The session layer provides a logical persistent connection between peer hosts. Which of the following is one of the modes used in the session layer to establish this connection?
Correct Answer: A
Section: Analysis and Monitoring Explanation/Reference: Layer 5 of the OSI model is the Session Layer. This layer provides a logical persistent connection between peer hosts. A session is analogous to a conversation that is necessary for applications to exchange information. The session layer is responsible for establishing, managing, and closing end-to-end connections, called sessions, between applications located at different network endpoints. Dialogue control management provided by the session layer includes full-duplex, half-duplex, and simplex communications. Session layer management also helps to ensure that multiple streams of data stay synchronized with each other, as in the case of multimedia applications like video conferencing, and assists with the prevention of application related data errors. The session layer is responsible for creating, maintaining, and tearing down the session. Three modes are offered: (Full) Duplex: Both hosts can exchange information simultaneously, independent of each other. Half Duplex: Hosts can exchange information, but only one host at a time. Simplex: Only one host can send information to its peer. Information travels in one direction only. Another aspect of performance that is worthy of some attention is the mode of operation of the network or connection. Obviously, whenever we connect together device A and device B, there must be some way for A to send to B and B to send to A. Many people don't realize, however, that networking technologies can differ in terms of how these two directions of communication are handled. Depending on how the network is set up, and the characteristics of the technologies used, performance may be improved through the selection of performance-enhancing modes. Basic Communication Modes of Operation Let's begin with a look at the three basic modes of operation that can exist for any network connection, communications channel, or interface. Simplex Operation In simplex operation, a network cable or communications channel can only send information in one direction; it's a "one-way street". This may seem counter-intuitive: what's the point of communications that only travel in one direction? In fact, there are at least two different places where simplex operation is encountered in modern networking. The first is when two distinct channels are used for communication: one transmits from A to B and the other from B to A. This is surprisingly common, even though not always obvious. For example, most if not all fiber optic communication is simplex, using one strand to send data in each direction. But this may not be obvious if the pair of fiber strands are combined into one cable. Simplex operation is also used in special types of technologies, especially ones that are asymmetric. For example, one type of satellite Internet access sends data over the satellite only for downloads, while a regular dial-up modem is used for upload to the service provider. In this case, both the satellite link and the dial-up connection are operating in a simplex mode. Half-Duplex Operation Technologies that employ half-duplex operation are capable of sending information in both directions between two nodes, but only one direction or the other can be utilized at a time. This is a fairly common mode of operation when there is only a single network medium (cable, radio frequency and so forth) between devices. While this term is often used to describe the behavior of a pair of devices, it can more generally refer to any number of connected devices that take turns transmitting. For example, in conventional Ethernet networks, any device can transmit, but only one may do so at a time. For this reason, regular (unswitched) Ethernet networks are often said to be "half-duplex", even though it may seem strange to describe a LAN that way. Full-Duplex Operation In full-duplex operation, a connection between two devices is capable of sending data in both directions simultaneously. Full-duplex channels can be constructed either as a pair of simplex links (as described above) or using one channel designed to permit bidirectional simultaneous transmissions. A full-duplex link can only connect two devices, so many such links are required if multiple devices are to be connected together. Note that the term "full-duplex" is somewhat redundant; "duplex" would suffice, but everyone still says "full- duplex" (likely, to differentiate this mode from half-duplex). For a listing of protocols associated with Layer 5 of the OSI model, see below: ADSP - AppleTalk Data Stream Protocol ASP - AppleTalk Session Protocol H.245 - Call Control Protocol for Multimedia Communication ISO-SP OSI session-layer protocol (X.225, ISO 8327) iSNS - Internet Storage Name Service The following are incorrect answers: Synchronous and Asynchronous are not session layer modes. Half simplex does not exist. By definition, simplex means that information travels one way only, so half-simplex is a oxymoron. Reference(s) 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 5603-5636). Auerbach Publications. Kindle Edition. and http://www.tcpipguide.com/free/t_SimplexFullDuplexandHalfDuplexOperation.htm and http://www.wisegeek.com/what-is-a-session-layer.htm
Question 47
Who of the following is responsible for ensuring that proper controls are in place to address integrity, confidentiality, and availability of IT systems and data?
Correct Answer: C
The system and information owners are responsible for ensuring that proper controls are in place to address integrity, confidentiality, and availability of the IT systems and data they own. IT security practitioners are responsible for proper implementation of security requirements in their IT systems. Source: STONEBURNER, Gary et al., NIST Special publication 800-30, Risk management Guide for Information Technology Systems, 2001 (page 6).
Question 48
Which of the following OSI layers provides routing and related services?
Correct Answer: A
The Network Layer performs network routing functions. The following answers are incorrect: Presentation Layer. Is incorrect because the Presentation Layer transforms the data to provide a standard interface for the Application layer. Session Layer. Is incorrect because the Session Layer controls the dialogues/connections (sessions) between computers. Physical Layer. is incorrect because the Physical Layer defines all the electrical and physical specifications for devices.
Question 49
When it comes to magnetic media sanitization, what difference can be made between clearing and purging information?
Correct Answer: B
The removal of information from a storage medium is called sanitization. Different kinds of sanitization provide different levels of protection. A distinction can be made between clearing information (rendering it unrecoverable by a keyboard attack) and purging (rendering it unrecoverable against laboratory attack). There are three general methods of purging media: overwriting, degaussing, and destruction. There should be continuous assurance that sensitive information is protected and not allowed to be placed in a circumstance wherein a possible compromise can occur. There are two primary levels of threat that the protector of information must guard against: keyboard attack (information scavenging through system software capabilities) and laboratory attack (information scavenging through laboratory means). Procedures should be implemented to address these threats before the Automated Information System (AIS) is procured, and the procedures should be continued throughout the life cycle of the AIS. Reference(s) use for this question: 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 (page 26). and A guide to understanding Data Remanence in Automated Information Systems
Question 50
Which protocol is used to send email?
Correct Answer: D
Simple Mail Transfer Protocol (SMTP) is a protocol for sending e-mail messages between servers. POP is a protocol used to retrieve e-mail from a mail server. NFS is a TCP/IP client/server application developed by Sun that enables different types of file systems to interoperate regardless of operating system or network architecture. FTP is the protocol that is used to facilitate file transfer between two machines. Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 88.
