Transcript Telecommunication, Internet, and E

Telecommunication, Internet, and
E-Commerce
Communication Channel Media
• Bandwidth: The speed at which information is
transmitted over a communication medium. It is
measured by the bits of data transmitted per second.
• Wire cables:
– twisted-pair (voiceband): 2MBPS
– coaxial: > 100 MBPS
• Broadband cable
– fiber-optic: 30 GBPS
– Broadband over Power Lines (BPL)
• Wireless channel:
– microwave (land-based, satellite-based):100 MBPS
– Satellite
– infrared: 4 MBPS
Digital Subscriber Line (DSL)
• DSL offers high-speed data access over the
single pair of the ordinary copper lines used
with basic telephone service.
– The Last Mile:
• The last mile is the final leg of delivering
connectivity from a communications provider to a
customer.
Types of Networks
• Local Area Network
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Within office
Cable or Wireless
peer-to-peer: all PCs are equal
client/server network
• Wireless local area network (WLAN)
• Metropolitan Area Network
– City area
– Fiber optic cable
• Wide Area Network
Wireless local area network
(WLAN)
• WI-FI: Wireless local area network (WLAN)
based on the IEEE802.11 specifications.
• Hotspot: A person with a Wi-Fi device, such as a
computer, cell telephone, or personal digital
assistant (PDA) can connect to the Internet when
in proximity of an Access Point. The region
covered by one or several access points is called a
hotspot.
Introduction to Internet
• A network of networks that connects
computers across the world.
• It is growing rapidly:
– Host computers
– Users
– Information
• It is a network that follows the TCP/IP
protocol (packet switch network).
Internet protocol
– Transmission Control Protocol – handles
communications between applications.
• A message is divided into pieces called packets.
• Packets are numbered and may be transmitted by different
routes.
– Internet Protocol – handles communications between
network addresses.
• A computer on the internet is assigned an unique address, IP
address, which consists of 4 numbers (each number is less than
256) separated by period. Exanple, 158.104.1.10
Domain Name System
• Domain:
– .com, .net, .org, ..edu, .int, .gov
– .info, .biz, .name, .etc.
• Domain names are the familiar, easy-to-remember
names for computers on the Internet.
– Yahoo.com
• Each domain name correlates to assigned IP
address:
– Yahoo.com – 66.218.71.102
Organizations that Regulate
Internet
• ICANN (Internet Corporation for Assigned
Names and Numbers):have responsibilities
in Internet Protocol addresses and domain
names.
• Domain name registry
Examples of Internet Services
• World Wide Web:
– A system of interlinked, hypertext documents
that runs over the Internet.
– Web publishing and browsing
• Email
• FTP - File Transfer
• Telnet
World Wide Web
• A service on the Internet that links
information so that the user can easily go
from one piece of information to another,
related piece.
• Web page:Hypertext/Hypermedia
– a document that contains hyperlink (link) to
another hypertext.
• Uniform Resource Locator (URL):
– http://Web site/Directory/Document
Intranet
• It is a corporate network that functions with
Internet technologies, such as browsers,
using Internet protocols.
• Major applications:
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Corporate/department/individual web pages
Database access
Interactive communication
Document distribution
Applications of Intranets
Communication and Collaboration
Existing E-Mail
Voice Mail
Systems
Communicate and
Collaborate with
E-mail, chat, conf.
Internet
Business Operations and Management
Existing
Database and
Enterprise appl.
Secure, universal
access. To view
corporate data
Web Publishing
HTML, MS Office
XML, Java
Author, publish and
share hypermedia
documents
Intranet Portal Management
Existing Hardware
and Networks
Centrally administer
clients, servers,
security, and traffic
Enterprise
Portal
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Extranet
Customers,
Suppliers
Extranet
• It is a network that links the intranets of business
partners over the Internet by Virtual Private
Network.
• Virtual Private Network:
– A secure network that uses the Internet as its main
backbone network to connect the intranets of a
company’s different locations, or establish extranet
links between business partners.
• Improved communications between business
partners
E-Commerce
• Buying and selling, and marketing and
servicing of products and services, and
information via computer networks.
E-Commerce Models
• B2C: Storefront model
– E-tailing (electronic retailing)
– Shopping cart, on-line shopping mall
• B2B:
– Electronic Data Interchange (EDI)
– Electronic Exchange: An electronic forum where manufacturers, suppliers,
and competitors buy and sell goods.
• Example: WorldWide Retail Exchange (WWRE)
• C2C:
– Auction model: e-Bay
• Moble Commerce (M-commerce)
– Wireless Application Protocol (WAP)
– PDA, Cell phone,
Electronic Payment Systems
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Authentication technologies
Digital certificate
Electronic cash
Electronic wallet:contains
– electronic cash or credit card info
– Owner identification
• Credit/debit/smart card
Internet Security
• Authenticity: Is the sender of a message who
they claim to be?
• Privacy: Are the contents of a message secret
and only known to the sender and receiver?
• Integrity: Have the contents of a message
been modified during transmission?
• Nonrepudiation: Can the sender of a message
deny that they actually sent the message?
Encryption (Cryptography)
• Plain text: the original message in humanreadable form.
• Ciphertext:the encrypted message
• Encryption algorithm: the mathematical
formula used to encrypt the plain text.
• Key: the secret key used to encrypt and
decrypt a message.
Encryption Example
• Digits: 0-9,
• Encryptor:
– Replace each digit by Mod(Digit + Key, 10)
• Key’s value is from 0 to 9
– If Key = 7, then:
• 0 -> 7, 1->8, 2->9, 3->0, 4->1, 5->2
• Decryptor:
– Replace ach digit byMod(Digit + (10-Key), 10)
– If key=7, then
• 7->0, 8->1, 9->2, 0->3
Encryption Algorithms
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Private key encryption
Public key encryption
Digital signature
Digital certificate
Private Key Encryption
• The same key is used by a sender (for
encryption) and a receiver (for decryption)
• The key must be transmitted to the receiver.
• Example:
– DES (Data Encryption Standard) algorithm
with 64-bit key
Public Key Encryption
• Uses two different keys: a public and a private key.
• Receiver’s public key must be delivered in advance.
• Sender uses receiver’s public key to encrypt the message and
receiver uses private key to decrypt the message (Sender can
be sure the receiver is the true receiver)
• Example:
– RSA (Rivest, Shamir, and Adelman) algorithm with 512-bit to 1024-bit
key.
• Note: Although the two keys are mathematically related,
deriving one from the other is “computationally infeasible”.
Digital Signature
• It is used for the authentication and
nonrepudiation of senders by applying
public key encryption in reverse.
• To make a digital signature, a sender
encrypts a message with his/her private key,
and any receivers with sender’s public key
can read it.
Ceritificate
• A certificate is an identification issued by a
trusted third-party certificate authority
(CA).
• A certificate contains records such as a
serial number, user’s name, owner’s public
key, name of CA, etc.
• Example of CA: VeriSign, U.S. Postal
Service.
Transaction Certificate
• A transaction certificate attests to some fact
about the conduct of a transaction that can
be used to prevent repudiation.
• SSL (Secure Socket Layer) Protocol
developed by Netscape.
• SET (Secure Electronic Transaction)
Protocol developed by Visa and
MasterCard.
Cookies
• Designed to hold information about a user.
• Created by a web site and saved on the
visitor’s machine.
• It contains:
– Web site that sets the cookie.
– One or more pieces of data.
– Expiration date for this cookie.
• Cookies directory:
• Browser sends cookie with the URL when
you visit the site that issued the cookie.