LANs and WLANs Chapter 5. 5 Chapter 5: LANs and WLANs2 Chapter Contents Section A: Network Building Blocks Section B: Wired Networks Section C:

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


5SECTION A

Network Building BlocksNetwork Building Blocks Network Classifications LAN Standards Network Devices Clients, Servers, and Peers Physical Topology Network Links Communications Protocols


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


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


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


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


5 Network Devices


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


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


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


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)


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?


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


5SECTION B

Wired NetworksWired Networks Wired Network Basics HomePNA and Powerline Networks Ethernet Ethernet Equipment Ethernet Setup


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


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


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


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.


5 Ethernet Equipment

Checking a workstation for an Ethernet port


5 Ethernet Equipment

Ethernet adapter - NIC (designed to support the Ethernet protocols)

Network hub Network switch Network router RJ45 connector


5 Typical Ethernet Setup

Technically, this device functions as an Ethernet switch, as well as an IP router.


5SECTION C

Wireless NetworksWireless Networks Wireless Basics Bluetooth Wi-Fi Wi-Fi Equipment Wi-Fi Setup


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


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)


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


5 Wi-Fi Equipment


5 Wi-Fi Equipment

If your computer is not pre-equipped with wireless circuitry, you can purchase and install a Wi-Fi card


5 Wi-Fi Equipment

Wireless network setups– Wireless ad-hoc networkad-hoc network– Wireless infrastructure networkinfrastructure network

• Wireless access point

• Wireless router


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


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)


5 Typical Wi-Fi Setup


5SECTION D

Using LANsUsing LANs LAN Advantages and Challenges Sharing Files Sharing Printers LAN Parties Troubleshooting


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”)


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


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


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.


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)


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


5 Sharing Printers

In Windows, use the Printers and Faxes dialog box to allow other users to share the printer attached to your workstation


5SECTION E

Security Through EncryptionSecurity Through Encryption Wi-Fi Security Encryption


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


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


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


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


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

Documents

LANs and WLANs Chapter 5. 5 Chapter 5: LANs and WLANs2 Chapter Contents Section A: Network Building Blocks Section B: Wired Networks Section C: