Transcript Ch 2

Networking I
Chapter II
The Internet
How does one Connect?
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Dial-Up Connection – Modem
ISDN – Integrated Services Digital Network
DSL – Digital Subscriber Line
Cable Modem
Satellite
Radio Waves
T1
T3
Telephone Modem
• Speed up to
– 56K bits/second (download)
– 32K bits/second (upload)
• Available everywhere
• Service Cost up to $25 monthly
• Modem cost “free” to $50 or so
ISDN
• Integrated Services Digital network
• Over Ordinary phone line but not always
available
• Can share a phone line with voice
• Speeds up to 128k bps.
• Service Cost up to $100 per month or so.
• No longer as popular as it was about 4 years
ago.
DSL
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Digital Subscriber Line
Service cost from 30 to 50 pre month
Not available in many places
Shares a line with voice.
Speed up to 7 or 8 megabits/second
Cable Modem
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(What I have at home)
Service about $40 per month
Always on
Requires a NIC for your computer and an RJ45 cable between modem and NIC.
• Modem costs about 150 to 200 (but is “free”
with most packages.
• NIC costs from $10 to $150 or more.
• Speed depends on the number of users but
ranges from standard modem speed up to
about 10 megabits/second.
Satellite
• Primarily for downloads.
• Typically use phone lines for uploads
• Speed is slow – 400k bits/second
download; 56k bits/second upload
• Expensive – up to about $125 per
month.
• Wireless and available everywhere,
much like satellite TV.
Radio Waves
• Available on some more advanced cell
phone plans.
• Cost typically $40 per month plus cost
of phone plan.
• Extremely fast (in the 100mb per
second range)
T1 and T3
• Expensive – T1 in the $500 to $2000 per
month depending on the distance from the
station; T3 in the $10,000 per month range.
• Fast – T1 is 1.5 megabits/second; and T3 is
45 megabits/second.
• [The campus network at the UofS is hooked
to the internet by a “partial” T3 line, which we
share with others. Our bandwidth is 25
mbps.]
ISPs – Intenet Service Providers
• Free – Typically heavily sponsored. Most of the free
services are no longer available because of
technology which kills ad windows.
• Basic – Few Features: dialup number, software
(which is free with windows anyway), limited tech
support, simple e-mail and perhaps USENet -- $10 to
16 monthly
• Full– ISPs such as AOL, MSN, Compuserve, 24/7
tech support, multiple e-mail accounts, web pages -$20 to $20 per month.
Choosing an ISP
• In your case if you are a resident student then
you have an account through the U for “free”
with purchase of a NIC
• Find what’s locally avaliable and what it costs.
• You can normally get a free trial for a month
from most major providers.
IP Addressing
• All machines on the Internet have an IP
address (internet protocol address)
• This address is 4 numbers from 0 through
255, so for example the machine in my office
is 134.198.169.33
• Some addresses are static and some are
dynamic.
Dynamic vs. Static Addressing
• Dynamic addressing gives you a possibly different
address each time you connect to the Internet.
• Static addressing gives you the same address all the
time.
• My office machine is static.
• My laptop is dynamic because it has different IP
addresses in my office and in the classroom.
• In my office it can also have different addresses on
different days.
Domain Name Addressing
• IP addresses are hard to remember.
• Domain name addressing uses several
“words” separated by dots.
• My office machine has a domain address of
peculier.cs.scranton.edu
• Domain addresses are normally used for email and web pages although you can use IP
addresses if you want to.
E-mail
• You already understand this.
• Addresses consist of a username followed by
an at sign @ followed by a domain for mail.
• I have several local e-mail addresses:
– [email protected]
– [email protected]
– [email protected]
• Typically e-mail user names ARE case
sensitive but domain names are NOT.
E-mail software
• Included in other software – e.g. Outlook
Express is part of Windows; AOL has e-mail
built in; Outlook is part of MS Office
• Web based e-mail. You don’t have software
for reading e-mail. It is read through a
browser and e-mail accounts are “free” from a
variety of sources.
• Separate e-mail programs – e.g. Eudora.
E-mail attachments
• MIME
– Multipurpose Internet Mail Extensions
• Types of attachments to mail messages
typically denoted by file name EXTENSION.
• A source of viruses but can also be used to
send files containing, voice, pictures,
animation, etc.
Instant Messaging
• The ability to “talk” via keyboard with other
individuals in real time.
• AOL/Netscape IM is currently the most
popular but the service is offered by MSN,
ICQ, Yahoo and others.
• Powerful features such as private chat room
for several people and file sharing are
available in many of these programs.
Mailing Lists
• E-mail that is sent to a list-serv for distribution to a
list of people
• Open mailing lists can be subscribed to by many,
while closed lists can only be subscribed to by invited
guests.
• Moderated lists have all their messages examined by
the moderator for appropriate content.
• Lists can either be a digest or separate message
form.
The World Wide Web
• Typically the content is multimedia – containing text,
graphics, sound, and “animation”.
• Hyperlinks enable convenient navigation.
• HyperText Markup Language (HTML) is used to write
web pages.
• Some pages contain special code to implement
features. This code is typically written in a
programming language called JavaScript.