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1. Networking Fundamentals
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 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networks based on connection speed is outdated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