This document provides an overview of networking fundamentals, including: - Computer networks allow computers to share resources, increasing productivity while decreasing hardware/software costs. - Key components include servers, clients, and shared resources like printers and storage. Networks can be configured in various topologies. - Network operating systems control communication and data flow across the network, enabling collaboration between connected devices.

1. Networking Fundamentals
Stand-alone computers were insufficient in
a business context
Hard-drive capacities were insufficient
Computers required a local printer
Sharing documents via the sneakernet was
cumbersome
E-mail didn't exist
Networks addressed these problems

2. Networking Fundamentals
Computer networks allow computers to
link to each other's resources
Networks can increase productivity as well
as decrease cash outlay for new hardware
and software

3. Networking Fundamentals
Networking today is a a relatively simple
plug-and-play process
Wireless network cards can automatically
detect and join networks
Of course, not all networks are that simple

4. Networking Fundamentals
Background information needed to
understand how networks work
LANs vs. WANs
Primary network components
Network operating systems (NOSs)
Network resource access
Network topologies
Network architectures
Transmitting data on a network

5. LANs vs. WANs
Local area networks (LANs) connect computers
in a single office
Wide area networks (WANs) expand the LANs to
include networks outside the local environment
Think of a WAN as multiple, disbursed LANs
connected together
LANs exist in many homes (wireless networks)
and nearly all businesses

6. Local Area Networks (LANs)

7. Local Area Networks (LANs)

8. Local Area Networks (LANs)
The earliest LANs could not cover large
distances
Only a few software programs supported
them
The first software programs were
constrained by file locking
Nowadays, multiple users can access a
program at one time

9. Wide Area Networks (WANs)

10. Primary Network Components
Three types of components available on a
network:
Servers
Clients or workstations
Resources

11. Blurring the Lines
LANs and WANs were often differentiated
by their connection speeds in the 1980s
and 90s
LANs connected computers with a 10Mbps
connection or faster
WANs often connected to each other by very
expensive T1 connections (a maximum
bandwidth of 1.544Mbps)

12. Blurring the Lines
Today, connections of 1Gbps are fairly common
WAN, while still slower than LAN connectivity,
can be several times faster than the T1
Because of the speed increases, categorizing
networks based on connection speed is outdated
Today, the most common way to classify a
network is based on geographical distance

13. Servers
Core component of the network
Provide a link to the resources needed to
perform tasks
Direct client computers
Centralize the control of resources and
security
Balance the load on computers
Compartmentalize files

14. Servers
Perform several different critical tasks
File servers
Print servers
Can be multipurpose or single-purpose
Can be dedicated or nondedicated

15. Dedicated Servers
Assigned to provide specific applications or
services for the network and nothing else
Requires fewer resources from the computer
that is hosting it
Savings in overhead may translate to a certain
efficiency
A web server is an example of a dedicated
server

16. Nondedicated Servers
Assigned to provide one or more network
services and local access
Slightly more flexible in its day-to-day use than a
dedicated server
Often serve as a front-end for the administrator
Can act as a workstation as well as a server
Can function well in a peer-to-peer environment

17. Dedicated and Nondedicated
Many networks use both dedicated and
nondedicated servers
Offers improved network performance and
flexibility

18. Workstations
The computers on which the network
users do their work
Connected to a network that offers
additional resources
Can range from diskless computer
systems to desktop systems
Also known as client computers

19. Workstations
Items needed to make a workstation into a
network client
Network interface card (NIC)
Special expansion card
Cabling system
Client software

20. Workstations
To users, being on a network changes a
few things:
They can store more information
They can share and receive information from
other users
They can use programs that would be too
large or complex for their computer
They can use hardware not attached directly
to their computer

21. Network Resources
A resource is any item that can be used on
a network
Resources can include
Printers and other peripherals
Disk storage and file access
Applications

22. Network Resources
Networks give users more storage space
to store files
Storing files on a server allows the
administrator to back up user files

23. Network Resources
Files that all users need to access can
also be stored on a server
Applications (programs) no longer need to
be on every computer in the office

24. Being on a Network Brings
Responsibilities
When you are on a network, you need to
take responsibility for your actions
You cannot randomly delete files or move
documents from server to server
You do not own your e-mail
Printing does not mean that if you send
something to print it will print immediately
If your workstation has also been set up as a
nondedicated server, you cannot turn it off

25. Network Operating Systems
(NOSs)
Networks use a NOS to control the
communication with resources and the
flow of data across the network
The NOS runs on the server
With today's NOSs, servers are able to
monitor memory, CPU time, disk space,
and peripherals without a babysitter

26. Network Operating Systems
(NOSs)
LANs and WANs allow for a wide range of
collaboration
NOSs provide this functionality on a
network

27. Network Resource Access
Peer-to-peer and client-server
Questions to ask
What is the size of the organization?
How much security does the company require?
What software or hardware does the resource
require?
How much administration does it need?
How much will it cost?
Will this resource meet the needs of the organization
today and in the future?
Will additional training be needed?

28. Peer-to-Peer Networks

29. Peer-to-Peer Networks
No centralized administration or control
Every station has unique control over the
resources the computer owns
Lack of centralized control can make it difficult to
administer the network
The network isn't very secure
May not be easy to locate resources
Users need more training

30. Peer-to-Peer Networks
The right choice for small companies that
don't expect future growth
Setting up a peer-to-peer resource model
simply because it is cheap and easy to
install could be a costly mistake

31. Client-Server Resource Model

32. Client-Server Resource Model
Server-based networks are also known as
domains
The key characteristic of a domain is that
security is centrally administered
When you log in to the network, the login request
is passed to the server responsible for security
In a peer-to-peer model, users need a user
account set up on each machine
In a domain, all user accounts are stored on the
server

33. Client-Server Resource Model
The desired model for companies that are
continually growing or that need to initially
support a large environment
Server-based networks offer flexibility
Hardware costs may be more, but managing
resources becomes less time consuming
Only a few administrators need to be trained
Users are only responsible for their own work
environment

34. Resource Access Model
Always take the time to plan your network
before installing it
You don't want the type of network you
chose to not meet the needs of the
company

35. Network Topologies
A way of laying out the network
Can be physical or logical
Five primary topologies
Bus (can be both logical and physical)
Star (physical only)
Ring (can be both logical and physical)
Mesh (can be both logical and physical)
Hybrid (usually physical)

36. Bus Topology

37. Bus Topology
Easy to install
Cheapest to install
Difficult to add a workstation
Expensive to maintain

38. Star Topology

39. Ring Topology

40. Mesh Topology

41. Mesh Topology
Expensive to install and maintain
The advantage you gain is high fault tolerance
Found in WANs to connect multiple sites across
WAN links
Routers are used to search multiple routes
through the mesh
Becomes inefficient with five or more entities

42. Hybrid Topology
A mix of the other topologies
Most networks today are not only hybrid
but heterogeneous
May be more expensive, but it exploits the
best features of all the other topologies

43. Network Topologies

44. Network Architectures
Define the structure of the network,
including hardware, software, and physical
layout
Performance is usually discussed in terms
of bandwidth
Major architectures used today are
Ethernet and Token Ring

45. Ethernet
Original definition of the IEEE 802.3 model
included a bus topology using coaxial cable and
baseband signaling
From this model came the first Ethernet
architecture
Has several specifications, each one specifying
the speed, communication method, and cable
Original Ethernet was given a designation of
10Base5

46. Token Ring
Exactly like the IEEE 802.5 specification
Uses a physical star, logical ring topology
Workstations are cabled to a central
device called a multistation access unit
(MAU)
Can use shielded or unshielded cable and
can transmit data at either 4Mbps or
16Mbps

47. Transmitting Data on a Network
To facilitate communication across a network,
computers use a common language called a
protocol
Protocols are a language with rules that need to
be followed so that both computers understand
the right communication behavior
Computers need standards to follow to keep
their communication
OSI model
IEEE 802 standards

48. OSI Model
The International Organization for
Standardization (ISO) introduced the Open
Systems Interconnection (OSI) model
The ISO put together a seven-layer model
providing a relationship between the
stages of communication
As transmission takes place data passes
through the layers

49. OSI Model
The OSI model layers from top to bottom
7. Application layer
6. Presentation layer
5. Session layer
4. Transport layer
3. Network layer
2. Data Link layer
1. Physical layer

50. OSI Model
Application layer
Allows access to network services
The layer at which file and print services operate
Presentation layer
Determines the format of the data
Performs protocol conversion and manages data
compression, data translation, and encryption
Character set information is determined at this level

51. OSI Model
Session layer
Allows applications on different computers to
establish, maintain, and end a session
Enables network procedures, such as identifying
passwords, logons, and network monitoring
Transport layer
Verifies that all packets were received by the
destination host on a TCP/IP network
Controls the data flow and troubleshoots any
problems with transmitting or receiving datagrams
Provides error checking and reliable, end-to-end
communications

52. OSI Model
Network layer
Responsible for logical addressing of messages
At this layer, the data is organized into chunks called
packets
Manages traffic through packet switching, routing, and
controlling congestion of data
Data Link layer
Arranges data into chunks called frames
Describes the unique physical address (MAC address)
Subdivided into two sections: Media Access Control
(MAC) and Logical Link Control (LLC)

53. OSI Model
Physical layer
Describes how the data gets transmitted over a
physical medium
Defines how long each piece of data is and the
translation of each into the electrical pulses that are
sent over the wires
Decides whether data travels unidirectionally or
bidirectionally across the hardware
Relates electrical, optical, mechanical, and functional
interfaces to the cable

54. OSI Model

55. IEEE 802 Standards
Designed primarily for enhancements to
the bottom three layers of the OSI model
Breaks the Data Link layer into two
sublayers
The LLC sublayer manages data link
communications
The MAC sublayer watches out for data
collisions and assigns physical addresses

56. IEEE 802.3 CSMA/CD (Ethernet)
Ethernet is the most well-known example of the
IEEE 802.3 CSMA/CD standard
The original 802.3 CSMA/CD standard
Defines a bus topology network that uses a 50 ohm
coaxial baseband cable
Carries transmissions at 10Mbps
Groups data bits into frames and uses the
CSMA/CD cable access method
Currently, the 802.3 standard has been
amended to include speeds up to 10Gbps

57. IEEE 802.3 CSMA/CD (Ethernet)
The CSMA/CD acronym illustrates how it works
Carrier Sense (CS) means that computers on the
network are listening to the wire at all times
Multiple Access (MA) means that multiple computers
have access to the line at the same time
Collision Detection (CD) detects collisions and
senders send again
CSMA/CD technology is considered a
contention-based access method

58. IEEE 802.3 CSMA/CD (Ethernet)
The only major downside to 802.3 is that
with large networks (more than 100
computers on the same cable), the number
of collisions increases to the point where
more collisions than transmissions are
taking place

59. IEEE 802.5 Token Ring
Specifies a physical star, logical ring
topology that uses a token-passing
technology to put the data on the cable
IBM developed this technology for its
mainframe and minicomputer networks

60. IEEE 802.5 Token Ring
A chunk of data called a token circulates the ring
A computer with data to transmit takes a free
token off the ring, modifies it, places the token
(along with the data) back on the ring
The token travels around the ring
The destination computer takes the token and
data off the wire and places the token back on
the wire
When the original sender receives the token
back, it modifies the token to make it free for use
and sends the token back on the ring

61. IEEE 802.5 Token Ring
Main advantage of the token-passing
access method is that it eliminates
collisions
Whole procedure takes place in a few
milliseconds
Scales very well
Not uncommon for Token Ring networks
based on the IEEE 802.5 standard to reach
hundreds of workstations on a single ring

62. Understanding Networking
Protocols
Computers use a protocol as a common
language for communication
A protocol is a set of rules that govern
communications
Protocols detail what "language" the
computers are speaking when they talk over a
network
If two computers are going to communicate,
they both must be using the same protocol

63. Understanding Networking
Protocols
The A+ exam objectives list two common
protocols: TCP/IP and NetBIOS
Other common protocols
IPX/SPX
AppleTalk

64. TCP/IP
Most popular network protocol in use today
Named after two of its hardest-working protocols,
Transmission Control Protocol (TCP) and
Internet Protocol (IP), but contains dozens of
protocols
Protocol of the Internet
Robust and flexible
Works on disparate operating systems such as
Unix, Linux, and Windows
Flexibility comes from its modular nature

65. TCP/IP

66. TCP/IP

67. TCP/IP

68. IP Addresses
Each device needs to have a unique IP
address
Any device with an IP address is referred
to as a host
Configure manually or automatically from
a DHCP server

69. IP Addresses
A 32-bit hierarchical address that identifies a
host on the network
Typically written in dotted-decimal notation, such
as 192.168.10.55
Each of the numbers represents eight bits (or one
byte) of the address, also known as an octet
The same address written in binary would be
11000000 10101000 00001010 00110111
Numbers will be between 0 and 255

70. IP Addresses
Addresses are said to be hierarchical
Numbers at the beginning of the address
identify groups of computers that belong to
the same network

71. Parts of the IP Address
Each IP address is made up of two
components: the network ID and the host
ID
Network portion comes before the host
portion
Network portion does not have to be a
specific fixed length

72. Parts of the IP Address
Computers differentiate where the network
address ends and the host address begins
through the subnet mask
A value written just like an IP address and
may look something like 255.255.255.0
Any bit that is set to a 1 in the subnet mask
makes the corresponding bit in the IP address
part of the network address
The number 255 is the highest number you
will ever see in IP addressing, and it means
that all bits in the octet are set to 1

73. Parts of the IP Address
An example
The subnet mask of 255.255.255.0
indicates that the first three octets are
the network portion of the address, and
the last octet is the host portion
In the IP address of 192.168.10.55, the
network portion is 192.168.10 and the
host portion is 55

74. IP Address Classes
Classes of networks are based on their size
Class A - huge companies with thousands of
computers
Class C - companies with few computers
Class B - medium-sized companies
Class D and E - reserved
The class of address can be identified by the first
octet of the IP address

75. Class A
Designed for very large networks
Default network portion for Class A networks is
the first 8 bits
Only 126 Class A network addresses available
Remaining 24 bits of the address allow each
Class A network to hold as many as 16,777,214
hosts
All possible Class A networks are in use; no
more are available

76. Class B
Designed for medium-sized networks
Default network portion for Class B
networks is the first 16 bits
Allows for 16,384 networks, each with as
many as 65,534 hosts attached
Class B networks are generally regarded
as unavailable

77. Class C
Designed for smaller networks
Default network portion for Class C networks is
the first 24 bits
Allows for 2,097,152 networks, but each network
can have a maximum of only 254 hosts
Most companies have Class C network
addresses
Class C networks are still available

78. IP Address Classes

79. Common Ports
Each protocol in the TCP/IP suite that
operates at the Process/Application layer
uses a port number to identify information
it sends or receives
The port number, when combined with the
host's IP address, is called a socket

80. Common Ports
65,536 ports numbered from 0 to 65535
Ports 0 through 1023 are called the well-
known ports
1024 through 49151 are called the
registered ports
Anything from 49152 to 65535 is free to be
used by application vendors

81. Common Ports

82. DHCP and DNS
Both are run off a server and provide key
services to network clients
A DHCP server can be configured to
automatically provide IP configuration
information to clients
IP address
Subnet mask
Default gateway (the "door" to the outside world)
DNS server address

83. DHCP and DNS
DNS resolves hostnames to IP
addresses
Allows your computer to get the
address of the website you want and
traverse the Internet to find it

84. DHCP and DNS
DNS works the same way on an intranet
Instead of helping you find google.com, it
may help you find Jenny's print server or
Joe's file server

85. Other Protocols
There probably aren't any reasons why
you would want to use a different protocol
Only knock on TCP/IP is that it can be
more difficult to configure than other
protocols
Only other protocol called out on the A+
Essentials exam objectives is NetBIOS

86. NetBEUI/NetBIOS
NetBIOS is an acronym formed from
network basic input/output system
Is a Session layer network protocol
Provides an interface with a consistent set
of commands for requesting lower-level
network services to transmit information
from node to node

87. NetBEUI/NetBIOS
NetBEUI is an acronym formed from NetBIOS
Extended User Interface
An implementation and extension of IBM's
NetBIOS transport protocol from Microsoft
Shipped with all versions of Microsoft's operating
systems and is generally considered to have a
lot of overhead
Has no networking layer and therefore no routing
capability

88. NetBEUI/NetBIOS
These protocols make up a very fast protocol
suite that most people call NetBEUI/NetBIOS
Good for small LANs
Allows users to find and use the network
services they need easily
Because it contains no Network layer protocol, it
cannot be routed and thus cannot be used on a
WAN

89. IPX/SPX
Default communication protocol for versions of
the Novell NetWare operating system before
NetWare 5
A communication protocol similar to TCP/IP
Used primarily in LANs
Two main protocols in IPX/SPX are IPX and SPX
SPX provides similar functions to TCP
IPX provides functions similar to the TCP/IP suite
protocols IP and UDP

90. IPX/SPX

91. AppleTalk
Not just a protocol - it is a proprietary network
architecture for Macintosh computers
Uses a Carrier Sense Multiple Access with
Collision Avoidance (CSMA/CA) technology to
put data on the cable
Unlike Ethernet, which uses a CSMA/CD method
(where the CD stands for Collision Detection), it
uses smart interface cards to detect traffic
before it tries to send data
A CSMA/CA card listens to the wire

92. AppleTalk
Big selling point of AppleTalk
Simple and cheap
Came installed on Macintosh computers
Assigned itself an address
Problems
Slow
Limited in capacity
Had to license it from Apple
Today, TCP/IP is the default networking protocol
on Macs

93. Network Interface Cards (NICs)
Physical interface between computer and
cabling
Prepares, sends, and controls flow of data
Considerations when choosing a NIC
Preparing data
Sending and controlling data
Configuration
Drivers
Compatibility
Performance

94. Preparing Data
In the computer, data moves along buses
in parallel
The NIC translates the data from the
computer into signals that can flow easily
along the cable
It translates digital signals into electrical
signals (and in the case of fiber-optic NICs,
to optical signals)

95. Sending and Controlling Data
For two computers to send and receive data, the
cards must agree on several things
Maximum size of the data frames
Amount of data sent before giving confirmation
Time needed between transmissions
Amount of time to wait before sending confirmation
Amount of data a card can hold
Speed at which data transmits

96. Sending and Controlling Data
To successfully send data on the network,
all NICs need to use the same media
access method
If you try to use cards of different types
neither of them would be able to
communicate with the other unless you
had a separate hardware device between
them that could translate

97. Sending and Controlling Data
NICs can send data using either full-duplex or
half-duplex mode
Half-duplex means that between the sender and
receiver, only one can transmit at any one time
In full-duplex communication, a computer can send
and receive data simultaneously
Main advantage of full-duplex over half-duplex
communication is performance
NICs can operate twice as fast (200Mbps) in full-
duplex mode as they do normally in half-duplex mode
(100Mbps)

98. NIC Configuration
The NIC's configuration may include
Manufacturer's hardware address
IRQ address
Base I/O port address
Base memory address
Each card must have a unique MAC address
If two cards on the same network have the same
MAC address, neither one will be able to
communicate
IEEE has established a standard for hardware
addresses

99. NIC Drivers
For the computer to use the NIC, it is very
important to install the proper device
drivers
Drivers communicate directly with the
network redirector and adapter
Operate in the Media Access Control
sublayer of the Data Link layer of the OSI
model

100. PC Bus Type
Choose NIC that fits the bus type of your
PC
If you have more than one type of bus in
your PC use a NIC that fits into the fastest
type
More and more computers are using
network cards that have either PC Card or
USB interfaces

101. Network Interface Card
Performance
Most important goal of the network
adapter card is to optimize network
performance and minimize the amount of
time needed to transfer data packets
across the network
Ensure you get the fastest card you can
for the type of network you're on

102. Cabling and Connectors
Cable properly moves the data to its
intended destination
Four main types of cabling methods
Coaxial cable
Twisted-pair cable
Fiber-optic cable
Wireless

103. Coaxial

104. Coaxial
Available in various specifications that are
rated according to the RG Type system
Distance and cost are considerations
when selecting coax cable
The thicker the copper, the farther a signal
can travel -- and with that comes a higher cost
and a less-flexible cable

105. Coaxial

106. Coax Connector Types

107. Coax Connector Types

108. Twisted Pair

109. Twisted Pair
Category 1: voice-only transmissions, two twisted pairs
Category 2: 4Mbps, four twisted pairs
Category 3: 10Mbps, four twisted pairs
Category 4: 16Mbps, four twisted pairs
Category 5: 100Mbps, four twisted pairs of copper wire
Category 5e: up to 1Gbps, four twisted pairs of copper
wire, but they are physically separated and contain more
twists per foot than Category 5
Category 6: up to 1Gbps and beyond, four twisted pairs
of copper wire, and they are oriented differently than in
Category 5 or 5e

110. Twisted-Pair Connector Types

111. Twisted-Pair Connector Types

112. Fiber-Optic

113. Fiber-Optic
Referred to as either single-mode or multimode
fiber
Mode refers to the bundles of light that enter the
fiber-optic cable
Single-mode
Uses only a single mode of light to propagate
Multimode
Allows multiple modes of light to propagate
Light bounces off the cable walls as it travels through
the cable, which causes the signal to weaken more
quickly

114. Fiber-Optic
Multimode
Most often used as horizontal cable
Permits multiple modes of light to propagate through the
cable, which shortens cable distances and delivers a less
available bandwidth
Devices that use multimode fiber-optic cable typically use
light-emitting diodes (LEDs)
Higher bandwidth network devices such as Gigabit
Ethernet are now using lasers with multimode fiber-optic
cable
ANSI/TIA/EIA-568-B recognizes two-fiber (duplex) 62.5/125
micron multimode fiber; ANSI/TIA/EIA-568-B also
recognizes 50/125 micron multimode fiber-optic cable

115. Fiber-Optic
Single-mode
Used as backbone cabling and in phone systems
Light travels straight down the fiber and does not bounce
off the cable walls
Supports higher bandwidth and longer distances
Devices that use single-mode typically use lasers to
generate the light that travels through the cable
ANSI/TIA/EIA-568-B recognizes 62.5/125 micron, 50/125
micron, 8.3/125 micron single-mode optical fiber cables
Maximum backbone distance using single-mode
is 3,000 meters; maximum backbone distance
using multimode is 2,000 meters

116. Fiber-Optic Connector Types

117. Fiber-Optic Connector Types

118. Wireless Networks
Offer the ability to extend a LAN without the use
of traditional cabling methods
Transmissions are made through the air by
infrared light, laser light, narrow-band radio,
microwave, or spread-spectrum radio
Most often in environments where standard
cabling methods are not possible or wanted
Not as fast or efficient as standard cabling
methods
More susceptible to eavesdropping and
interference than standard cabling methods

119. Networking Components
Connectivity devices
Allow communications to break the
boundaries of local networks
Let your computers talk to other computers in
the next building, the next city, or the next
country

120. Networking Components
There are several categories of connectivity
devices
Repeaters
Hubs
Switches
Bridges
Routers
Make it possible to lengthen networks to almost
unlimited distances

121. Repeaters
Allow a cabling system to extend beyond its
maximum allowed length by amplifying the
network voltages
Very inexpensive
Operate at the Physical layer of the OSI model
Only used to regenerate signals between similar
network segments
Main disadvantage is that they just amplify
signals
Not only network signals but any noise on the wire
Used only as a temporary fix

122. Hubs
Used to link several computers together
Most often used on Ethernet networks
Just multiport repeaters and work at Layer
1 of the OSI model just as repeaters do
Repeat any signal that comes in on one
port and copy it to the other ports (a
process that is also called broadcasting)

123. Hubs
Two types of hubs
Passive Hubs
 Connect all ports together electrically
 Do not have their own power source
Active hubs
 Use electronics to amplify and clean up the signal
before it is broadcast to the other ports
 Includes a class called intelligent hubs, which can
be remotely managed on the network

124. Switches
Provide centralized connectivity just as hubs do
(usually on twisted-pair Ethernet networks); often
look similar, so it's easy to confuse them
Switches examine the Layer 2 header of the
incoming packet and forward it properly to the
right port and only that port
Greatly reduces overhead and thus performance
as there is essentially a virtual connection
between sender and receiver

125. Indicator Lights
Nearly every hub or switch has one or more
status indicator lights
If there is a connection to that port of the switch, a
light will light up
If traffic is crossing the port, the light may flash, or
there may be a secondary light
Many devices can also detect a problem in the
connection
Bridges and routers will also have similar status
lights on them, as do network cards

126. Bridges
Operate in the Data Link layer of the OSI model
Join similar topologies and used to divide network
segments
Keep traffic on one side from crossing to the other
Often used to increase performance on a high-traffic
segment
Not able to distinguish one protocol from another,
because higher levels of the OSI model are not available
to them
If a bridge is aware of the destination MAC address, it
can forward packets; otherwise, it forwards the packets to
all segments

127. Bridges
More intelligent than repeaters
Unable to move data across multiple
networks simultaneously
Main disadvantage is that they forward
broadcast packets
Broadcasts are addressed to all computers, so
the bridge just does its job and forwards the
packets
Cannot perform intelligent path selection

128. Routers
Highly intelligent devices that connect multiple network
types
Route packets across multiple networks
Use routing tables to store network addresses
Operate at the Network layer of the OSI model
Can determine the best path for data to take to get to its
destination
Like bridges, they can segment large networks
Slower than bridges because they analyze every packet
More expensive

129. Routers
Normally used to connect one LAN to
another
Typically, when a WAN is set up, at least
two routers are used
Wireless routers have become all the rage
for small and home networks
Possess all of the functionality of routers
historically associated with networking, but
they are relatively inexpensive

130. Wired Networks
A network where you are using a cable to plug
into a socket in the wall or a connectivity device
on your table
Historically, using wires was the only way to
connect several machines together
Today, wired options are becoming few and far
between
Two broad categories of choices to get online
Dial-up
Broadband

131. Dial-up
One of the oldest ways of communicating with
ISPs and remote networks
Not used much anymore due to limitations on
modem speed, which top out at 56Kbps
Cannot compare to speeds possible with DSL
and cable modems
Dial-up Internet connections dropped from 74
percent in 2000 to 15 percent in 2008
Most of the people who still use dial-up do it because
it's cheaper than broadband or high-speed isn't
available where they live

132. Dial-up
Biggest advantage to dial-up is that it's
cheap and relatively easy to configure
Companies can grant users dial-up access
to their networks
ISPs and RAS servers would use the Data
Link layer Point-to-Point Protocol (PPP) to
establish and maintain the connection

133. Broadband
A connection that is capable of
transmitting multiple pieces of data
simultaneously in order to achieve higher
data rates
The opposite of broadband is baseband
Several different types of broadband
Internet access are available, including
DSL, Cable, fiber-optic, and satellite

134. DSL

135. DSL
There are several different forms of DSL,
including
High bit-rate DSL (HDSL)
Symmetric DSL (SDSL)
Very high bit-rate DSL (VDSL)
Rate-adaptive DSL (RADSL)
Asymmetric DSL (ADSL)
The most popular in home use is ADSL
It's asymmetrical because it supports faster download
speeds than upload speeds

136. DSL

137. DSL
First ADSL standard was approved in 1998 and
offered maximum download speeds of 8Mbps
and upload speeds of 1Mbps
The newest standard supports speeds up to
24Mbps download and 3.5Mbps upload
Most ADSL communications are full-duplex
One major advantage that ADSL providers tout
is that with DSL you do not share bandwidth with
other customers

138. Cable Modem
Provides high-speed Internet access through
your cable service
You plug your computer into the cable modem
using a standard Ethernet cable
In theory, cable Internet connections are faster
than DSL connections
Download speeds up to 30Mbps or 50Mbps and
uploads of 5Mbps
A caveat to these speeds is that they are not
guaranteed and they can vary

139. Cable Modem
Speeds vary because you are sharing
available bandwidth within your distribution
network
Size of the network is usually between 100
and 2,000 customers
Access can be slower during peak usage
times

140. Cable Modem
A simplified example
Two users are sharing a connection that has a
maximum capacity of 40Mbps
Each person gets 20Mbps of bandwidth
One user gets a boost that allows her to
download 30Mbps
The other user is left with 10Mbps of available
bandwidth

141. Cable Modem
In practice, the speeds of a cable modem are
pretty comparable to those of DSL
Both have pros and cons when it comes to
reliability and speed of service
A lot varies by service provider and isn't
necessarily reflective of the technology
The choice you make between DSL and cable
may depend on which company you get the best
package deal from

142. Fiber-Optic Cable
Used mostly for high-speed
telecommunications and network
backbones
Much more expensive than copper to
install and operate
Some phone and media companies are
now offering fiber-optic Internet
connections for home subscribers

143. Fiber-Optic Cable
Fiber-to-the-Home (FTTH) service
As of the time of this writing, the fastest speeds
offered are 50Mbps download and 20Mbps upload
FTTH is capable of reaching speeds of 100Mbps, and
400Mbps implementations are being planned
Fiber-to-the-Node (FTTN)
Runs fiber to the phone or cable company's utility box
near the street and then runs copper from there to
your house
Maximum speeds for this type of service are around
25Mbps

144. Satellite
Transmits signals through the air to you as opposed to
using a cable
Service provider beams a microwave signal from a dish
on the ground to an orbiting satellite, which in turn sends
the signal back down to your receiver
Receivers are typically small satellite dishes but can also
be portable satellite modems or portable satellite phones
Called point-to-multipoint because one satellite can
provide a signal to a number of receivers
Used in a variety of applications from
telecommunications to handheld GPSs to television and
radio broadcasts

145. Satellite
Considerations to keep in mind regarding
satellite
Installation can be tricky
Line of sight is required

146. Satellite
More considerations
Latency can be a problem
Connections are pretty slow

147. Wireless Networks
As a technician, you must make sure that
their computers can connect
Four methods of wireless communication
802.11x
Bluetooth
Cellular
Infrared

148. 802.11x
WLAN standards are created and managed by
the IEEE
Most commonly used WLAN standards used
today are in the IEEE 802.11x family
IEEE 802.11 was ratified in 1997, and was the
first standardized WLAN implementation
Over twenty 802.11 standards defined, but you
will only see a few in common operation:
802.11a, b, and g
Among all of the wireless technologies covered,
802.11 is the one best suited for WLANs

149. 802.11x Networks
Just like an Ethernet network, only wireless
At the center of the network is a connectivity
device such as a hub or a router, and all
computers connect to it
In order to connect to the wireless hub or router,
the client needs to know the SSID of the device
Wireless access points eventually connect back
to a wired connection with the rest of the network

150. 802.11x Technical Specifications
802.11x networks use the CSMA/CA
access method
Similar to that of shared Ethernet
Packet collisions are generally avoided
If they do happen, the sender waits a random
period of time (called a back-off time) before
transmitting again

151. 802.11x Technical Specifications
802.11
Defines WLANs transmitting at 1Mbps or 2Mbps
bandwidths using the 2.4GHz frequency spectrum
Uses FHSS or DSSS for data encoding
802.11a
Provides WLAN bandwidth of up to 54Mbps in the
5GHz frequency spectrum
Uses OFDM, rather than FHSS or DSSS
Never gained widespread popularity because 802.11b
devices were significantly cheaper and it's highly
susceptible to external interference

152. 802.11x Technical Specifications
802.11b
Provides for bandwidths of up to 11Mbps in the 2.4GHz
frequency spectrum
Also called WiFi or 802.11 high rate
Uses DSSS for data
802.11g
Provides for bandwidths of 54Mbps+ in the 2.4GHz frequency
spectrum
Uses OFDM encoding
Is backward compatible with 802.11b
Some devices marked as 802.11b/g that can run on
either network, and can be commingled on the same
network

153. 802.11x Technical Specifications
Interoperability concerns
Not capable of understanding OFDM transmissions
To counteract this problem, uses an additional
signaling mechanism RTS/CTS to provide backward
compatibility
 The client must first send an RTS signal to the access point
 Once the access point sends a CTS back to the client, the
client can transmit
 Other clients interpret the CTS signal, they interpret it as a
"do not send" message and wait for an all-clear to send

154. 802.11x Technical Specifications
More interoperability concerns
When operating in mixed mode, 802.11g will
use the less-efficient 802.11b back-off timing
Slows down the throughput of the 802.11g
access point
The pros of 802.11g/b backward
compatibility still far outweigh the cons

155. 802.11x Technical Specifications
802.11n
At the time of this writing, still in development
Provides bandwidths from 54Mbps to
600Mbps, but more realistic to expect
maximum throughput in the 300Mbps range
Achieves faster throughput a couple of ways
 MIMO
 Channel bonding
 SDM technologies

156. 802.11x Technical Specifications
802.11n is backward compatible with
802.11a/b/g
802.11n hardware is on the market today,
but as the standard is still not official these
devices are called "pre-N" devices
May have compatibility issues between
different vendors' pre-N products

157. 802.11x Technical Specifications

158. 802.11x Technical Specifications
Signal modulation techniques used in the
802.11 standards
Direct-Sequence Spread Spectrum (DSSS)
Frequency-Hopping Spread Spectrum (FHSS)
Orthogonal Frequency Division Multiplexing
(OFDM)

159. 802.11x Devices

160. 802.11x Security
The growth of wireless systems has
created several opportunities for attackers
Using SSID configurations doesn't
necessarily prevent wireless networks from
being compromised

161. WEP
A security standard for wireless devices
Encrypts data to provide data security
Has always been under scrutiny for not
being as secure as initially intended

162. WEP
Vulnerable due to weaknesses in the
encryption algorithms
This makes WEP one of the more
vulnerable protocols available for security

163. WPA
An improvement on WEP that was
developed in 2003
Implements some of the standards defined
in the IEEE 802.11i specification
Improvement over WPA is WPA2, which
implements the full 802.11i standard

164. MAC Filtering
Can be used on a wireless network to
prevent certain clients from accessing the
network
You tell your wireless router to only allow
access to certain MAC addresses
Your router will allow you to deny service to a
set list of MAC addresses (and allow all
others) or allow service only to a set of MAC
addresses (and deny all others)

165. Bluetooth
Makers of Bluetooth were trying to unite
disparate technology industries
First Bluetooth device arrived on the scene in
2000
By 2002, there were over 500 Bluetooth certified
products
As of 2005 over 5 million Bluetooth chipsets
shipped each week
Current Bluetooth specification is Version 2.1+
Enhanced Data Rate

166. Bluetooth Networks
"Bluetooth wireless technology is a short-range
communications technology intended to replace the
cables connecting portable and/or fixed devices while
maintaining high levels of security."
Operates at low power and low cost and can handle
simultaneous voice and data transmissions
One of the unusual features of Bluetooth networks is
their temporary nature
This dynamically created network is called a piconet
A Bluetooth-enabled device can communicate with up to seven
other devices in one piconet

167. Bluetooth Networks
Within the piconet, one device is the master and
the other seven devices are slaves
Communication can occur only between the master
and a slave
Role of master rotates quickly among the devices in a
round-robin fashion
All devices in a piconet can communicate with each
other directly
Current Bluetooth specifications allow for connecting
two or more piconets together in a scatternet

168. Bluetooth Technical Specifications
Version 1.2
Adopted in November 2003
Supports data transmissions of up to 1Mbps
Version 2.0+ Enhanced Data Rate (EDR)
Adopted in November 2004
Supports data rates up to 3Mbps
Version 2.1+EDR
Adopted in July 2007
Supports data rates up to 3Mbps
All standards transmit in the 2.4-2.485GHz range

169. Bluetooth Technical Specifications

170. Bluetooth Devices
The first device was a wireless headset for a cell
phone
Bluetooth-enabled computer peripherals include
Keyboards and mice
Printers
Digital cameras
MP3 players
PDAs and handheld computers
Cars

171. Bluetooth Devices

172. Bluetooth Devices

173. Infrared
Longer than light waves but shorter than
microwaves
Most common use of infrared technology
is the television remote control
"Walk-up" and "point-to-point"
You need to be at very close range
Designed for one-to-one communication
Requires line of sight

174. Infrared

175. Infrared Networks
A point-to-point network between two
devices
No master or slave
No hub-type device required
Point one infrared-enabled device at
another and transmit

176. Infrared Technical Specifications
Current IrDA specifications allow transmission of
data up to 16Mbps and IrDA claims that
100Mbps and 500Mbps standards are on the
horizon
No concerns of interference or signal conflicts
Atmospheric conditions can play a role in
disrupting infrared waves
Security is not an issue
Data is directional, and you choose when and where
to send it

177. Infrared Devices
Mice
Keyboards
Printers
Keyboards for PDAs
PDAs
Cell phones
Remote control

178. Cellular (Cellular WAN)
Industry has revolutionized the way we
communicate
Primarily been developing in the realm of
small handheld communications devices
(phones and the BlackBerrys)
Converging technologies -- cell phones
and computers

179. Cellular Networks
Very complex behind the scenes
Cell communications require the use of a
central access point, generally a cell tower,
which is connected to a main hub
Very large mesh networks with extensive
range

180. Cellular Technical Specifications
Two major cell standards in the United States:
GSM and CDMA
Not compatible with each other
GSM uses a variety of bands to transmit
Most popular are 900MHz and 1800MHz
400, 450, and 850MHz are also used
GSM splits up its channels by time division, in a
process called Time Division Multiple Access
(TDMA)

181. Cellular Technical Specifications
Maximum rate for GSM is about 270 kilobits per
second (Kbps)
Maximum functional distance of GSM is about 22
miles (35 kilometers)
For security, GSM uses the A5/1 and A5/2
stream ciphers
Newer enhancement to GSM is called General
Packet Radio Service (GPRS)
Designed to provide data transmissions over a GSM
network at up to 171Kbps

182. Cellular Technical Specifications
CDMA is considered a superior technology to GSM
Doesn't break up its channels by time but rather by a
code inserted into the communicated message
Transmissions to occur at the same time without
interference
Used in GPSs
CDMA supports download rates of over 3Mbps, with
upload speeds of nearly 2Mbps
Works in ranges up to 100 kilometers
Newer takeoffs of the CDMA technology include W-
CDMA, CDMA2000, and EVDO

183. Cellular Devices
Further developed in the phone industry
than the computer industry
Cell phones and BlackBerrys are the most
common cellular-equipped devices
Cellular modems are widely available for
laptops, most of them with a PC Card
interface

184. Virtual Private Networks (VPNs)
Not necessarily wired or wireless
Not a LAN or a WAN but rather something
in between
Makes computers that are on opposite
sides of a WAN link think they are on the
same safe and secure LAN with each
other
The key word for VPNs really is security

185. Virtual Private Networks (VPNs)
Device that provides VPN service is called
a VPN concentrator
Create virtual private networks for users
logging in using remote access or for a large
site-to-site VPN
VPNs provide higher data throughput and
authentication and encryption options