Section 1. Exploring the Functions of Networking

Question 1

Q1-What is a network?

Answer 1

A network is a collection of devices and end systems. Networks consist of computers, servers, and network devices, such as switches, routers, wireless access points, and firewalls that are interconnected, communicating with each other and sharing resources with each other. They are found in homes, small business, and large enterprises. A network is a collection of devices and end systems.

Question 2

Q2-What four major categories make up the physical components of a network?

Answer 2

The four major categories found in networks are Endpoints: These devices receive data and are endpoints of the network. Examples include PCs, servers, laptops, tablets, and so on. Interconnections: The components that provide a means for data to travel across the network. This includes network interface cards (NIC), network media, and connectors. Switches: Provide network access for compute devices and other network devices. Routers: Interconnect networks.

Question 3

Q3-What are the four major resources that are shared on a computer network?

Answer 3

The four major resources that are shared on a computer network are as follows: Data and applications: Consist of computer data and network-aware applications such as e-mail Resources: Include input and output devices such as cameras and printers Network storage: Consists of directly attached storage devices (physical storage that is directly attached to a computer and a shared server), network attached storage, and storage-area networks Backup devices: Can back up files and data from multiple computers

Question 4

Q4-What are common network user applications on today’s networks?

Answer 4

Common network user applications on today’s networks are Email Web (this includes web applications or any application the uses HTTP/HTTPS) Instant messaging Video/collaboration Databases File sharing

Question 5

Q5-List three categories of network applications.

Answer 5

Three categories of network applications are as follows: Batch applications: Examples are FTP and TFTP. They are started by a person and complete with no other interaction. Bandwidth is important but not critical. Interactive applications: Include database updates and queries. A person requests data from a server and waits for a reply. Response time depends more on the server and storage than the network. Real-time applications: Include VoIP and video. Network bandwidth is critical because these applications are time sensitive. Quality of service (QoS) and sufficient network bandwidth are mandatory for these applications.

Question 6

Q6-What are three types of network-monitoring software?

Answer 6

Three types of network-monitoring software are Protocol analyzers: Capture network packets between network devices and decode the packets so that one can view what applications are being transmitted on a network. Sniffers: Work like a wiretap and allow one to observe network communication and view the data that is being transmitted. Availability and performance programs: Use protocols use as ICMP and SNMP to view the availability of network devices and performance in real time.

Question 7

Q7-Your company wants to provide streaming video services to all branches and sales representatives. What two network characteristics are the most critical to achieving this goal?

Answer 7

The most critical characteristics are bandwidth and latency. Time-sensitive applications such as video and VoIP are dependent on bandwidth and latency to function properly. When implementing time-sensitive applications, one needs to ensure that the network has enough bandwidth and low delay to ensure a proper end-user experience.

Question 8

Q8-When describing the characteristics of a network, what does speed refer to?

Answer 8

Speed refers to how fast data is transmitted over the network. Today’s networks consist of speeds of 100 Mbps, 1Gbps, 10 Gbps, 40 Gbps, and 100 Gbps.

Question 9

Q9-When describing the characteristics of a network, what does cost refer to?

Answer 9

Cost refers to the general financial value of network components, installation, and maintenance.

Question 10

Q10-When describing the characteristics of a network, what does security refer to?

Answer 10

Security refers to protecting the network devices and data from both internal and external sources.

Question 11

Q11-When describing the characteristics of a network, what does availability refer to?

Answer 11

Availability is the measurement of the network uptime compared to its downtime. Network availability percentage can be calculated using the following formula, which calculates the number of minutes of downtime compared to the number of minutes in a year: ([525,600 – Minutes downtime] / [525,600]) * 100

Question 12

Q12-Your CIO wants to know the network availability of your company’s network for the past year. During the past year, the network was down for 30 minutes. What was the total availability of the network?

Answer 12

The total availability was 99.994%. ([525,600 – 30] / [525,600]) * 100 = 99.994%

Question 13

Q13-When describing the characteristics of a network, what does scalability refer to?

Answer 13

Scalability refers to how well the network can accommodate more users and more data—in other words, how easily the network can grow and expand.

Question 14

Q14-When describing the characteristics of a network, what does reliability refer to?

Answer 14

Reliability refers to the dependability of the devices that make up the network (switches, routers, computers, servers, access points, software, and so on).

Question 15

Q15-What is the difference between the physical and logical network topology?

Answer 15

Physical topology defines the physical layout of devices and network media—cables, network devices, computers, and so on—and how these components are physically connected and configured. Logical topology refers to the data path or logical paths of the network in which data accesses the media and transmits packets across it. This includes IP addresses as well as routing paths.

Question 16

Q16-What are the six types of physical topologies implemented in today’s networks?

Answer 16

The six types of physical topologies implemented in today’s networks are Star Extended star Mesh Partial mesh Bus Ring

Question 17

Q17-What physical network topology connects all devices to one cable?

Answer 17

The bus topology connects all devices to one cable. This cable connects one computer to another. In a logical bus topology, only one packet can be transmitted at a time.

Question 18

Q18-Describe a ring physical network topology.

Answer 18

In a ring topology, all hosts and devices are connected in the form of a ring or circle. The following two types of ring networks exist: Single-ring: In a single-ring network, all devices share a single cable and data travels in one direction. Each device waits its turn to send data over the network. Dual-ring: A dual-ring network has a second ring to add redundancy and allows data to be sent in both directions.

Question 19

Q19-Describe a star and extended star physical topology.

Answer 19

Star and extended star physical topologies are made up of a central connection point, such as a hub or switch, where all cable segments connect. A star topology resembles spokes in a bicycle wheel and is the network topology of choice in Ethernet networks. When multiple star topologies are connected to a common independent centralized device, it is called an extended star topology.

Question 20

Q20-What physical network topology connects all devices to each other?

Answer 20

A mesh network topology connects all devices to each other for fault tolerance and redundancy.

Question 21

Q21-What is the difference between a full-mesh and a partial-mesh topology?

Answer 21

A full-mesh topology connects all nodes to one another for full redundancy. In a partial-mesh topology, at least one node maintains multiple connections to all other devices and one node cannot connect to all other nodes as well.

Question 22

Q22-What are the seven layers of the OSI reference model? Include the layer number and name of each layer in your answer.

Answer 22

The seven layers of the OSI reference model are as follows: Layer 7: Application layer Layer 6: Presentation layer Layer 5: Session layer Layer 4: Transport layer Layer 3: Network layer Layer 2: Data link layer Layer 1: Physical layer

Question 23

Q23-What are six reasons that the OSI reference model was created?

Answer 23

Six reasons that the OSI reference model was created are as follows: 1. To ensure that different vendors’ products can work together 2. To create standards to enable ease of interoperability by defining standards for the operations at each level 3. To clarify general functions of internetworking 4. To divide the complexity of networking into smaller, more manageable sublayers 5. To simplify troubleshooting 6. To enable developers to modify or improve components at one layer without having to rewrite an entire protocol stack

Question 24

Q24-What is the function of the physical layer (Layer 1) in the OSI model? Give some examples of physical layer implementation.

Answer 24

The physical layer defines the physical medium. It defines the media type, the connector type, and the signaling type (baseband versus broadband). This includes voltage levels, physical data rates, and maximum cable lengths. The physical layer is responsible for converting frames into electronic bits of data, which are then sent or received across the physical medium. Twisted-pair, coaxial, and fiber-optic cable operate at this level. Other implementations at this layer are repeaters/hubs.

Question 25

Q25-What is the responsibility of the data link layer (Layer 2)?

Answer 25

The data link layer defines how data is formatted from transmission and how access to the physical media is controlled. This layer also typically includes error correction to ensure reliable delivery of data. The data link layer translates messages from the network layer into bits for the physical layer, and it enables the network layer to control the interconnection of data circuits within the physical layer. Its specifications define different network and protocol characteristics, including physical addressing, error notification, network topology, and sequencing of frames. Data-link protocols provide the delivery across individual links and are concerned with the different media types, such 802.3. The data link layer is responsible for putting 1s and 0s into a logical group. These 1s and 0s are then put on the physical wire. Some examples of data link layer implementations are IEEE 802.3, packet trailer (for Ethernet, frame check sequence [FCS] or cyclic redundancy check [CRC]), Fiber Distributed Data Interface (FDDI), High-Level Data Link Control (HDLC), and Frame Relay.

Question 26

Q26-The Institute of Electrical and Electronics Engineers (IEEE) defines what sublayer of the data link layer?

Answer 26

The IEEE defines the Media Access Control (MAC) sublayer of the data link layer.

Question 27

Q27-What functions does the Media Access Control (MAC) sublayer provide?

Answer 27

The MAC sublayer specifies how data is placed and transported over the physical wire. It controls access to the physical medium. The MAC sublayer communicates downward directly to the physical layer. Physical addressing (MAC addresses), network topologies, error notification, and delivery of frames are defined at the MAC sublayer.

Question 28

Q28-What are examples of network devices that operate at the data link layer (Layer 2)?

Answer 28

Bridges and switches operate at the data link layer. Both devices make decisions about what traffic to forward or drop (filter) by MAC addresses; logical network address are not used at this layer. Data link layer devices assume a flat address space.

Question 29

Q29-Describe the function of the network layer (Layer 3) of the OSI model. Give some examples of network layer implementations.

Answer 29

The network layer provides internetwork routing and logical network addresses. It defines how to transport traffic between devices that are not locally attached. The network layer also supports connection-oriented and connectionless service from higher-layer protocols. Routers and multilayer switches operate at the network layer. IP and IPv6 are examples of network layer implementations.

Question 30

Q30-Are network layer addresses physical or logical?

Answer 30

Network layer addresses are logical. These addresses are logical addresses that are specific to the network layer protocol being run on the network. Each network layer protocol has a different addressing scheme. They are usually hierarchical and define networks first and then hosts or devices on that network. An administrator typically assigns network layer addresses either by static configuration or dynamic configuration. An example of a network address is an IP address. For example, IPv4 has 32-bit addresses often expressed in decimal format. An example of an IPv4 address in decimal format is 192.168.0.1.

Question 31

Q31-What is the transport layer (Layer 4) of the OSI model responsible for? Give some examples of transport layer implementations.

Answer 31

The transport layer segments and reassembles data from upper-layer applications into data streams. It provides reliable data transmission to upper layers. End-to-end communications, flow control, multiplexing, error detection and correction, and virtual circuit management are typical transport layer functions. Some examples include Transmission Control Protocol (TCP) and User Datagram Protocol (UDP).

Question 32

Q32-What layer of the OSI model handles the reliability of network communications between hosts using flow control, sequencing, and acknowledgments?

Answer 32

The transport layer handles this reliability. The transport layer uses acknowledgments and sequence numbers for reliable delivery of data. Flow control is used to avoid network or host congestion.

Question 33

Q33-What is flow control, and what are the three methods of implementing it?

Answer 33

Flow control is the method of controlling the rate at which a computer sends data, thus preventing network congestion. The three methods of implementing flow control are as follows: Buffering Congestion avoidance Windowing

Question 34

Q34-How do network devices use buffering for flow control?

Answer 34

Buffering is used by network devices to temporarily store bursts of extra data in memory until they can be processed and sent. Buffering can handle occasional data bursts; however, buffer overflows can occur if data bursts are continuous.

Question 35

Q35-What are the functions of the session layer (Layer 5) of the OSI model? Provide some examples.

Answer 35

The session layer is responsible for creating, managing, and ending communication sessions between presentation layer entities. These sessions consist of service requests and responses that develop between applications located on different network devices. Some examples include Structured Query Language (SQL), remote-procedure call (RPC), and SSL.

Question 36

Q36-What is the responsibility of the presentation layer (Layer 6)? Give some examples of Layer 6 implementations.

Answer 36

Also known as the translator, the presentation layer provides coding and conversion functions to application layer data. This guarantees that the application layer on one system can read data transferred from the application layer of a different system. Some examples of the presentation layer are Image Compression, decompression, and encryption Image JPEG, TIFF, GIF, PICT, QuickTime, MPEG, EBCDIC, and ASCII file types

Question 37

Q37-What does the application layer (Layer 7) of the OSI model do, and what are some examples of this layer?

Answer 37

The application layer is the layer that is closest to the user. This means that this layer interacts directly with the software application. The application layer’s main functions are to identify and establish communication partners, determine resource availability, and synchronize communication. Some examples include TCP/IP applications protocols such as Telnet, FTP, Simple Mail Transfer Protocol (SMTP), and HTTP.

Question 38

Q38-How do the different layers of the OSI model communicate with each other?

Answer 38

Each layer of the OSI model can communicate only with the layer above it, below it, and parallel to it (a peer layer on a remote host). For example, the presentation layer can communicate with only the application layer and session layer on the local host, and the presentation layer on the remote host. These layers communicate with each other using service access points (SAP) and protocol data units (PDU). The SAP is a conceptual location at which one OSI layer can request the services of another OSI layer. PDUs control information that is added to the user data at each layer of the model. This information resides in fields called headers (the front of the data field) and trailers (the end of the data field).

Question 39

Q39-Which layer of the OSI model uses the hardware address of a device to ensure proper message delivery to a host on a LAN?

Answer 39

The data link layer uses physical addresses or hardware addresses for message delivery on a LAN.

Question 40

Q40-Which network layer protocols are responsible for path determination and traffic switching?

Answer 40

Routing protocols are responsible for path determination and traffic switching.

Question 41

Q41-At which layer on the OSI model is a logical path created between two host systems?

Answer 41

The network layer creates a logical path between two host systems. The logical path consists of logical addresses. Logical addresses are also known as network layer addresses.

Question 42

Q42-At which layers of the OSI model do WANs operate?

Answer 42

WANs operate at the data link and physical layers. The physical and data link layers work together to deliver data across a variety of types of physical networks like LANs, MANs, and WANs.

Question 43

Q43-What are the four layers of the TCP/IP stack?

Answer 43

The four layers of the TCP/IP stack are as follows: Application Transport Internet Network Access

Question 44

Q44-On what layer are physical data rates, connectors, and MAC addresses located in the TCP/IP stack?

Answer 44

Physical data rates, connectors, and MAC addresses are located on the network access layer.

Question 45

Q45-What are some protocols that operate at the TCP/IP Internet layer?

Answer 45

Some protocols that operate at the TCP/IP Internet layer are as follows: IP ICMP (Internet Control Message Protocol) ARP (Address Resolution Protocol) RARP (Reverse Address Resolution Protocol) IP is the main connectionless routed protocol at the Internet layer (or OSI network layer). IP has various associated protocols, such as ICMP, ARP, and RARP.

Question 46

Q46-What is data encapsulation as it relates to the OSI model?

Answer 46

Encapsulation wraps data with the necessary protocol information before network transmission. A protocol data unit (PDU) can include different information as it goes up or down the OSI model. It is given a different name according to the information it is carrying (the layer where it is located). When the transport layer receives upper-layer data, it adds a TCP header to the data; this is called a segment. The segment is then passed to the network layer, and an IP header is added; thus, the data becomes a packet. The packet is passed to the data link layer, thus becoming a frame. This frame is then converted into bits and is passed across the network medium. This is data encapsulation. For the ICND test, you should know the following: Session layer and higher: Data Transport layer: Segment Network layer: Packet Data link layer: Frame Physical layer: Bits

Question 47

Q47-What is the process that data goes through when a host transmits data across a network to another host?

Answer 47

This process is known as encapsulation. Encapsulation wraps data with the necessary protocol information before network transmission. For data to be transferred to other hosts on a network, it is encapsulated into a PDU.