Mod6

Question 1

What is the core responsibility of the Data Link Layer (Layer 2) in the OSI model?

A) To provide logical addressing and path determination between different networks.
B) To manage the conversion of data into electrical, radio, or light signals.
C) To prepare network data for the physical network and handle NIC-to-NIC communications.
D) To establish, manage, and terminate sessions between applications.

Answer 1

C) To prepare network data for the physical network and handle NIC-to-NIC communications.

Explanation: The text states that the data link layer “prepares network data for the physical network” and is “responsible for network interface card (NIC) to network interface card communications.” This defines its primary scope as local delivery on the same network segment.

Question 2

What does the Data Link Layer encapsulate Layer 3 packets into?

A) Segments
B) Datagrams
C) Frames
D) Packets

Answer 2

C) Frames

Explanation: The text explicitly says the data link layer “accepts data, usually Layer 3 packets (i.e., IPv4 or IPv6), and encapsulates them into Layer 2 frames.” The frame header contains information like the source and destination MAC addresses.

Question 3

How does the Data Link Layer enable upper layers to be independent of the physical media used?

A) By encrypting all data before transmission.
B) By converting IP addresses to MAC addresses.
C) By handling all media-specific preparation, so upper layers don’t have to.
D) By routing packets based on the media type.

Answer 3

C) By handling all media-specific preparation, so upper layers don’t have to.

Explanation: The text notes that a key function is to “enable upper layers to access the media.” It clarifies that “The upper layer protocol is completely unaware of the type of media that is used,” because the Data Link Layer handles all the details of placing data onto that specific media (e.g., Ethernet, Wi-Fi).

Question 4

What action does the Data Link Layer take when it receives a corrupt frame?

A) It corrects the errors using the Frame Check Sequence.
B) It forwards the frame to a router for correction.
C) It performs error detection and rejects the corrupt frame.
D) It passes the frame up to the Network Layer for handling.

Answer 4

C) It performs error detection band rejects the corrupt frame.

Explanation: The text lists “Performs error detection and rejects any corrupt frame” as a core function. It uses the Frame Check Sequence (FCS) trailer to detect errors. It does not correct them; it simply discards bad frames.

Question 5

Over what scope does the Data Link Layer exchange frames?

A) Between endpoints over the network media.
B) From the original source host to the final destination host anywhere on the internet.
C) Only between routers.
D) Only between switches on the same network.

Answer 5

A) Between endpoints over the network media.

Explanation: The text states the data link layer “exchanges frames between endpoints over the network media.” This emphasizes its role in the local delivery of data between devices on the same network segment (like between a PC and a switch, or between two switches).

Question 6

After creating the frame, what is the final step the Data Link Layer takes to prepare the data for transmission?

A) It routes the frame to the final destination.
B) It converts the frame into a format supported by the Physical Layer.
C) It encrypts the frame for security.
D) It forwards the frame to the Transport Layer.

Answer 6

B) It converts the frame into a format supported by the Physical Layer.

Explanation: The text concludes the process by stating the data link layer then “convert[s] this information to a format supported by the physical layer (i.e., Layer 1).” This means it prepares the bits for transmission as electrical, optical, or radio signals.

Question 7

What specific addressing information does the Data Link Layer add to a Layer 3 packet to create a frame?

A) Source and Destination IP addresses.
B) Source and Destination port numbers.
C) Source and Destination NIC (MAC) addresses.
D) Source and Destination hostnames.

Answer 7

C) Source and Destination NIC (MAC) addresses.

Explanation: The text describes the encapsulation process: “the data link layer adds Layer 2 Ethernet destination and source NIC information to a Layer 3 packet.” This NIC information is the MAC address, which is used for local delivery on the network segment.

Question 8

According to the text, what would be a consequence for IP if a new network technology were developed and there was no Data Link Layer?

A) The new technology would be automatically compatible with all existing devices.
B) IP would have to be adapted to work with the new technology.
C) The new technology would be unable to connect to the internet.
D) The Data Link Layer would automatically update itself.

Answer 8

B) IP would have to be adapted to work with the new technology.

Explanation: The text states that without the data link layer, “every time a new network technology or medium was developed, IP would have to adapt.” The data link layer prevents this by providing a consistent interface for IP, making the network stack more modular and flexible.

Question 9

What major problem does the Data Link Layer solve for upper-layer protocols like IP?

A) It provides global logical addressing.
B) It handles the physical connection to every type of media, so IP doesn’t have to.
C) It encrypts data to ensure secure transmission.
D) It establishes sessions between applications.

Answer 9

B) It handles the physical connection to every type of media, so IP doesn’t have to.

Explanation: The text explains that without the data link layer, network layer protocols like IP “would have to make provisions for connecting to every type of media.” The data link layer acts as an abstraction layer, allowing IP to work the same way over Ethernet, Wi-Fi, or any other media.

Question 10

In a computer network, what is a “node”?

A) A device that can only create or receive data.
B) A device that can receive, create, store, or forward data along a path.
C) Only the end devices like laptops and servers.
D) Only the intermediary devices like routers and switches.

Answer 10

B) A device that can receive, create, store, or forward data along a path.

Explanation: The text provides a broad definition: a node is “a device that can receive, create, store, or forward data along a communications path.” This definition correctly includes both end devices (laptops, phones) and intermediary devices (switches, routers).

Question 11

Which IEEE standard defines the MAC sublayer for a traditional Ethernet LAN?

A) IEEE 802.2
B) IEEE 802.11
C) IEEE 802.3
D) IEEE 802.1

Answer 11

C) IEEE 802.3

Explanation: The text provides examples, noting that the MAC sublayer is implemented in standards like “IEEE 802.3, 802.11, or 802.15.” IEEE 802.3 is the standard for Ethernet (wired) LANs.

Question 12

What are the two primary responsibilities of the MAC sublayer?

A) Session management and data encryption.
B) Data encapsulation and media access control.
C) Logical addressing and path determination.
D) Protocol identification and error recovery.

Answer 12

B) Data encapsulation and media access control.

Explanation: The text clearly lists the MAC sublayer’s core duties: “It is responsible for data encapsulation and media access control.” Encapsulation involves framing, and media access control involves methods like CSMA/CD or CSMA/CA.

Question 13

How is the Media Access Control (MAC) sublayer typically implemented?

A) As software in the operating system.
B) In hardware on the network interface card (NIC).
C) As a cloud-based service.
D) In the router’s configuration file.

Answer 13

B) In hardware on the network interface card (NIC).

Explanation: The text specifies that the MAC sublayer is “implemented… in hardware.” This is why it’s often associated directly with the physical NIC, allowing for high-speed, low-level frame handling.

Question 14

How does the LLC sublayer allow a single network interface to be used by multiple Network Layer protocols (like IPv4 and IPv6)?

A) By assigning a unique MAC address for each protocol.
B) By encrypting the data from each protocol differently.
C) By placing information in the frame that identifies the Network Layer protocol being used.
D) By routing packets based on their size.

Answer 14

C) By placing information in the frame that identifies the Network Layer protocol being used.

Explanation: The text explains that the LLC “places information in the frame that identifies which network layer protocol is being used for the frame.” When the receiving device gets the frame, the LLC reads this information to determine which Network Layer protocol (e.g., the IPv4 stack or IPv6 stack) should receive the data.

Question 15

What is the primary role of the Logical Link Control (LLC) sublayer?

A) To control access to the physical media.
B) To provide data link layer addressing.
C) To communicate between upper-layer software and lower-layer hardware.
D) To convert data into electrical signals.

Answer 15

C) To communicate between upper-layer software and lower-layer hardware.

Explanation: The text defines the LLC as the sublayer that “communicates between the networking software at the upper layers and the device hardware at the lower layers.” It acts as a translator or interface between the Network layer and the media-specific hardware.

Question 16

What types of networks are defined by the IEEE 802 LAN/MAN standards?

A) Only Ethernet wired networks.
B) Only wireless local area networks (WLAN).
C) Only Wide Area Networks (WAN).
D) Various types, including Ethernet LANs, WLANs, and wireless personal area networks (WPAN).

Answer 16

D) Various types, including Ethernet LANs, WLANs, and wireless personal area networks (WPAN).

Explanation: The text states that the IEEE 802 standards are specific to “Ethernet LANs, wireless LANs (WLAN), wireless personal area networks (WPAN) and other types of local and metropolitan area networks.” This shows it’s a broad family of standards for local networking.

Question 17

What is the primary function of the LLC sublayer regarding a network packet?

A) It controls the NIC hardware directly.
B) It adds Layer 2 control information to help deliver the packet.
C) It provides source and destination MAC addressing.
D) It converts the packet into electrical signals.

Answer 17

B) It adds Layer 2 control information to help deliver the packet.

Explanation: The text states that the LLC “takes the network protocol data… and adds Layer 2 control information to help deliver the packet.” This control information is used to manage the flow of data and identify the upper-layer protocol.

Question 18

What hardware component does the MAC sublayer directly control?

A) The CPU and system RAM
B) The hard drive and storage controller
C) The Network Interface Card (NIC)
D) The monitor and graphics card

Answer 18

C) The Network Interface Card (NIC)

Explanation: The text explicitly says the “MAC sublayer controls the NIC and other hardware that is responsible for sending and receiving data.” This is consistent with its implementation in hardware.

Question 19

What is the purpose of “frame delimiting” performed by the MAC sublayer?

A) To encrypt the data payload for security.
B) To identify fields within a frame and provide synchronization between nodes.
C) To assign a unique IP address to the frame.
D) To compress the data to save bandwidth.

Answer 19

B) To identify fields within a frame and provide synchronization between nodes.

Explanation: The text explains that frame delimiting provides “important delimiters to identify fields within a frame” and that these bits provide “synchronization between the transmitting and receiving nodes,” ensuring they agree on where the frame starts and ends.

Question 20

The addressing provided by the MAC sublayer is used for transporting frames between devices on what scope?

A) Between any two devices on the global internet.
B) Between devices on different IP subnets.
C) Between devices on the same shared medium (local network).
D) Between an application and a server.

Answer 20

C) Between devices on the same shared medium (local network).

Explanation: The text specifies that MAC addressing provides “source and destination addressing for transporting the Layer 2 frame between devices on the same shared medium.” This highlights the local nature of Layer 2 communication.

Question 21

When is media access control provided by the MAC sublayer NOT required?

A) When communicating over a wireless LAN (WLAN).
B) When using a legacy hub-based network.
C) During full-duplex communications.
D) When using half-duplex communications.

Answer 21

C) During full-duplex communications.

Explanation: The text concludes by stating that media access control is for “multiple devices to communicate over a shared (half-duplex) medium,” and explicitly notes that “Full-duplex communications do not require access control.” In full-duplex, a dedicated channel eliminates the need for contention protocols.

Question 22

Why do different network environments require different Data Link Layer handling?

A) Because all networks use the same type of cables.
B) Because each environment can have different characteristics, like the number of devices contending for access.
C) Because the Network Layer packet changes at every hop.
D) Because routers can only process one type of frame.

Answer 22

B) Because each environment can have different characteristics, like the number of devices contending for access.

Explanation: The text begins by stating that “each network environment… can have different characteristics,” using the example of a busy Ethernet LAN versus a simple two-device serial link. This variability is why the Data Link Layer must adapt.

Question 23

What is the purpose of the MAC sublayer in a network like an Ethernet LAN?

A) To provide a direct connection between two routers.
B) To resolve contention when many hosts are competing for access to the network medium.
C) To assign IP addresses to end devices.
D) To encrypt data for secure transmission.

Answer 23

B) To resolve contention when many hosts are competing for access to the network medium.

Explanation: The text directly states that in a multi-host Ethernet environment, “The MAC sublayer resolves this” contention for access. It manages how devices share the medium to prevent collisions (in half-duplex) or coordinates transmission.

Question 24

Why does a serial link between two routers NOT require complex MAC techniques like CSMA/CD?

A) Because serial links are much faster than Ethernet.
B) Because it consists of a direct connection between only two devices with dedicated access.
C) Because routers do not have MAC addresses.
D) Because serial links use a different version of IP.

Answer 24

B) Because it consists of a direct connection between only two devices with dedicated access.

Explanation: The text contrasts Ethernet with serial links, noting that serial links “consist of a direct connection between only two devices.” There is no contention because the link is dedicated, eliminating the need for access control methods.

Question 25

What is the second step a router performs at each hop when processing a frame? A) Forwards the new frame onto the medium. B) Accepts the frame from the incoming medium. C) De-encapsulates the frame to extract the packet. D) Re-encapsulates the packet into a new frame.

Answer 25

C) De-encapsulates the frame to extract the packet. Explanation: The text lists the router's Layer 2 functions in order. Step 2 is to "De-encapsulates the frame." This means it strips off the Layer 2 header and trailer to get to the Layer 3 packet inside, which is the PDU that needs to be routed.

Question 26

Why must a router re-encapsulate a Layer 3 packet into a new Layer 2 frame at each hop? A) To change the source and destination IP addresses. B) Because the original frame is always corrupted during transmission. C) To make the packet appropriate for the medium of the next network link. D) To increase the transmission speed of the packet.

Answer 26

C) To make the packet appropriate for the medium of the next network link. Explanation: The text explains that the router forwards the new frame in a way that is "appropriate to the medium of that segment of the physical network." Each link (e.g., Ethernet, serial) may require a different frame type with its own specific addressing and structure.

Question 27

In a journey from a local host to a remote host, how many data link layers and frames are typically involved? A) One data link layer and one frame for the entire journey. B) Two data link layers: one for the LAN and one for the WAN. C) Numerous data link layers and media transitions; a new frame for each link. D) The same frame is used by all routers along the path.

Answer 27

C) Numerous data link layers and media transitions; a new frame for each link. Explanation: The text emphasizes that "in any given exchange... there may be numerous data link layers and media transitions." This is a key concept: the Layer 3 packet is carried end-to-end, but it is encapsulated in a new Layer 2 frame for each individual physical link along the path.

Question 28

How are Data Link Layer protocols typically defined, unlike upper-layer TCP/IP protocols? A) They are defined by the IETF in Request for Comments (RFCs). B) They are generally not defined by RFCs, but by other engineering organizations. C) They are defined by the World Wide Web Consortium (W3C). D) Each vendor defines their own proprietary standards.

Answer 28

B) They are generally not defined by RFCs, but by other engineering organizations. Explanation: The text makes a clear distinction, stating that "data link layer protocols are generally not defined by Request for Comments (RFCs), unlike the protocols of the upper layers of the TCP/IP suite." This is a fundamental difference in how these layers are standardized

Question 29

What is the scope of the protocols and services maintained by the Internet Engineering Task Force (IETF)? A) They define the functional protocols for the entire TCP/IP suite, including the network access layer. B) They maintain the functional protocols and services for the upper layers of the TCP/IP suite. C) They are responsible for defining international electrical safety standards. D) They standardize the operation of all Layer 1 and Layer 2 technologies.

Answer 29

B) They maintain the functional protocols and services for the upper layers of the TCP/IP suite. Explanation: The text specifies that the IETF maintains protocols for the "upper layers," but explicitly states "they do not define the functions and operation of the TCP/IP network access layer." The IETF focuses on layers 3 and above.

Question 30

Which of the following organizations is responsible for defining standards like Ethernet (802.3) and Wi-Fi (802.11)? A) International Telecommunication Union (ITU) B) Institute of Electrical and Electronics Engineers (IEEE) C) American National Standards Institute (ANSI) D) International Organization for Standardization (ISO)

Answer 30

B) Institute of Electrical and Electronics Engineers (IEEE)  Explanation: While all listed organizations are involved in standardization, the IEEE is the primary body that defines the 802 series of standards, which include Ethernet (802.3) and Wi-Fi (802.11) at the physical and data link layers.

Question 31

The engineering organizations listed (IEEE, ITU, ISO, ANSI) define standards that apply to which part of the networking model? A) The TCP/IP application layer (e.g., HTTP, DNS). B) The TCP/IP network access layer (OSI physical and data link layers). C) Only the network layer (IP). D) Only the physical cabling and connectors.

Answer 31

B) The TCP/IP network access layer (OSI physical and data link layers). Explanation: The text states that these organizations "define open standards and protocols that apply to the network access layer (i.e., the OSI physical and data link layers)." This is the layer responsible for local network connectivity and hardware.

Question 32

Which organization's logo is known for its stylized name and is associated with standards for everything from film speed to quality management, in addition to networking? A) IEEE B) ITU C) ISO D) ANSI

Answer 32

C) ISO Explanation: While not explicitly stated in the text, this is a key fact. The International Organization for Standardization (ISO) is widely recognized for standards like ISO 9001 (quality management) and, crucially, it co-developed the OSI model with the ITU. Its logo features the word "ISO" in a distinctive blue and white design.

Question 33

What does the term "network topology" refer to? A) The speed and bandwidth of the network connections. B) The brand of the networking equipment used. C) The arrangement or relationship of network devices and their interconnections. D) The security protocols implemented on the network.

Answer 33

C) The arrangement or relationship of network devices and their interconnections. Explanation: The text provides a clear definition: "The topology of a network is the arrangement, or the relationship, of the network devices and the interconnections between them." It's about how the network is structured.

Question 34

What does a physical topology identify? A) The IP addressing scheme used by the devices. B) The virtual connections between devices. C) The physical connections and how devices are interconnected, including specific location details. D) The type of data frames being transferred

Answer 34

C) The physical connections and how devices are interconnected, including specific location details. Explanation: The text states that a physical topology "identifies the physical connections and how end devices and intermediary devices... are interconnected" and that it "may also include specific device location." It's about the actual, tangible layout.

Question 35

What does a logical topology refer to? A) The color-coding of the network cables. B) The way a network transfers frames from one node to the next, using virtual connections. C) The physical room numbers where devices are located. D) the model numbers of the routers and switches.

Answer 35

B) The way a network transfers frames from one node to the next, using virtual connections. Explanation: The text defines logical topology as how a network "transfers frames from one node to the next," identifying "virtual connections using device interfaces and Layer 3 IP addressing." It's about the path data takes, not the physical wire.

Question 36

Which topology does the data link layer "see" and use to control data access to the media? A) The Physical Topology B) The Logical Topology C) The Geographical Topology D) The Administrative Topology

Answer 36

B) The Logical Topology Explanation: The text explicitly states, "The data link layer 'sees' the logical topology of a network when controlling data access to the media." It uses this logical view to determine how to forward frames.

Question 37

What is influenced by the logical topology of a network? A) The type of network framing and media access control used. B) The length of the network cables. C) The specific location of devices on an equipment rack. D) The brand of the network interface cards.

Answer 37

A) The type of network framing and media access control used. Explanation: The text concludes by explaining the importance of the logical topology: "It is the logical topology that influences the type of network framing and media access control used." For example, a logical bus topology (like traditional Ethernet) requires CSMA/CD, while a logical point-to-point topology does not.

Question 38

This is the simplest and most common WAN topology. It consists of a permanent link between two endpoints

Answer 38

Point to point

Question 39

This is a WAN version of the star topology in which a central site interconnects branch sites through the use of point-to-point links. Branch sites cannot exchange data with other branch sites without going through the central site.

Answer 39

Hub & spoke

Question 40

This topology provides high availability but requires that every end system is interconnected to every other system. Therefore, the administrative and physical costs can be significant. Each link is essentially a point-to-point link to the other node

Answer 40

Mesh

Question 41

How many nodes does a physical point-to-point topology directly connect? A) Three or more nodes in a ring. B) Two nodes. C) A single node to a central switch. D) All nodes on the local network.

Answer 41

B) Two nodes. Explanation: The text defines a physical point-to-point topology as one that "directly connect two nodes." This is its most fundamental characteristic, creating an exclusive communication link.

Question 42

In a point-to-point topology, what must the two nodes do regarding the media? A) They must share the media with many other hosts. B) They do not have to share the media with other hosts. C) They must contend for access using a protocol like CSMA/CD. D) They take turns using the media on a fixed schedule.

Answer 42

B) They do not have to share the media with other hosts. Explanation: A major advantage of a point-to-point topology is that the two nodes have a dedicated connection. The text states that in this arrangement, the two nodes "do not have to share the media with other hosts," eliminating contention.

Question 43

Why can logical data link protocols be very simple in a point-to-point topology? A) Because frames use complex encryption that simplifies addressing. B) Because a node does not have to determine if an incoming frame is for it or another node. C) Because all frames are broadcast to every node on the internet. D) Because the nodes use a single, shared MAC address.

Answer 43

B) Because a node does not have to determine if an incoming frame is for it or another node. Explanation: The text explains that in a point-to-point link, "a node does not have to make any determination about whether an incoming frame is destined for it or another node." Since there is only one other possible destination, all frames on the media are inherently for the other node, simplifying the logic needed.

Question 44

In a point-to-point circuit, what is the path of all frames on the media? A) Frames can travel to or from any node on the wider network. B) Frames are broadcast to all nodes simultaneously. C) Frames can only travel to or from the two connected nodes. D) Frames are randomly routed to different destinations.

Answer 44

C) Frames can only travel to or from the two connected nodes. Explanation: The text emphasizes the exclusivity of the connection: "all frames on the media can only travel to or from the two nodes." This closed circuit is what makes the topology so simple and efficient for its purpose.

Question 45

What is an example of a serial communications protocol mentioned that is used in point-to-point topologies? A) Ethernet (IEEE 802.3) B) Point-to-Point Protocol (PPP) C) Address Resolution Protocol (ARP) D) Spanning Tree Protocol (STP)

Answer 45

B) Point-to-Point Protocol (PPP) Explanation: The text provides "Point-to-Point Protocol (PPP)" as a specific example of a serial communications protocol used in this context. PPP is a common data link layer protocol for direct connections between two nodes, like a dial-up connection or a WAN link between two routers.

Question 46

ow can a source and destination node be connected over a large geographical distance? A) Only by using a single, very long cable. B) By using multiple intermediary devices. C) They cannot be connected over large distances. D) Only by using wireless media.

Answer 46

B) By using multiple intermediary devices. Explanation: The text states that nodes "may be indirectly connected to each other over some geographical distance using multiple intermediary devices." This is how wide area networks (WANs) are built, using devices like routers and switches to create a path

Question 47

What is the relationship between the physical devices in a network and the logical topology? A) The number of physical devices directly defines the logical topology. B) The use of physical devices in the network does not affect the logical topology. C) Every physical device creates a new logical topology. D) The logical topology is determined solely by the brand of physical devices

Answer 47

B) The use of physical devices in the network does not affect the logical topology. Explanation: This is a key point in the text: "the use of physical devices in the network does not affect the logical topology." The logical topology is about the virtual path data takes, which can remain the same even as the physical path changes.

Question 48

What happens to the logical point-to-point connection when intermediary physical devices are added between two nodes? A) It becomes a multipoint connection. B) It is split into multiple smaller connections. C) The logical point-to-point connection remains the same. D) It becomes a broadcast domain.

Answer 48

C) The logical point-to-point connection remains the same. Explanation: The text uses the figure to illustrate that "adding intermediary physical connections may not change the logical topology." It concludes, "The logical point-to-point connection is the same." From the perspective of the data link protocol (like PPP), it still appears as a direct, exclusive link between the two endpoints.

Question 49

What is the main idea conveyed about the difference between physical and logical topologies in this text? A) They are always identical. B) The logical topology is a virtual representation that can be independent of the physical path. C) The physical topology is more important than the logical topology. D) Intermediary devices always change the logical topology.

Answer 49

B) The logical topology is a virtual representation that can be independent of the physical path. Explanation: The core concept here is abstraction. The text shows that even with a complex physical path involving many devices, the data link layer can operate as if it has a simple, direct (point-to-point) logical connection to the other end. The logical view is what matters for framing and media access control.

Question 50

What is the most common physical topology used in modern multiaccess LANs? A) Bus B) Ring C) Star or Extended Star D) Mesh

Answer 50

C) Star or Extended Star Explanation: The text states that in modern multiaccess LANs, "end devices (i.e., nodes) are interconnected using star or extended star topologies." This topology uses a central intermediary device, like a switch, to connect all end devices.

Question 51

In a star topology, what device are the end devices connected to? A) A router B) A server C) A central intermediary device (e.g., an Ethernet switch) D) Each other in a daisy chain

Answer 51

C) A central intermediary device (e.g., an Ethernet switch) Explanation: The text specifies that in a star topology, "end devices are connected to a central intermediary device, in this case, an Ethernet switch." This central device manages the connections between all nodes.

Question 52

What are the advantages of using a star or extended star topology? (Choose all that apply) A) Easy to install B) Very scalable (easy to add/remove devices) C) Easy to troubleshoot D) All of the above

Answer 52

D) All of the above Explanation: The text lists these three advantages together: star and extended topologies are "easy to install, very scalable (easy to add and remove end devices), and easy to troubleshoot." The failure of a single cable usually only affects one device, making isolation simple.

Question 53

Which characteristic describes a legacy bus topology? A) End systems are connected to a central switch. B) All end systems are chained to each other and terminated at both ends. C) End systems form a loop without termination. D) It requires extensive infrastructure devices to operate.

Answer 53

B) All end systems are chained to each other and terminated at both ends. Explanation: The text defines a bus topology: "All end systems are chained to each other and terminated in some form on each end." It also notes that "infrastructure devices such as switches are not required," using a single, shared coaxial cable backbone.

Question 54

How does a ring topology differ from a bus topology regarding termination? A) Both require termination at each end. B) Only the ring topology requires termination. C) The ring does not need to be terminated, unlike the bus topology. D) Neither topology requires termination.

Answer 54

C) The ring does not need to be terminated, unlike the bus topology. Explanation: The text makes a direct comparison: "The ring does not need to be terminated unlike in the bus topology." In a ring, the physical or logical path forms a closed loop, so signal termination is not needed as it is in a linear bus.

Question 55

When can Ethernet be used in a point-to-point topology? A) Only when using legacy hubs. B) When there are only two devices connected on the LAN. C) Never; Ethernet is only for multiaccess networks. D) Only in a star topology with more than two devices.

Answer 55

B) When there are only two devices connected on the LAN. Explanation: The text provides a specific example: "At times there may be only two devices connected on the Ethernet LAN. An example is two interconnected routers. This would be an example of Ethernet used on a point-to-point topology." This is common for router-to-router links.

Question 56

What does "duplex communication" refer to in networking? A) The speed of data transmission. B) The type of cable used for connection. C) The direction of data transmission between two devices. D) The encryption method for data.

Answer 56

C) The direction of data transmission between two devices. Explanation: The text begins by defining duplex communication as central to understanding LAN topologies because it "refers to the direction of data transmission between two devices." It's about how data flows on the link.

Question 57

What is the key characteristic of full-duplex communication? A) Devices must take turns transmitting and receiving. B) Both devices can simultaneously transmit and receive. C) Data can only flow in one fixed direction. D) Communication is restricted to one direction at a time.

Answer 57

B) Both devices can simultaneously transmit and receive. Explanation: The text defines full-duplex by stating "Both devices can simultaneously transmit and receive on the shared media." This is like a two-lane highway where traffic can flow in both directions at the same time.

Question 58

What is the default duplex mode of operation for an Ethernet switch? A) Half-Duplex B) Simplex C) Full-Duplex D) Auto-Duplex

Answer 58

C) Full-Duplex Explanation: The text explicitly states, "Ethernet switches operate in full-duplex mode by default." This is because switches provide a dedicated connection to each device, eliminating the need for contention and allowing simultaneous communication. <

Question 59

What is the fundamental restriction in half-duplex communication? A) Devices cannot transmit or receive data. B) Devices can transmit and receive but not simultaneously. C) Data transmission speed is cut in half. D) Only one device can exist on the link.

Answer 59

B) Devices can transmit and receive but not simultaneously. Explanation: The text explains that in half-duplex, "Both devices can transmit and receive on the media but cannot do so simultaneously." It is a "one-way-at-a-time" system, like a single-lane bridge where traffic must take turns.

Question 60

Which of the following is an example of a technology that uses half-duplex mode? A) A direct point-to-point link between two routers. B) WLANs (Wireless LANs) and legacy bus topologies with hubs. C) Modern switched Ethernet networks. D) Fiber optic links.

Answer 60

B) WLANs (Wireless LANs) and legacy bus topologies with hubs. Explanation: The text provides these specific examples: "WLANs and legacy bus topologies with Ethernet hubs use the half-duplex mode." These are shared media environments where only one device should transmit at a time to avoid collisions.

Question 61

What problem occurs if two interconnected interfaces operate using different duplex modes? A) The connection will be fully blocked. B) There will be a duplex mismatch creating inefficiency and latency. C) The link will automatically upgrade to full-duplex. D) The devices will negotiate the fastest possible speed.

Answer 61

B) There will be a duplex mismatch creating inefficiency and latency. Explanation: The text highlights a critical configuration point: "two interconnected interfaces... must operate using the same duplex mode. Otherwise, there will be a duplex mismatch creating inefficiency and latency on the link." This is a common cause of poor network performance.

Question 62

What is a defining characteristic of a multiaccess network? A) Only two devices can be connected. B) Two or more end devices can attempt to access the network simultaneously. C) Each device has a dedicated, point-to-point connection. D) Access is always controlled by a central authority.

Answer 62

B) Two or more end devices can attempt to access the network simultaneously. Explanation: The text defines a multiaccess network as one "that can have two or more end devices attempting to access the network simultaneously." This potential for simultaneous access attempts is why rules (access control methods) are needed.

Question 63

What are the two basic access control methods for shared media? A) Wired and Wireless B) Full-Duplex and Half-Duplex C) Contention-based access and Controlled access D) Centralized and Distributed

Answer 63

C) Contention-based access and Controlled access Explanation: The text clearly states, "There are two basic access control methods for shared media: Contention-based access [and] Controlled access." These are the two fundamental philosophies for managing shared medium access.

Question 64

What is a key characteristic of contention-based access networks? A) Each node has a guaranteed, scheduled time to use the medium. B) All nodes operate in half-duplex and compete for the medium. C) They are deterministic and highly efficient. D) They require a special token to transmit.

Answer 64

B) All nodes operate in half-duplex and compete for the medium. Explanation: The text explains that in contention-based networks, "all nodes are operating in half-duplex, competing for the use of the medium." Because they compete, a process is needed to handle when multiple devices transmit simultaneously (collisions).

Question 65

Which contention-based access method is used by Wireless LANs (WLANs)? A) Carrier Sense Multiple Access with Collision Detection (CSMA/CD) B) Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) C) Token Passing D) Polling

Answer 65

B) Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) Explanation: The text provides specific examples: CSMA/CD is for "legacy bus-topology Ethernet LANs," while CSMA/CA is used "on Wireless LANs." In wireless, a device cannot detect a collision while transmitting, so it focuses on avoiding them beforehand.

Question 66

How does a device in a controlled access network know when it can transmit? A) It listens to see if the medium is free and then transmits immediately. B) It transmits randomly and hopes no one else is transmitting. C) It has its own specific, scheduled time to use the medium. D) It must wait for a broadcast signal from a central server.

Answer 66

C) It has its own specific, scheduled time to use the medium. Explanation: The text describes controlled access as a method where "each node has its own time to use the medium." This deterministic approach means a device must wait for its assigned turn, which can be inefficient.

Question 67

Which of the following is an example of a legacy network that used controlled access? A) Modern Ethernet B) Legacy Token Ring C) Wi-Fi (IEEE 802.11) D) Legacy Bus Ethernet

Answer 67

B) Legacy Token Ring Explanation: The text lists "Legacy Token Ring" and "Legacy ARCNET" as examples of networks that used controlled access. In Token Ring, a special packet called a "token" was passed around the ring, and only the device holding the token was permitted to transmit.

Question 68

Which of the following is a characteristic shared by all contention-based access networks? A) They operate in full-duplex mode. B) They use a deterministic, scheduled access method. C) They operate in half-duplex mode. D) They use a special token to transmit.

Answer 68

C) They operate in half-duplex mode. Explanation: The text explicitly states that contention-based networks like Wireless LANs and legacy Ethernet with hubs "operate in half-duplex mode, meaning only one device can send or receive at a time." This shared medium is why a contention method is necessary.

Question 69

What is the key difference between CSMA/CD and CSMA/CA? A) CSMA/CD is for wireless, CSMA/CA is for wired networks. B) CSMA/CD detects collisions, while CSMA/CA tries to avoid them. C) CSMA/CD is more modern than CSMA/CA. D) CSMA/CA allows full-duplex operation.

Answer 69

*B) CSMA/CD *detects* collisions, while CSMA/CA tries to *avoid* them. Explanation: The text shows that legacy Ethernet uses CSMA/CD (Collision Detection), where devices detect collisions after they happen. In contrast, Wireless LANs use CSMA/CA (Collision Avoidance), which uses techniques like waiting for an acknowledgment to avoid collisions altogether, as detection is difficult in wireless.

Question 70

How does a device in a CSMA/CD network detect that a collision has occurred? A) By noticing that the signal amplitude on the media is higher than normal. B) By receiving a special "collision" packet from the hub. C) By failing to receive a token. D) By checking the IP address of the incoming frame.

Answer 70

A) By noticing that the signal amplitude on the media is higher than normal. Explanation: The text describes the collision detection process: "The NIC compares data transmitted with data received, or by recognizing that the signal amplitude is higher than normal on the media." When two signals interfere, their combined amplitude increases, which the NIC can detect

Question 71

What is the primary function of an Ethernet hub? A) To filter and forward frames based on MAC addresses. B) To route packets between different IP networks. C) To act as a multiport repeater, regenerating and sending bits out all other ports. D) To assign IP addresses to connected devices.

Answer 71

C) To act as a multiport repeater, regenerating and sending bits out all other ports. Explanation: The text defines a hub clearly: "An Ethernet hub is also known as a multiport repeater. Any bits received on an incoming port are regenerated and sent out all other ports." This creates a single shared medium and collision domain.

Question 72

In a network with a hub, what determines whether a device accepts and processes a frame? A) The device will accept all frames sent through the hub. B) The device's NIC checks the destination data link (MAC) address in the frame. C) The device's operating system checks the destination IP address. D) The hub tells the device which frames to accept.

Answer 72

B) The device's NIC checks the destination data link (MAC) address in the frame. Explanation: The text explains that while all devices receive the frame from the hub, "because the frame has a destination data link address for PC3, only that device will accept and copy in the entire frame. All other device NICs will ignore the frame." The MAC address is the key.

Question 73

What must a device do if it wants to transmit but detects that the medium is busy (i.e., it is receiving a frame)? A) It should transmit immediately to signal its intent. B) It must wait until the channel is clear. C) It should send a jamming signal to clear the medium. D) It can transmit at a higher power to override the current signal.

Answer 73

B) It must wait until the channel is clear. Explanation: The text uses PC2 as an example: "If another device, such as PC2, wants to transmit, but is currently receiving a frame, it must wait until the channel is clear." This is the "Carrier Sense" part of CSMA - listening before talking.