Bay Networks | UPS45 | Lesson 1-2: Connectivity and Internetworking Devices

Unit 1: Internetworking Overview
Lesson 1-2: Connectivity and Internetworking Devices
At a Glance
Connectivity devices are devices used to make physical network
connections. They do not make changes to the data or transmission route.
Connectivity devices operate at the physical layer of the Open Systems
Interconnection (OSI) model.
Internetworking devices move data across a network. They may direct
data to specific locations within the network and/or convert data into
alternative formats. Internetworking devices operate at OSI layers above
the physical layer.
Understanding the functions of these devices and how they fit within the
OSI model will help you learn how networks function.
What You Will Learn
After completing this lesson, you will be able to:
1-
•
Identify network connectivity and internetworking devices.
•
Match the appropriate level within the OSI model to which each device
is assigned.
•
Compare the functionality of connectivity and internetworking devices.
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Tech Talk
36
•
BridgeNetwork segments that typically use the same
communication protocol use bridges to pass information from one
network segment to the other.
•
GatewayWhen different communications protocols are used by
networks, gateways are used to convert the data from the sender’s
•
HubAnother name for a hub is a concentrator. Hubs reside in the
core of the LAN cabling system. The hub connects workstations and
sends every transmission to all the connected workstations.
•
Media Dependent AdapterA MDA is a plug-in module allowing
selection among fiber-optic, twisted pair, and coaxial cable.
•
Media FilterWhen the electrical characteristics of various networks
are different, media filter adapter connectors make the connections
possible.
•
Multistation Access UnitMAUs are special concentrators or hubs
for use in Token Ring networks instead of Ethernet networks.
•
Network Interface CardNICs are printed circuit boards that are
installed in computer workstations. They provide the physical
connection and circuitry required to access the network.
•
RepeaterConnectivity device used to regenerate and amplify weak
signals, thus extending the length of the network. Repeaters perform
no other action on the data.
•
RouterLinks two or more networks together, such as an Internet
Protocol network. A router receives packets and selects the optimum
path to forward the packets to other networks.
•
SwitchA connection device in a network that functions much like a
bridge, but directs transmissions to specific workstations rather than
forwarding data to all workstations on the network.
•
TransceiverThe name transceiver is derived from the combination
of the words transmitter and receiver. It is a device that both transmits
and receives signals and connects a computer to the network. A
transceiver may be external or located internally on the NIC.
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Unit 1: Internetworking Overview
Connectivity Devices
Connectivity devices are those devices used to make physical network
connections. Connectivity devices operate at the physical layer of the Open
Systems Interconnection Reference Model (OSI) model. The OSI model
describes how computer services and procedures are standardized. This
standardization allows computers to share information and enables the
interconnection of various networking connectivity devices regardless of
vendor.
The OSI model uses the concept of seven stacked layers to define a network
communications system.
The lower three layers: Physical, Data Link, and Network, deal mostly
with network-dependent (hardware) functions.
The OSI Model
Application
7
Presentation
6
Session
5
Transport
4
Network
3
Data Link
2
Physical
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Lesson 1-2: Connectivity and Internetworking Devices
The upper four layers: Transport, Session, Presentation, and Application,
deal more with application-oriented (user or software) functions.
Generally speaking, these connectivity devices are passive in their actions,
meaning that they do not make changes to either the data or the
transmission route of that data. These devices simply provide the physical
link between workstations and other network devices.
Network Interface Card
Network interface cards (NICs) are printed circuit boards that are
installed in workstations. They provide the physical connection between
the network cable and the workstation. In addition, they possess the
circuitry necessary to gain access to the network.
In the past, computers did not come with a pre-installed NIC. However,
most modern computers are shipped with NIC already installed and ready
to be connected to a network.
Network Interface Cards are Installed Inside Workstations
NIC
Workstation
RJ-45 Connector
Cat. 5 UTP Cable
38
•
Each NIC has a distinctive 6-byte hardware address that identifies the
workstation within a segment, such as Ethernet 00-00-A2-9A-4E-10.
•
Each NIC has at least one connection port where the network cable is
attached. Only one port may be used at any one time.
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Unit 1: Internetworking Overview
•
The NIC formats information from the workstation so that it can be
transmitted across the network.
•
Although the NIC operates at the physical layer of the OSI model, it is
also considered a data link layer device. Part of the NIC’s function is to
format information between the workstation and the network, and also,
to control the transmission of data onto the wire.
Transceivers
The name transceiver is derived from the combination of the words
transmitter and receiver. It is a device that both transmits and receives
signals along the network cable and connects a computer to the network.
Transceivers May Be External or Located on the NIC
Hub
Nor
t
Net el
wor
ks
Cable
10BASE-T
transceiver
Workstation
1-
•
Today, most transceivers are built into the network interface cards.
Older transceivers were clamped onto the network cable and then
connected to the NIC.
•
The transceiver does not make changes to information transmitted
across the network, it adapts the signals so devices connected by
varying media can interpret them.
•
A transceiver operates at the physical layer of the OSI model.
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Lesson 1-2: Connectivity and Internetworking Devices
Repeaters
As data travels through cabling systems, a certain amount of electrical
interference and signal loss is inevitable. As the need for larger networks
that span greater distances developed, a solution was needed to resolve
signal loss over the network. Repeaters were created to regenerate and
amplify weak signals, thus extending the length o f the network. The basic
function of a repeater is to retime, reshape, and reamplify the data signal
to its original level.
Repeaters Amplify Weak Signals
500 meters
Sending
Workstation
Repeater
Receiving
Workstation
40
•
Repeaters perform no other action on the data.
•
Repeaters were originally separate devices. Today, a repeater may be a
separate device or it may be incorporated into a hub.
•
Repeaters operate at the physical layer of the OSI model.
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Unit 1: Internetworking Overview
Hubs
Hubs, sometimes called concentrators, reside in the core of the LAN
cabling system. They are basically multiport repeaters. The hub connects
workstations and sends every transmission to all the connected
workstations. They work much like the old telephone party lines, where
only one computer can “talk” at a time.
Hubs Connect Workstations Together
Hubs send all information
to all other workstations
Hub
Workstations
send packets of
information to the hub
1-
•
The receptacles on the front of the hub are called ports. There are
usually from 4 to 32 ports on a hub, depending on the size of the
network.
•
Some hubs have an additional interface port that connects to another
hub, thus increasing the size of the network.
•
Hubs operate at the physical layer of the OSI model.
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Lesson 1-2: Connectivity and Internetworking Devices
Media Dependent Adapter
A media dependent adapter (MDA), sometimes referred to as transceivers,
is a module added to a hub to provide flexible cable connectivity. These
optional devices provide a connection port for a cable connector that is
different than the hub’s ports. For example, a MDA can be used to connect
a fiber-optic cable to a hub with RJ-45 connectors otherwise not compatible
with fiber-optic connectors.
•
Media dependent adapters are also used on servers, switches, routers,
transceivers, and to make direct connections to end stations.
•
MDAs function at the physical layer of the OSI model.
Media Filters
A media filter is a very specialized kind of adapter used on token ring
networks. When token ring networks were first implemented, they used
shielded-twisted pair (STP) cabling. Token ring networks now use
unshielded-twisted pair (UTP) cables.
There is a difference in the electrical characteristics between these cabling
systems. If a STP-specific network interface card in a token ring network is
connected to a UTP cable, the network data signal will be damaged.
Attaching media filters between the NIC and the UTP cable reduces the
interference and prevents damage to the data. Media filters function at
the physical layer of the OSI model.
Check Your Understanding
♦ Explain why a network interface card may be considered part of
both the physical layer and the data link layer of the OSI model.
♦ Diagram a functioning hub and explain how a hub functions.
Internetworking Devices
As networks became increasingly complex, the need for internetworking
devices also increased. Internetworking devices are active components
rather than passive. They are considered active because they do more than
simply pass data across a network. They make “intelligent” decisions and
may interpret, reformat, and/or direct data as it passes through a network.
Internetworking devices typically operate at OSI model layers other than
the physical layer.
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Bridges
Bridges connect network segments typically using the same
communication protocol, passing information from one network to the
other. A bridge may divide an overloaded network into smaller, more
efficient networks. Bridges break networks into separate segments and
direct transmission to the appropriate segment much like a police officer
directs automobile traffic.
Bridges Segment Networks and Direct Traffic
LAN 1
Data
STOP
Bridge
Data
STOP
Data
LAN 2
1-
•
Bridges learn which workstations are on what network segment by
looking at the hardware address in the frames it receives and entering
this information into a table.
•
Bridges function at the data link layer of the OSI model.
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Lesson 1-2: Connectivity and Internetworking Devices
•
A bridge monitors information passing over a network segment and
restricts the flow of unnecessary information. It also listens to all
traffic on the segment, determines the destination address, looks up the
destination address in the table, and then passes the frame to the
correct segment.
•
Bridges can be used to connect different types of cabling from one LAN
to another.
Switches
One way of relieving network congestion is to use a switch, either in place
of a hub or bridge, or in addition to a hub.
Switches Direct Information to Specific Workstations
Sending
Workstation
44
Data
Data
Data
Data
Switch
Receiving
Workstation
•
Switches allow each workstation to transmit information over the
network independent of the other workstations.
•
These transmissions between computers may be simultaneous. As
opposed to hubs, switches are more like the modern telephone system
where several private conversations take place at one time.
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•
Some switches can operate at different speeds, allowing the connection
of cables using different bandwidths (example, 10 Mps and 100 Mps).
•
There are different types of switches. Layer 3 switches function at the
network layer because they can perform translation activities between
network segments. Layer 2 switches function at the data link layer
because they primarily direct traffic to specific workstations.
Routers
Routers link two or more different networks together, such as an Internet
Protocol network. These networks can consist of various types of LAN
segments, for example, Ethernet, token ring, or Fiber Distributed Data
Interface (FDDI). A router receives packets and selects the optimum path
to forward the packet across the network. Routers build a table of all the
device addresses (routing table) across the networks. Using this table, the
router forwards a transmission from the sending station to the receiving
station across the best path.
Routers Direct Traffic from Different Networks via Optimum Paths
Sending
Token
Ring
Data
Internet
168.192.2.13
168.192.1.1
Router
168.192.2.14
Data
Data
168.192.2.1
168.192.3.140
168.192.3.134
168.192.3.3
168.192.3.130
168.192.3.1
Data
168.192.3.129
168.192.3.4
168.192.3.7
Bridge
•
1-
168.192.2.17
10BaseT
LAN
168.192.3.132
Data
Data
10BaseT
LAN
168.192.3.152
Receiving
168.192.3.8
Bridges know the 6-byte hardware address of all workstations on the
network segment. In contrast, routers maintain a table of all learned
network addresses, for example, 168.192.1.0, 168.192.2.0, and
168.192.3.0 are three IP network addresses.
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Lesson 1-2: Connectivity and Internetworking Devices
•
Routers can increase network efficiency by filtering out broadcast
traffic between networks, thus reducing unnecessary traffic between
networks.
•
Routers can connect different network types such as Ethernet, token
ring, and FDDI.
•
Routers operate at the network level of the OSI model.
Gateways
Gateways are multi-purpose connection devices. They are able to convert
the format of data in one computing environment to a format that is usable
in another computer environment (for example, AppleTalk and DECnet).
The term gateway is sometimes used when referring to a router. For the
purpose of this lesson, gateways are devices that link different network
types and protocols. For example, gateways translate different electronic
mail protocols and convey email across the Internet.
Gateways Translate Different Network Protocols
10BaseT
LAN
AppleTalk
LAN
Internet
Data
Data
SMTP
Mail
Data
Data
Internet Mail
Protocol
IP LAN
Gateway
POP
Mail
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Unit 1: Internetworking Overview
Gateways can operate at all layers of the OSI model since they:
•
Can provide a physical link between networks.
•
Create junctions between dissimilar networks.
•
Translate different network protocols and/ or applications (for example,
electronic mail between the Internet and a commercial online service
with its own mail protocol).
Check Your Understanding
♦ Diagram the difference between a switch and a hub and explain the
function of each.
1-
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Lesson 1-2: Connectivity and Internetworking Devices
Try It Out
Connectivity and Internetworking Devices
Take some time to examine each of the internetworking devices. Notice the similarities
and differences among the components.
Materials Needed
•
•
•
•
•
•
•
Computer and Pre-Installed Network Interface Card
Drivers necessary for NIC, if needed
BayStack 152 and/or 153 Hubs and manufacturer’s manuals
BayStack 350T Switch and manufacturer’s manual
BayStack ARN Router and manufacturer’s manual
Static GuardWrist strap
Screwdriver
Directions: Examining Networking Equipment
Examine and sketch each piece of equipment carefully. Include the fine details in the
illustrations, such as the correct number of ports, pins in the ports, and so on. Title each
illustration and include it in your portfolio. You will be using them again in the next
lesson. Your sketches must show both a front view and a back view. Use the computer
or traditional means to produce your media drawings.
Notice that each piece of equipment tells you what it is, for example BayStack 152
10BASE-T hub. As you can see, the devices’ faces look quite similar, so that sometimes
the only way you can tell its function is to read the identification name or number.
Notice that there are different types of ports for inserting the various cables. In the next
lesson, we will discuss the different cable and connector types. Not all cables and
connectors can be used with every piece of equipment. It is important when purchasing
networking equipment that you pay attention to the ports. Be sure your drawing shows
all of the different ports.
Take time to look through the documentation that comes with the equipment so that you
are familiar with its contents. The documentation may help you with your drawing.
Procedures: Removing and Re-installing a Network Interface Card
Before a workstation is attached to a piece of network equipment, a network interface
card (NIC) must be installed in the workstation. This is a simple installation, but it
requires attention to detail and safety precautions. In order to get you familiar with how
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to install a NIC, in this lab you will first remove the pre-installed NIC from your
computer before re-installing it.
Before Installation
Computers are made from microchips, which are built from transistors. Transistors
require only a small amount of electrical current to run powerful computers. Voltage
associated with static electricity can be as high as 25,000 volts, enough to damage a
computer’s electronic circuitry; therefore, static guard wrist straps for grounding
purposes are essential for preventing unwanted static electricity discharges from
destroying computer components. Also, review personal safety rules for prevention of
electrical shock.
As you complete this activity, keep a record of your activities and observations for
inclusion in your Logbook. Once again, record problems encountered, positive outcomes,
and so on.
You will remove and re-install a NIC. It is vital that you keep detailed, labeled
drawings/sketches of the steps you take, cable placements, and so on, when you remove
the NIC. In that way, you can be sure of replacing everything properly, without affecting
the operation of your workstation.
1. Wear a wrist strap that connects you to the computer. See your
instructor if you are unsure of how to use the wrist strap. The
resistance end needs to be wrapped firmly to the wrist. The metal end
needs to be attached to the housing of the power supply. This process
provides a source to ground, reducing the chance of static electricity
damaging the workstation.
2. Keep notes and detailed sketches as you complete this installation and
record in your Logbook any problems or frustrations that occur.
3. Turn off the computer.
4. Disconnect the power cord to the computer workstation.
5. Disconnect any external cables attached to the workstation.
6. Sketch the workstation and ports. Label cable and connections as a
reference for re-installation.
7. Locate the screws that secure the chassis and remove them. Gently
remove the cover from the workstation.
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Lesson 1-2: Connectivity and Internetworking Devices
Install Small
Screw
8. Locate the NIC installed in the workstation. If necessary, remove the screw(s)
securing the NIC to the chassis. Gently remove the card from its slot.
Ø NEVER TOUCH THE ELECTRICAL CONTACT POINTS WHEN
HANDLING COMPUTER COMPONENTS. THE MOISTURE
FROM YOUR BODY CAN CAUSE DAMAGE TO THE CIRCUIT
BOARDS.
9. Set the NIC gently down on a clean table or static pad to examine.
10. Sketch the NIC from various vantagepoints. The end view should include all
the ports. Note the brand name and number of the NIC if it is available.
11. When you have finished sketching the NIC, using care not to touch any of the
circuitry, align the NIC with the slot.
12. Gently, but firmly, press the card into the slot. Do not rock the card.
NIC
NIC Installation Slot
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13. If the card is fully seated in the slot, the bottom edge of the card will be
hidden.
14. Fasten the flanges into the exterior opening with screws to secure the NIC in
place.
15. Place the case over the workstation and replace all screws and cables. Test the
connectivity of the NIC by attempting to connect the network.
16. Restart your computer.
17. From the desktop window, double click
.
18. Double-click
.
19. Computers in your workgroup will appear as icons
Rubric: Suggested Evaluation Criteria and Weightings
Criteria
Participation and teamwork
Detailed diagram of hubs, switches, and routers
with attention paid to accuracy of ports
Successful removal and re-installation of NIC
Detailed notes and comments on re-installation
integrated into Logbook for future reference
TOTAL
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%
25
25
Your Score
25
25
100
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Lesson 1-2: Connectivity and Internetworking Devices
Stretch Yourself
WINIPCFG: Windows 95/98 Network Utility
In order for data signals to be transmitted and received, computer nodes must have
unique addresses, much like your home address is needed to receive mail from the post
office. Your home address is unique. Its uniqueness is what allows your mail to be
delivered to your unique address and not to another location. Computer workstations on
networks need unique addresses also so data is transmitted between the source and
destination devices accurately.
Although there is much more to learn about networks, their components, and protocols, it
is possible to view the addresses of workstations.
Materials Needed
•
Networked computer with Windows 95 or 98
Directions: Configuring TCP/IP Protocols
TCP/IP is one of the most important sets of protocolsin networking today.It is the
backbone of the Internet and is everywhere from the smallest to the largest network. You
will learn more about TCP/IP later in this course. It comes with Windows95/98. In this
activity, you will set up the TCP/IP protocols for your workstation.
Procedures: Configuring TCP/IP Protocols
1. Start your computer.
2. Click
.
• Select Settings.
• Select Control Panel.
3. In the Control Panel window, double-click the Network
icon.
4. In the Network window, highlight File and print sharing for Microsoft
Networks.
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5. Click
.
6. In the Select Network Component Type window, highlight Protocol.
7. Click
.
8. In the Select Network Protocol window, highlight Microsoft and TCP/IP.
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Lesson 1-2: Connectivity and Internetworking Devices
9. Click
.
10. You will see the Network Configuration window next. Notice that the TCP/IP
protocol has been added.
Directions: WINIPCFG
WINIPCFG is a network utility packaged with the Windows 95/98 operating system. In
this portion of the lab, you will run WINIPCFG and discover the Internet Protocol (IP)
addresses of your workstation and the other internetworking devices on the network.
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Procedures: WINIPCFG
1.
2.
At a workstation connected to a Network, click the Start menu of your PC.
Highlight Run. In the dialog box that appears, type winipcfg.
3.
4.
Click
.
The IP Configuration box will appear. Depending on how the network is set
up and how many network interface cards are installed in the workstation,
there may be more than one configuration.
If the IP Address is all 0s, you may have to choose a NIC (often called an
Ethernet adapter) from the pull-down menu. Once you have chosen the NIC,
you will see the addresses of the adapter, the workstation’s IP, the subnet
mask, and the gateway. The subnet is a network that is a component of a
larger network.
6. Copy the following information from your workstation’s IP Configuration.
Note that this address is unique for your workstation.
• Adapter Address _____________________________________
• IP Address __________________________________________
• Subnet Mask ________________________________________
• Default Gateway _____________________________________
5.
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Lesson 1-2: Connectivity and Internetworking Devices
7.
Click
. Much of what will be displayed will not make sense right
now. However, it is possible to see each workstation, and using the hardware
(adapter) and IP, track network device addresses. Bridges, routers, and
gateways are able to learn these addresses and direct traffic to the correct
workstation.
Create a diagram of the network devices and workstations connected to your
network.
9. Gather the Adapter and IP addresses of the other network workstations from
your fellow students and label each workstation on the diagram with the
correct addresses. Save the diagram in your Portfolio for future use.
10. In a short paragraph in your Logbook, note any discoveries made from the
diagram and the addresses corresponding to the network devices and
workstations.
8.
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Rubric: Suggested Evaluation Criteria and Weightings
Criteria
Participation and teamwork
Detailed network diagram with correct IP and
Adapter Addresses
Analysis and synthesis of information
TOTAL
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%
25
50
Your Score
25
100
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Lesson 1-2: Connectivity and Internetworking Devices
Network Wizards
IP Addressing Research
Materials Needed
•
Internet connection
Directions
1. During this lesson and the Stretch Yourself lab, the concept of addressing was
introduced. There is significance to the numbers and their sequence in an address.
2. How are the numbers in the addresses related to the information learned from the
data transmission lesson?
3. Using the Internet, research IP addressing.
4. Write a one-page paper on IP addressing and the significance of the numbers and
sequence to put in your Portfolio. Include your references at the end of the paper.
Rubric: Suggested Evaluation Criteria and Weight
Criteria
On-time delivery of assignment
Content and quality of one-page research paper
Organization, spelling, grammar
References
TOTAL
%
10
50
25
15
100
Your Score
Summary
In this lesson, you learned the following:
58
•
The identification of network connectivity and internetworking devices.
•
To match the appropriate level within the OSI model to which each
device is assigned.
•
The comparison of the functionality between connectivity and
internetworking devices.
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Unit 1: Internetworking Overview
Review Questions
Name__________________
Lesson 1-2: Connectivity and Internetworking Devices
Part A
Identify each item as either a connectivity device or an internetworking
device by placing a “C” or an “I” next to the item.
1. Bridge
7. Switch
2. Multistation Access Unit
8. Gateway
3. Transceiver
9. Router
4. Network Interface Card
10. Repeater
5. Hub
11. Media Filter
6. Media Dependent Adapter
Part B
Identify which layer of the OSI model each device is assigned.
1. Bridge
2. Repeater
3. Network Interface Card
4. Router
5. Transceiver
6. Multistation Access Unit
7. Hub
8. Switch
9. Media Dependent Adapter
10. Media Filter
11. Gateway
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Lesson 1-2: Connectivity and Internetworking Devices
Part C
1. Compare the functions of bridges, hubs, repeaters, routers, and
switches. Tell which layer of the OSI each device functions.
Scoring
Rubric: Suggested Evaluation Criteria and Weightings
Criteria
%
Part A: Identify network connectivity and
internetworking devices.
22
Part B: Identify the appropriate level within
the OSI model to which each device is
assigned.
22
Part C: Compare the functionality of
connectivity and internetworking devices.
56
TOTAL
100
Try It Out
100
Stretch Yourself
100
Network Wizards
100
FINAL TOTAL
400
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Unit 1: Internetworking Overview
Resources
Advanced Computer Networks (1998). Networking Solutions Guide. (1998)
[Online]. Available: www.compnetworks.com/solution.htm [1999, March 1].
Aschermann, Robert (1998). MCSE Networking Essentials for Dummies.
IDG Books Worldwide, Inc. Foster City, California.
Bay Networks. (1998). Internetworking Fundamentals, Bay Networks,
Inc., Billerica, Massachusetts.
Bert, Glen (1998). MCSE Networking Essentials: Next Generation
Training Second Edition. New Riders Publishing, Indianapolis, Indiana.
Casad, Joe. et al. (1997). MSCE TestPrep Networking Essentials. New
Riders Publishing, Indianapolis, Indiana.
Chellis, James; Perkins, Charles; & Strebe, Matthew (1997). MCSE
Networking Essentials Study Guide. Sybex Inc., Alameda, California.
Computing and Communications Services Office, University of Illinois at
Urbana-Champaign (1999). Network Administrator’s Survival Handbook.
Available: www.ntx2.cso.uiuc.edu/nas/network_adminstrator.htm [1999, May
13].
Derfler, Jr., Frank J., & Freed, L. (1998). How Networks Work, Fourth
Edition. Macmillan Computer Publishing/Que Corporation, Indianapolis,
Indiana.
Groth, David. Bergersen, Ben. Catura-Houser, Tim (1999). Network+
Study Guide. Sybex Inc., Alameda, California.
Hayden, Matt. (1998). Sam's Teach Yourself Networking in 24 Hours.
Sam's Publishing, Indianapolis, Indiana.
Lowe, Doug. (1998). Networking for Dummies. Third Edition. IDG Books
Worldwide, Inc., Foster City, California.
Microsoft Corporation (1998). Dictionary of Computer Terms, Microsoft
Press, Redmond, Washington.
Nortel Networks (1998). Internetworking Fundamentals: Student Guide.
Bay Networks Inc. Billerica, Massachusetts.
Nortel Networks (1999). NetKnowledge: Internetworking Fundamentals.
Nortel Networks, Billerica, Massachusetts.
Palmer , Michael J. (1998) Hands-On Networking Essentials with Projects,
Course Technology, Inc. Cambridge, Massachusetts.
The Siemon Company (1997). Siemon Guidelines to Industry Standards
[Online]. Available: www.siemon.com/horiz.html [1999, March 3].
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Lesson 1-2: Connectivity and Internetworking Devices
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ST0025803A
Internetworking Fundamentals
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