Ethernet frames are identified at the data link layer by their MAC addresses, which
are unique to each NIC. IP addresses are used at the network layer, and TCP and UDP port
numbers are used at the transport layer. Sequence numbers are fields in TCP headers.
17. What attribute of a NIC would place it at the data link layer of the OSI model?
The data link layer describes media access and physical addressing. The encoding
of a MAC address on a NIC places it at that layer. Ports and cables are placed at the physical
layer of the OSI model. IP addresses are placed at the network layer. The TCP/IP protocol stack
describes a different model.
18. Which two engineering organizations define open standards and protocols that apply to the data
link layer? (Choose two.)
A. Internet Society (ISOC)
B. International Telecommunication Union (ITU)
C. Institute of Electrical and Electronics Engineers (IEEE)
The IANA is responsible for overseeing and managing IP address allocation,
domain name management, and protocol identifiers. The EIA is an international standards and
trade alliance for electronics organizations, and is best known for its standards related to
electrical wiring, connectors, and the 19-inch racks used to mount networking equipment. IEEE
defines open standards and protocols that apply to the network access layer.
19. What is true concerning physical and logical topologies?
A. Physical topologies display the IP addressing scheme of each network.
B. Physical topologies are concerned with how a network transfers frames
C. The logical topology is always the same as the physical topology.
D. Logical topologies refer to how a network transfers data between devices.
Carrier sense multiple access with collision avoidance (CSMA/CA) is used with
wireless networking technology to mediate media contention. Carrier sense multiple access with
collision detection (CSMA/CD) is used with wired Ethernet technology to mediate media
contention. Priority ordering and token passing are not used (or not a method) for media access
21. A technician has been asked to develop a physical topology for a network that provides a high
level of redundancy. Which physical topology requires that every node is attached to every other
node on the network?
The mesh topology provides high availability because every node is connected to
all other nodes. Mesh topologies can be found in WANs. A partial mesh topology can also be
used where some, but not all, end points connect to one another.
22. Which statement describes the half-duplex mode of data transmission?
A. Data that is transmitted over the network flows in one direction to many different destinations simultaneously.
B. Data that is transmitted over the network flows in one direction at a time.
C. Data that is transmitted over the network flows in both directions at the same time.
D. Data that is transmitted over the network can only flow in one direction.
The data that is transmitted over the network can flow using one of three modes:
o Simplex – Data can only flow in one direction.
o Half-duplex – Data flows in one direction at a time.
o Full-duplex – Data flows in both directions at the same time.
23. Which is a function of the Logical Link Control (LLC) sublayer?
A. To provide data link layer addressing
B. To identify which network layer protocol is being used
C. To define the media access processes that are performed by the hardware
D. To accept segments and package them into data units that are called packets
Defining the media access processes that are performed by the hardware and
providing data link layer addressing are functions of the MAC sublayer. The data link layer
accepts Layer 3 packets and packages them into data units that are called frames.
24. Which data link layer media access control method does Ethernet use with legacy Ethernet hubs?
The data link layer is responsible for the exchange of frames between nodes over a
physical network media. Specifically the data link layer performs two basic services:
o It accepts Layer 3 packets and encapsulates them into frames.
o It provides media access control and performs error detection.
Path determination is a service provided at Layer 3. A Layer 2 switch builds a MAC address
table as part of its operation, but path determination is not the service that is provided by the data
29. Although CSMA/CD is still a feature of Ethernet, why is it no longer necessary?
A. The use of Gigabit Ethernet speeds
B. The virtually unlimited availability of IPv6 addresses
C. The use of full-duplex capable Layer 2 switches
D. The use of CSMA/CA
E. The development of half-duplex switch operation