Chapter 3
After completion of this chapter, you should be able to:
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Explain how rules are used to facilitate communication.
Explain the role of protocols and standards organizations in facilitating interoperability in
network communications.
Explain how devices on a LAN access resources in a small to medium-sized business network.
3.1 Rules of Communication
1. All communication methods have three elements in common, these are?
a. Source or sender
b. Destination or receiver
c. Channel or media
2. List the common computer protocols.
a. Message encoding
b. Message formatting and encapsulation
c. Message size
d. Message timing
e. Message delivery options
3. The first step to sending a message is encoding it. What is encoding?
Encoding is the process of converting information into another, acceptable form, for
transmission.
4. How is decoding different from encoding?
Decoding reverses this process in order to interpret the information.
5. What is encapsulation?
The process of placing one message format (the letter) inside another message format (the
envelope) is called encapsulation.
6. Explain how long messages or large frames are handled in a network to ensure delivery?
The size restrictions of frames require the source host to break a long message into individual
pieces that meet both the minimum and maximum size requirements of the sender.
7. Explain the following terms.
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a. Message Timing –
People use timing to determine when to speak, how fast or slow to talk, and how long to wait
for a response. These are the rules of engagement.
b. Access Method –
Access method determines when someone is able to send a message.
c. Collision –
If two people talk at the same time, a collision of information occurs and it is necessary for the
two to back off and start again
d. Flow Control –
Timing affects how much information can be sent and the speed that it can be delivered.
Source and destination hosts use flow control to negotiate correct timing for successful
communication.
e. Response Timeout –
Hosts on the network have rules that specify how long to wait for responses and what action to
take if a response timeout occurs.
8. Explain the following terms.
a. Unicast –
A one-to-one delivery option is referred to as a unicast, meaning that there is only a single
destination for the message.
b. Multicast –
When a host needs to send messages using a one-to-many delivery option, it is referred to as a
multicast. Multicasting is the delivery of the same message to a group of host destinations
simultaneously.
c. Broadcast –
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If all hosts on the network need to receive the message at the same time, a broadcast is used.
Broadcasting represents a one-to-all message delivery option. Additionally, hosts have
requirements for acknowledged versus unacknowledged messages.
3.2 Network Protocols and Standards
9. Explain what a protocol suite is and what devices implement or use them?
A group of inter-related protocols necessary to perform a communication function. Protocol suites are
implemented by hosts and networking devices in software, hardware or both.
10. What is a protocol stack?
A protocol stack shows how the individual protocols within a suite are implemented.
11. In a protocol stack the protocols are viewed in terms of layers. How do these layers interact with
each other?
Each higher level service depends on the functionality defined by the protocols shown in the
lower levels
12. What do the lower layers in the protocol stack focus on?
a. Moving data over the network
b. Providing services to the upper layers
12. What do the upper layers in the protocol stack focus on?
The content of the message being sent.
13. What are the three layers in the protocol stack?
a. Physical layer
b. Rules layer
c. Content layer
14. For devices to successfully communicate, a network protocol suite must describe precise
requirements and interactions. What do networking protocols define?
A common format and set of rules for exchanging messages between devices.
15. List some common networking protocols.
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a. IP
b. HTTP
c. DHCP
16. Describe some of the processes networking protocols are responsible for.
a. How the message is formatted or structured.
b. The process by which networking devices share information about pathways with other
networks.
c. How and when error and system messages are passed between devices.
d. The setup and termination of data transfer sessions.
17. Explain in detail how the following protocols operate. (in detail means more than one sentence)
Application Protocol - Hypertext Transfer Protocol (HTTP) –
Is a protocol that governs the way a web server and a web client interact. HTTP defines the
content and formatting of the requests and responses that are exchanged between the client
and server.
Transport Protocol - Transmission Control Protocol (TCP) –
Is the transport protocol that manages the individual conversations between web servers and
web clients. TCP divides the HTTP messages into smaller pieces, called segments. These
segments are sent between the web server and client processes running at the destination
host. TCP is also responsible for controlling the size and rate at which messages are exchanged
between the server and the client.
Internet Protocol – IP –
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Is responsible for taking the formatted segments from TCP, encapsulating them into packets,
assigning them the appropriate addresses, and delivering them across the best path to the
destination host.
Network Access Protocols –
Network access protocols describe two primary functions, communication over a data link and
the physical transmission of data on the network media. Data-link management protocols take
the packets from IP and format them to be transmitted over the media. The standards and
protocols for the physical media govern how the signals are sent and how they are interpreted
by the receiving clients. An example of a network access protocol is Ethernet.
18. The protocols IP, HTTP, and DHCP are all part of the Internet protocol suite known as:
Transmission Control Protocol/IP (TCP/IP)
19. The TCP/IP protocol suite is an open standard. Explain what that means.
These protocols are freely available to the public, and any vendor is able to implement these
protocols on their hardware or in their software.
20. Explain what a standards-based protocol is.
It is a process or protocol that has been endorsed by the networking industry and ratified, or
approved, by a standards organization.
21. Explain in detail why it’s important to have standard based protocols.
The use of standards in developing and implementing protocols ensures that products from
different manufacturers can interoperate successfully. If a protocol is not rigidly observed by a
particular manufacturer, their equipment or software may not be able to successfully
communicate with products made by other manufacturers.
22. Explain in detail what proprietary protocols are.
Proprietary means that one company or vendor controls the definition of the protocol and how
it functions. Some proprietary protocols can be used by different organizations with permission
from the owner. Others can only be implemented on equipment manufactured by the
proprietary vendor.
23. Is Cisco’s EIGRP routing protocol proprietary or non-proprietary?
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Non-proprietary
24. The IP suite is a suite of protocols required for transmitting and receiving information using the
Internet. It is commonly known as TCP/IP.
25. What year was the TCP and IP protocols formalized?
1981
26. What year did Cisco launch its first routing innovation?
1986
27. Explain the protocol steps involved in during the communication process after a remote computer
requests a webpage from a web server.
a. The web server’s Hypertext Markup Language (HTML) page is the data to be sent.
b. The application protocol HTTP header is added to the front of the HTML data. The header
contains various information, including the HTTP version the server is using and a status code
indicating it has information for the web client.
c. The HTTP application layer protocol delivers the HTML-formatted web page data to the
transport layer. The TCP transport layer protocol is used to manage the individual conversation
between the web server and web client.
d. Next, the IP information is added to the front of the TCP information. IP assigns the
appropriate source and destination IP addresses. This information is known as an IP packet.
e. The Ethernet protocol adds information to both ends of the IP packet, known as a data link
frame. This frame is delivered to the nearest router along the path towards the web client. This
router removes the Ethernet information, analyzes the IP packet, determines the best path for
the packet, inserts the packet into a new frame, and sends it to the next neighboring router
towards the destination. Each router removes and adds new data link information before
forwarding the packet.
f. This data is now transported through the internetwork, which consists of media and
intermediary devices.
g. The client receives the data link frames that contain the data and each protocol header is
processed and then removed in the opposite order that it was added. The Ethernet information
is processed and removed, followed by the IP protocol information, then the TCP information,
and finally the HTTP information.
h. The web page information is then passed on to the client’s web browser software.
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28. Fill in the correct protocols.
29. Standards organizations are usually vendor-neutral, non-profit organizations established to develop
and promote the concept of open standards.
30. Explain the function and responsibility of each of the following standards organizations.
a. The Internet Society (ISOC) –
Is responsible for promoting open development, evolution, and Internet use throughout the
world. ISOC facilitates the open development of standards and protocols for the technical
infrastructure of the Internet, including the oversight of the Internet Architecture Board (IAB).
b. The Internet Architecture Board (IAB) –
Is responsible for the overall management and development of Internet standards. The IAB
provides oversight of the architecture for protocols and procedures used by the Internet.
c. The Internet Engineering Task Force (IETF) –
The IETF’s mission is to develop, update, and maintain Internet and TCP/IP technologies. One of
the key responsibilities of the IETF is to produce Request for Comments (RFC) documents,
which are a memorandum describing protocols, processes, and technologies for the Internet.
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d. The Institute of Electrical and Electronics Engineers (IEEE) pronounced “I-triple-E” –
Is a professional organization for those in the electrical engineering and electronics fields who
are dedicated to advancing technological innovation and creating standards.
e. The International Organization for Standardization (ISO) –
Is the world’s largest developer of international standards for a wide variety of products and
services.
f. The Electronic Industries Alliance (EIA) –
Is an international standards and trade organization for electronics organizations. The EIA is
best known for its standards related to electrical wiring, connectors, and the 19-inch racks used
to mount networking equipment.
g. The Telecommunications Industry Association (TIA) –
Is responsible for developing communication standards in a variety of areas including radio
equipment, cellular towers, Voice over IP (VoIP) devices, satellite communications, and more.
h. The International Telecommunications Union-Telecommunication Standardization Sector (ITU-T) –
The ITU-T defines standards for video compression, Internet Protocol Television (IPTV), and
broadband communications, such as a digital subscriber line (DSL).
i. The Internet Corporation for Assigned Names and Numbers (ICANN) –
Coordinates IP address allocation, the management of domain names used by DNS, and the
protocol identifiers or port numbers used by TCP and UDP protocols.
j. The Internet Assigned Numbers Authority (IANA) –
Is a department of ICANN responsible for overseeing and managing IP address allocation,
domain name management, and protocol identifiers for ICANN.
31. The IEEE 802.3 and IEEE 802.11 standards are significant IEEE standards in computer networking.
Explain why.
a. 802.3 –
Defines Media Access Control (MAC) for wired Ethernet. This technology is usually for LANs, but
also has wide-area network (WAN) applications.
b. 802.11 –
Defines a set of standards for implementing wireless local-area networks (WLANs). This
standard defines the Open Systems Interconnection (OSI) physical and data link MAC for
wireless communications.
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32. Match the standards organization to its correct description.
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33. Explain the benefits to using a layered model to describe network protocols and operations.
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a. Assists in protocol design, because protocols that operate at a specific layer have defined
information that they act upon and a defined interface to the layers above and below.
b. Fosters competition because products from different vendors can work together.
c. Prevents technology or capability changes in one layer from affecting other layers above and
below.
d. Provides a common language to describe networking functions and capabilities.
34. There are two basic types of networking models. Explain both:
a. Protocol model –
This model closely matches the structure of a particular protocol suite. The hierarchical set of
related protocols in a suite typically represents all the functionality required to interface the
human network with the data network. The TCP/IP model is a protocol model, because it
describes the functions that occur at each layer of protocols within the TCP/IP suite.
b. Reference model –
This model provides consistency within all types of network protocols and services by
describing what has to be done at a particular layer, but not prescribing how it should be
accomplished. A reference model is not intended to be an implementation specification or to
provide a sufficient level of detail to define precisely the services of the network architecture.
The primary purpose of a reference model is to aid in clearer understanding of the functions
and processes involved
35. What are the two most commonly used network models when discussing network functionality?
a. OSI
b. TCP/IP
36. Fill in the correct information to complete the two network models.
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37. Explain what happens at each of the OSI model layers.
a. Application Layer –
Provides the means for end-to-end connectivity between individuals in the human network
using data networks.
b. Presentation Layer –
Provides for common representation of the data transferred between application layer
services.
c. Session Layer –
Provides services to the presentation layer to organize its dialogue and to manage data
exchange.
d. Transport Layer –
Defines services to segment, transfer, and reassemble the data for individual communications
between the end devices.
e. Network Layer –
Provides services to exchange the individual pieces of data over the network between identified
end devices.
f. Data Link Layer –
Protocols describe methods for exchanging data frames between devices over a common
media.
g. Physical Layer –
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Describe the mechanical, electrical, functional, and procedural means to activate, maintain, and
de-activate physical-connections for bit transmission to and from a network device.
38. Explain what happens at each of the TCP/IP model layers.
a. Application Layer –
Represents data to the user, plus encoding and dialog control
b. Transport Layer –
Supports communication between diverse devices across diverse networks
c. Internet Layer –
Determines the best path through the network
d. Network Access Layer –
Controls the hardware devices and media that make up the network
39. Match the following terms to their definitions.
Data Link
Manages data exchange
Presentation
Bit Transmission
Session
Data Representation
Network
Exchanges frames between devices
Physical
Provides a data path or route
Application
Exchanges frames between devices
Network Access
Segments, transfers, and reassembles data
Transport
Determines the best path through a network
Internet
Organizes dialog – manages data exchange
3.3 Moving Data in the Network
40. What is segmentation?
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Segmentation divides data into smaller, more manageable pieces to send over the network.
41. What are two primary benefits to segmenting data over a network?
a. By sending smaller individual pieces from source to destination, many different conversations
can be interleaved on the network.
b. Segmentation can increase the reliability of network communications.
42. The process used to interleave the pieces of separate conversations together on the network is
called?
Multiplexing.
43. What is the downside to using segmentation and multiplexing to transmit messages across a
network?
It is the level of complexity that is added to the process
44. As application data is passed down the protocol stack on its way to be transmitted across the
network media, various protocols add information to it at each level. This is commonly known as?
The encapsulation process
45. Explain what data encapsulation is.
Data encapsulation is the process that adds additional protocol header information to the data
before transmission.
46. How does de-encapsulation differ from encapsulation?
De-encapsulation is the process used by a receiving device to remove one or more of the
protocol headers.
47. Fill in the blanks on the graphic with the correct PDU name.
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48. OSI model describes the processes of encoding, formatting, segmenting, and encapsulating data for
transmission over the network. What happens at the network layer and data link layer?
They are responsible for delivering the data from the source device or sender, to the
destination device or receiver.
49. A Layer 3 or Network layer IP address has two parts, list and explain both.
a. Network prefix –
The network prefix is used by routers to forward the packet to the proper network.
b. Host part –
The host part is used by the last router in the path to deliver the packet to the destination
device.
50. An IP packet contains two IP addresses, list and explain both.
a. Source IP address –
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The IP address of the sending device.
b. Destination IP address –
The IP address of the receiving device. The destination IP address is used by routers to forward
a packet to its destination.
51. What is the purpose of a data link address?
The purpose of the data link address is to deliver the data link frame from one network
interface to another network interface on the same network.
52. What are other names for a data link address?
a. MAC address
b. Physical address
c. Burned-in address (BIA)
53. Which two addresses are required to send data to another host on the same network?
a. physical address
b. logical address
54. How can a source host can learn the numeric destination IP address of another host?
a. it may learn the IP address through the use of the Domain Name System (DNS)
b. it may know the destination IP address because the address is entered in the application
manually
55. What is Address Resolution Protocol or ARP used for?
To discover the MAC address of any host on the same local network.
56. Explain in detail how Address Resolution Protocol or ARP works?
The sending host sends an ARP Request message to the entire LAN. The ARP Request is a
broadcast message. The ARP Request contains the IP address of the destination device. Every
device on the LAN examines the ARP Request to see if it contains its own IP address. Only the
device with the IP address contained in the ARP Request responds with an ARP Reply. The ARP
Reply includes the MAC address associated with the IP address in the ARP Request.
57. Explain how a host sends a message to another host located on the same network?
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It will forward the message directly. A host will use ARP to discover the MAC address of the destination
host. It includes the destination IP address within the packet header and encapsulates the packet into a
frame containing the MAC address of the destination and forwards it.
58. Explain how a host sends a message to a remote network?
It must use the router, also known as the default gateway. The default gateway is the IP address of an
interface on a router on the same network as the sending host.
59. If no default gateway address is configured in the host TCP/IP settings, or if the wrong default
gateway is specified, what happens to messages addressed to hosts on remote networks?
They cannot be delivered.
60. How does a local host learn the MAC address of its default gateway router?
It can use ARP to determine the MAC address
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