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COMPUTER NETWORKS
HIMA 4160
Fall 2009
House Keeping
• Assignment 3 is due next Thursday
LEARNING OBJECTIVES
• Define a network and its purpose.
• Describe several uses for communications
technology.
• Understand the various topologies and
architectures a computer network might use.
• Explain the difference between a LAN, a WAN,
and a PAN, and between an intranet, an extranet,
and a VPN.
LEARNING OBJECTIVES,
CONT’D
• Understand characteristics about data and how
it travels over a network.
• Name specific types of wired and wireless
transmission media and explain how they
transmit data.
• Identify different protocols that can be used to
connect the devices on a network.
• List several types of networking hardware and
explain the purpose of each.
OVERVIEW
• This class covers:
Networking concepts and terminology
Common networking and communications applications
Technical issues related to networks, including the
major types of networks, how data is transmitted
over a network, and types of transmission media
involved
o Explanation of the various ways networked devices
communicate with one another
o Various types of hardware used in conjunction with a
computer network
o
o
o
WHAT IS A NETWORK?
• Network: a connected system of
objects or people
• Computer network: a collection of
computers and other hardware
devices connected together so that
users can share hardware, software,
and data, as well as electronically
communicate with each other
• Internet: largest computer network
WHAT ARE SOME OF THE
APPLICATIONS OF
NETWORKING AND
COMMUNICATION?
NETWORKING AND COMMUNICATIONS
APPLICATIONS
• Mobile phones (wireless phones)
o Cellular
(cell) phones (most common)
o Satellite
phones (used where cell
service isn’t available)
o Wi-Fi
phones
NETWORKING AND COMMUNICATIONS
APPLICATIONS, CONT’D
• Paging: sending short
numeric or text messages to
a person’s pager
o Most often used for
onsite paging applications
• Messaging: two-way paging
o Most
often takes place
today via a mobile phone
NETWORKING AND COMMUNICATIONS
APPLICATIONS, CONT’D
• Global positioning system
(GPS): Uses satellites and
a receiver to determine
the exact geographic
location of the receiver
o
o
o
Commonly found in cars today
Available as handheld units
Used by the military, hikers,
travelers, and others who
need to know their precise
location
NETWORKING AND COMMUNICATIONS
APPLICATIONS, CONT’D
• Monitoring systems—monitor status of or
location of individuals, vehicles, assets, etc.
o Electronic medical monitors
o GPS-based monitoring systems
o RFID short-range monitoring systems
• Monitoring via the Internet
Satellite radio—delivers digital radio content to
satellite receivers, which can be
o Car-mounted
o Placed in the home
o Carried around
o
NETWORKING AND COMMUNICATIONS
APPLICATIONS, CONT’D
• eICU: use of communications technology to
monitor ICU patients remotely
o Remote monitoring and consultations
NETWORKING AND COMMUNICATIONS
APPLICATIONS, CONT’D
• Videoconferencing: use of communications
technology for real-time, face-to-face meetings
between individuals located in different places
o Online conferencing (via the Internet)
o Dedicated videoconferencing room
o Video phone calls
• Collaborative computing (workgroup
computing):using a computer and communications
technology to work together on documents and
other project components
NETWORKING AND COMMUNICATIONS
APPLICATIONS, CONT’D
• Telecommuting: individuals work at home and
communicate with their place of business and
clients via communications technologies
• Digital data distribution: transferring digital
data(digital photos, music, movies, TV broadcasts,
medical imaging files, etc.) electronically from one
place to another
o Home use
o Business use
o Digital movie distribution
NETWORKING AND COMMUNICATIONS
APPLICATIONS, CONT’D
• Telemedicine: use of communications technology
to provide medical information and services
o Remote monitoring and consultations
o Remote diagnosis
o Tele-surgery
TYPES OF NETWORKS
• Networks can be identified by their
o
o
o
Topology (physical arrangement)
Architecture (the way they are designed to
communicate)
Size (how large of an area the network
services)
NETWORK TOPOLOGIES
• Star networks (all devices connect to a central
device or hub)
• Bus networks (all devices connect to a central
cable)
• Ring networks (devices connect to one another in
a ring)
• Mesh networks (multiple connections between
devices)
• Some networks use a combination of topologies
Network Architecture
• Client-server
• Peer to peer
NETWORK ARCHITECTURES
• Client-server networks
o
o
Client: PC or other
device on the network
that requests and
utilizes network
resources
Server: computer
dedicated to
processing client
requests
NETWORK ARCHITECTURES,
CONT’D
• Peer-to-peer networks (all computers at the
same level)
o Internet peer-to-peer (P2P) computing:
performed via the Internet
Network Size
•
•
•
•
•
•
•
LAN
WAN
MAN
PAN
Intranet
Extranet
VPN
LANS, WANS, AND OTHER
TYPES OF NETWORKS
• Local area network (LAN): covers a relatively
small geographical area, such as a home, office
building, or school
• Wide area network (WAN): covers a large
geographical area; may consist of two or more
LANs, which could be relatively close to one
another (such as in the same city) or far apart
• Metropolitan area network (MAN): designed for
a metropolitan area, typically a city or county
LANS, WANS, AND OTHER
TYPES OF NETWORKS, CONT’D
• Personal area network (PAN):connects personal devices
for one individual, such as his or her portable PC, cell
phone, and portable printer
• Intranet: private network, such as a company LAN, set
up by an organization for use by its employees
• Extranet: intranet that is at least partially accessible
to authorized outsiders
• Virtual private network (VPN): group of secure paths
over the Internet that provide authorized users a
secure means of accessing a private network via the
Internet
HOW DOES DATA TRAVEL
OVER A NETWORK?
• Data transmitted over a network has specific
characteristics
• Data can travel over a network in various ways
• Network devices can communicate through a
o
o
Wired connection: via physical cables
Wireless connection: typically through radio
signals
DATA TRANSMISSION
CHARACTERISTICS
• Analog vs. digital: continuous wave
vs. discrete 0s and 1s
• Bandwidth (throughput):amount of
data that can be transmitted over
a communications medium at one
time (higher bandwidth will deliver
data faster)
• Serial vs. parallel transmission
o
o
Serial: one bit a time (more
common in communication)
Parallel: at least one byte at a
time
DATA TRANSMISSION
CHARACTERISTICS, CONT’D
• Transmission timing
Synchronous transmission (at regular, specified
intervals)
o Asynchronous transmission (sent when ready)
o Isochronous transmission (sent at the same
time as other related data)
o
• Transmission directions
o
o
o
Simplex transmission (one way only)
Half-duplex transmission (one way at a time)
Full-duplex transmission (both ways at the
same time)
WIRED VS. WIRELESS
CONNECTIONS
• Wired network connection: the PC is physically
cabled to the network
o Common in schools, business, and government
facilities
• Wireless networks: typically use radio waves to
send data through the air
o Rapidly becoming more popular in homes and
businesses; wireless hotspots are commonly
available in public locations
WIRED NETWORK
TRANSMISSION MEDIA
• Twisted-pair cable
o
o
Pairs of wires twisted together
Used for telephone and network connections
• Coaxial cable
o
o
Thick center wire
Used for computer networks, short-run telephone
transmissions, cable television delivery
• Fiber-optic cable
Glass or fiber strands through which light can
pass
o Used for high-speed communications
o
WIRELESS NETWORK
TRANSMISSION MEDIA
• Broadcast radio transmissions
o Short-range
(such as Bluetooth): can
connect a wireless keyboard or mouse to a
PC
o Medium-range (such as Wi-Fi): used for
wireless LANs and to connect portable PC
users to the Internet at public hot spots
• Microwave and satellite transmissions
o Microwave stations (earth based)
o Communications satellites (placed
in orbit)
Unites States Frequency Allocations
The Radio Spectrum
Wireless Network Transmission
Media, Cont’d
WIRELESS NETWORK
TRANSMISSION MEDIA, CONT’D
• Cellular radio transmissions
o
o
o
o
Use cellular towers within cells
Calls are transferred from cell tower to cell tower
as the individual moves
Different transmission frequencies are used to
avoid interference and allow multiple conversations
to take place via a single tower at one time
Widely used, but cell service not available
everywhere
ETHERNET
• Ethernet: a widely used communications protocol
for LANs
o
o
o
Typically used with LANs that have a bus or star
topology and use twisted-pair or coaxial cables
Original (10Base-T) Ethernet networks run at 10
Mbps; newer 100 Mbps and 1 Gbps versions are
now available
Utilizes a set of procedures (CSMA/CD) to send
data and make sure it arrives
COMMUNICATIONS
PROTOCOLS
• Communications protocol: an agreed-upon
standard for transmitting data between
two devices on a network
• Protocols specify how
o Devices physically connect to a network
o Data is packaged for transmission
o Receiving devices acknowledge signals
(handshaking)
o Errors are handled
TOKEN RING
• Token Ring: Communications protocol usually used with a ring
network topology
o
Utilizes a token to send and retrieve data
o
Token circulates in one direction
o
o
o
Token is either free or carries a message to be
delivered to a device
Each device checks to see if the message is
addressed to it
Devices can grab a free token and add a message
WI-FI (802.11)
• Wi-Fi (802.11): family of wireless networking standards
o
o
o
o
802.11b: original standard (11 Mbps)
802.11a (Wi-Fi5):about five times faster than 802.11b;
more expensive, uses a different radio frequency (5
GHz) than 802.11b (2.4 GHz), making the two standards
incompatible
802.11g:current Wi-Fi standard; supports data transfer
rates of 54 Mbps; it uses the same 2.4 GHz frequency as
802.11b, so their products are compatible
802.11n (Fast Wi-Fi):in development, 248 MBps speed.
MESH NETWORKS, WIMAX,
MOBILE-FI, AND XMAX
• Mesh networks:use a mesh topology, so messages
can take any of several possible paths from
source to destination
o
Used to connect wireless networks
o
Can be used to enlarge hotspot areas
o
o
Can be used to allow emergency workers to
communicate with one another
Most often used to create MANs
MESH NETWORKS, WIMAX, MOBILEFI,AND XMAX, CONT’D
• WiMAX (802.16):emerging wireless networking standard
that is faster and has a greater range than Wi-Fi
o
o
Expected to provide fast wireless Internet
access over a distance of up to 30 miles
Mobile WiMAX is under development
• Mobile-Fi (802.20):high-speed mobile Internet
technology currently in development
o
Expected to be used while moving, such as in cars
and trains
• xMax:recently developed,for longer range wireless
connections; uses unused portions of radio channels
BLUETOOTH
• Bluetooth: communications standard for very
short-range wireless connections
o
o
o
The devices are automatically connected once
they get within the allowable range
Designed for communications between personal
devices (within 10 meters or 33 feet), such as
keyboards and PCs, cell phones and earpieces,
PCs and printers, etc.
Devices form piconets of up to 8 devices each
ULTRA WIDEBAND (UWB)
• Ultra Wide Band (UWB): another short-range wireless
technology
o
Faster and has a greater range than Bluetooth
o
Originally developed for the military in the
1960s
o
o
Beginning to be used to wirelessly network
consumer multimedia devices to wireless deliver
digital data (video, music, photos, etc.)
Emerging Bluetooth standards may use UWB to
speed up connections between devices
TCP/IP AND WIRELESS APPLICATION
PROTOCOL (WAP)
• TCP/IP: Protocol used for transferring data over
the Internet
o Uses packet switching to facilitate the
transmission of messages
o
Packets are sent separately and reassembled at
the final destination
o
Also used with home networking
• Wireless Application Protocol (WAP): Standard
for delivering content, such as Web pages, to
mobile devices
PHONELINE AND POWERLINE
NETWORKS
• Phone line or Home PNA standard
o Allows computers to be networked
through
ordinary phone wiring and phone jacks, without
interfering with voice telephone calls
o
Geared toward setting up quick and easy home
networks
• Powerline standard
o Allows PCs to be
networked over existing power
lines using conventional electrical outlets
o
Emerging standard will also connect home
entertainment devices
NETWORKING HARDWARE
• Network adapters:used to connect a PC to a
network
o Also called network interface card (NIC) when
in the form of an expansion card
o
Come in a variety of formats
 PCI
 USB
 PC Card
• Adapter must match the type of network being
used (Ethernet, Wi-Fi, Bluetooth, etc.)
NETWORKING HARDWARE, CONT’D
• Modem: device that connects a computer to the
Internet
o Term used even if not connecting via a phone
line
o
Type of modem needed depends on the type of
Internet access being used
 Conventional dial-up
 ISDN
 DSL
 Cable
 Satellite
NETWORKING HARDWARE,
CONT’D
• Hubs, switches, routers, and wireless access points:used
to connect devices and route data to the devices on a
network
o Hub: all data goes to all devices
o
Switch: data goes to just appropriate device
o
Router: more efficiently delivers data
o
Wireless access point: connects wireless devices to a
wired network
o
Some devices contain more than one of these
capabilities
NETWORKING HARDWARE,
CONT’D
• Gateways and bridges: connect one network to
another
o Gateway: connects dissimilar networks
o Bridge: connects similar networks
• Repeaters: amplify signals on a network so they
can travel further
• Multiplexers and concentrators: combine
transmissions from multiple devices to send over
a medium and then separates them again at the
destination
OSI sample protocols
1. Physical: T1, 802.11a/.b/g/n etc.
2. Data Link: MAC, ethernet etc.
3. Network: IP etc.
4. Transport: TCP, UDP etc.
5. Session: NetBIOS etc.
6. Presentation: ASCII, MPEG etc.
7. Application: FTP, HL7, Http, SMTP, Telnet etc.
SUMMARY
• What is a Network?
• Networking and Communications Applications
• Types of Networks
• How Does Data Travel Over a Network?
• Communications Protocols
• Networking Hardware