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Networking BASICS
Network
Architectures
Unit 2
Lesson 4
Lesson 4—Networking BASICS
1
Objectives
• Explain why standards were
developed for LANs.
• Give several examples of
Ethernet architectures.
• List the features of a token ring
network.
Lesson 4—Networking BASICS
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Objectives (continued)
• Tell how a wireless LAN
functions.
• Provide guidelines for designing
a network.
Lesson 4—Networking BASICS
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Standards
• Different architectures could
restrict the growth of
networking.
• The Institute of Electrical and
Electronic Engineers (IEEE)
developed computer network
architecture standards.
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Standards
• The IEEE efforts were called
Project 802.
• There are three dominant
standards: Ethernet (802.3),
token ring (802.5), and
wireless (802.11).
Lesson 4—Networking BASICS
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Ethernet
• Ethernet is the most popular LAN architecture
today.
• It is easy to install and inexpensive.
• Data transmission is broken into packets.
• The standard method of labeling different
versions is Maximum Speed-Transmission
Mode-Segment Length or Media Type.
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10Base2
• It is a bus topology that uses contention
(CSMA/CD) and thin coax.
• Segments are connected together
through a repeater.
• It can connect up to five 200-meter
segments using four repeaters (5-4-3
rule).
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10Base2
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10Base-T
• It runs 10 Mbps and uses
CSMA/CD.
• It is a star-wired bus
topology.
• It is still used today due to its
reliability and ease of use.
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10Base-T
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100Base-T
• It uses CMSA/CD as a star-wired
bus.
• There are three subcategories of
100Base-T networks with different
cable requirements.
• The most common is 100Base-TX
(Category 5 or higher UTP).
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Switched Ethernet
• A switch knows which segment
belongs to which device.
• It uses a table stored in memory
to send a packet.
• It increases bandwidth by
decreasing traffic and collisions.
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Switched Ethernet
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100VG-AnyLAN
• It uses Category 3 or higher cabling or
fiber optic cable.
• It is a true star network topology with
central hubs controlling the network.
• It uses the demand priority channel
access method.
• It supports other network architectures.
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Gigabit Ethernet
• 1000Base-T is a star topology
that uses Category 5 or higher
cabling.
• It increases speed by sending
more bits and using 4 pairs of
wires simultaneously.
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10G Ethernet
• It can be used in both LANs
and WANs.
• It requires fiber optic cable.
• Networks do not encounter
collisions.
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Token Ring
• It has the ability to diagnose and
avoid network problems.
• It does not slow down when more
devices are added to the network.
• The packet size can be larger than
on an Ethernet network.
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Token Ring
• IEEE Project 802.5
• 16-Mbps speed
• It uses twisted pair cable in a hybrid
star ring topology
• The packets go to a central hub
called the Multistation Access Unit
(MAU).
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Token Ring
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WLAN
• Wireless local area network
• It is used when mobility is needed,
but it still must remain connected to
the network.
• 802.11b or Wi-Fi (11 Mbps)
• 802.11a or Wi-Fi5 (108 Mbps)
• 802.11g (54 Mbps)
Lesson 4—Networking BASICS
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WLAN
• Only wireless network interface cards
and access points are needed.
• An access point acts as a link between
wireless and wired networks.
• 802.11b uses Carrier Sense Multiple
Access with Collision Avoidance
(CSMA/CA).
Lesson 4—Networking BASICS
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WLAN
Lesson 4—Networking BASICS
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Network Design
• Basic rules should be followed for a
good network design.
• The switches in an Ethernet network
must be configured in a hierarchy.
• Smaller network segments are better
than larger network segments.
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Summary
• In the early 1980s, the Institute of Electrical and Electronic
Engineers (IEEE) began work on developing computer network
architecture standards. Known as Project 802, this work established the foundation for three network architecture standards
that make up over 95 percent of the LANs in use today. These
three dominant standards are Ethernet (802.3), token ring
(802.5), and wireless (802.11).
• IEEE Project 802.3 set specifications for a type of local area
network known as Ethernet. Several versions of Ethernet transmit at 10 Mbps, but these are rarely used today. 10Base5, also
called Standard Ethernet, required the use of thick coaxial
cable. Other versions of 10 Mbps Ethernet were designed to run
over fiber optic cable in specific settings.
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Summary (continued)
• 10Base2 is a version of Ethernet that used to be very popular
and is still used today, although not as extensively. 10Base2 is a
bus topology that uses contention (CSMA/CD) and requires thin
coax cable as the transmission media. 10Base-T also runs at 10
Mbps, uses CSMA/CD, and can support a total of 1,024 devices
on the network. 10Base-T is a star-wired bus topology, which
means it functions like a bus (in that each packet makes a stop
at every device), but is wired like a star (with one central
controlling device).
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Summary (continued)
• As faster network architectures were needed beyond 10 Mbps,
the IEEE subcommittee began work on creating a new Ethernet
standard called 100Base-T (or Fast Ethernet). 100Base-T has
many of the same basic characteristics as 10Base-T. It uses
CSMA/CD as its channel access method, the topology is a starwired bus, and it continues to use the same basic equipment
(such as hubs in distribution racks with patch panels). The only
new items for 100Base-T networks were 100-Mbps NICs and
100-Mbps hubs. To increase the speed even more, a switch (or
a switching hub) is used. A switch knows which segment goes to
which network device. This dramatically increases the bandwidth on the network because it decreases the traffic and the
number of collisions. Ethernet networks that use switching hubs
are often called Switched Ethernet.
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Summary (continued)
•
•
100VG-AnyLAN also runs at 100 Mbps. The network topology is a true
star, with central hubs controlling the network. 100VG-AnyLAN uses the
demand priority channel access method instead of CSMA/CD. This
means that when a device needs to transmit a packet, it must first send
a request to the hub and then wait for permission before transmitting.
Unlike CSMA/CD, demand priority prevents collisions that slow down
the network. Another advantage of 100VG-AnyLAN is its ability to
support other network architectures.
Gigabit Ethernet (or 1000Base-T) is the standard that most closely
resembles 100Base-TX. 1000Base-T is a star topology that uses
Category 5 or higher cabling. 1000Base-T achieves its higher speed by
increasing the number of bits sent and sending data in over all four
pairs of wires simultaneously. 10G Ethernet transmits at 10 billion bits
per second.
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Summary (continued)
• IEEE Project 802.5 set specifications for a type of local area
network known as token ring. Token ring runs at 16 Mbps and
uses twisted pair cable in a hybrid star ring topology. The
packets in a star ring do not go directly to the next device on the
ring; instead, they go to a central hub, which then sends the
packet to the next device on the ring. At the center of a token
ring network is a hub, called the Multistation Access Unit (MAU).
Token ring also has the ability to diagnose and avoid network
problems.
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Summary (continued)
• Wireless local area networks (WLANs) are found anywhere a
user needs mobility but still must remain connected to a network. The list of components necessary for a WLAN is short.
Only wireless network interface cards and access points are
needed for communication to take place. A wireless NIC performs the same functions as a wired NIC except an antenna is
used to send and receive radio frequency signals. An access
point (AP) is a device that contains a radio transceiver (to send
and receive signals) along with an RJ-45 wired network interface, which allows it to connect by cable to a standard wired
network.
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Summary (continued)
•
Some basic rules should be followed for good network design. First,
switches in an Ethernet network must be configured in a hierarchy,
sometimes known as an inverted tree. In a hierarchy, only one possible
path exists between any two devices. Secondly, smaller network segments are better than larger network segments. Smaller segments
make managing a network easy to do. Segmenting can also be accomplished by dividing the network into a hierarchy using switches. Core
switches are those switches that are farther up in the hierarchy and
carry traffic between switches. Workgroup switches are connected
directly to the devices on the network. Lower-cost hubs can often be
substituted for switches at the workgroup level. Segmenting can also
be accomplished by grouping devices into logical groupings. This is
known as creating a virtual LAN (VLAN).
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