1 communications and networks reading: chapter 9
TRANSCRIPT
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Communications and Networks
Reading: Chapter 9
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Why are networks so useful?
They fa
cilit
ate
com
mu...
They a
llow
for s
harin
g ..
Both
of the
abo
ve
33% 33%33%1. They facilitate
communications2. They allow for
sharing of resources3. Both of the above
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NetworkNetwork
Uses of communications technologies Internet Global Positioning System (GPS) Short Message Service (SMS)
Network Interconnected group of computers and devices connected
via communications devices and media Facilitates sharing of resources and supports communications Requires
Sending & receiving devices Communications devices Communications channel or path Network OS (NOS)
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Networks – Communications Devices
Communications Device Hardware capable of sending/receiving data Convert signals so that they are suitable for
the communications channel May convert between analog and digital
Common types Dial-up modems ISDN and DSL modems Cable modems Network interface cards Wireless access points Routers
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Networks – Communications Devices
Networks – Communications Devices
Dial-up Modem Modulate/demodulate External modem
Connects to serial or RS-232 port Internal modem
Card inserted to expansion slot/PC Slot
ISDN and DSL ModemsDo not modulate/demodulateExternalSends and receives data over a digital telephone line
ISDN lineDSL line
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Networks – Communications Devices
Cable modem Cable television network Faster than dial-up access or ISDN line Splitter runs separate cables to TV’s and cable modem External
USB port or Ethernet NIC via a cable
Network Interface Card (NIC) Coordinates transmission/receipt of data to/from the
device Card installed in an expansion slot of a PC, printer, PC
slot Wireless transmission includes antenna Works with a particular network technology
Ethernet or token ring
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Networks – Communications Devices
Hub Provides a central
point of connectivity for cables in a network
May include a router Router
Connects multiple computers and routers together
Transmits packets to correct destination
May include built-in firewall
Wireless access point Allows computers
and devices to communicate wirelessly
Allows data transfer to a wired network
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Communications devices include ______.
route
rshubs
modem
sNIC
s
All of t
he a
bove
20% 20% 20%20%20%
1. routers2. hubs3. modems4. NICs5. All of the above
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Networks – Communications Channels
Channel Communications path between two devices Transmission rate
Speed at which data flows through the channel Bandwidth of the channel
Bits per second (bps), Hertz (cycles per second) Transmission media
Materials or techniques capable of carrying one or more signals
Baseband media – carry one signal at a time Broadband media – carry multiple signals concurrently
Physical transmission media Twisted pair, Coaxial, Fiber Optic
Wireless transmission media Infrared, Radio Frequency, Infrared, Microwave
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Networks –Physical Transmission Media
Twisted-pair cable Used for network cabling and
telephone systems One or more twisted-pair wires
bundled together Each pair has two insulated
copper wires twisted togetherCoaxial cable (coax)
Used for network cabling and cable TVSingle copper wire surrounded by 3 layers
Insulating materialWoven/braided metalPlastic outer coating
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Networks –Physical Transmission Media
Fiber optic cable Light used to send signals Thin glass or plastic
strands Surrounded by insulating
glass cladding and a protective coating
Carries many signals High speed Less noise Smaller size Expensive, difficult to
install and modify
glass cladding
optical fiber core
Protective coating
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Networks –Physical Transmission Media
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All of the following except ______ are examples of physical media.
coax
ial c
able
twis
ted p
air
mic
rowav
e ca
ble
fiber
optic
cab
le
25% 25%25%25%
1. coaxial cable2. twisted pair3. microwave cable4. fiber optic cable
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Networks –Wireless Transmission Media
Radio Frequency Antenna, transmitter,
receiver Bluetooth (2.45 GHz) 802.11b & g (2.4 GHz) Cellular Radio Waves
Cell phones, mobile devices
High frequency radio waves
824 to 849 MHz
MicrowavesHigh-speed signal transmissionSignals sent between microwave stations
Fixed-point wirelessRequires line-of-sight
Communications SatellitesSatellite receives microwave signal and amplifiesRetransmits over wide-area, to a number of land-based stations
Infrared SignalsIR light waves with line-of-sight transmission
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Networks –Wireless Transmission Media
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All of the following except ______ are examples of wireless media.
mic
rowav
es
sate
llite
s
radio
freq
uency
wav
es
fiber
optic
wav
es
25% 25%25%25%
1. microwaves2. satellites3. radio frequency
waves4. fiber optic waves
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Networks
Classified according to Geography – Geographic Distribution
LAN MAN WAN
Architecture Topology Protocol/Communications Technology
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Networks –Geographic Distribution
Networks –Geographic Distribution
Local Area Network (LAN) Connects computers in a
limited geographical area
Each computer and device is a node
Metropolitan Area Network (MAN)
High-speed network that connects LANs in a metropolitan area
Managed by a consortium of users or a single network provider
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Networks –Geographic Distribution
Wide Area Network (WAN)Connects computers and devices in a large geographical area
Connected via many types of mediaOne large network or two or more interconnected LANs, MANs
OthersCANHANTAN
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A ______ is a network that encompasses a limited geographic area.
MAN
WAN
LANPAN
25% 25%25%25%
1. MAN2. WAN3. LAN4. PAN
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Networks
Classified according to Geography
Architecture – Broad outline of the network
Peer-to-Peer Client/Server
Topology Protocol/Communications Technology
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Network Architectures –Client/Server and Peer-to-
Peer
Peer-to-Peer Share peripheral devices Up to 10 “peer” computers
NOS & applications software, storage
Internet Peer-to-Peer (P2P) Users connect directly to each
other’s hard disk Popular, inexpensive
client client client
serverprinter
Client/Server Server controls resources
More storage space, power Serves as a repository
Dedicated servers Client relies on the server for
access to resources
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Networks
Can be classified according to Geography Architecture
Topology – Physical arrangement of devices connected to the network
Bus Ring Star
Networks often use a combination of topologies
Protocol/Communications Technology
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Network Topologies –Bus and Ring Networks
Bus Network Single central cable connects computers and devices Transmits in both directions If a device fails, network continues to function
Reliable Popular, inexpensive Ring Network
Cable forms a closed ring Transmits in only one direction If one device fails, all those after
the device cannot function Spans larger distance than bus
network LANs and WANs
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Network Topologies –Star and Other Networks
Star Network Devices connect to a
central computer Hub
If one device fails, only that device is affected
Hub fails
Other Topologies Mesh
Redundant interconnections between nodes Tree
Star networks connected together via a bus
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With ______ topology, the devices on the network are connected together in a closed loop.
BusRin
gSta
rtre
e
25% 25%25%25%
1. bus2. ring3. star4. tree
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Networks
Can be classified according to Geography Architecture Topology
Protocol/Communications Technology – Standards that govern how data/instructions flow over the network
Ethernet Token Ring TCP/IP WAP Others
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Networks –Network Communications
Technologies
Networks –Network Communications
Technologies Communications Protocol
Set of rules and procedures for exchanging information among computers
Ethernet Token ring TCP/IP WAP Others
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Network Communications Technologies –
Ethernet
Network Communications Technologies –
Ethernet
Ethernet Widely used LAN standard Developed by Xerox, DEC, Intel - 1976
Fast Ethernet (100Base-T) - 100 Mbps Gigabit Ethernet - 1000 Mbps 10-Gigabit Ethernet – 10 Gbps
Bus or star topology PCs in the network to contend for
access Collision
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Network Communications Technologies –
Token Ring
Network Communications Technologies –
Token Ring
Token Ring Ring or star topology LAN standard Passes a signal called a token
Special bit pattern Only device with token can transmit Device catches the token, attaches message ,
sends it to travel around the network to receiving device
Receiving device catches token, strips off the message, resends token
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Network Communications Technologies –
TCP/IP
Network Communications Technologies –
TCP/IP TCP/IP
Used to connect hosts on the Internet Includes several protocols
Transmission Control Protocol and Internet Protocol Data broken up into small packets
Origin information Destination information Sequence information Data/information/instructions
Packet switching Break up message into packets, route packets,
destination reassembles the message Routers direct packets individually along fastest path
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Network Communications Technologies –
WAP
Wireless Application Protocol (WAP) Access Internet via mobile devices 2.0 Specification
Open Mobile Alliance (OMA) Web sites provide wireless content
to display on microbrowsers WML – XML application designed for
small screens
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Network Communications Technologies –
802.11, Bluetooth, IrDA
IEEE 802.11 (802.11b, g – “WiFi”) Family of standards used with wireless LANs
Used for public Internet access points
Bluetooth Devices contain special chip Short-range radio waves transmit between Bluetooth
devices Short distance
IrDA IrDA devices contain IrDA ports Infrared light waves Line-of-sight transmission
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With TCP/IP is used to send data over the Internet, the data is divided into small pieces or ______.
bundle
s
packe
ts
toke
nshubs
25% 25%25%25%
1. bundles2. packets3. tokens4. hubs
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Networks –Intranets
Networks –Intranets
Intranet Internal network in an organization used to share
information Uses Internet technologies (TCP/IP, Web server, Web
pages) Enterprise network Connects to the Internet
Extranet - Allows outside user access Firewall
Designed to prevent unauthorized access to a private network
Firewall blocks messages that do not meet security criteria Uses hardware, software, combination of both All messages entering or leaving the intranet must pass
through the firewall
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Networks – Home Area Networks
(HAN) Network within a home
Connects digital devicesHomePLC – electrical lines; cables connect card/USB/parallel port to wall outletPhoneline – telephone lines; cables connect NIC/PC card to telephone jack
Network card that plugs into PCI slot and wall outlet for home power-line network
Howstuffworks.com
HomeRF, 802.11b – radio waves; NIC connects to transceiver with antenna or to wireless access pointEthernet – twisted pair cables; Ethernet NIC cards and cables to connect devices
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Do you have a home area network?
Yes No
50%50%1. Yes2. No
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Networks Summary Uses of Communications Technology Networks
Communications Devices Communications Channels
Physical and Wireless Transmission Media Geographic
LAN, MAN, WAN Architectures
Peer-to-Peer, Client/Server Topologies
Bus, Ring, Star Protocols
Ethernet, Token Ring, TCP/IP, WAP, 802.11, others Intranets and Firewalls Home Networks