Transcript WEB Architectures

IT 210
The Internet & World Wide Web
introduction
What is the Internet?
The Internet is a network of networks, that is an
Inter-Network, that connects different networks from
all over the world that use the same communication
protocols (e.g., IP/TCP).
The Internet is spelled with uppercase “I”. There’s
only one!
It is the infrastructure upon which the World Wide
Web (and other things like e-mail) resides.
What is the World Wide Web?
It is not the Internet.
It is not any computer network
It is a set of documents and other resources
(e.g., images) linked together by hyperlinks,
made available by web servers, and “read” by
client web browsers
WWW documents are requested and sent
using the HTTP protocol.
Network and the OSI Model
Key Internet/Web Challenge
Problem: How can we get so many different devices
to interact well together on the Internet? How can
we request so many different types of content on the
Web?
Answer: Get hardware/software creators to use
standard protocols & languages
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E.g., IP/TCP for Internet communication
E.g., HTTP for Web communication
E.g., HTML, CSS, Javascript, PHP for web content
Your Key Challenge
The Protocols and
Languages are
constantly changing!
A day in the life of a webpage
BIRTH: A website is born when a creator
opens a text editor and adds some
content using HTML (or other web
standard-based language)
Let’s give it a try…
• Open a text editor & create main.html
HTML
Markup language (NOT programming
language)
Defines structure and content
HTML 4, XHTML 1 & 2, HTML 5
(different related standards). Know your
audience and what browsers they’re
using and use appropriate one.
Viewing a Webpage
Browsers are applications designed to render
HTML and other web content
Browsers do many other things such as cache
data locally, run Javascript code in webpages,
help avert malicious code… (See
20thingsilearned)
Browsers render differently & have different
features and bugs!
Posting to the Web
You’ll need…
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A Web Server (software that accepts HTTP
requests from browsers and “serves up”
the requested files stored on the server)
A registered domain name and its
associated IP address (e.g., byu.edu)
A live connection to the Internet for your
server
Accessing a Webpage
Use your browser to specify a web resource’s URL
Your Browser contacts a DNS Server to translate the
domain name of the URL into an IP address of the
Web Server
The IP address is used to route messages from the
browser (on the client) to the Web Server by using
the IP protocol
Your browser will use the TCP & HTTP protocols to
request and send the resource from the server
(assuming it has it)
Simple Universal Resource
Locator (URL) Example
Detailed URL Example
More on URLs
Other Protocols:
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HTTPS:
secure HTTP
FTP:
File Transfer Protocol
Also: Gopher:, mailto:, telnet:, news: etc.
Many companies allow you to register
domain names (e.g.,
http://www.register.com/). ICANN is
ultimately responsible.
What’s a resource?
HTML document
XML document
Anything a server can present as either
of the above.
Anything a browser can present using
the services of the client (MS Word doc,
PDF doc, etc.)
Domain Name Service (DNS)
Goal of DNS Server: “domain name
resolution” – map a domain name (e.g.,
www.byu.edu) to an IP address
(128.187.16.242)
No single DNS Server includes all of the
billions of IP addresses. Instead, they store
what they need (and cache recently used
pairs for a limited time – TimeToLive) and
request from other DNS servers what they
need.
DNS Server Network
How http works
Play demo
URL Reference Scenario
Network
Stack
Server Computer
File Read
DNS
Server
File Data
Server Computer
Network
Cloud-
User computer
Browser Network
Stack
Theon port 80
TCP Open
HTTP file request
TCP
Terminate
Session
TCP Session
ACK
Internet
HTTP file data
TCP Terminate ACK
Web
Server
Network
Stack
URL Reference Scenario with Query
Network
Stack
Network
Cloud-
User computer
Browser Network
Stack
TCP Open on port 80
HTTP file request
? Other data
The
TCP Terminate
Session
TCP Session
ACK
Server Computer
File Read
DNS
Server
File Data
Server Computer
Web server calculates
and does actions,
manufactures dynamic
HTML page
Dynamic HTML
Internet
TCP Terminate ACK
Web
Server
Network
Stack
Virtual Machines Setup for 210
Lab server accounts:
Remote Server
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Inside the lab address 192.168.201.XXX
Outside the lab addresses
 SSH access – it.et.byu.edu:51XXX
 HTML access – it.et.byu.edu:41XXX
Network Attached Storage (NAS)
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IP address is 192.168.0.83
 Inside lab only
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You will use it to backup your data
More Details in Labs 1 & 2
WEB Architecture:
How one links together documents.
How one presents document
relationships.
How one interfaces to dynamic content.
How one keeps context in the network
of documents.
WEB SYSTEM Architecture
How one organizes the network of
services to present the WEB
architecture.
How one allocates tasks between the
browser, the web server, and other
support servers to implement the
network of services of the WEB
Architecture.
Course: WEB SYSTEM Development
Overview of WEB Architectures and Design
Principles
Study of WEB SYSTEM Architectures to
implement various WEB Architectures.
Design and Implementation of WEB based
systems.
Questions:
What is a protocol and why is it important to
web systems?
How are the Internet and WWW different?
How are they related?
Describe the process through which a website
is accessed.
What are HTTP, DNS servers, IP/TCP, IP
addresses, URLs?
Name the parts of a URL.