Types of Computer Networks

Chapter 5 Local Area Networks 1

Types of Computer NetworksBy 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

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

Chapter 5 Local Area Networks 3

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 ISOChapter 5 Local Area Networks 4

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

Chapter 5 Local Area Networks 5

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 serversChapter 5 Local Area Networks 9

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 on-line; 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 noiseChapter 5 Local Area Networks 15

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 OSChapter 5 Local Area Networks 17

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 soldChapter 5 Local Area Networks 20

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 Chapter 5 Local Area Networks 25

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)

Chapter 5 Local Area Networks 26

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

Chapter 5 Local Area Networks 29

Bluetooth

• Bluetooth nodes set up peer-to-peer piconets with other devices

• Limited distance; speed2.4 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

Chapter 5 Local Area Networks 30

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 Chapter 5 Local Area Networks 31

Speeds of Wi-Fi

• Speeds of about 11 Mbps (b), 54 Mbps (g), 144Mbps (100Mbps throughput) for n

Chapter 5 Local Area Networks 32

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

Chapter 5 Local Area Networks 33