Transcript Getting on the Internet

Getting on the Internet
Internet Service Providers
Transport Media
Sending Information Back & Forth
Internet Service Providers (ISP)
• Internet Service Providers (ISP) provide you
with a connection between your computer
and the Internet
• ISP provide varied Internet services (access to
the WWW, email, listservs, etc.
• Depending on the service, you are usually
charged either by the month or by the hour
So who is your ISP?
There are many ISP out there
•
The top 3 ISP are*:
1.
2.
3.
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AT&T with 12.9 subscribers
Comcast with 12.1 million subscribers
AOL with 12.0 million subscribers
Some other ISPs include, NetZero, Earthlink, Juno,
etc.
Many colleges serve as an ISP, MCCC provides
access to the WWW (email for faculty & staffat
present).
Let’s go to http://www.thelist.com/ and see some
of what else is available.
*New York Times, May 3, 2007
Transport Media
• Transport medium is the physical connection
which connects your computer to the internet.
• The Internet backbone consists of high speed
fiber optic cables & copper transmission lines.
• This physical connection determines the speed
and bandwidth capabilities of your Internet
connection.
Using Telephone Lines
• Home connection using phone lines or is plain
old telephone service (POTS) is still common.
• Modulators and demodulators (modems)
send and receive digital information over
analog phone lines
• Common modem speeds 28.8 Kbps & 56 Kbps
Kbps = kilobytes per second
Telephone Modem
Follow the signal to see how modems work by modulating the
computer’s digital signal into an analog signal that can be transmitted
over telephone lines to your ISP, where the signal is demodulated.
Ethernet
• Fast Ethernet network speeds led to growth of local
area networks (LANs)
– LANs transmit data at 10 megabits per second (Mbps)
• Ethernet speeds are increasing
– Twisted-pair telephone lines are 10/100BaseT (100
megabits/second)
– Fiber optic speeds are 10 gigabits/second (10 Gbps) or 10
billion bits per second
ISDN
• Integrated Services Digital Network (ISDN)
allows for digital transmission of data over
regular phone lines.
• ISDN carries both voice and data and
supports real-time video conferencing
• ISDNs are being superseded by Digital
Subscriber Lines (DSL)
DSL
• DSL means Digital Subscriber Line
– Broadband connection over telephone lines
– DSL is available to over 75% of United States
• There are two kinds of DSL
– Synchronous DSL (SDSL) uses same speed for all
transmissions
– Asynchronous DSL (ADSL) uses a higher rate for
downloads than uploads
ADSL
• Reduces the DSL cost.
• More common in home applications
• Typical users download more than they
upload (e.g. movies)
• ADSL can use the same line for simultaneous
voice and data transmission while SDSL
cannot
Cable Modems
• Cable modems connect PCs to TV cables
using both Ethernet and television signals
• The term broadband refers to these
connections that carry multiple channels over
a single cable
• Speeds can vary depending on the number of
simultaneous users on the cable’s network
Satellite
• If cable or DSL is not available, satellite Internet
service is good if user has a view of the southern sky
– Bad weather can impact speeds
• Satellite features
– Typical speeds are 500 Kbps downstream and 150 Kbps
upstream
– Only one computer can be used per subscription: DSL
vendors allow more
Transmission Control Protocol (TCP)
• Recall that TCP governs how information gets
transmitted in packets over the Internet
– TCP divides information into packets
– TCP routes data to destinations
– TCP re-assembles the information
• TCP/IP are built in to the Windows and
Macintosh operating systems
Comparing the Ways to Connect
Direct Connections
• An Internet connection that is always on is a direct
connection
– Dial-up modems are not direct connections
• Direct connections are
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Ethernet
ISDN
Cable modem
DSL
Satellite
Let’s see how fast our connection is
Go to:
http://www.bandwidthplace.com/speedtest/