Topic 2

• Learning Objectives


  In this chapter, you will learn:
• Learning Objectives


  • About the origin, growth, and current structure of the Internet
  • How packet-switched networks are combined to form the Internet
  • How Internet, e-mail, and Web protocols work
  • About Internet addressing and how Web domain names are constructed
  • About the history and use of markup languages on the Web
  • How HTML tags and links work
  • About the cost and performance of Internet connections technologies
  • About Internet2 and the Semantic Web
• Computer network


  Any technology allowing people to connect computers to each other
• internet (small "i")


  A group of interconnected computer networks
• Internet (capital "I")


  Connects networks all over the world
• World Wide Web (Web)


  • A subset of Internet computers that are connected to each other
  • Includes easy-to-use interfaces
• Origins of the Internet

  1. Early 1960s: Defense Department nuclear attack concerns

  2. 1969 Advanced Research Projects Agency (ARPA): Packet network connected four computers

  3. ARPANET: earliest network (became the Internet)

  4. Academic research use (1970s and 1980s)
• New Uses for the Internet

  1. E-mail (1972) became widely used quickly

  2. 1979: Usenet (User's News Network) created

  3. Network applications improved and tested by an increasing number of users from 1979 to 1989

  4. 1980s: personal computer use explosion

  5. Academic and research networks merged into the Internet
• Commercial Use of the Internet

  1. National Science Foundation (NSF) provided funding

  2. 1989: NSF permitted two commercial e-mail services (MCI Mail and CompuServe)

  3. Commercial enterprises could send e-mail

  4. Research, education communities sent e-mail directly to MCI Mail and CompuServe
• Growth of the Internet

  1. In 1991 the NSF further eased commercial Internet activity restrictions

  2. Privatization of the Internet completed in 1995

  3. Operations turned over to privately owned companies

  4. Internet based on four network access points (NAPs)

  5. Network access providers sell Internet access rights directly and through Internet service providers (ISPs)
• Consistent and dramatic growth in the number of Internet hosts (computers directly connected to the Internet) to more than 1 billion today
• The Internet of Things

  • Connection of devices not used by persons is rapidly increasing
  • Switches, optical scanners, and sensors can be connected to the Internet and used to automatically manage environmental or security issues
  • Some business transactions can be conducted without human intervention
  • The Internet of things is the term used for these devices and automatic transaction processing
• Estimated 10 billion devices now and expected to reach 40 billion by 2020
• Local area network (LAN)


  A network of computers located close together
• Wide area network (WAN)


  A network of computers connected over greater distances
• Circuit switching


  • Centrally controlled, single-connection model
  • Not resistant to failure because a break in any circuit causes interruption and data loss
• Packet-Switched Networks


  1. Breaks files and e-mail messages into small pieces called packets

  2. Labelled electronically with origin, sequences and destination addresses

  3. Travel along interconnected networks until reaching destination

  4. Can take different paths

  5. May arrive out of order

  6. Destination computer collects packets and reassembles original file or e-mail message
• Routing


  • Routing computers forward each packet
  • Routers, gateway computers, border or edge routers
  • Routing algorithms are applied to information stored in routing tables or configuration tables
  • Hubs, switches, and bridges move packets from one part of the network to another
  • Routers connect networks to other networks and usually perform the required translation function
  • Internet backbone are telecommunication lines and routers between Internet's main collecting points
• Public network

  Available to the public and does not provide much security as part of its basic structure
• Private network


  • A leased-line connection between two companies that physically connects their computers or networks together
  • Advantage: security
  • Drawback: cost
• Virtual Private Network (VPN)

  • Connection via public networks to send data in a way that protects it as well as a private network at a lower cost
  • Uses IP tunneling (encapsulation) system to create a private passageway through public Internet
  • Encapsulation encrypts packet content and places it inside another packet
  • IP wrapper: outer packet
  • "Virtual" since connection seems permanent but is actually a temporary connection
• Intranet


  • An Internet within the boundaries of the organization
  • Interconnected private networks
• Extranet


  • An Internet that extends beyond the organization and incorporates networks of outside entities
  • Technologies (public networks, private networks, or VPNs)
  • Independent of organizational boundaries
• Protocol


  • A collection of rules across a network
  • Computers that communicate with each other must use same protocol for data transmission
• ARPANET: Network Control Protocol (NCP)


  • Proprietary architecture (closed architecture)
  • Manufacturer creates own protocol
• Open architecture (Internet core)

  • Uses common protocol
  • Four key message-handling rules
  • Contributed to the Internet's success
• TCP/IP


  • Transmission Control Protocol (TCP): Controls message or file disassembly into packets before Internet transmission
  • Controls packet reassembly into original formats at destinations
  • Internet Protocol (IP): Specifies addressing details for each packet
  • Labels packet with origination and destination addresses
• Internet Protocol version 4 (IPv4)


  • IP address is a 32-bit number identifying computers
  • Computers use base 2 (binary) number system
  • Four billion different addresses
  • Router breaks message into packets that contain source and destination IP address
  • Dotted decimal notation IP addresses appear as four numbers separated by periods
  • Three NFP organizations assign IP addresses
• Subnetting


  The use of reserved private IP LAN (WAN) addresses to provide more space
• Internet Protocol version 6 (IPv6)

  • Replaces IPv4 and uses 128-bit number for addresses
  • Available addresses: 34 followed by 37 zeros
  • More complex hexadecimal (16) notation system
• Electronic mail (e-mail)


  • Most organizations use a client/server structure
  • E-mail server computer devoted to e-mail handling
  • Software stores and forwards e-mail messages
  • E-mail client software reads and sends e-mail
  • Communicates with e-mail server software
  • Many e-mail services are offered by Web sites
• Simple Mail Transfer Protocol (SMTP)


  Specifies mail message format, and describes mail administration and transmission
• Post Office Protocol (POP)


  Messages send mail to user's computer and either deletes or does not delete it or asks if new mail has arrived
• Multipurpose Internet Mail Extensions (MIME)


  A set of rules for handling binary files
• Interactive Mail Access Protocol (IMAP)


  Performs the same basic POP functions but has some additional features
• Web client computers


  Run Web client software (Web browser software)
• Electronic mail (e-mail)


  Must be formatted according to common set of rules
• Most organizations


  • Use a client/server structure
• 1. mail server


  Computer devoted to e-mail handling and forwarding e-mail messages
• 1. mail client software


  Reads and sends e-mail, communicates with e-mail server software