Fall 2000C.Watters1 World Wide Web and E-Commerce Internet and WWW Basics.
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Transcript of 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
Fall 2000 C.Watters 2
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?
Fall 2000 C.Watters 3
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!
Fall 2000 C.Watters 4
Internet Web
• Hosts– 80 million
• Servers– 80 million x ?
• web pages– 1 billion
• Web databases – Terabytes x ?
deliverycontent
Fall 2000 C.Watters 5
Internet
• TCP/IP protocol for passing data between nodes on the Internet
Fall 2000 C.Watters 6
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
7C.WattersFall 2000
Public/ExternalInternet Users
Intranet
Clients
ServersERP
Legacy systems
E-mail servers
Web servers
Databases
Firewalls
7
An Intranet
© Prentice Hall, 2000
Fall 2000 C.Watters 8
• Often on a LAN (local Area Network) or WAN (Wide Area Network)
• Your department is no doubt on an Intranet!!
Intranet Examples
Fall 2000 C.Watters 9
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
10C.WattersFall 2000
Tunneling Internet
Extranet
IntranetFirewall
Intranet
Firewall
10
An Extranet
SuppliersVPN
Distributors VPN
Customers
VPN
© Prentice Hall, 2000
11C.WattersFall 2000
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)
Fall 2000 C.Watters 12
• 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
Fall 2000 C.Watters 13
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”
Fall 2000 C.Watters 14
The WEB
Communication protocol using the Internet
Fall 2000 C.Watters 15
Search Engine Sizes (800M)Feb2000
Fall 2000 C.Watters 16
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
Fall 2000 C.Watters 17
1. Client-Server & Web
• Cloud model
• Based on TCP/IP
• HTTP and MIME types
Fall 2000 C.Watters 18
Client-Server Model
Fall 2000 C.Watters 19
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
Fall 2000 C.Watters 20
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!!!
Fall 2000 C.Watters 21
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
Fall 2000 C.Watters 22
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??
Fall 2000 C.Watters 23
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
Fall 2000 C.Watters 24
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>
Fall 2000 C.Watters 25
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
Fall 2000 C.Watters 26
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
Fall 2000 C.Watters 27
Footprints (clickprints)
• What can you do with this data– Rearrange your site– Change your marketing strategy– Make a mailing list
Fall 2000 C.Watters 28
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
Fall 2000 C.Watters 29
2. URLs: NAMES and ADDRESSES
What’s in a name, anyway?
www.abc.magic.ca
1011010011001110000111001100110
Fall 2000 C.Watters 30
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
Fall 2000 C.Watters 31
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?
Fall 2000 C.Watters 32
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???
Fall 2000 C.Watters 33
That may be a big problem!
Fall 2000 C.Watters 34
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
Fall 2000 C.Watters 35
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.
Fall 2000 C.Watters 36
IPv4 address transits to IPv6
• IPv4-compatible IPv6 address
• 80 bits 16 bits 32 bits• 0000…000 0000 IPv4 address
Fall 2000 C.Watters 37
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
Fall 2000 C.Watters 38
How do we get the network address from network name?
• Domain name servers translate name to network address
www.govcanada.ca129.167.69.45
Fall 2000 C.Watters 39
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.
Fall 2000 C.Watters 40
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.
Fall 2000 C.Watters 41
Domain Hierarchy
edu com gov mil org net uk ca
arizona….mit acm ieee
cs ece physics
bas che opt
govcanada dal
cs
Fall 2000 C.Watters 42
Name Resolution
ClientLocal name server
Root name server
Arizona name server
CS name server
cheltenham.cs.arizona.edu
1 cheltenham.cs.arizona.edu
2
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
3
4
5
6
7
8
Fall 2000 C.Watters 43
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