Transcript Local Area Networks

Types of Computer Networks
By geographic distance
• Local Area Networks (LANs)
• Metropolitan Area Networks (MANs)
• Wide Area Networks (WANs)
• Personal Area Networks (PANs)
• also SANs
By media
• Wired (copper, fiber), Wireless
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How to set up/ troubleshoot your
LAN
• In the Windows search box
type Network and Sharing Center
• Click troubleshoot problems and investigate
some of the options. The option Network
Adapter will tell you the name of your wires
connection.
• Click Local Area Connection icon
• Click Internet Options at the bottom left
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Information about LAN connections
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LANs
• LANs are data networks of computers
within a limited geographic area
– LANs of wired and wireless technologies are
frequently connected.
• Protocols are standardized to facilitate
interconnection, interface to manufacturers,
module reuse
• IEEE 802.x standards accepted by ISO
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Ethernet
• “Ethernet” has 90+% of wired LAN market
• Metcalfe and Boggs developed a wired
LAN; first standardized LAN (IEEE 802.3)
– Used coaxial cable (somewhat similar to cable
TV); called it the “Ether”
– Clamp for stations to attach to the cable (tap)
– Station Interface Controller (NIC) to handle
data translation and interference
– With Xerox and Intel, placed in public domain
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Popular standards today
• IEEE802.3 (wired LAN, called Ethernet)
– Place command mode in search bar, type
ipconfig | more
• IEEE802.11 (wireless LAN, called WiFi)
– FDU has a wireless network (using access pts)
• IEEE802.15 (WPANs, specifically
Bluetooth)
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Network devices
• Nodes – devices on the network
– Computers (Hosts or stations)
– Network connecting devices
• Routers, switches, hubs, gateways
– Network peripherals (printers, scanners, storage
devices)
– Repeaters (boost signal)
– Modem (used to connect to the Internet)
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Network Interface Card
• NIC (or adapter)
– Can be added onto the system board, attached
to USB port, although typically NICs are
bought with current systems
• Laptops will have a wired and a wireless NIC
• NICs contain a MAC (physical) address
• NICs contain the network software
(protocol) in firmware
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Client/server mode
• Servers are frequently dedicated to specific
applications
– File server
– Print server
– Web server
• (Multiple) client machines request services
from servers
• Clients connect to web servers
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Peer-to-peer mode
• Workstations, laptops, etc. (perhaps using
Bluetooth) cooperate in running the network
and the devices
– File sharing systems such as Kazaa, BitTorrent
• Wi-Fi supports both peer-to-peer (ad hoc)
and client-server (infrastructure) modes.
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Physical topology
• Bus topology (MANs such as optimum online; original Ethernet implementation)
• Star topology – local loop; switched
Ethernet; cellular phones; Wi-Fi with access
points
• Tree topology (hierarchical)
• Graph (WANs)
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Interconnecting networks
• Bridges connect similar LANs
• Gateways connect any types of networks
– Typically used to connect home or school LAN
to the Internet
– Translate between different types of addresses,
protocols, etc.
• They all have to accommodate potential
differences in speed
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Networks Links
• Data travels either on cable or thru the air
– Each data stream must be assigned a unique
channel so that streams do not get garbled
• The range of frequencies of the link
(bandwidth) determines the maximum
amount of transmission capacity
– Bandwidth is measured in hertz (Hz);
transmission capacity in bps
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Broadband or narrowband
• Narrowband channels
– Up to 56kbps for dial-up access
• Broadband channels
– Gigabit Ethernet (802.3ba 100Gbps)
– 802.11n has maximum thruput of 100Mbps
– Internet surfing would be slow on narrowband
channels
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Transmission Noise
• Data can be corrupted by noise, such as
– Energy bursts
– White noise
– Different signals sent on the same frequency
band (WiFi and Bluetooth devices use the same
channels)
– Hidden station problem
• Network protocols recover from noise
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Packet Switching
• Messages (phone calls, downloads, mail)
are divided into smaller units called packets
– Bits are added to allow them to be reassembled
– Source and Destination addresses are added to
each packet to allow individual routing
– Packets can be multiplexed (combined) onto a
higher speed line
• Network protocols reassemble packets into
messages, retransmit lost packets, etc. .
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Types of Network Addresses
• MAC (physical) address is assigned to NIC
• In Ethernet, in hardware by the manufacturer
• A Domain address is assigned by The
International Corporation for Assigned
Names and Numbers (ICANN) to FDU, etc.
• An IP desktop address may be assigned by
DHCP or by your ISP (IPv4 and IPv6)
• Network Apps are assigned ports by the OS
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Internet Infrastructure
• Internet Infrastructure is maintained by NSPs
(1st tier ISPs)
– High speed routers deliver packets to destination
– Links may be wired or wireless
• Most infrastructure links are fiber
• FCC obtained some free bandwidth by the
replacement of analog television by digital television
– For use as high speed wireless transmission
channel
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Advantages of Wired
Connections
• Wired networks use cables, either fiber or
copper (land phone lines, cable TV, FIOS)
• Faster
• More secure
• Less noise
• Typically easy to configure
– Almost plug and play
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Disadvantages of wired
connections
• Inconvenient
– People don’t like cables (rat’s nest)
– Limited mobility
– Harder to install LAN cables – perhaps through
walls, ceilings
– Harder to fix breaks in links
• Animals have bitten through fiber cables
• Copper wires have been dug up and sold
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Advantages of Ethernet
• Public domain software
• Many vendors manufacture equipment
– NICs are cheap- typically included with a
desktop or lap top
• Mature and reliable
• Very fast
• Wi-Fi became popular because it is
compatible with Ethernet
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Ethernet equipment
•
•
•
•
Get two or more Ethernet-ready computers
An Ethernet router
Surge strip
Cables for each computer
– Twisted pair cat 5 or cat 6
• Internet access device such as modem
– (router may provide all of these functions)
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Devices to connect computers
• Hub, switch or router?
– Hub – incoming data is resent to all stations
• Cheap - you can get some for $5 to $15
– Switch
• Sends data to destination computer only
• More secure if you have multiple users on network
– Router/ gateway
• Connects to the Internet and switches data
• Adapts to the speed of the sending devices
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Cabling
• Network cables are terminated with RJ45
connectors (they look similar to telephone
cables, but connectors are a bit larger)
– Category 5 or 6 UTP recommended
• Maximum length of about 100 meters (328 feet)
• Just plug in the cables at each end
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Set up
• Turn off all devices
• Attach cables into ports in each pair of
devices
– Secure cables
• Power up the devices (using surge strips)
• OS should automatically detect and set up
the network
• Use network utilities, task bar to verify
connection
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Wireless networks
• Radio, microwave or infrared signals
– Infrared – 1012 – 1014 Hz band
• These do not go through objects
• Used for channel changers
– Microwave -108 – 1012 Hz band
• Do not go through objects
• Susceptible to interference by birds, rain
• Used by satellites, long distance signals
– Radio signals – 104 – 108 Hz band
• go through most objects (not metal, stacked paper)
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FCC
• In the U.S., frequency bands are assigned
by FCC
– Licensed bands are paid for by radio stations,
television stations
– Some bands are unlicensed and available to the
public, but portions of these are agreed upon for
specific usage
• Garage door openers, pagers, wireless LANs
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Advantages of wireless networks
• Mobility
• No electromagnetic interference,
specifically no power spikes (surges)
• No cables, jacks
– No breakage of cables, jacks
• Ease of installation
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Disadvantages
• Slower transmission rates
• Signals must be boosted more often than
wired LANs
• Interference from other broadcasts and
devices, some objects block transmission
• Security
– Broadcasts can be easily captured
– Encrypt your data; lock your system
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Bluetooth
• Bluetooth nodes set up peer-to-peer
piconets with other devices
• Limited distance; speed
2.4 GHz band up to 3Mbps; up to about 300 ft
6-9 GHz band up to 480 Mbps
Appropriate for connecting devices together such
as a mouse to a computer
Also connects cell phones to a wireless headset
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Wi-Fi speed
• The term Wi-Fi refers to a set of IEEE
802.11 standards: 802.11b, a, g, n, y
• Frequencies used by b, g, and n are in the
2.4GHz unlicensed band, same as basic
Bluetooth and some cellular phones
– Bluetooth is slower, and typically its signals
knock out 802.11 (not vice versa)
• g and n are backward compatible with b
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Speeds of Wi-Fi
• Speeds of about 11 Mbps (b), 54 Mbps (g),
144Mbps (100Mbps throughput) for n
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Wi-Fi
• Wi-Fi LANs require an access point (base
station) in infrastructure mode
– Functionality can be built into wireless router
– Stations transmit to access point which then
forwards packets to destination station of LAN,
or out through a wired connection to the
Internet
– All wireless devices must have at least one
antenna to receive and send packets
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