Chapter Quizzes Flashcards
Which of the following are layers of the OSI reference model? (Choose 3)
Transmission Layer
Application Layer
Presentation Layer
Session Layer
Encryption Layer
Connection Layer
WAN Layer
Application Layer
Presentation Layer
Session Layer
What is a Protocol Data Unit (PDU)?
A type of encryption used in data transmission
A device that manages data transmission rates
A measure of data transmission speed
A chunk of data with protocol-specific headers added at each OSI layer
A chunk of data with protocol-specific headers added at each OSI layer.
What is the primary purpose of data encapsulation in network protocols?
To encrypt data for secure transmission
To convert data into an analog signal for transmission
To compress data for faster transmission
To add additional data headers for routing and delivery
To add additional data headers for routing and delivery
Explanation
Data encapsulation is a fundamental process in network communication, where data at each layer of the OSI model is wrapped with protocol-specific headers (and sometimes footers). These headers provide essential information such as source and destination addresses, error checking, and more, which are necessary for the correct routing and delivery of data across a network. This process ensures that data packets are handled appropriately at each hop along their path to the destination.
Encapsulation is not about compressing data but organizing it for transmission. Compression is a separate process that might be applied to data before encapsulation.
Encapsulation itself does not involve encryption. Encryption may be applied to data as part of the security protocols at various layers but is distinct from the encapsulation process.
Encapsulation deals with the digital organization of data for transmission, not the conversion of digital signals to analog. The conversion to analog signals, if necessary, is handled at the Physical layer, separate from the encapsulation process.
An engineer uses a type of network adapter to connect a fiber link to a router. The
transceiver fits into an optical interface on a layer 3 Ethernet router.
Of the choices, which layer 1 implementation does the engineer utilize?
Media converter
Switch
Bridge
VoIP endpoint
Media converter
Explanation
Media converters are layer 1 devices and are used to convert one cable type to another.
These components alter the characteristics of one type of cable to match those of another.
A switch is a layer 2 device. Switches can handle traffic based on a node’s physical address
which is also known as a Media Access Control (MAC) address.
A bridge is a layer 2 appliance or application that connects different networks as if they
were one network.
A VoIP (Voice over Internet Protocol) endpoint is a phone system component that can be
implemented as software running on a computer or smartphone, or as a dedicated
traditional handset
A communications engineer notices that every time it rains the signal becomes very
degraded.
Which layer of the OSI model is the engineer most likely troubleshooting?
Data Link
Transport
Application
Physical
Physical
Explanation
The physical layer (PHY) of the OSI model (layer 1) is responsible for the transmission and
receipt of the signals that represent bits of data from one node to another node. Wireless is
one medium.
The data link layer (layer 2) is responsible for transferring data between nodes on the same
logical segment.
At the transport layer on the sending host, the system packages data from the upper layers
as a series of layer 4 protocol data units (PDUs), referred to as segments.
The application layer (layer 7) is at the top of the OSI stack. An application-layer protocol
does not encapsulate any other protocols or provide services to any protocol.
Which of the following devices operate at the Data Link layer of the OSI model? (Select
three.)
Routers
Gateways
Repeaters
Hubs
Network interface cards (NICs)
Bridges
Switches
Network Interface Cards (NICs)
Bridges
Switches
Explanation
Network interface cards (NICs), bridges, and switches all operate at the OSI Data Link layer.
They use the physical device address (MAC address) to identify packets.
Hubs and repeaters operate at the Physical layer. They simply repeat packets without
regard to addresses.
Routers and gateways function at the Network layer. They examine the logical device and
network address to perform routing tasks.
When the Data Link layer performs encapsulation, it adds control information to the
payload in the form of header fields.
Which of the following are header fields added by the Data Link layer during
encapsulation? (Select three.)
TTL (Time to Live)
Destination hardware address
Sequence number
Source hardware address
Encryption type
Checksum for basic error checking
Window size
Destination hardware address
Source hardware address
Checksum for basic error checking
What is the role of an Access Control List (ACL) at Layer 3 (Network layer) of the OSI model?
To serve as a list of permissions for file access on the network
To filter network traffic by permitting or blocking packets based on IP
addresses and other criteria
To act as a routing protocol for determining the best path for data
packets
To define the maximum size for packets transmitted across the
network
To filter network traffic by permitting or blocking packets based on IP
addresses and other criteria
Explanation
At Layer 3, ACLs are used to enforce security policies by filtering traffic. They determine
which packets are allowed to pass through a network device, such as a router, based on
rules that include IP addresses, protocol types, ports, and other criteria.
ACLs do not define packet sizes; this is typically managed by the network protocols in use,
such as TCP/IP.
ACLs are not routing protocols. Routing protocols like OSPF or BGP are used to determine
the best path for data packets.
ACLs at Layer 3 do not manage file access permissions; they control network traffic. File
access permissions are typically managed by the operating system or file system
In the OSI model, what is the primary function of the Network layer?
The primary function of the Network layer is to move data around an internetwork using logical network and host IDs.
The primary function of the Network layer is to encode and convert
data into signals suitable for transmission over the physical medium.
The primary function of the Network layer is to ensure reliable
transmission of data across a physical link.
The primary function of the Network layer is to establish, manage,
and terminate connections between applications on different hosts.
The primary function of the Network layer is to move data around an internetwork using logical network and host IDs.
Explanation
The primary function of the Network layer is to move data around an internetwork using
logical network and host IDs. The Network layer, or Layer 3 of the OSI model, is responsible
for the logical addressing of data and its delivery across different networks, or an
internetwork. It uses logical addresses, such as IP addresses, to ensure data packets are
routed to the correct destination network and ultimately to the correct host within that
network. Routers, which operate at this layer, use the information contained in the packet’s
network layer header to make forwarding decisions, guiding the packet through the
internetwork hop by hop until it reaches its destination.
Which of the following functions are performed by the OSI Transport layer? (Select three.)
Packet formatting for delivery through a medium
Data segmentation and reassembly
Media access control, logical topology, and device identification
Consistent data formatting between dissimilar systems
Path identification and selection
End-to-end flow control
Reliable message delivery
Data segmentation and reassembly
End-to-end flow control
Reliable message delivery
Explanation
The Transport layer is responsible for breaking upper-layer data into segments and
allowing reliable communication through end-to-end flow control, error detection, and
error correction.
Message transmission through a medium is performed at the Physical layer.
Media access, logical topology, and device identification occur at the Data Link layer.
Path identification and selection is a function of the Network layer.
Data formatting is performed at the Presentation layer.
A security engineer configures software-based port security on a hardware firewall.
Which OSI model layer identifies the application ports to configure?
Layer 3
Layer 1
Layer 4
Layer 2
Layer 4
Explanation
The transport layer (layer 4) manages end-to-end communications. At layer 4, a port
number identifies each application, such as 80 for hypertext transfer protocol (HTTP) web
traffic.
What role does the Presentation layer (layer 6) of the OSI model play in terms of data
compression and encryption?
The Presentation layer handles the routing of data between different
networks and supports encryption protocols like IPsec.
The Presentation layer supports data compression and encryption to
prepare data for network transmission.
The Presentation layer is primarily responsible for the physical
encryption of data using hardware-based methods.
The Presentation layer is involved in the logical organization of data
into frames for transmission.
The Presentation layer supports data compression and encryption to
prepare data for network transmission.
Explanation
The Presentation layer transforms data to ensure that it is in the correct format for the
application or network. This includes data compression to reduce the size of the data for
transmission and encryption to secure the data during transfer.
The Presentation layer deals with data transformation and representation, not physical
encryption methods, which are typically implemented at lower layers or by specific security
hardware.
Which of the following statements accurately describes the function of the Session layer
(layer 5) in the OSI model?
The Session layer is used for character set conversion, such as
between ASCII and Unicode.
The Session layer administers the process of establishing, managing,
and terminating a dialog between client and server.
The Session layer provides the physical transmission of data over
network media.
The Session layer is responsible for routing packets across different
networks.
The Session layer administers the process of establishing, managing,
and terminating a dialog between client and server.
Explanation
The correct answer is that the Session layer administers the process of establishing,
managing, and terminating a dialog between client and server. The Session layer is crucial
for controlling the dialog between two computers or network devices. It establishes,
manages, and terminates connections, ensuring that data is properly synchronized and
organized during communication sessions.
A network engineer is designing a network in various offices to create multiple broadcast
domains. Each has its own Virtual Local Area Network (VLAN).
When configuring these multiple broadcast domains on the switch, the switch will be
operating at what layer of the OSI model?
Layer 4 (Transport Layer)
Layer 7 (Application Layer)
Layer 2 (Data Link Layer)
Layer 1 (Physical Layer)
Layer 2 (Data Link)
Explanation
Layer 2 (Datalink Layer) is the correct answer. VLANs (Virtual Local Area Networks) are a
Layer 2 technology. When configuring VLANs on a switch, the network engineer is working
at the Data Link Layer. This layer is responsible for segmenting the network into multiple
broadcast domains using VLAN IDs. Devices like switches and bridges operate at this layer
to manage MAC addresses and frames, which are essential for VLAN functionality.
Which of the following network geographies refers to a network that spans several buildings within walking distance of each other, such as at a business park?
CAN
WAN
PAN
MAN
CAN
A campus area network (CAN) is a computer network that spans a limited geographic area. CANs interconnect multiple local area networks (LAN) within an educational or corporate campus. A WAN (Wide Area Network) is a network that spans a large geographical area, such as multiple cities or countries. A PAN (Personal Area Network) is a network that connects devices within an individual’s personal space, typically within a range of a few meters. A MAN (Metropolitan Area Network) is a network that spans a larger area than a LAN (Local Area Network), often covering a city or a metropolitan area.
Which of the following type of network models doesn’t differentiate between the devices that provide services and those that request services?
Client-server
Point-to-point
Hub-and-spoke
Peer-to-peer
Peer-to-peer
A peer-to-peer network model does not differentiate between the clients and the servers, and every node can become a client and a server when requesting and responding to service requests. In a client-server network model, there is a clear distinction between client devices that request services and server devices that provide services. A Point-to-point network is a direct connection between two devices. One device acts as the sender and the other as the receiver. A Hub-and-spoke network model has a central hub that connects other devices (spokes). The hub provides services to the spokes.
HongHong, a network administrator, was asked by the Chief Information Officer (CIO) to set up a new office with a network that has full redundancy. What topology would BEST meet the CIO’s requirement?
Hybrid
Bus
Mesh
Star
Mesh
A mesh topology connects every endpoint to every other endpoint, creating a fully redundant network. While a hybrid topology combines different topologies, it does not inherently provide full redundancy. The redundancy level depends on the specific combination of topologies used. In a bus topology, all devices are connected to a single shared communication line. If a device on it fails, the entire network can be affected. It lacks redundancy. In a star topology, devices are connected to a central hub or switch. If the hub or switch fails, the network can be disrupted.A mesh topology connects every endpoint to every other endpoint, creating a fully redundant network. While a hybrid topology combines different topologies, it does not inherently provide full redundancy. The redundancy level depends on the specific combination of topologies used. In a bus topology, all devices are connected to a single shared communication line. If a device on it fails, the entire network can be affected. It lacks redundancy. In a star topology, devices are connected to a central hub or switch. If the hub or switch fails, the network can be disrupted.
Dion Worldwide has created a network architecture that relies on two main data centers, one in the United States and one in Japan. Each satellite office in the United States and Canada will connect back to the American data center, while each satellite office in Asia will connect back to the Japanese data center. Both the American and Japanese data centers are interconnected, as well. Therefore, if a client in the Philippines wants to send a file to the office in Miami, it will go first to the Japanese datacenter, then route across to the American datacenter, and then to the Miami satellite office. Which of the following network topologies best describes the Dion Worldwide network?
Hub and spoke
Bus
Star
Ring
Hub and spoke
A hub and spoke topology is a network topology where a central device (the hub) is connected to multiple other devices (the spokes). A Bus topology has a single communication line where all devices are connected. It does not have distinct hubs and spokes. A star topology has a central hub that connects all devices in a point-to-point manner. While the Dion Worldwide network has hubs, not a single central hub connecting all devices. A Ring topology connects devices in a circular manner, where each device is connected to two neighboring devices. It doesn’t have distinct hubs and spokes.
Which type of network device operates at layer 1 of the OSI model and requires connected devices to operate at half-duplex using CSMA/CD?
Switch
Hub
Bridge
Router
Hub
A hub is a network hardware device for connecting multiple Ethernet devices together and making them act as a single network segment. It operates at the physical layer (Layer 1) of the OSI model. All devices connected by a hub are in a single collision domain and a single broadcast domain, so it must use half-duplex for communication and CSMA/CD. A switch operates at layer 2 of the OSI model and provides more advanced functionality than a hub. A bridge also operates at layer 2. It connects two separate network segments. A router operates at layer 3 and forwards data packets among networks.
Which of the following applies to data as it travels from Layer 1 to Layer 7 of the OSI model?
Tagging
Encapsulation
Tunneling
De-encapsulation
De-encapsulation
De-encapsulation in networking is performed at the receiver side or destination side as data moves from layer 1 to layer 7 of the OSI model. As information travels up the layers of the OSI layer, information added from the sender’s encapsulation process is removed layer by layer. Tagging typically refers to the process of adding additional information or labels to data packets for specific purposes. Tunneling involves encapsulating one network protocol within another protocol for data transference. Encapsulation is the reverse process of de-encapsulation.
According to the OSI model, at which of the following layers is data encapsulated into a frame?
Layer 1
Layer 2
Layer 3
Layer 4
Layer 2
The data layer, or layer 2, is the second layer of the seven-layer OSI model. The data link layer encapsulates data into frames for delivery between nodes on the same network. Data is transmitted at Layers 5, 6, and 7 of the OSI model. At Layer 4, the data is encapsulated into segments. At layer 3, the segments are encapsulated into packets. At layer 2, the packets are encapsulated into frames. At layer 1, the frames are encapsulated into bits.
Which network device operates at layer 2?
Repeater
Switch
Router
Firewall
Switch
A basic switch operates at layer 2 of the OSI model. For the exam, unless they mention a “multilayer switch” or “layer 3 switch”, always assume they are referencing a basic layer 2 switch. A router is a layer 3 device. A repeater is a layer 1 device. A firewall will operate layers 3 through 7, depending on the type of firewall.
What layer of the OSI model is responsible for data encryption and character set conversion, such as ASCII to UTF-8?
Layer 7
Layer 6
Layer 5
Layer 4
Layer 6
The presentation layer (layer 6) establishes how information is presented, typically for display or printing. Data encryption and character set conversion (such as ASCII to EBCDIC) are usually associated with this layer. The presentation layer translates information in a way that the application layer understands. This layer also translates information from the application layer to the session layer. Layer 7, the Application Layer, deals with end-user services. Layer 5, the session layer, manages sessions. Layer 4, the transport layer, controls end-to-end communication and error-checking.
