CHAPTER 9
RECAP: COMPUTER NETWORKS
LAN
WAN
HARDWARE
Hub:
 LAN hardware that transmits data to the nodes on
the LAN “rude”.
Switch:
 Hardware connectivity through which data travels.
More efficient. keeps a record of the MAC
addresses of all the devices connected to it.
TRANSMISSION LINE TYPES, USES,
AND SPEED
WHAT IS INTERNET?
A network of networks, joining many government, university
and private computers together and providing an
infrastructure for the use of E-mail, bulletin boards, file
archives, hypertext documents, databases and other
computational resources
The vast collection of computer networks which form and
act as a single huge network for transport of data and
messages across distances which can be anywhere
from the same office to anywhere in the world.
Written by William F. Slater, III
1996
President of the Chicago Chapter of the Internet Society
HISTORY OF THE INTERNET
1969 : ARPANET was born. 4 nodes were inter-connected: UCLA,SRI,UCSB, U. of Utah Charley Kline from UCLA sent 1st
packet.
1972 : First computer-to-computer chat program at UCLA.
1975 : First mailing list was created by Steve Walker.
1984 : DNS (Domain Name System) was introduced.
1988 : First Internet Worm.
1990 : AOL, CompuServe provided dial-up service.
1991 : WWW was created by Tim Berners-Lee from CERN
1994 : Commercial network. Shopping mall. Can order pizza online.
1998 : 2M domain names registered. Compaq bought altavista.com for $3.3M. Google founded
2003 : Facebook launched
THE INTERNET
 A global network of computers that communicate
using a common language (network of networks)
 Internet is composed of two parts: the
infrastructure (hardware), and the software
(applications and protocols)
 Hardware:
 cables, routers, computers, and servers.
 Software:
 applications, programming languages, databases, and protocols
that make communication
INTERNET CHARACTERISTICS
The power of the Internet:
1.
2.
3.
4.
5.
Ubiquity
Low cost
Global Reach
Open and Shared ownership
Richness – complexity and content of the
message
6. Interactivity
WWW

The world wide web is a sophisticated system for universal information
capture and delivery
 The world wide web consortium (W3C) definition of the web: "The
World Wide Web is the universe of network-accessible information, an
embodiment of human knowledge"
 Provides information access in ways not previously possible
– Hyperlinked (Hypertext)
– Graphical user interface
– Pictorial and non-text information
– Information that changes rapidly
– Immediate access
– Anyone can author a web site
– Multi-user access to the same information (try that with a book)
– Easily searchable information
The functionality of the WWW is based on 3 main standards:
 URL (Universal Resource Locator)
 HTML (Hypertext Markup Language)
 HTTP (Hypertext transfer Protocol)
THE UNIVERSAL RESOURCE LOCATOR (URL)
Each page of information on the web has a unique address called the
URL at which it can be found
http://faculty.uscupstate.edu/atzacheva/lecture1.html
The document
can be obtained
using the
Hypertext
Transfer Protocol
(HTTP)
1
Protocol
Host Name The Name of
Web Server
2
Host Name
Path to the Web
Page
File Name
Denotes that the File
is Written in HTML
HyperText Markup
Language
3
File Name
HTML
HTML is a universal, simple language for formatting text. It also allows embedding of
graphics, and linking of documents via ‘hyperlinks’.
‘Hypertext’ documents allow readers to freely move around the document, following
links to subjects of interest.
HTML is a language that is used to specify the structure of documents for retrieval
across the Internet using browsers.
HTTP
The standard Web transfer protocol is HTTP (HyperText Transfer Protocols). It is used
for document exchange between servers and clients (typically browsers) in the
WWW.
To retrieve a document, the client first sends a request to the web server and waits
for a reply
An HTTP daemon/service (a program that waits for http requests) on the server then
handles the request and the document is sent to the client (over a connection
established using TCP/IP – Transmission Control Protocol / Internet Protocol)
We recall from previous lectures, that a Protocol is “Agreed upon sets of rules that
provide order to a system or situation.” In this case, a set of rules/standards for
communicating on the Internet.
Key Digital Networking
Technologies
• Packet switching
 Method of slicing digital messages into parcels (packets),
sending packets along different communication paths as
they become available, and then reassembling packets
at destination
Packet-Switched Networks and
Packet Communications
TCP/IP
TCP = TRANSMISSION
CONTROL
PROTOCOL
(Breaks messages into packets,
Checks the integrity of incoming
Packets and reassembles them)
IP = INTERNET
PROTOCOL
(routes packets around
the Internet)
WWW: WHAT IS IT?
Is a distributed collection of hypermedia documents
that are inter-linked together. Web servers store
the information (text, images, sound clips, video
clips), and Web clients or browsers access this
information.
Domain addresses are governed by the standard
Universal Resource Locator (URL) and end in
suffixes that indicate the type of domain
ownership.
 i.e commercial sites end in .com, not-for profit entities use
the .org suffix, government (.gov)
INTERNET ADDRESSING AND
ARCHITECTURE
• The Domain Name
System:
 Converts IP address to domain
names
 Hierarchical structure top is
root domain, followed by toplevel domains, second-level
domains, and third-level
domains
Example:
 Domain name: www.orbitz.com
 IP: 198.151.61.100
 Convert Domain Name to IP address
The Domain Name System is a hierarchical
system with a root domain, top-level
domains, second-level domains, and host
computers at the third level.
INTERNET ADDRESSING AND
ARCHITECTURE
•
Internet Architecture and Governance
The Internet Corporation for Assigned Names and Numbers (ICANN), assigns IP
addresses
The World Wide Web Consortium (W3C), sets hypertext markup language and
other programming standards for the web
CLIENT-SERVER RELATIONSHIP
Client
 issues HTTP requests
 process documents
 displays documents
Server
 responds to HTTP requests
CLIENT-SERVER ARCHITECTURE
SERVER
Server responds
Client makes requests
INTERNET
Client/Server Computing on the
Internet
Client computers
running Web browser
and other software
can access an array of
services on servers
over the Internet.
These services may all
run on a single server
or on multiple
specialized servers.