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LANs and WLANsLANs and WLANs
Chapter 5Chapter 5
Chapter 5: LANs and WLANs 2
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
Chapter 5: LANs and WLANs 3
5SECTION A
Network Building BlocksNetwork Building Blocks Network Classifications LAN Standards Network Devices Clients, Servers, and Peers Physical Topology Network Links Communications Protocols
Chapter 5: LANs and WLANs 4
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)Local Area Network (LAN) – usually connects computers in a single building
Metropolitan Area Network (MAN) – public high-speed network with range of about 50 miles
Wide Area Network (WAN)Wide Area Network (WAN) – consists of several smaller networks
Chapter 5: LANs and WLANs 5
5 LAN Standards LAN technologies are standardized by the
Institute of Electrical and Electronics Engineers (IEEE) Project 802 – Local Network Standards– IEEE 802.3IEEE 802.3 specifies the standards for EthernetEthernet
wired local area networks• How devices physically signal each other, how devices
“share the wire in the wall”, etc.
– Ethernet is the de factode facto standard standard for wired LAN in use today
Chapter 5: LANs and WLANs 6
5 Ethernet Frame StructureIEEE 802.3 Ethernet frameIEEE 802.3 Ethernet frame
Preamble: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:Addresses: 6 bytes, frame is received by all adapters on a LAN and dropped if address does not match
Type (Length):Type (Length): 2 bytes, length of data segment (min. 46 bytes) CRC (Cyclic Redundancy Check):CRC (Cyclic Redundancy Check): 4 bytes, created by sender,
checked by receiver, if error detected, the frame is simply dropped
Typ
eT
ype
64 – 1518 bytes in length
Chapter 5: LANs and WLANs 7
5 Network Devices Each connection point on a network is referred to
as a nodenode To connect to a LAN, a computer requires network
circuitry, sometimes referred to as a network network interface card (NIC)interface card (NIC)
A networked peripheralnetworked peripheral, or network-enabled peripheral, is any device that contains network circuitry to directly connect to a network
A network devicenetwork device, or network appliance, is any electronic device that broadcasts/re-broadcasts network data, boosts signals, or routes data to its destination
Chapter 5: LANs and WLANs 8
5 Network Devices
Chapter 5: LANs and WLANs 9
5 Clients, Servers, and Peers Network devices can function as clients or as serversclients or as servers
– Application server
– File server
– Print server Networks that include one or more servers can operate
in client/server modeclient/server mode
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5 Physical Topology The arrangement of devicesarrangement 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 bridgebridge (or switchswitch)
GatewayGateway is a generic term for any device or software code used to join two networks
Chapter 5: LANs and WLANs 11
5 Network Links
A communications channelcommunications channel, or linkor link, is a physical path or frequency for signal transmissions
BandwidthBandwidth is the transmission capacity of a communications channel (usually expressed in bits/sec, bps)– Broadband– Narrowband
Chapter 5: LANs and WLANs 12
5 Communications Protocols Rules (Standards) for efficiently and
effectively transmitting datatransmitting data from one network node to another. They define how to:– Divide messages into packetspackets– Affix addressesaddresses (of the nodes) to packets– Initiate transmissiontransmission (arbitrate access)– RegulateRegulate flow of data– Check for transmission errorserrors– AcknowledgeAcknowledge receipt of transmitted data (in some
protocols)
Chapter 5: LANs and WLANs 13
5 Communications Protocols A packetpacket is a “parcel” of
data that is sent across a computer network– Circuit-switchingCircuit-switching
technology vs. – Packet switchingPacket switching
technology• The Internet• Voice over IP (VoIP)
– Advantages of one vs. the other?
Chapter 5: LANs and WLANs 14
5 Communications Protocols Every packetEvery 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 addressMAC address is a unique number assigned to a
network interface card when it is manufactured An IP addressIP 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 DHCPDHCP
Chapter 5: LANs and WLANs 15
5SECTION B
Wired NetworksWired Networks Wired Network Basics HomePNA and Powerline Networks Ethernet Ethernet Equipment Ethernet Setup
Chapter 5: LANs and WLANs 16
5 Wired Network Basics
A wired network uses cablescables to connect network devices
Wired networks are fastfast, securesecure, and simplesimple to configure and well-proven
Devices tethered to cables have limited mobilitylimited mobility
Chapter 5: LANs and WLANs 17
5 HomePNA and Powerline Networks
HomePNA (HPNA) HomePNA (HPNA) networks utilize existing telephone wiring to connect network devices– Special NICs and cables are required
PowerlinePowerline networks transmit data over power lines as low-frequency radio waves
Chapter 5: LANs and WLANs 18
5 Ethernet
Simultaneously broadcastsbroadcasts data packets to all network devices (a star topology)– IEEE 802.3 defines the Ethernet protocol– CSMA/CDCSMA/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 collisioncollision occurs.That data must be resentresent.
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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
Chapter 5: LANs and WLANs 22
5 Typical Ethernet Setup
Technically, this device functions as an Ethernet switch, as well as an IP router.
Chapter 5: LANs and WLANs 25
5SECTION C
Wireless NetworksWireless Networks Wireless Basics Bluetooth Wi-Fi Wi-Fi Equipment Wi-Fi Setup
Chapter 5: LANs and WLANs 26
5 Wireless Basics
A wireless network transports data from one device to another without cables or wireswithout cables or wires– RFRF signals
• Transceiver
– MicrowavesMicrowaves– Infrared light
SlowerSlower than wired networks SecuritySecurity concerns
Chapter 5: LANs and WLANs 27
5 Bluetooth
Bluetooth is a short-range, wireless network technology designed to make its own connections between electronic devicesconnections between electronic devices, without wires, cables or any direct action from a user (a piconet)
Chapter 5: LANs and WLANs 28
5 Wi-Fi
Wireless networking technologies that are compatible with Ethernet (per IEEE 802.11)compatible with Ethernet (per IEEE 802.11)
MIMO technologyMIMO technology uses two or more antennae to send multiple sets of signals
Chapter 5: LANs and WLANs 29
5 Wi-Fi Equipment
Chapter 5: LANs and WLANs 30
5 Wi-Fi Equipment
If your computer is not pre-equipped with wireless circuitry, you can purchase and install a Wi-Fi card
Chapter 5: LANs and WLANs 31
5 Wi-Fi Equipment
Wireless network setups– Wireless ad-hoc networkad-hoc network– Wireless infrastructure networkinfrastructure network
• Wireless access point
• Wireless router
Chapter 5: LANs and WLANs 32
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
Chapter 5: LANs and WLANs 33
5 Wi-Fi Setup
Enter an SSIDSSID for the network Activate WEP, WPA, or WPA2 and create an create an
encryption key(!!)encryption key(!!) Set up the wireless workstations Connect an Internet access deviceInternet access device
– Generally a modemmodem that will connect to the service available in your area (cable, DSL, etc.) from your service provider (ISP)
Chapter 5: LANs and WLANs 34
5 Typical Wi-Fi Setup
Chapter 5: LANs and WLANs 36
5SECTION D
Using LANsUsing LANs LAN Advantages and Challenges Sharing Files Sharing Printers LAN Parties Troubleshooting
Chapter 5: LANs and WLANs 37
5 LAN Advantages
LANs enable people to work together SharingSharing networked softwaresoftware can reduce costs Sharing dataSharing data on a LAN can increase productivity SharingSharing networked hardware hardware can reduce costs SharingSharing networked hardware can provide
access to a wide range of services and specialized peripheral devices specialized peripheral devices (read “expensive”)
Chapter 5: LANs and WLANs 38
5 LAN Challenges Resources become unavailable when network network
malfunctionsmalfunctions Networks may be vulnerable to unauthorized unauthorized
accessaccess– More vulnerable than standalone computers
Wireless networks can be tapped from a “snooping” computer
Networked computers are susceptiblesusceptible to an increasing number of worms, Trojan horses, and blended threats
Chapter 5: LANs and WLANs 39
5 Sharing Files If you use Windows, it
automatically detectsautomatically detects available LANs any time you turn on a workstation
To connect to a shared shared resourceresource, you might be asked for a user ID and password
Chapter 5: LANs and WLANs 40
5 Sharing Files
In this drive mappingexample, a server’s driveC is mapped as drive Fby 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 just as though it were a drivewere a drive connected directly to the workstation.
Chapter 5: LANs and WLANs 41
5 Sharing Files
To allow other network users to access files or folders on your Windows computer, you have to designate them as designate them as sharedshared (commonly, via Windows Explorer)
Chapter 5: LANs and WLANs 42
5 Sharing Printers
Three setups allow for printer sharing:– Set up printer sharing using a workstation printerworkstation printer– Set up printer sharing using a print serverprint server– Install printer with built-in networkingprinter with built-in networking
Chapter 5: LANs and WLANs 43
5 Sharing Printers
In Windows, use the Printers and Faxes dialog box to allow other users to share the printer attached to your workstation
Chapter 5: LANs and WLANs 46
5SECTION E
Security Through EncryptionSecurity Through Encryption Wi-Fi Security Encryption
Chapter 5: LANs and WLANs 47
5 Wi-Fi Security
Wireless networks are much more susceptible to unauthorized accesssusceptible 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
Chapter 5: LANs and WLANs 49
5 Wi-Fi Security Wireless encryptionencryption 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
Chapter 5: LANs and WLANs 51
5 Encryption Encryption transforms a message so that its
contents are hidden (encrypted) from unauthorized readers– PlaintextPlaintext has not yet been encrypted– An encrypted message is referred to as
ciphertextciphertext Decryption is the opposite of encryption
– Cryptographic algorithmalgorithm– Cryptographic keykey
Chapter 5: LANs and WLANs 52
5 Encryption
Weak vs. strongWeak vs. strong encryption AES (Advanced Encryption Standard) Encryption methods can be broken by the
use of expensive, specialized, code-breaking computers– Brute-forceBrute-force method
Chapter 5: LANs and WLANs 53
5 Encryption
Public key encryptionPublic key encryption (PKE) eliminates key-distribution problem, by using one key to encrypt a message and another key to decrypt the message
Chapter 5 CompleteChapter 5 Complete
LANs and WLANsLANs and WLANs
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