Chapter 5
LANs and WLANs
5 Chapter Contents
Section A: Network Building Blocks
Section B: Wired Networks
Section C: Wireless Networks
Section D: Using LANs
Section E: Security Through Encryption
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5
SECTION
A
Network Building Blocks
Network Classifications
LAN Standards
Network Devices
Clients, Servers, and Peers
Physical Topology
Network Links
Communications Protocols
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5 Network Classifications
Personal Area Network (PAN) – interconnection of
personal digital devices
Neighborhood Area Network (NAN) – connectivity
spread over several buildings
Local Area Network (LAN) – usually connects
computers in a single building
Metropolitan Area Network (MAN) – public highspeed network with range of about 50 miles
Wide Area Network (WAN) – consists of several
smaller networks
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5 LAN Standards
LAN technologies are standardized by the
Institute of Electrical and Electronics
Engineers (IEEE) Project 802 – Local
Network Standards
– IEEE 802.3 specifies the standards for Ethernet
wired local area networks
• How devices physically signal each other, how devices
“share the wire in the wall”, etc.
– Ethernet is the de facto standard for wired LAN in
use today
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5 Ethernet Frame Structure
Type
IEEE 802.3 Ethernet frame
64 – 1518 bytes in length
 Preamble: 8 bytes
 7 bytes with pattern 10101010, followed by one byte with pattern
10101011 (frame delimiter)
 used to synchronize receiver, sender clock rates
 Addresses: 6 bytes, frame is received by all adapters on a LAN and
dropped if address does not match
 Type (Length): 2 bytes, length of data segment (min. 46 bytes)
 CRC (Cyclic Redundancy Check): 4 bytes, created by sender,
checked by receiver, if error detected, the frame is simply dropped
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5 Network Devices
Each connection point on a network is referred to
as a node
To connect to a LAN, a computer requires network
circuitry, sometimes referred to as a network
interface card (NIC)
A networked peripheral, or network-enabled
peripheral, is any device that contains network
circuitry to directly connect to a network
A network device, or network appliance, is any
electronic device that broadcasts/re-broadcasts
network data, boosts signals, or routes data to its
destination
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5 Network Devices
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5 Clients, Servers, and Peers
 Network devices can function as clients or as servers
– Application server
– File server
– Print server
 Networks that include one or more servers can operate
in client/server mode
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5 Physical Topology
 The arrangement of devices in a network is referred to as its
physical topology
–
–
–
–
–
Star: central connection point
Ring: attached to 2 neighbors
Bus: common, shared backbone
Mesh: multiple interconnections
Tree: stars on a bus
 Two similar networks can
be connected by a device
called a bridge (or switch)
 Gateway is a generic term
for any device or software
code used to join two networks
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5 Network Links
A communications channel, or link, is a
physical path or frequency for signal
transmissions
Bandwidth is the transmission capacity of a
communications channel (usually expressed
in bits/sec, bps)
– Broadband
– Narrowband
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5 Communications Protocols
Rules (Standards) for efficiently and
effectively transmitting data from one network
node to another. They define how to:
– Divide messages into packets
– Affix addresses (of the nodes) to packets
– Initiate transmission (arbitrate access)
– Regulate flow of data
– Check for transmission errors
– Acknowledge receipt of transmitted data (in some
protocols)
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5 Communications Protocols
A packet is a “parcel” of
data that is sent across
a computer network
– Circuit-switching
technology vs.
– Packet switching
technology
• The Internet
• Voice over IP (VoIP)
– Advantages of one vs.
the other?
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5 Communications Protocols
Every packet that travels over a packet-switched
network includes the address of its destination
device
Most physical devices have more than one address
A MAC address is a unique number assigned to a
network interface card when it is manufactured
An IP address is a series of numbers used to
identify a network device in an internet
IP addresses can be assigned by registration, or
obtained dynamically through DHCP
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5
SECTION
B
Wired Networks
Wired Network Basics
HomePNA and Powerline Networks
Ethernet
Ethernet Equipment
Ethernet Setup
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5 Wired Network Basics
A wired network uses cables to connect
network devices
Wired networks are fast, secure, and simple
to configure and well-proven
Devices tethered to cables
have limited mobility
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5 HomePNA and
Powerline Networks
HomePNA (HPNA) networks utilize existing
telephone wiring to connect network devices
– Special NICs and cables are required
Powerline networks transmit data over power
lines as low-frequency radio waves
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5 Ethernet
Simultaneously broadcasts data packets to
all network devices (a star topology)
– IEEE 802.3 defines the Ethernet protocol
– CSMA/CD protocol used to share the channel
Vary in speed from 10Mbps to 10Gbps
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5 Ethernet
On an Ethernet, data
travels on a first come,
first served basis. If two
workstations attempt to
send data at the same
time, a collision occurs.
That data must be
resent.
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5 Ethernet Equipment
Checking a workstation
for an Ethernet port
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5 Ethernet Equipment
Ethernet adapter - NIC (designed to support
the Ethernet protocols)
Network hub
Network switch
Network router
RJ45 connector
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5 Typical Ethernet Setup
Technically, this
device functions as
an Ethernet switch,
as well as an IP
router.
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5
SECTION
C
Wireless Networks
Wireless Basics
Bluetooth
Wi-Fi
Wi-Fi Equipment
Wi-Fi Setup
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5 Wireless Basics
A wireless network transports data from one
device to another without cables or wires
– RF signals
• Transceiver
– Microwaves
– Infrared light
Slower than wired networks
Security concerns
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5 Bluetooth
Bluetooth is a short-range, wireless network
technology designed to make its own
connections between electronic devices,
without wires, cables or any direct action from
a user (a piconet)
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5 Wi-Fi
Wireless networking technologies that are
compatible with Ethernet (per IEEE 802.11)
MIMO technology uses two or more
antennae to send multiple sets of signals
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5 Wi-Fi Equipment
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5 Wi-Fi Equipment
If your computer is not pre-equipped with
wireless circuitry, you can purchase and
install a Wi-Fi card
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5 Wi-Fi Equipment
Wireless network setups
– Wireless ad-hoc network
– Wireless infrastructure network
• Wireless
access point
• Wireless
router
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5 Wi-Fi Setup
Set up the router
Connect to the router with a computer
Configure the router
Access the router setup utility
Create a new router password
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5 Wi-Fi Setup
Enter an SSID for the network
Activate WEP, WPA, or WPA2 and create an
encryption key(!!)
Set up the wireless workstations
Connect an Internet access device
– Generally a modem that will connect to the
service available in your area (cable, DSL, etc.)
from your service provider (ISP)
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5 Typical Wi-Fi Setup
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5
SECTION
D
Using LANs
LAN Advantages and Challenges
Sharing Files
Sharing Printers
LAN Parties
Troubleshooting
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5 LAN Advantages
LANs enable people to work together
Sharing networked software can reduce costs
Sharing data on a LAN can increase productivity
Sharing networked hardware can reduce costs
Sharing networked hardware can provide access
to a wide range of services and specialized
peripheral devices (read “expensive”)
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5 LAN Challenges
Resources become unavailable when network
malfunctions
Networks may be vulnerable to unauthorized
access
– More vulnerable than standalone computers
Wireless networks can be tapped from a
“snooping” computer
Networked computers are susceptible to an
increasing number of worms, Trojan horses, and
blended threats
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5 Sharing Files
If you use Windows, it
automatically detects
available LANs any
time you turn on a
workstation
To connect to a shared
resource, you might be
asked for a user ID and
password
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5 Sharing Files
In this drive mapping
example, a server’s drive
C is mapped as drive F
by a workstation. After the
mapping is complete, the
server’s hard disk appears
in the workstation’s
directory as drive F and
can be used just as though
it were a drive connected
directly to the workstation.
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5 Sharing Files
To allow other network
users to access files or
folders on your Windows
computer, you have to
designate them as
shared (commonly, via
Windows Explorer)
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5 Sharing Printers
Three setups allow for printer sharing:
– Set up printer sharing using a workstation printer
– Set up printer sharing using a print server
– Install printer with built-in networking
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5 Sharing Printers
In Windows, use the Printers and Faxes
dialog box to allow other users to share the
printer attached to your workstation
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5
SECTION
E
Security Through Encryption
Wi-Fi Security
Encryption
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5 Wi-Fi Security
Wireless networks are much more
susceptible to unauthorized access and use
by casual users than wired networks
LAN jacking, or war driving, is the practice of
intercepting wireless signals by cruising
through an area
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5 Wi-Fi Security
Wireless encryption scrambles data
transmitted between wireless devices and
then unscrambles the data only on devices
that have a valid encryption key
– WEP (Wired Equivalent Privacy)
– WPA (Wi-Fi Protected Access)
– WPA2
Activate encryption by using a wireless
network key
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5 Encryption
Encryption transforms a message so that its
contents are hidden (encrypted) from
unauthorized readers
– Plaintext has not yet been encrypted
– An encrypted message is referred to as
ciphertext
Decryption is the opposite of encryption
– Cryptographic algorithm
– Cryptographic key
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5 Encryption
Weak vs. strong encryption
AES (Advanced Encryption Standard)
Encryption methods can be broken by the
use of expensive, specialized, code-breaking
computers
– Brute-force method
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5 Encryption
Public key encryption (PKE) eliminates keydistribution problem, by using one key to
encrypt a message and another key to
decrypt the message
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Chapter 5 Complete
LANs and WLANs