Ethernet bus topology was the first commercially viable network
topology, and consists of all workstations connected to a single coaxial cable. Since the cable must be properly terminated on both ends, a break in the cable stops all communications on the bus.
* the physical star topology acts like a logical bus, but provides better fault tolerance, as a cable break only disconnects the workstation or hub directly affected.
* logical ring topology, is used by Token Ring and FDDI and is highly resilient. Token Ring employs a beacon frame, which, in case of a cable break, initiates auto reconfiguration and attempts to reroute the network around the failed mode. Also, the Token Ring active monitor station performs ring maintenance
functions, like removing continuously circulating frames from the
ring. FDDI employs a second ring to provide redundancy. Sources:
Virtual LANs by Mariana Smith (McGraw-Hill, 1998) and Internetworking
Technologies Handbook, Second Edition (Cisco Press, 1998).

The goal of a noninterference model is to strictly separate differing security levels to assure that higher-level actions do not determine what lower-level users can see. This is in contrast to other security models that control information flows between differing levels of users, By maintaining strict separation of security levels, a noninterference model minimizes leakages that might happen through a covert channel.
The Bell-LaPadula model is incorrect. The Bell-LaPadula model is concerned with confidentiality and bases access control decsions on the classfication of objects and the clearences of subjects.
The information flow model is incorrect. The information flow models have a similar framework to the Bell-LaPadula model and control how information may flow between objects based on security classes.
The Biba model is incorrect. The Biba model is concerned with integrity and is a complement to the Bell-LaPadula model in that higher levels of integrity are more trusted than lower levels. Access control us based on these integrity levels to assure that read/write operations do not decrease an object's integrity.
References: CBK, pp 325 - 326 AIO3, pp. 290 - 291

Explanation/Reference:
Explanation:
PPP (Point-to-Point Protocol) is a data link protocol used to establish a direct connection between two nodes. PPP has replaced the older SLIP and CSLIP protocols.
Incorrect Answers:
B: SLIP, CSLIP, and PPP all work at the data link layer, not at the transport layer.
C: SLIP, CSLIP, and PPP all work at the data link layer, not at the presentation layer.
D: SLIP, CSLIP, and PPP all work at the data link layer, not at the application layer.
References:
Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, New York, 2013, p. 683