Fall 2000C.Watters1 World Wide Web and E-Commerce Internet and WWW Basics.

Fall 2000 C.Watters 1

World Wide Web and E-Commerce

Internet and WWW

Basics


Objectives

• What is the World Wide Web (web or WWW)?

• How does the web use HTTP and TCP/IP?

• How do the URLs work?

• What’s the problem that IPv6 is a solution for?


So, what is the web?

The Web is a protocol that uses the Internet as the communication structure

The Web links documents stored in computers that communicate on the Internet

Informal sort of arrangement!


Internet Web

• Hosts– 80 million

• Servers– 80 million x ?

• web pages– 1 billion

• Web databases – Terabytes x ?

deliverycontent


Internet

• TCP/IP protocol for passing data between nodes on the Internet


Intranet

• Corporate network using Internet technology but secured behind a firewall

• Use TCP/IP like the Internet

• Operate as a private network

• Connected to the Internet thru firewall

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Public/ExternalInternet Users

Intranet

Clients

ServersERP

Legacy systems

E-mail servers

Web servers

Databases

Firewalls

7

An Intranet

© Prentice Hall, 2000


• Often on a LAN (local Area Network) or WAN (Wide Area Network)

• Your department is no doubt on an Intranet!!

Intranet Examples


Extranet

• An extended intranet that connects remote intranets

• Uses TCP/IP Internet protocols

• Employs secure channels between the intranets

• VPN is technology that provides this virtual private network on the Internet

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Tunneling Internet

Extranet

IntranetFirewall

Intranet

Firewall

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An Extranet

SuppliersVPN

Distributors VPN

Customers

VPN

© Prentice Hall, 2000

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Virtual Private Network (VPN)• VPN is a secure network on the Internet using

tunneling schemes• The major objective of a VPN is to use the

Internet rather than a private line ($$)• When two sites are connected across a VPN, each

must have a VPN-capable router, firewall, or VPN access device installed

• When VPN is used to link mobile clients with Internet dial-up connections, the laptops must be equipped with VPN client software equipped with the addresses and associated encryption keys for corporate host sites

Virtual Private Network (VPN)


• Reduced Product Development Cycle Time: Caterpillar, Inc.– Customers can use the extranet to retrieve and

modify detailed order information while the vehicle remains on the assembly line

Extranet Cases

• Sears– Suppliers for just-in-time production

• Govt. select suppliers and govt. procurement


The Internet

• No quality control

• No central control

• No guarantees of delivery

• No guarantees of security

• No guarantees of privacy

• No place where the “buck stops”


The WEB

Communication protocol using the Internet


Search Engine Sizes (800M)Feb2000


Basics

• Web server - machine that services internet request

• Web client - machine that initiates internet request

• Browser - software to interact with web data at the client

• TCP/IP - internet data transfer protocol

• FTP - internet file transfer protocol

• HTTP - hypertext transfer protocol

• HTML - hypertext display markup language


1. Client-Server & Web

• Cloud model

• Based on TCP/IP

• HTTP and MIME types


Client-Server Model


HTTPHyperText Transport Protocol

• Native protocol for WWW

• sits on top of internet’s TCP/IP protocol

• HTTP is a 4 step process per transaction

• uses a predefined set of document formats from MIME


MIME defines data types

• MIME - multipurpose internet mail extensions– defines file formats (images, video, text, etc)– e.g. Content-type: text/html– Data type/subtype

» text/html» text/plain» image/gif» video/mpeg» application/msword » etc!!!


HTTP Connection

• 1. Client – makes an HTTP request for a web page– makes a TCP/IP connection

• 2. Server accepts request– sends page as HTTP

• 3. Client downloads page

• 4. Server breaks the connection


HTTP is Stateless!!!!

• Each operation or transaction makes a new connection

• each operation is unaware of any other connection

• each click is a new connection

• So how do they do those shopping carts??


What does HTTP look like?

• Header data + object file• Header

– plain text– info about the object (MIME etc)– methods allowed– etc

• browser sends a header to server each time you ask for information

• server sends a header and possibly content


HTTP Header Example

GET /catalog/ip/ip.htm HTTP 1.0

Accept: text/html

Accept: image/gif

Referer: http://www.cs.dal.ca/catalog.html

User-Agent: Mozilla/2.0

<CR/LF>


Side Effect of HTTP transfers

A record is left of all web transactionsReside in Log files generated at the serverGood news: use-data galoreBad news: what about user privacy


Common Log File (CLF) Format

cast39.cs.dal.ca - - [12/Jan/2000:16:09:50 -0400]

"GET /~watters/webcourse/refSer.html HTTP/1.0"

304 -

host identity Authuser date request status bytes


Footprints (clickprints)

• What can you do with this data– Rearrange your site– Change your marketing strategy– Make a mailing list


TCP/IP applications

• TCP/IP software usually includes:– remote terminal client using TELNET protocol

for remote login– electronic mail client using SMTP protocol to

transfer e-mail to remote system – file transfer client using FTP protocol to

transfer files between 2 machines


2. URLs: NAMES and ADDRESSES

What’s in a name, anyway?

www.abc.magic.ca

1011010011001110000111001100110


Internet Node Addresses

• Each node has – unique network name

• hierarchical composition based on name granting authority

• www.cs.dal.ca

– unique network address• hierarchical composition based on topographical

• 129.173.66.61


What is the network IP address?

• 32 bits (4 bytes) per node (IPv4)

• schemes– class-based addresses– subnet addresses– classless addresses

Is there a problem here?


Class-based Addressing IPv4

• General form network.host• eg. UC Berkeley is 128.32.0.0 • eg. Borg 129.173.66.61

• large networks have few network bytes – (more room for hosts on them)

• small networks have longer network address (fewer hosts expected)

• What if the host addresses are not all used???


That may be a big problem!


IPv6 Features

• 128 bits address space

• total 3.4 x 1038 addresses

• Advanced Routing Capability

• Better Options Support

• Better Quality of service Support

• Authentication and Security


IPv6 Summary

•IPv6 simplifies packet header formats.

•IPv6 provides a much larger address space of 128 bits. This overhead in the header has been reduced by simplifying the header formats.

•IPv6 supports authentication and encryption of packet contents at the network layer.


IPv4 address transits to IPv6

• IPv4-compatible IPv6 address

• 80 bits 16 bits 32 bits• 0000…000 0000 IPv4 address


Transition Planning

• Maintain complete IPv4 routing system until run-out

• Upgrade IPv4 router to IPv4/6 dual router

• Building up IPv6 only (6 bone)

• Shutdown IPv4 in areas where there is no need for IPv4


How do we get the network address from network name?

• Domain name servers translate name to network address

www.govcanada.ca129.167.69.45


Domain Hierarchy

• DNS hierarchy can be viewed as a tree – Node in the tree corresponding to a domain.– Leaves in the tree corresponding to the host

being named.

• DNS names are processed from right to left and use period as separator.


Name Servers do the work

Root name server

Dalhousie name server

Gov. Canada name server

…...

Cs name server

IS2 name server

–each name server contains IP addr for each lower level server.


Domain Hierarchy

edu com gov mil org net uk ca

arizona….mit acm ieee

cs ece physics

bas che opt

govcanada dal

cs


Name Resolution

ClientLocal name server

Root name server

Arizona name server

CS name server

cheltenham.cs.arizona.edu

1 cheltenham.cs.arizona.edu

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Arizona.edu, 128.196.128.233

cheltenham.cs.arizona.edu

Cs.arizona.edu, 192.12.69.5cheltenham.cs.arizona.edu

cheltenham.cs.arizona.edu,

192.12.69.60

192.12.69.60

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Recap

The World Wide Web (WWW or web) is a protocolHTTP is the workhorse of WWW protocolEvery click on the web is recordedURL’s need to be mapped into Internet addressesWe may run out of Internet addresses IPv6

Fall 2000C.Watters1 World Wide Web and E-Commerce Internet and WWW Basics.

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