is an abstract machine that mediates all accesses to objects by subjects. The security kernel can be software, firmware or hardware components in a trusted system and is the actual instantiation of the reference monitor. The reference perimeter is not defined and is a distracter.
Source: HARE, Chris, Security Architecture and Models, Area 6 CISSP Open Study Guide, January 2002.

Explanation/Reference:
Electronic vaulting refers to the transfer of backup data to an off-site location. This is primarily a batch process of dumping backup data through communications lines to a server at an alternate location.
Electronic vaulting is accomplished by backing up system data over a network. The backup location is usually at a separate geographical location known as the vault site. Vaulting can be used as a mirror or a backup mechanism using the standard incremental or differential backup cycle. Changes to the host system are sent to the vault server in real-time when the backup method is implemented as a mirror. If vaulting updates are recorded in real-time, then it will be necessary to perform regular backups at the off- site location to provide recovery services due to inadvertent or malicious alterations to user or system data.
The following are incorrect answers:
Remote journaling refers to the parallel processing of transactions to an alternate site (as opposed to a batch dump process). Journaling is a technique used by database management systems to provide redundancy for their transactions. When a transaction is completed, the database management system duplicates the journal entry at a remote location. The journal provides sufficient detail for the transaction to be replayed on the remote system. This provides for database recovery in the event that the database becomes corrupted or unavailable.
Database shadowing uses the live processing of remote journaling, but creates even more redundancy by duplicating the database sets to multiple servers. There are also additional redundancy options available within application and database software platforms. For example, database shadowing may be used where a database management system updates records in multiple locations. This technique updates an entire copy of the database at a remote location.
Data clustering refers to the classification of data into groups (clusters). Clustering may also be used, although it should not be confused with redundancy. In clustering, two or more "partners" are joined into the cluster and may all provide service at the same time. For example, in an active-active pair, both systems may provide services at any time. In the case of a failure, the remaining partners may continue to provide service but at a decreased capacity.
The following resource(s) were used for this question:
Hernandez CISSP, Steven (2012-12-21). Official (ISC)2 Guide to the CISSP CBK, Third Edition ((ISC)2 Press) (Kindle Locations 20403-20407 and 20411-20414 and 20375-20377 and 20280-20283). Auerbach Publications. Kindle Edition.

In response to an access-request from a client, a RADIUS server returns one of three authentication responses: access-accept, access-reject, or access-challenge, the latter being a request for additional authentication information such as a one-time password from a token or a callback identifier. Source: TIPTON, Harold F. & KRAUSE, MICKI, Information Security Management Handbook, 4th Edition, Volume 2, 2001, CRC Press, NY, page 36.

Section: Risk, Response and Recovery
Explanation/Reference:
Risk management consists of two primary and one underlying activity; risk assessment and risk mitigation are the primary activities and uncertainty analysis is the underlying one. After having performed risk assessment and mitigation, an uncertainty analysis should be performed. Risk management must often rely on speculation, best guesses, incomplete data, and many unproven assumptions. A documented uncertainty analysis allows the risk management results to be used knowledgeably. A vulnerability analysis, likelihood assessment and threat identification are all parts of the collection and analysis of data part of the risk assessment, one of the primary activities of risk management.
Source: SWANSON, Marianne & GUTTMAN, Barbara, National Institute of Standards and Technology (NIST), NIST Special Publication 800-14, Generally Accepted Principles and Practices for Securing Information Technology Systems, September 1996 (pages 19-21).