Network+ Guide to Networks, Fourth Edition
Chapter 2
Networking Standards and the OSI Model
At a Glance
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Objectives
Teaching Tips
Quick Quizzes
Class Discussion Topics
Additional Projects
Additional Resources
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Network+ Guide to Networks, Fourth Edition
Lecture Notes
Chapter Objectives
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Identify organizations that set standards for networking
Describe the purpose of the OSI Model and each of its layers
Explain specific functions belonging to each OSI Model layer
Understand how two network nodes communicate through the OSI Model
Discuss the structure and purpose of data packets and frames
Describe the two types of addressing covered by the OSI Model
Networking Standards Organizations
Discuss the concept of standards. Explain that standards are vital for ensuring that products, processes, and
services developed by different parties are able to work together.
Mention that standards define a minimum set of specifications for acceptable performance.
ANSI
Explain that the American National Standards Institute (ANSI) is composed of many industry and
governmental representatives and develops standards for a wide range of technical fields, including
computers and networking.
If the classroom is equipped to do so, show the students ANSI’s Web site to illustrate that standards
documents can be obtained online.
EIA and TIA
Present a brief overview of the missions of the Electronic Industries Alliance (EIA) and the
Telecommunications Industries Alliance (TIA). Mention the TIA/EIA 568-B Series of network cabling
installation guidelines.
IEEE
Describe the overall goals and mission of the Institute of Electrical and Electronics Engineers (IEEE).
Mention that IEEE technical publications are highly regarded and are used in the networking field.
If the classroom is equipped to do so, show the students the IEEE Web site.
ISO
Discuss the mission of the International Organization for Standardization (ISO). Mention that this
organization represents 146 countries and that the scope of its standards covers a wide range of industries
and disciplines.
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Network+ Guide to Networks, Fourth Edition
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ITU
Discuss the mission and power of the International Telecommunication Union (ITU). Stress that the ITU
addresses global telecommunications issues more than industry technical specifications.
ISOC
Describe the overall goal of the Internet Society (ISOC). Mention that the ISOC oversees a number of
groups with specific missions.
Discuss the Internet Architecture Board (IAB) and the Internet Engineering Task Force (IETF), including
their respective missions, their relationship with ISOC, and their relationship with other standards
organizations (such as ITU).
IANA and ICANN
Give a brief overview of Internet protocol (IP) addresses. Stress that these addresses are used to ensure that
each computer on a network has a unique address.
Describe the original purpose and responsibilities of the Internet Assigned Numbers Authority (IANA).
Describe the purpose of Regional Internet Registries (RIRs) and their relationship to IANA.
Discuss the Internet Corporation for Assigned Names and Numbers (ICANN) and the U.S. Department of
Commerce’s (DOC’s) role in IP addressing standards. Mention that the DOC was ultimately responsible for
the creation of ICANN. Also mention IANA’s continued role in IP address administration after ICANN
was created.
Present a brief overview of Internet service providers (ISPs) and their position between individuals and the
organizations presented above.
The OSI Model
Present a brief overview of the Open Systems Interconnection (OSI) model. Name the seven model layers
and describe the general purpose of a layer in the model. Be sure to stress the intimate relationship between
a protocol and a layer of the model.
Mention that the OSI Model is a theoretical representation of network communication. Point out that the
OSI Model is imperfect and that real-world network implementations often do not strictly adhere to the OSI
specifications.
Using Figure 2-1 as an example, illustrate the path that data takes between two computers under the OSI
Model. Stress the fact that a given layer on one computer communicates with the corresponding layer on
another computer.
Teaching
Tip
Networking professionals often devise a mnemonic way of remembering the seven layers of the
OSI Model. For instance, Programmers Dare Not Throw Salty Pretzels Away.
Network+ Guide to Networks, Fourth Edition
Application Layer
Present a brief overview of the Application layer. Mention that is it the top layer in the OSI Model. Stress
that this layer’s services facilitate communication between software applications and lower-level layers of
the OSI Model.
Describe the Hypertext Transfer Protocol (HTTP). Give an overview of its function as an application layer
protocol. Describe how this protocol is used in network communication using the example presented on
page 46 of the text as a guide.
Presentation Layer
Present a brief overview of the Presentation layer. Stress the fact that this layer often serves as a translator
between data formats, such as various graphics file formats.
Mention that the Presentation layer is responsible for encryption and decryption in network
communications.
Session Layer
Briefly describe the purpose of Session layer protocols. Mention that session refers to connection for
ongoing data exchange between two parties.
List some of the Session layer’s functions: Establishing and maintaining the communications link for the
duration of the session; keeping the communication secure; synchronizing the dialogue between the two
nodes; determining whether communications have been cut off; terminating communications; setting s of
communication by deciding which node will communicate first and how long a node can communicate; and
monitoring the identification of session participants.
Transport Layer
Give an overview of the functionality provided by the Transport layer protocols. Mention that Transmission
Control Protocol (TCP) is a Transport layer protocol.
Describe the difference between connection-oriented and connectionless protocols. Review the steps
involved in a client requesting a Web page from a server via TCP. These steps are described on page 48 of
the text.
Describe the concept of a checksum and discuss how it is employed to ensure data integrity during network
communication.
Discuss the processes of segmentation, reassembly, and sequencing. Use Figure 2-2 to illustrate
segmentation and reassembly. Mention the importance of the maximum transmission unit (MTU) and
synchronization in these respective processes.
Network Layer
Present a brief overview of the Network layer protocols. Discuss the purpose of addressing.
Discuss network addresses. Explain the example presented on page 51 of the text. Briefly touch on the
concept of packets and explain that data units become packets as they pass through the Network layer.
Present the concept of routing and discuss how the Network layer fits in with this concept.
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Network+ Guide to Networks, Fourth Edition
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Briefly introduce the IP protocol. Use Figure 2-4 in the text to illustrate an IP packet.
Briefly introduce the concept of fragmentation. Mention that fragmentation at the Network layer is very
similar to segmentation at the Transport layer.
Data Link Layer
Present a brief overview of the Data Link layer. Discuss the function of frames in network communication.
Explain the purpose of the Frame Check Sequence (FCS). Mention that the FCS is calculated via a Cyclic
Redundancy Check (CRC).
Mention that the Data Link layer is divided into two sub-layers: the Logical Link Control (LLC) and the
Media Access Control (MAC) sub-layers. Use Figure 2-5 to illustrate.
Explain the function of the LLC and MAC sub-layers. Mention that the LLC sub-layer communicates with
the Network layer, while the MAC sub-layer communicates with the Physical layer.
Discuss the two pieces of a MAC (MAC) address: the Block ID and Device ID. Illustrate how a MAC
address for a Network Interface Card (NIC) can be identified, using Figure 2-6. Mention that a NIC’s MAC
address can also be identified through your computer’s protocol configuration utility.
Physical Layer
Give a brief overview of the Physical layer. Explain that the protocols at this layer are responsible for
physically sending and receiving signals.
Discuss some of the hardware that operates at the Physical layer. Mention that a NIC operates at both the
Physical and Data Link layers.
Teaching
Tip
Explain to the students that network administrators are generally concerned with the bottom four
layers of the OSI Model, while programmers would be more concerned with the top three layers.
For this reason, this text and the Network+ exam concentrate on the bottom four layers of the
OSI Model.
Network+ Guide to Networks, Fourth Edition
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Quick Quiz 1
1.
Standards define the _____ acceptable performance of a product or service.
Answer: minimum
2.
Addresses used to identify computers on the Internet and other TCP/IP-based networks are known
as _____ addresses.
Answer: Internet Protocol (IP)
3.
Which OSI Model layer is HTTP a protocol for?
a. Network
b. Presentation
c. Application
d. Data Link
Answer: c
4.
Transport layer protocols that do not establish a connection before transmitting and make no effort
to ensure that data is delivered error-free are called _____ protocols.
Answer: connectionless
Applying the OSI Model
Review the seven OSI Model layers and their functions, using Table 2-1 as a guide.
Communication Between Two Systems
Review the method by which data is passed from one network node to another in a typical client/server
exchange. To illustrate, use Figure 2-7 and the detailed example presented on pages 56 through 58 of the
text.
Briefly describe the concept of encapsulation and discuss how it is used in network communication.
Review s frame, packet, datagram, and PDU. Mention that, although these terms are often used
interchangeably, there are differences among some of these terms.
Frame Specifications
Describe the two major categories of frame types: Ethernet and Token Ring. Stress the fact that these two
categories of frame type will not interact on a network, and that most LANs only support one of these two
frame types.
Teaching
Tip
Make sure that students understand the importance of realizing the frame type(s) that a given
network requires. This information is important when installing NOSs, configuring servers and
client workstations, installing NICs, troubleshooting network problems, and purchasing network
equipment.
IEEE Networking Specifications
Discuss IEEE’s 802 family of specifications. Using Table 2-2 as a guide, review some of the more
important IEEE 802 standards.
Network+ Guide to Networks, Fourth Edition
Teaching
Tip
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Remind students that the Network+ certification exam includes questions about IEEE 802
specifications, so they should begin to become familiar with a number of the standards listed in
Table 2-2.
Quick Quiz 2
1.
Which OSI layer establishes, maintains, and terminates user connections?
a. Application
b. Session
c. Data Link
d. Physical
Answer: b
2.
Which OSI layer packages data in frames appropriate to network transmission method?
a. Session
b. Physical
c. Data Link
d. Network
Answer: c
3.
_____ is a networking technology that relies upon direct links between nodes and a ring topology.
Answer: Token Ring
4.
Which of the following IEEE 802 standards addresses standards for wireless networking for many
different broadcast frequencies and usage techniques?
a. 802.2
b. 802.8
c. 802.11
d. 802.12
Answer: c
Class Discussion Topics
1.
There are a number of standards organizations that specify standards relating to networking. Ask
the students whether they feel that it is more efficient to have multiple standardization
organizations, or if it would be more efficient to have a unified standards organization for the
networking field. Do the students feel that it would be feasible to create such an organization?
2.
Ask students what benefits they see in the OSI Model’s division of network communication into
seven distinct layers. What are the advantages and disadvantages of this approach?
Additional Projects
1.
Have students use the Internet to research one or two organizations not mentioned in this chapter
that are involved in creating standards for the computer industry (preferably standards that relate
to the networking field). Compile the students’ results into a list, which can be distributed to the
class.
2.
Have students research some common protocols used at the Application layer of the OSI Model.
Compile a list of the students’ results. Ask the students to identify any protocols on this list with
which they are familiar.
Network+ Guide to Networks, Fourth Edition
Additional Resources
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OSI Model Practice Quiz: http://gocertify.com/quizzes/osi/
OSI Protocols: http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/osi_prot.htm
TCP/IP Tutorial: http://www.cse.ohio-state.edu/~jain/cis677-00/e_8ip.htm
Network Protocols Tutorial (two parts):
o http://www.networkmagazine.com/article/NMG20000720S0002
o http://www.networkmagazine.com/article/NMG20000726S0007
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