Chapter Topics. The History of the Internet. Chapter 7: Computer Networks, the Internet, and the World Wide Web

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1 Chapter Topics Chapter 7: Computer Networks, the Internet, and the World Wide Web CS10051: Intro. to Computer Science Kent State University History of the Internet History of the World Wide Web Internet Activity Networks: Fundamentals and benefits Data transmissions, speeds and standards Components and topologies The OSI Model Chapter 7: Computer Networks, the Internet, and the World Wide Web 1 Chapter 7: Computer Networks, the Internet, and the World Wide Web 2 The History of the Internet MIT Research (1962) World-wide group of connected computers Purpose to share data and software Advanced Research Projects Agency ( ) Wartime communications Packet-switched network ARPANET node connection UCLA and Stanford Research Institute The History of the Internet Scientific/proprietary networks (1970s) Built to suit the particular application Internetworking standards developed Common addressing scheme Communication protocols TCP/IP FTP Telnet Infrastructure foundations developed Chapter 7: Computer Networks, the Internet, and the World Wide Web 3 Chapter 7: Computer Networks, the Internet, and the World Wide Web 4 1

2 The History of the Internet National Science Foundation (1984) Initiated expansion beyond the DoD scope Linked all communities Backbone connected with regional networks via gateways Government agencies Libraries Museums Medical centers Schools The History of the Internet The Internet (1990s) Immediate success ARPANET dropped Global connections NSF exited ISPs emerged Providers for regional and local service Connected to the backbone Linked to each other Chapter 7: Computer Networks, the Internet, and the World Wide Web 5 Chapter 7: Computer Networks, the Internet, and the World Wide Web 6 The History of the Internet The History of the World Wide Web CERN in Geneva, Switzerland (1989) Purpose was to share physics information Conceptualized by Tim Berners-Lee Utilized linking documents (hypertext) Chapter 7: Computer Networks, the Internet, and the World Wide Web 7 Chapter 7: Computer Networks, the Internet, and the World Wide Web 8 2

3 The History of the World Wide Web Stored documents on servers Internet Activity Using the Internet: Three Primary Reasons Located by URLs Viewed in Web browsers Launched in May 1991 COMMUNICATION MULTIMEDIA E-COMMERCE Chapter 7: Computer Networks, the Internet, and the World Wide Web 9 Chapter 7: Computer Networks, the Internet, and the World Wide Web 10 Internet Activity Communication Dependable Messages reach destinations because of packet-switching Non-interactive communication Sender and receiver write and view at different times Convenient and fast No postage and no long distance charges Supports all types of attachments Internet Activity Communication IM or Instant Messaging Real-time communication Chat sessions with others online Requires special software Supplied by large ISPs Other forms of communication Wikis, Webcasts, Podcasts, VoIP, Blogs Chapter 7: Computer Networks, the Internet, and the World Wide Web 11 Chapter 7: Computer Networks, the Internet, and the World Wide Web 12 3

4 Internet Activity Conducting business online or through electronic means (paperless transactions) Types include B2C: Business to consumers Online shopping and banking B2B: Business to business C2C: Consumer to consumer ebay E-commerce Network Fundamentals A network is two or more nodes connected by hardware or software so that they can communicate with each other s Devices connected to a network Computers Peripherals Modems Chapter 7: Computer Networks, the Internet, and the World Wide Web 13 Chapter 7: Computer Networks, the Internet, and the World Wide Web 14 Benefits of Client/Server Networks PERIPHERALS FILES CONNECTIONS Cost effective Quality resources It s all about sharing. Space savings Backup services Groupware Fast transfer Global access Networks: Data Transmission Circuit Switching (analog) First open systems protocol (telephone) Connection established between two points Connection remains active for duration of transmission Communications received and sent in order Inefficient for computers Digital processing and transmission in bursts Circuit remains open and unavailable Chapter 7: Computer Networks, the Internet, and the World Wide Web 15 Chapter 7: Computer Networks, the Internet, and the World Wide Web 16 4

5 Networks: Networks: Data Data Transmission Transmission Networks: Networks: Data Data Transmission Transmission Dial-up connections Efficient transmission for computers No dedicated connection needed Goal is to travel an alternative route to destination Standard phone line and modem Modem modulates Converts the computer s digital signal Signal travels over the phone line Receiving computer s modem demodulates Understandable by the computer 17 Networks: Networks: Data Data Transmission Transmission Chapter 7: Computer Networks, the Internet, and the World Wide Web 18 Networks: Networks: Data Data Transmission Transmission Broadband connections P a c k e t DSL Same line is shared by data and phone Service through your phone company S w i t c h i n g Chapter 7: Computer Networks, the Internet, and the World Wide Web disabled destroyed Various routes are used to reach the final destination Converts the analog signal back to the digital Chapter 7: Computer Networks, the Internet, and the World Wide Web Packet Switching (digital) Faster than dial-up with no phone tie-up Unaffected by other users sharing the line so speed is not affected during peak times Not available in all areas 19 Chapter 7: Computer Networks, the Internet, and the World Wide Web 20 5

6 Networks: Data Transmission Broadband connections Cable Uses cable modem to translate the cable signal to digital and back Slightly faster than DSL Delays experienced during peak times Networks: Transmission Speeds Bandwidth Maximum speed of transmission between nodes Measured in Mbps Throughput Actual speed of transmission between nodes Measured in Mbps Often less than bandwidth Chapter 7: Computer Networks, the Internet, and the World Wide Web 21 Chapter 7: Computer Networks, the Internet, and the World Wide Web 22 Networks: Transmission Standards Wired Ethernet Data transmission rate = 100Mbps or 1,000Mpbs (Fast or Gigabit) Transmission media is cable or fiberoptics Cable runs 328 Repeaters amplify signal beyond run length Wireless Fidelity Transmission media is radio waves Transceivers convert data into radio waves and broadcast Run lengths 250 Wireless access points extend signal between nodes Prone to interference Networks: Components Layout of the hardware and software Network O/S Navigation Devices Servers Topologies Adapters Transmission Media Chapter 7: Computer Networks, the Internet, and the World Wide Web 23 Chapter 7: Computer Networks, the Internet, and the World Wide Web 24 6

7 Networks: Topologies Bus topology Terminator Terminator All the nodes are connected in a linear sequence on a single cable. Networks: Topologies Bus topology s communicate directly with each other s listen before transmitting Data collisions occur easily Passive topology because nodes just move data along the media Recipient node hears its data and removes it from the media Media is capped off by terminators that absorb the signal Chapter 7: Computer Networks, the Internet, and the World Wide Web 25 Chapter 7: Computer Networks, the Internet, and the World Wide Web 26 Networks: Topologies Ring topology Token Chapter 7: Computer Networks, the Internet, and the World Wide Web 27 Networks: Topologies Ring topology Data flows in one direction Token controls the transmission Active topology because nodes have responsibilities Grab the token to transmit data Release the token when finished Recipient node sends acknowledgment Access method avoids data collisions Fairer allocation of resources Chapter 7: Computer Networks, the Internet, and the World Wide Web 28 7

8 Networks: Topologies Star topology Switch Networks: Topologies Star topology s are connected to a central switch Switch manages the data transmission Active topology because nodes have responsibilities s listen before transmitting s examine the transmission but only pick up data addressed to them Data collisions handled through jam signals and re-transmission Chapter 7: Computer Networks, the Internet, and the World Wide Web 29 Chapter 7: Computer Networks, the Internet, and the World Wide Web 30 Networks: The OSI Model OSI Model: Open Systems Interconnection Developed by the IEEE Gives protocol guidelines to the NOS Communication tasks are divided into layers Layers provide more efficient communication Layers interact with layers above and layers below Networks: The OSI Model Application Layer Interacts between application software and the network Examples: HTTP or Hypertext Transfer Protocol Uses URLs to locate Web pages SMTP and MIME for messages FTP for uploading and downloading server files TELNET for remote machine access Chapter 7: Computer Networks, the Internet, and the World Wide Web 31 Chapter 7: Computer Networks, the Internet, and the World Wide Web 32 8

9 Networks: The OSI Model Presentation Layer Performs data encryption if specified Reformats the data for the Session layer Session Layer Sets up and manages a virtual connection between sender and receiver Tracks transmission until all data is sent Networks: The OSI Model Transport Layer TCP or Transport Control Protocol Breaks up data into packets and sequences them Preserves the order of the data Handles acknowledgment of packets Delivers data to the proper port and software application Chapter 7: Computer Networks, the Internet, and the World Wide Web 33 Chapter 7: Computer Networks, the Internet, and the World Wide Web 34 Networks: The OSI Model Network Layer IP or Internet Protocol Examines packet address Assigns IP addresses to nodes Resolves IP address symbolic name Uses DNS mapping Determines best route for transfer Dijkstra s shortest path algorithm Networks: The OSI Model Data Link Layer Assembles data into frames Addresses the frames Passes the frames to the Physical layer Examples: Ethernet protocol Error detection and correction Chapter 7: Computer Networks, the Internet, and the World Wide Web 35 Chapter 7: Computer Networks, the Internet, and the World Wide Web 36 9

10 Networks: The OSI Model Physical Layer Converts data into a signal Transmits the data Delivers the data to the final destination Examples: Modem DSL Cable modem Chapter 7: Computer Networks, the Internet, and the World Wide Web 37 10