Transcript Computer Confluence 6/e

Networking & Connectivity
Mendelsohn
A Computer Network
• What is a network?
– A system of two or more computing devices
that are linked together.
• Why are networks useful?
– Share information (e.g. databases, software,
other data)
– Share peripherals (e.g. printers)
– Share access (e.g. internet)
– Allow people to work together
Early Networks
• Telegraph
• Voice (telephone)
What type of information does a
computer network typically carry ?
• Voice
• Data
• Both
Copyright 2008 M J Davidson
What type of signal does the
network carry ?
• Digital
• Analog
Copyright 2008 M J Davidson
Terminology
• Node: Any device on the network such as
computers or peripherals (printers, routers, etc)
is called a node.
• Nodes are typically connected to hubs (or
sometimes switches).
– Think of how you get your electronics on the electrical
“network” by plugging them into an outlet.
– Similarly, to get devices onto a network, you need to
plug them into the network. Frequently this is done by
connecting the node to a hub.
A Hub
Ethernet cable
A network can be as simple as two computers connected
to each other
• Most networks involve at least a few computers
frequently with some peripherals (printer).
• With multiple computers, the nodes need to be
plugged into a hub.
Home networks
• Most people create a home network for
the purpose of sharing an internet
connection.
• However it is also possible to share
peripherals such as scanners and printers.
A Home Network Sharing an Internet Connection
wall
outlet
Connecting a device to the network
• Wired
– Various types of cabling are available
• Wireless
– Requires the use of a shared or agreed-upon
standard such as WiFi
Wired – Types of Cables
• Twisted Pair (shielded, unshielded)
• Coaxial
• Fiber-Optic
Modems
• One wired method of connecting to a network
– Increasingly obselete
• Networks such as telephone systems use analog signals
(as opposed to digital)
• Before a computer can work with the data, it has to be
“translated” into digital
• The process of converting an analog signal to digital is
called MO-dulation.
• Converting digital to analog is called DEM-odulation.
• These days, modems are becoming less common as
most people are networked digitally.
– They don’t have to “dial in” using a telephone line.
Bandwidth
• If your online experience seems slow and jerky—
particularly when dealing with multimedia (audio, video),
your problem is likely a question of bandwidth.
• When talking about internet connections, bandwidth
refers to the quantity of data that can be transferred from
an ISP to your PC in a given period of time (e.g. each
second).
• These days, is typically measured in megabits per
second (mps).
Broadband
• Broadband refers to a high-bandwidth connection.
– Typically several mps
– That said, there is typically a large difference between your
theoretical bandwidth and the actual bandwidth you get at home.
• Types of broadband:
–
–
–
–
DSL: uses standard phone lines – therefore, widely available
Cable: requires a cable line (same as TV cable)
Wireless: such as WiFi, Satellite, Infrared, Bluetooth
Fiber-Optic: far faster than any other technology. However, fiberoptic wiring is still only available in a small number of locations.
• 1 FO cable can transmit the equivalent of 10,000 copper (e.g. cable) cables
Broadband Penetration Worldwide
Wireless Technologies/Standards
• In terms of connectivity, wireless technologies include
Satellite, Infrared, WiFi, Bluetooth, and others
WiFi (IEEE 802.11)
• More and more people every day are connecting to
networks such as the internet using WiFi
• Not surprisingly, WiFi is the fastest growing networking
technology.
• The IEEE standard is known as 802.11
– Versions: 802.11a, 802.b, 802.11g, 802.11n
– These versions have varying ranges and speeds
• Speed ranges from 10 mps to 100+ depending on the
version (Version ‘n’ is the fastest, ‘b’ is the slowest)
• Very limited range: about 30 meters.
– Version ‘n’ has a greater range – but still measured in meters
• Not as fast as Ethernet, but still quite fast and good
enough for multimedia networking
WiMax (802.16a)
• A new wireless standard
• WiMax towers have a range covering
about a 25 square mile area
Broadband Comparison
Bluetooth (IEEE 802.15)
• Another wireless standard
• Very low range (about 10 m)
• Low bandwidth (about 1-3
mps in practice)
• Costs less – therefore
popular with manufacturers
• Given low range and
bandwidth, not widely used
for network connectivity
• Much more popular for
wirelessly connecting two
devices together
– provided they are in close
proximity
Read this!!!
• There will be an exam question that
comes from reading this article….
• http://dvice.com/archives/2006/08/shift_ver
izons_fios_and_sprint.php
Connecting a PC to a Network
• Wired
– Requires a network
adapter or “network
interface card” (NIC)
• Wireless
– Requires a wireless
network adapter
A typical home cable/DSL broadband connection
1.
Pre-existing cable wires are
extended to the interior of your
home.
•
2.
3.
4.
This cabling may already be in place
(e.g. if you have cable TV)
Your internet service provider
(ISP) provides a cable or DSL
“modem” that establishes the
connection between the cable
wiring and the internet.
The cable/DSL modem is
typically connected either directly
to a PC or sometimes to a
wireless router.
If a wireless router is in place, the
internet signal to and from the
wireless router is broadcast
throughout the home.
Classifying networks
• By Distance (LAN, WAN), Relationship
(e.g. client-server), Protocol (e.g. TCP/IP)
Copyright 2008 M J Davidson
Classify by Distance
• PAN – personal
– E.g. a home network:
• sharing one internet connection
• sharing a printer
• LAN – local
– Usually implies that the networked computers are in the same
building
– E.g. a small business
• WAN – wide
– A network spanning a wider area such as a city or even larger.
– DePaul’s network on several campuses around the Chicagoland
area
– City-wide networks are sometimes referred to as ‘MAN’s
(metropolitan area networks)
Classify by Relationship
• Client-server
• Peer-to-peer
Copyright 2008 M J Davidson
Classify by Protocol
• a set of rules for the exchange of data
over a communications channel
• Examples
– SNA
– TCP/IP
• The internet is classified based on the type
of protocol it uses (TCP/IP)
– More on this in a later lecture
Copyright 2008 M J Davidson
Wired Communication Ports
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–
–
–
–
–
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Serial - single bit at a time
Parallel – eight bits at a time
FireWire (IEEE 1394 )
Universal Serial Bus (USB)
Ethernet
VGA
Etc
Parallel Port
– Parallel – eight bits at a
time
• Before USB, was
commonly used for
printers. Many printers still
come with cables to
connect to a parallel port.
• Before faster and more
efficient ports were
developed, was also used
for CD ROMs, Zip drives,
etc
VGA Port
• These days, pretty much exclusively
limited to connecting a monitor to a PC.
USB Port
– USB Universal Serial Bus
• 1.0 (11 Mbps) or
• 2.0 (480Mbps) - the current standard
– Developed to replace
connections that previously
were limited to serial or
parallel ports.
•
•
•
•
Printers
Keyboard
Mice
You name it….
IEEE 1394 (Firewire, i.Link)
– High-speed communications
– Brand names:
• Firewire (Apple)
• i.Link (Sony)
– Fast!
– Popular uses: Devices that
require speedy transfer
• external hard drives
• Camcorders (transfer of large
data devices from camera to
PC)
Ethernet Port
• Ethernet wiring is far and away the
most popular (wired) method of
connecting a computer to a network
• Pros:
– Faster than wireless
– More reliable than wireless
– Easier to set up
• Cons
– Wired!