Transcript Types of Networks - CS 153 Introduction to Computing I

2004-2005 Academic Year, Spring Semester
Bilkent University - Faculty of Art, Design and Architecture Department of Communication and Design
CS 153 Introduction to
Computing I
Lesson 2
Network


A group of computers and associated devices
connected by communications facilities (both
hardware and software) to share information
and peripheral devices, such as printers and
modems.
Any time you connect 2 or more computers
together so that they can share resources, you
have a computer network. Connect 2 or more
networks together and you have an internet.
Types of Networks

Server Based

Single or multiple servers “serve” the resources (data and
even the processing power) to the clients.


Peer to Peer


Thin Client, Thick Client?
The members of the network share each other’s resources
Hybrid

Most of the networks fall on this category, combination of
both technologies.
Types of Network( Size)s

LAN
Local Area Network
A data communications network covering a small area, usually
within the confines of a building or floors within a building; a
relatively high-speed computer communications network for
in-building data transfer and applications. Cheap, and easy to
setup!
 Examples:



A company network of several hundered PCs that might be partly
open to public.
A home network of few PCs.
Uses:


Ethernet
Token Ring (no longer widely used)
Ethernet, Token Ring
Token Ring
Ethernet
Types of Network( Size)s

WAN
Wide Area Network. The networks of LANs and some more...
A system of interconnecting many computers over a large geographic area, making
use of telephone lines, satellite links, and other long-range communications
technologies. Because of the much greater hardware expense, reduced bandwidth,
and the reliance on existing infrastructure that is shared by general-purpose
communications, different protocols are used in WANs from those typically used
in LANs.
 Examples:




Internet!
Army, police networks.
Private large firms networks.
Uses:






Modem (MOdulator DEModulator): standard phone lines (called POTS (Plain Old
Telephone Service)
PSTN (Public Switched Telephone Network)),
ISDN (Integrated Services Digital Network),
Frame Relay,
ATM (Asynchronous Transfer Mode)
or other high speed services
Types of Network Connections
BUS
TOKEN RING
STAR
Types of Network Connections

BUS
PC to PC (to PC to PC...)
 For each pair of connection 2
Network Cards Required.


Star
PCs to a Hub or Switch.
 A hub/switch is needed and for
per connection a network card is
needed.

Types of Network Connections
(cont’d)

Ring



Better than BUS.
For each computer a Network Card is
enough.
If connected A  B  C  D  A


If A wants to send data to C, it sends to B,
B forwards to C.
Performance of these connections:

Star >= Bus > Ring
Hub, Switch and Router

Hub
Most simple central connection device. It basicly
connects all the computers that are connected to it.
 The problem with a hub is: when two PC’s are
talking at the full speed, the other PC’s connected to
Hub have connection speed problems.


Switch

Same as Hub, but solves the speed problem of the
hub.
Hub, Switch and Router

Router
Routers allow completely different networks, (ie
LANs or WANs) to talk to each other.
 The networks are connected through a router.
 Consider a home network (LAN) is connected to the
Internet through ADSL. You cannot connect ADSL
modem directly to a switch or a hub. You need a
router to seperate the LAN and the Internet (WAN).

Types of Cables

Twisted Pair




Coaxial



Cheap
Telephone lines
Slow
TV
Fast
Coaxial
Fiber Optic



Expensive
Longest Range
Highest Speed
Fiber Optic
Twisted Pair
Some Examples of Connections and
Speeds

Speed of connection is measured through bits
per second.
Carrier Technology
Description
Speed*
Physical Medium
Dial-up Access
On demand access using a modem and
regular telephone line.
2400 bps to 56 Kbps
Twisted pair (regular
phone lines)
ISDN
Dedicated telephone line and router
required.
64 Kbps to 128 Kbps
Twisted pair
Cable
Special cable modem and cable line
required.
512 Kbps to 10 Mbps
Coaxial cable; in
some cases
telephone lines used
for upstream
requests.
ADSL
Asymmetric Digital
Subscriber Line
This technology uses the unused digital
portion of a regular copper telephone line
(i.e. your fax line) to transmit and receive
information. ADSL is asymmetric since it
recieves at 6 to 9 Mbps per second but
can only send data at between 16 to 640
Kbps.
A special modem and adapter card are
required.
128 Kbps to 9 Mbps
Twisted pair (used as
a digital, broadband
medium)
Carrier Technology
Description
Speed*
Physical Medium
Wireless (LMCS)
Access is gained by connection to a
high speed cellular like local
multi-point communications
system (LMCS) network via
wireless transmitter/receiver.
2 Mbps or more
Airwaves
Requires outside
antenna.
Satellite
The computer sends request for
information to an ISP via normal
phone dial-up communications
and data is returned via high
speed satellite to rooftop dish,
which relays it to the computer via
a decoder box.
400 Kbps
Airwaves
Requires outside
antenna.
Frame Relay
Provides a type of "party line"
connection to the Internet.
Requires a FRAD (Frame Relay Access
Device) similar to a modem, or a
DSU/CSU.
56 Kbps to 1.544
Mbps
Various
Carrier
Technology
Description
Speed*
Physical Medium
Fractional T1
(Flexible DS1)
Only a portion of the 23
channels available in a T1
line is actually used.
64 Kbps to
1.544 Mbps
Twisted-pair or coaxial cable
T1
Special lines and
equipment (DSU/CSU and
router) required.
1.544 Mbps
Twisted-pair, coaxial cable, or optical fiber
T3
Typically used for ISP to
Internet infrastructure.
44.736 Mbps
Optical fiber
OC-1
Typically used for ISP to
Internet infrastructure
within Internet
infrastructure.
51.84 Mbps
Optical fiber
OC-3
Typically used for large
company backbone or
Internet backbone.
155.52 Mbps
Optical fiber
Connection of Networks

Gateway

A device that connects two dissimilar networks.


Bridge


If you want to connect a ATM network to a ISDN use Gateway
A device that connects LANs, of the same type.
Router

A device that connects several networks. A router is smart
enough to pick the right path for communications traffic. If
there is a partial failure of the network, a router looks for an
alternate route.
Some Network Servers

File Server



Client Server



Serves only files. Has huge amount of disk space.
If you request something from this server, it sends the file.
Serves processing power. Has huge amount of memory and
very powerful processors.
If you request something from this server, it sends the result
to your screen.
Web Server



Has specialized software for serving web pages.
Has very fast disks, big memory, fast internet connection.
If it server dynamic web pages, should have fast processor.
The Internet


Internet is the collection of the different networks.
Internet has started in 1969 as a military project for
reliable and secure form of communication for the
possibility of nuclear war. It expanded in 1970s for
researchers and scientists to communicate their ideas
and interests with their long-distance colleagues.
Starting from the end of 1980s, it has been developing
very fast.
Homework:


Read and check related links at
http://en.wikipedia.org/wiki/Internet
Read “A brief history of the Internet” from
http://www.isoc.org/internet/history/
Possible Usages of the Internet

The good:






The World Wide Web
Remote access
Collaboration
File-sharing
Cultural awareness
And the bad:






Child abuse
Copyright infringement
Viruses
Security cracking
Dated technology
Self-destructive subcultures
The Domain Name System : DNS!

The unique name that identifies an Internet site.
Domain Names always have 2 or more parts,
separated by dots. The part on the left is the
most specific, and the part on the right is the
most general. For example:
Nasa.gov
 Stanford.edu
 Bilkent.edu.tr
 Garanti.com.tr

The Domain Name System

Consider
www.bcc.bilkent.edu.tr
www: is the server’s name.
bcc: is a subdomain.
bilkent: is the domain name.
edu: domain suffix.
tr: is the country (tr suffix is controlled by only
METU).
Country Suffixes

http://ftp.ics.uci.edu/pub/websoft/wwwstat/c
ountry-codes.txt
.tr: Turkey
 .uk: United Kingdom
 .us: United States (but nearly no sites have .us in
USA, why?)
 .fr: France
 .de: Germany
 .tv: Tuvalu (www.mtv.tv etc.) (why?)

Tuvalu
Domain Suffixes














AERO Air-transport industry
BIZ Businesses
COM Unrestricted (but intended for commercial registrants)
COOP Cooperatives
EDU Educational institutions
GOV Government
INFO Unrestricted use
INT Organizations established by international treaties between governments
MIL Military
MUSEUM Museums
NAME For registration by individuals
NET Unrestricted (but intended for network providers, etc.)
ORG Unrestricted (but intended for organizations that do not fit elsewhere)
PRO Accountants, lawyers, physicians, and other professionals
Domain Suffixes (Turkey)

Homework: find all the domain names at
Turkish .tr suffix, with who can apply for it.,
restrictions, and yearly fees.
IP



IP is Internet Protocol.
Every computer connected to the Internet
should have an IP address.
The IP address of
Bilkent University web page is 139.179.10.16
 Mtv’s web site is 217.147.241.192
 Computer Science Department’s secretery’s machine
is: 139.179.21.51...

Back To DNS





Each computer can be associated with a name.
Each computer must have a IP address.
Internet works on IP protocol. How do I know
which computer has which IP?
DNS Servers tell you that!
www.mtv.tv  DNS Server 217.147.241.192
 Go to 217.147.241.192
Email






Electronic Mail
[email protected]
[username]@[domain]
DNS Server of [domain], tells to your mail
server which server to drop the mails.
POP3: protocol to
get your mails
SMTP: protocol to
deliver your mails




Email Fields
To: write the full email address of the recipient
Cc: (carbon copy) other recipients 1 or more (each
email is separated by comma or semicolon from the
next - each recipient will see the emails of the others)
Bcc: (blind carbon copy) other recipients in the list will
not be seen by others)
Subject: Subject of the e-mail goes here.
Common Email Actions



reply all: Your reply to the message goes to all
recipients in from and cc fields.
reply: Your reply to the message goes to the
recipient in from field.
forward: To forward the e-mail to others.
Do not do SPAM!
 Read http://www.spam.org.tr

Ways of E-mail

Web Based





mail.yahoo.com
www.hotmail.com
www.gmail.com
https://charon.bcc.bilkent.edu.tr/basilix
POP3 Based

E-mail clients


Pine: login to your unix account, type pine, and your Bilkent mails are
there.
Outlook Express, Office Outlook, The Bat, Eudora
Remote Connection: Telnet

Telnet is an application program that allows remote log
in to computer systems on the Internet. By Telnet, a
user can remotely contact any e-mail account or even
contact Internet resources.



Hostname: you will supply a server name or full domain
name for this field.
Username: you will type your username.
Password: you will type your password here but it will be
displayed in the form of astrixes (*****).
After entering to the system you can just run that
operating system's commands.
File Transfer Protocol: FTP






One of the most common uses of computer to computer
communications is to transfer files.
Programs that manage this process include many file
management features. Such a program will also handle the
process of connecting to the other computer such as a FTP
Server.
Many of the names of these programs include the letters FTP,
which stands for File Transfer Protocol.
Downloading means to transfer a file to your computer from
elsewhere.
Uploading means to transfer a file from your computer to
another.
Transfer Types: ASCII, Binary
Web Browser and WWW



World Wide Web is a technology based upon hypertext which means that
selected words in the text can forward the user to other locations in the
WWW. These words are links to other documents which may take the form
of text, images, movie or sound files.
Browsers are software/program whose role is to present information
resources on the Internet into a format with the capability of displaying
graphical images, movies, and sound as well as text.
In its simplest form, a browser such as Internet Explorer or Firefox will read
a “page” or file from a server which is stored in a special format called
HTML. This format allows text, image, movie and sound files to appear in
side-by-side. Thus, when directing or “pointing” a browser to a certain
“page”, the browser automatically decodes its HTML commands, including
the text and images, and then presents them on the computer screen.
Hypertext Transfer Protocol: HTTP


Hyper Text Transfer Protocol is the standard
protocol or language that allows hypertext
information to be transferred between
computers on the Internet.
Hypertext is the basis for “linking” documents
to one another and then navigating with the aid
of a WWW browser program. Hypertext allows
the reader to move easily from one document to
another via a hyperlink.
Hyperlink


The unique feature of hypertext, a hyperlink is
simply a special word, phrase, or object that
takes the reader to another page.
A text hyperlink is denoted by a different color.
In many browsers, the hyperlink is underlined
and blue in color. Once the mouse pointer is
moved onto a hyperlink, the pointer arrow
changes into a hand which means that it
acknowledges the hyperlink.
Unified Resource Locator: URL


An acronym for Uniform Resource Locator, a URL is a form of
address or, more specifically, the description of the location for a
resource on the Internet. It is also referred to as a Location, or
simply a WWW address.
http://www.bilkent.edu.tr/~ussakli/index.html






http://  protocol name.
www.bilkent.edu.tr  domain name
/~ussakli  folder name in the domain.
/index.html  the file name to open in the domain.
Bookmark is a browser function that keeps a link to desired
pages. To make a bookmark, simply find the desired web site and
click on Bookmarks|Add Bookmark and the site is stored in the
bookmark file. To return to a bookmarked location, simply click
on Bookmarks and select the bookmark to return to.
If an address starts with https: (HyperText Transfer Protocol,
Secure.) then it is a good indication that information transfers
are secure.
Some Protocols





Http: Hypertext transfer protocol
Ftp: File transfer protocol
Email: (opens your e-mail program)
Gopher: Gopher is a Client and Server style
program’s protocol.
News: (opens your news reader)
Search Engines



Due to the increasing amount of information on the World
Wide Web, universities and companies have constructed search
engines which enable the user to locate indexes according to
subject, author, dates, titles, or simply keywords.
Some engines search titles or headers of documents, others
search the documents themselves, and still others restrict their
search to only indexes and/or directories.
Most used search engines:




www.google.com
search.msn.com
www.yahoo.com
www.altavista.com
End of Lesson

But!

I asked you what was Kibi Byte, Mebi Byte, Gibi
Byte.

Actually the term kilo in kilobyte means 1000 bytes. But
it actually represents 1024 bytes. In order to clearify the
difference between 1024 and 1000, it’s proposed to use
kibi for 1024 and use kilo for 1000 bytes. Will we use kibi
instead of kilo in the future? Who knows?
Homework (%5)
Name 2 Peer to Peer networks.
Read and check related links at http://en.wikipedia.org/wiki/Internet
Read “A brief history of the Internet” from http://www.isoc.org/internet/history/
List 10 web page addresses and do the following decompositon.
http://www.bilkent.edu.tr/~ussakli/index.html
1.
2.
3.
4.




5.
6.
7.
8.
9.
http://  protocol name.
www.bilkent.edu.tr  domain name
/~ussakli  folder name in the domain.
/index.html  the file name to open in the domain.
Send a e-mail to me with the topic “Homework Question 5” and your name and number at
the body, of which I cannot see who you send the mail to. (so my outlook will say Undisclosed
recipients at to: field of the mail I receive.)
Search and find five FTP Client Programs and a FTP Server program using your favorite web
search engine. (Do not just take the list from your friends.)
Define the cycle of processing and state which computer hardware is used in the cycle of
processing. Which stages do we store data, if we don’t store the data what happens?
Give two reasons why today we start to have 64 bit processors(i.e. Athlon 64, Itanium). Wasn’t
32 bit processor (i.e. Pentium 4, Athlon XP) enough for todays computing needs?
What is a DVD and name and list the capacities of a DVD.
Submit your work to [email protected], Topic: ID Number Surname Name Homework 5.