Transcript week3 - Siena College

Recap of last class

History of the Internet
–
–
–

DARPA
ARPANet
Key Players
Other non-sense
–
–
File sharing (Napster)
Personal information security
(Experian)
Today’s Agenda

WWW Infastructure
–
–
–
URL details
Server details
How things work
Homework


Read pages 15-33 in IT.
Finish lab
–
–
All questions answered on
paper
Be prepared to show me your
webpage and all the required
components.
Questions





What does DARPA stand for?
What does ARPA stand for?
What is TCP/IP?
Who invented it?
Name 5 different types of content available on
the WWW
Questions

Approximately how many hosts currently make
up the internet
–
–
–
–


2 million
50 million
300 million
3 billion
What exactly is an internet host?
Is a packet router part of the Internet or part of
the World Wide Web (choose one).
What is a web server?


Web server is an example of a host.
Its just a computer with an
1.
2.
3.
4.
5.
Internet connection with
Software that delivers
Content (files such as html, jpg, etc.) over
The World Wide Web using
HTTP
What exactly is HTTP?

Hypertext Transfer Protocol
–
–
an application-level protocol over TCP (Transfer
Control Protocol)
for distributed, collaborative hypermedia information
systems
How does the protocol work?
1.
User’s computer establishes a TCP connection with a
server



2.
3.
Server is specified in the URL
Server listens for connection requests at a given port
Port is just a “communication channel”
If no host is given in the URL, connect to the local
host.
If no port is given in the URL, connect to port 80 (the
default port).
How does the protocol work?
4.
5.
6.
User’s computer sends an HTTP request
Example: GET index.html
User’s computer receives the requested
document from the server
Close the TCP connection
What exactly is a URL?



Universal (Uniform) Resource Locator
Its essentially a street address for content on
the WWW
Its not a street address for a computer on the
Internet.
–

Computers have IP addresses
A URL is an address of a file, a service or
even a person
URL’s



Each one of you has a URL
Does anyone know theirs?
Hint: Did you every receive email?
What exactly is a URL?





http://<host>/<path>?<query>
ftp://<user>:<pass>@<host>:<port>/<cwd1>/<name>
home is a
mailto:<account@site>
directory on the
web server
Example:
http://www.cs.siena.edu/home/index.html
cs.siena.edu
is the network
location of www
Which protocol
to use?
www is the name of the
web server (ares)
index.html is the
name of a file in
the home
directory
Translating URL’s
This is the actual directory path on the
file server
http://www.cs.siena.edu/home/index.html
First, you need to
know what protocol
to use to get the file
edu tells us the general domain/classification.
siena directs us to a campus DNS server
cs directs us to a sub network
www is a computer on that sub-network
Web Servers






Want to see the files on our
web server?
There are about 600 files
(mostly html and jpg)
I created them all
400-500 man hours
Had I been hired as a
consultant I would have
charged at least $75,000
Would have been a bargain for
a company
Web Servers

Any computer can be a web server
–
–
–


CS Server: Compaq Intel Pentium III running an Apache web
server for RedHat Linux 7.1
CS Server: Adequate for about 50-60 http requests per
minute
CS Server: Actually get about 250 request per day
Why is the CS website so slow?
It depends on where you are?
Web Servers

Rough map of the world as seen from our
web server
Siena College
Roger Bacon
Ken Swarner’s
office
www
(ares)
Web Servers

Web servers do NOT have to be dedicated
–
–
–

There can be other software
Other processes running
Other purposes
Web servers are often
–
–
–
–
Application servers
Database servers
Domain name servers
Personal computers
Web Servers

Powerful servers
–
–
Multiple processors for handling simultaneous requests
Lots of memory (RAM) so file don’t have to be retrieved from
slow hard drives


–

Called swapping
RAM is perhaps the most important investment
Thick bandwidth for dishing out lots of content
Who has powerful servers
–
–
–
Yahoo & Google
Major networks: CNN, ABC, NBC, CBS, etc. (ESPN)
Microsoft, IBM, & ??? (Dell???)
Web Servers

How can I set up my own web server.
1.
2.
3.
4.


First, you need to get software
Second, you need a pretty good internet connection
Third, you need to register a domain name
Finally, you need to actually make some webpages
How much does this all cost?
How hard is it?
Web server software

Apache (its free and its very good)
–
–
–
–

UNIX and Windows versions
Problems:
Not super easy to setup or configure
If you are not already a nerd, you’ll probably need a lot of
time.
Microsoft makes several different servers
–
–
Somewhat affordable
Somewhat easier to setup than Apache
Internet connections



Dial-up $10/month
DSL $30/month
Cable $40-50/month
Internet connections

T1
–
–

$500 to $1000/month
1-3 Mbps
T3
–
–
$5000 to $15,000/month
3-45 Mbps
Internet connections

OC-3
–
–

OC-12
–
–

$30,000 to $50,000/month
150+ Mbps
Over $1,000,000 year
600+ Mbps
OC-48
–
–
–
Good luck finding one
used internally by companies like MCI who sell the above
connections
2400+ Mbps
Internet Connections

Siena
–
–
–

3 or 4 dedicated T-1 lines (bundled?)
I’d estimate that we have 4-5 Mbps
I’ll get back to you on exact details
RPI (2 years ago)
–
–
–
Equivalent of 2 dedicated T-3’s
50+ Mbps
10-15 times Siena’s bandwidth.
Domain Names

Once managed by the InterNIC

–
–
–

Internet Network Information Center
Non-profit organization of professional
Public interest in mind
Still manages .org in North America
Who manages domains now?
Domain Names

The Internet Assigned Numbers Authority (IANA) is the
overall authority for the IP Addresses, the Domain Names,
and many other parameters, used in the Internet.
–
APNIC (Asia Pacific Network Information Centre) - Asia/Pacific
Region
–
ARIN (American Registry for Internet Numbers) - North
America and Sub-Sahara Africa
–
LACNIC (Latin American and Caribbean IP address Regional
Registry) - Latin America and some Caribbean Islands
–
RIPE NCC (Réseaux IP Européens) - Europe, the Middle East,
Central Asia, and African countries located north of the
equator
Domain Names



Many companies act as a 3rd (and even 4th)
party and will register your domain name with
the proper authorities.
The InterNIC itself acts as a 3rd party in
registering many domain names.
Registering a domain just reserves the
name.
Spoofing




Ultimately, Domain name servers determine
Which domain names are associated with
Which hosts.
Remind me to tell you a story.
Domain Names
Domain Names


To get the Internet to recognize your domain you
have to get your ISP to add your domain to is
Domain Name Server
This will have a cascading effect and eventually your
domain can be reached.
Domain Name Table
…
www.breimer.org  204.168.0.207
IP Address:
204.168.0.207
ISP
…
My computer
DNS
Authority
Multi-tiered
Domain Names & Hosting


Companies that register your domain name
are often ISP’s and
Will set you up with:
–
–
–
–
A domain name
A dedicated IP address
And, they make sure you get added to the right
tables
Associates your IP address with your domain.
On-site vs. Off-site

Most hosting companies have their own
servers and will provide off-site hosting
–
–

Off-site means they host your stuff on their servers
You don’t have your own servers on-site
Most ISP can set you up on-site if you have
–
–
–
Your own server
Your own support personal
Your own infrastructure
Other hosting options

Free services (under their domain name)
–
–

Cheap services (under their domain name)
–
–

Angelfire
Geocities
Roadrunner
AOL
Piggy-backing (under their domain name)
–
–
College
Company