Class_notes_InternetTechnology

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Class_notes_InternetTechnology

  1. 1. <ul><li>Introduction to Networks </li></ul><ul><li>What is a computer Network? </li></ul><ul><li>A network is any collection of independent computers that communicate with one another over a shared network medium. When these computers are joined in a network, people can share files and peripherals such as modems, printers, tape backup drives, or CD-ROM drives </li></ul><ul><li>Every network includes: </li></ul><ul><li>  </li></ul><ul><li>At least two computers Server or Client workstation. </li></ul><ul><li>Networking Interface Card's (NIC) </li></ul><ul><li>A connection medium, usually a wire or cable </li></ul><ul><li>Network Operating system software, such as Microsoft Windows NT or 2000 </li></ul>
  2. 2. Types of Networks LANs (Local Area Networks) LANs are networks usually confined to a geographic area, such as a single building or a college campus. WANs (Wide Area Networks) Wide area networking combines multiple LANs that are geographically separate Internet The Internet is a system of linked networks that are worldwide in scope and facilitate data communication services such as remote login, file transfer, electronic mail, the World Wide Web and newsgroups. Intranet An intranet is a private network utilizing Internet-type tools, but available only within that organization i.e. for large organizations. MANs (Metropolitan area Networks) This refers to a network of computers with in a City. VPN (Virtual Private Network) VPN uses a technique known as tunneling to transfer data securely on the Internet to a remote access server on your workplace network .
  3. 3. OSI Reference Model Seven layers of OSI Model: The Open Systems Interconnection model (OSI model) is a product of the Open Systems Interconnection effort at the International Organization for Standardization. It is a prescription of characterizing and standardizing the functions of a communications system in terms of abstraction layers  
  4. 4. ISO OSI Layering Architecture
  5. 5. <ul><li>Layer 1: Physical Layer </li></ul><ul><li>  </li></ul><ul><li>Functions: </li></ul><ul><li>Transmission of a raw bit stream </li></ul><ul><li>Forms the physical interface between devices </li></ul><ul><li>Which modulation technique (bits to pulse)? </li></ul><ul><li>How long will a bit last? </li></ul><ul><li>Bit-serial or parallel transmission? </li></ul><ul><li>Half- or Full-duplex transmission? </li></ul><ul><li>How many pins does the network connector have? </li></ul><ul><li>How is a connection set up or torn down? </li></ul>
  6. 6. <ul><li>Layer 2: Data Link Layer </li></ul><ul><li>  </li></ul><ul><li>Functions: </li></ul><ul><li>Provides reliable transfer of information between two adjacent nodes </li></ul><ul><li>Creates frames from bits and vice versa </li></ul><ul><li>Provides frame-level error control </li></ul><ul><li>Provides flow control </li></ul><ul><li>The data link layer provides the network layer with what appears to be an error-free link for packets </li></ul><ul><li>  </li></ul><ul><li>Layer 3: Network Layer </li></ul><ul><li>  </li></ul><ul><li>Functions: </li></ul><ul><li>Responsible for routing decisions </li></ul><ul><li>Dynamic routing </li></ul><ul><li>Fixed routing </li></ul><ul><li>Performs congestion control </li></ul>
  7. 7. <ul><li>Layer 4: Transport Layer </li></ul><ul><li>  </li></ul><ul><li>Functions: </li></ul><ul><li>Hide the details of the network from the session layer </li></ul><ul><li>Provides reliable end-to-end communication </li></ul><ul><li>Perform end-to-end flow control </li></ul><ul><li>Perform packet retransmission when packets are lost by the network </li></ul><ul><li>  </li></ul><ul><li>Layer 5: Session Layer </li></ul><ul><li>  </li></ul><ul><li>May perform synchronization between several communicating applications or logical transmissions </li></ul><ul><li>Groups several user-level connections into a single “session” </li></ul><ul><li>Examples: </li></ul><ul><li>Banking session </li></ul><ul><li>Network meetings </li></ul>
  8. 8. Layer 6: Presentation Layer   Performs specific functions that are requested regularly by applications Examples: encryption ASCII to Unicode, Unicode to ASCII LSB-first representations to MSB-first representations   Layer 7: Application Layer   Application layer protocols are application-dependent Implements communication between two applications of the same type Examples: FTP HTTP SMTP (email)
  9. 9. Overview of Layers:
  10. 10. Introduction to TCP/IP Networks: They are based on an open specification that is not controlled by any vendor. What Is TCP/IP? TCP stands for Transmission Control Protocol and IP stands for Internet Protocol. The term TCP/IP is used to refer to a group of protocols related to the TCP and IP protocols such as the User Datagram Protocol (UDP), File Transfer Protocol (FTP), Terminal Emulation Protocol (TELNET), and so on. TCP/IP Layering Architecture: <ul><li>A simplified model </li></ul><ul><li>The network layer: </li></ul><ul><li>Hosts drop packets into this layer, layer routes towards destination- only promise- try my best </li></ul><ul><li>The transport layer: </li></ul><ul><li>reliable byte-oriented stream </li></ul>
  11. 11. TCP/IP Protocol Architecture: <ul><li>1) Physical layer: </li></ul><ul><li>Physical interface between data transmission device </li></ul><ul><li>Characteristics of transmission medium </li></ul><ul><li>Signal levels </li></ul><ul><li>Data rates </li></ul><ul><li>2) N/W Access Layer:   </li></ul><ul><li>Exchange of data between end system and network </li></ul><ul><li>Destination address provision </li></ul><ul><li>Invoking services like priority </li></ul><ul><li>3) Internet Layer (IP): </li></ul><ul><li>Systems may be attached to different networks </li></ul><ul><li>Routing functions across multiple networks </li></ul><ul><li>Implemented in end systems and routers </li></ul>
  12. 12. <ul><li>4) Transport Layer (TCP) </li></ul><ul><li>  </li></ul><ul><li>Reliable delivery of data </li></ul><ul><li>Ordering of delivery </li></ul><ul><li>5) Application Layer </li></ul><ul><li>  </li></ul><ul><li>Support for user applications </li></ul><ul><li>Ex. http, SMPT </li></ul>
  13. 13. Local-Area Network Connect computers within a limited physical area such as an office, classroom, or building
  14. 14. Wide-Area Network WANs typically connect fewer computers than LANs and normally operate at lower speeds than LANs. WANs, however, provide the means for connecting single computers and many LANs over large distances.
  15. 15. <ul><li>LAN Topologies </li></ul><ul><li>Many LAN technologies have been invented but how specific technologies are similar and how they differ. Each network is classified into a category according to its topology or general shape </li></ul><ul><li>The four basic topologies are: </li></ul><ul><li>Bus Topology </li></ul><ul><li>Ring Topology </li></ul><ul><li>Mesh Topology </li></ul><ul><li>Star Topology </li></ul>
  16. 16. <ul><li>Bus Topology: </li></ul><ul><li>Bus topology usually consists of a single cable to which computers attach </li></ul><ul><li>The ends of a bus network must be terminated to prevent electrical signals from reflecting back along the bus. </li></ul><ul><li>Any computer attached to a bus can send on the cable and all computers receive the signal because all computers attach directly to the cable. </li></ul><ul><li>The computers attached to a bus network must coordinate to ensure that . only one computer sends a signal at any time </li></ul>
  17. 17. <ul><li>Ring Topology: </li></ul><ul><li>Ring topology arranges for computers to be connected in a closed loop </li></ul><ul><ul><li>A cable connects the first computer to a second computer, another cable connects the second computer to a third, and so on, until a cable connects the final computer back to the first. </li></ul></ul><ul><ul><li>name ring arises because one can imagine the computers and the cables connecting them arranged in a circle. </li></ul></ul><ul><ul><li>In practice, the cables in a ring network do not form a circle. </li></ul></ul><ul><li>Ring topology requires a computer to connect to a small device that forms the ring </li></ul><ul><ul><li>this is needed for the ring to continue operation even if some of the computers are disconnected </li></ul></ul>
  18. 18. <ul><li>Mesh Topology: </li></ul><ul><li>A network that uses a mesh topology provides a direct connection between each pair of computers </li></ul><ul><li>The chief disadvantage of a mesh arises from the cost: </li></ul><ul><ul><li>A mesh network connecting n computers requires: </li></ul></ul><ul><ul><li>The important point is that the number of connections needed for a mesh network grows faster than the number of computers </li></ul></ul>
  19. 19. <ul><li>Star Topology: </li></ul><ul><li>In star topology, all computers attach to a central point </li></ul><ul><li>The center of a star network is often called a hub </li></ul><ul><li>A typical hub consists of an electronic device </li></ul><ul><ul><li>That accepts data from a sending computer and delivers it to the appropriate destination </li></ul></ul><ul><li>In practice, star networks seldom have a symmetric shape (hub is located an equal distance from all computers) </li></ul><ul><ul><li>Instead, a hub often resides in a location separate from the computers attached to it </li></ul></ul>
  20. 20. <ul><li>Network Interface Card </li></ul><ul><li>A Network Interface Card (NIC) is a device that plugs into a motherboard and provides ports for the network cable connections. It is the computer's interface with the LAN. </li></ul>
  21. 21. <ul><li>Protocol: </li></ul><ul><li>In networking and Communications, the formal specification that defines the procedures to be followed when transmitting and receiving data. </li></ul><ul><li>Protocols define the format, timing, sequence and error checking used on the network. </li></ul><ul><li>HTTP- Hypertext Transfer Protocol is the stateless protocol used for data transfer within WWW. </li></ul>
  22. 22. <ul><li>IP Address: </li></ul><ul><li>A 32-bit address assigned to a computer that uses the TCP/IP protocols. The sender must know the IP address of the destination computer before sending a packet. </li></ul><ul><li>This is like a phone number for the computer. </li></ul><ul><li>A program on one computer communicates with a program on another computer, by connecting to its IP address. </li></ul><ul><li>The 32-bit address is usually represented as four 8-bit decimal numbers separated by periods. </li></ul><ul><li>Example: www.utm.edu (IP address is 208.47.4.80) </li></ul>
  23. 23. Communication Technologies Communication Hardware… Communication Network…
  24. 24. <ul><li>Communications Networks: </li></ul><ul><li>Activity associated with distributing or exchanging information. </li></ul><ul><li>Telecommunications – </li></ul><ul><li>Technology of communications at a distance that permits information to be created any where and used everywhere with little delay </li></ul><ul><li>It involves </li></ul><ul><ul><li>Data: digital and analog </li></ul></ul><ul><ul><li>Voice: spoken word </li></ul></ul><ul><ul><li>Video: telecommunication imaging </li></ul></ul>
  25. 25. <ul><li>Essentials for Communications: </li></ul><ul><li>Must have a message </li></ul><ul><li>Message must have a transmitter </li></ul><ul><li>Message must have a medium </li></ul><ul><li>Message must be understood </li></ul><ul><li>Message must have some level of security </li></ul><ul><li>(Flow Diagram) </li></ul>Source  Transmitter  Transmission  Receiver  Destination Source System Destination System Workstation/PC Workstation/PC Medium
  26. 26. <ul><li>Network: </li></ul><ul><li>point to point or point to multiple point connected media </li></ul><ul><li>A network is a group of computers connected together. </li></ul><ul><li>low cost, reliable, and efficient means of communicating at a distance. </li></ul><ul><li>Node: </li></ul><ul><li>Anything connected to the network </li></ul><ul><li>Usually a computer </li></ul><ul><li>A printer or a scanner </li></ul><ul><li>Segment: Any portion of a network that is separated by a switch, bridge or a router from another part of a network. </li></ul><ul><li>Backbone: </li></ul><ul><li>The main cabling of a network that all of the segment connect to. </li></ul><ul><li>Backbone is capable of carrying more information than the individual segments. </li></ul>
  27. 27. Simplex: Information flows in only one direction Half-duplex: Information flows in two directions, but only in one direction at a time. Full-duplex: Information flows in two directions at the same time
  28. 28. Basic Signal Terminologies Bit - binary digit, either 0 or 1 Baud - one electronic state change per second Bit rate- a method for measuring data transmission speed (bits/second) Mbps - millions of bits per second (data speed; measure of bandwidth = total information flow over a given time) on a telecommunication medium 8 bits = 1 byte Mb - million bits (quantity of data) MB - million bytes (quantity of data) Gbps - Billion bits per second (data speed) Teraflops - trillion operations per second
  29. 29. Data rate - bits per second Bandwidth - bandwidth or signal in cycles per second or hertz Noise - Average level of noise over the communication path. Error rate - rate at which errors occur where error in 1 or 0 bit occurs
  30. 30. <ul><li>Communication Hardware: </li></ul><ul><li>Transmission medium- </li></ul><ul><li>Guided Medium: waves are guided along a solid medium path (twisted pair, coaxial cable, and optical fiber). </li></ul><ul><li>Unguided medium: waves are propagated through the atmosphere and inner/outer space (satellite, laser, and wireless transmissions) </li></ul><ul><li>Conductive: twisted pairs and coaxial cables </li></ul><ul><li>Electromagnetic: microwave </li></ul><ul><li>Light: lasers and optical fibers (need clear line of sight) </li></ul><ul><li>Wireless – inner/outer space, satellite (Omni directional) </li></ul>
  31. 31. <ul><li>Hubs: </li></ul><ul><li>A place where data converges from one or more directions and is forwarded out in one or more directions. </li></ul><ul><li>Seen in local area networks </li></ul>
  32. 32. <ul><li>Gateways: </li></ul><ul><li>A gateway is a network point that acts as an entrance to another network. In terms of routing, the network consists of gateway nodes and host nodes. </li></ul><ul><li>Host nodes are computer of network users and the computers that serve contents (such as Web pages). </li></ul><ul><li>Gateway nodes are computers that control traffic within your company’s network or at your local internet service provider (ISP) </li></ul><ul><li>Routers: </li></ul><ul><li>A router is a device or a software in a computer that determines the next network point to which a packet should be forwarded toward its destination. </li></ul><ul><li>Allow different networks to communicate with each other </li></ul><ul><li>A router creates and maintain a table of the available routes and their conditions and uses this information along with distance and cost algorithms to determine the best route for a given packet. </li></ul><ul><li>A packet will travel through a number of network points with routers before arriving at its destination. </li></ul>
  33. 33. <ul><li>Bridge: </li></ul><ul><li>A bridge is a product that connects a local area network (LAN) to another local area network that uses the same protocol (for example, Ethernet or token ring). </li></ul><ul><li>A bridge examines each message on a LAN, &quot;passing&quot; those known to be within the same LAN, and forwarding those known to be on the other interconnected LAN (or LANs). </li></ul><ul><li>Difference between (Bridge, Router, Gateway): </li></ul><ul><li>Bridge: device to interconnect two LANs that use the SAME logical link control protocol but may use different medium access control protocols. </li></ul><ul><li>Router: device to interconnect SIMILAR networks, e.g. similar protocols and workstations and servers. </li></ul><ul><li>Gateway: device to interconnect DISSIMILAR protocols and servers, and Macintosh and IBM LANs and equipment </li></ul>
  34. 34. (Bridge Diagram)
  35. 35. <ul><li>Switches: </li></ul><ul><li>Allow different nodes of a network to communicate directly with each other. </li></ul><ul><li>Allow several users to send information over a network at the same time without slowing each other down. </li></ul>
  36. 36. Modulation: In a modem, the MODULATION process involves the conversion of the digital computer signals (high/low, on/off or logic 1 and 0 states) to audio-frequency tones. Demodulation: The DEMODULATION process converts the audio tones back into digital signals that a computer can understand directly.
  37. 37. <ul><li>Internet Technology: </li></ul><ul><li>Internet technology refer- </li></ul><ul><ul><li>Architecture </li></ul></ul><ul><ul><li>Services </li></ul></ul><ul><li>Architecture-wise: </li></ul>
  38. 38. <ul><li>Service-wise (applications): </li></ul><ul><li>Electronic mail </li></ul><ul><li>Remote terminal </li></ul><ul><li>File transfer </li></ul><ul><li>Newsgroups </li></ul><ul><li>File sharing </li></ul><ul><li>Resource distribution </li></ul><ul><li>World Wide Web </li></ul><ul><li>Video conferencing </li></ul><ul><li>Games </li></ul>
  39. 39. <ul><li>Packet: </li></ul><ul><li>A small, self-contained parcel of data sent across a computer network. </li></ul><ul><li>Each packet contains a header that identifies the sender and recipient, and a payload area that contains the data being sent. </li></ul><ul><li>All messages sent on a network such as the Internet are broken into small chucks called packets. </li></ul>To From Payload / Data 208.47.4.80:80 10.11.1.115 GET /index.html Header <ul><li>Packet: </li></ul><ul><li>A small, self-contained parcel of data sent across a computer network. </li></ul><ul><li>Each packet contains a header that identifies the sender and recipient, and a payload area that contains the data being sent. </li></ul><ul><li>All messages sent on a network such as the Internet are broken into small chucks called packets. </li></ul>To From <ul><li>Packet: </li></ul><ul><li>A small, self-contained parcel of data sent across a computer network. </li></ul><ul><li>Each packet contains a header that identifies the sender and recipient, and a payload area that contains the data being sent. </li></ul><ul><li>All messages sent on a network such as the Internet are broken into small chucks called packets. </li></ul>To <ul><li>Packet: </li></ul><ul><li>A small, self-contained parcel of data sent across a computer network. </li></ul><ul><li>Each packet contains a header that identifies the sender and recipient, and a payload area that contains the data being sent. </li></ul><ul><li>All messages sent on a network such as the Internet are broken into small chucks called packets. </li></ul>From <ul><li>Packet: </li></ul><ul><li>A small, self-contained parcel of data sent across a computer network. </li></ul><ul><li>Each packet contains a header that identifies the sender and recipient, and a payload area that contains the data being sent. </li></ul><ul><li>All messages sent on a network such as the Internet are broken into small chucks called packets. </li></ul>To Payload / Data <ul><li>Packet: </li></ul><ul><li>A small, self-contained parcel of data sent across a computer network. </li></ul><ul><li>Each packet contains a header that identifies the sender and recipient, and a payload area that contains the data being sent. </li></ul><ul><li>All messages sent on a network such as the Internet are broken into small chucks called packets. </li></ul>From <ul><li>Packet: </li></ul><ul><li>A small, self-contained parcel of data sent across a computer network. </li></ul><ul><li>Each packet contains a header that identifies the sender and recipient, and a payload area that contains the data being sent. </li></ul><ul><li>All messages sent on a network such as the Internet are broken into small chucks called packets. </li></ul>To Payload / Data <ul><li>Packet: </li></ul><ul><li>A small, self-contained parcel of data sent across a computer network. </li></ul><ul><li>Each packet contains a header that identifies the sender and recipient, and a payload area that contains the data being sent. </li></ul><ul><li>All messages sent on a network such as the Internet are broken into small chucks called packets. </li></ul>From <ul><li>Packet: </li></ul><ul><li>A small, self-contained parcel of data sent across a computer network. </li></ul><ul><li>Each packet contains a header that identifies the sender and recipient, and a payload area that contains the data being sent. </li></ul><ul><li>All messages sent on a network such as the Internet are broken into small chucks called packets. </li></ul>To GET /index.html Payload / Data <ul><li>Packet: </li></ul><ul><li>A small, self-contained parcel of data sent across a computer network. </li></ul><ul><li>Each packet contains a header that identifies the sender and recipient, and a payload area that contains the data being sent. </li></ul><ul><li>All messages sent on a network such as the Internet are broken into small chucks called packets. </li></ul>From <ul><li>Packet: </li></ul><ul><li>A small, self-contained parcel of data sent across a computer network. </li></ul><ul><li>Each packet contains a header that identifies the sender and recipient, and a payload area that contains the data being sent. </li></ul><ul><li>All messages sent on a network such as the Internet are broken into small chucks called packets. </li></ul>To GET /index.html Payload / Data <ul><li>Packet: </li></ul><ul><li>A small, self-contained parcel of data sent across a computer network. </li></ul><ul><li>Each packet contains a header that identifies the sender and recipient, and a payload area that contains the data being sent. </li></ul><ul><li>All messages sent on a network such as the Internet are broken into small chucks called packets. </li></ul>From <ul><li>Packet: </li></ul><ul><li>A small, self-contained parcel of data sent across a computer network. </li></ul><ul><li>Each packet contains a header that identifies the sender and recipient, and a payload area that contains the data being sent. </li></ul><ul><li>All messages sent on a network such as the Internet are broken into small chucks called packets. </li></ul>To 10.11.1.115 GET /index.html Payload / Data <ul><li>Packet: </li></ul><ul><li>A small, self-contained parcel of data sent across a computer network. </li></ul><ul><li>Each packet contains a header that identifies the sender and recipient, and a payload area that contains the data being sent. </li></ul><ul><li>All messages sent on a network such as the Internet are broken into small chucks called packets. </li></ul>From <ul><li>Packet: </li></ul><ul><li>A small, self-contained parcel of data sent across a computer network. </li></ul><ul><li>Each packet contains a header that identifies the sender and recipient, and a payload area that contains the data being sent. </li></ul><ul><li>All messages sent on a network such as the Internet are broken into small chucks called packets. </li></ul>To 208.47.4.80:80 10.11.1.115 GET /index.html Payload / Data <ul><li>Packet: </li></ul><ul><li>A small, self-contained parcel of data sent across a computer network. </li></ul><ul><li>Each packet contains a header that identifies the sender and recipient, and a payload area that contains the data being sent. </li></ul><ul><li>All messages sent on a network such as the Internet are broken into small chucks called packets. </li></ul>From <ul><li>Packet: </li></ul><ul><li>A small, self-contained parcel of data sent across a computer network. </li></ul><ul><li>Each packet contains a header that identifies the sender and recipient, and a payload area that contains the data being sent. </li></ul><ul><li>All messages sent on a network such as the Internet are broken into small chucks called packets. </li></ul>To
  40. 40. When the web server receives this request, it will send the web page back to my computer by breaking it down into smaller parts and sending each part in a packet Part 1 of web page Part 2 of web page 10.11.1.115 208.47.4.80 10.11.1.115 208.47.4.80 To From Payload / Data Packet 1 Packet 2
  41. 41. <ul><li>The Client/Server: </li></ul><ul><li>clients </li></ul><ul><li>Nodes that use the network's resources are called clients (usually computers), and nodes that manage the sharing of resources are called servers . </li></ul><ul><li>Servers are specialized computers with their own operating systems and network administration software. </li></ul>Client Server http
  42. 42. <ul><li>Performance: Latency and Bandwidth: </li></ul><ul><li>Latency </li></ul><ul><ul><li>How long minimum communication takes in seconds (s) </li></ul></ul><ul><ul><li>Round trip vs. single trip </li></ul></ul><ul><ul><li>More difficult to overcome than bandwidth </li></ul></ul><ul><li>Bandwidth </li></ul><ul><ul><li>Number of bits per time unit usually seconds (bps) </li></ul></ul>bandwidth latency link
  43. 43. <ul><li>Architectural Approaches: </li></ul><ul><li>Connection oriented </li></ul><ul><li>Connectionless </li></ul><ul><li>Connection-oriented </li></ul><ul><ul><li>Circuit switched </li></ul></ul><ul><ul><li>(Persistent connection set up between sender and receiver </li></ul></ul><ul><ul><li>Example: telephone system) </li></ul></ul><ul><li>Connectionless </li></ul><ul><ul><li>Packet switched </li></ul></ul><ul><ul><ul><li>(Data partitioned into packets and sent individually from sender to receiver and reassembled at receiver.) </li></ul></ul></ul>
  44. 44. <ul><li>Switching Schemes: </li></ul><ul><li>Circuit Switching </li></ul><ul><li>Message Switching (Store-and-Forward) </li></ul><ul><li>Packet Switching (Store-and-Forward) </li></ul><ul><li>Circuit Switching: </li></ul><ul><li>Provides service by setting up the total path of connected lines hop-by-hop from the origin to the destination </li></ul><ul><li>Example: Telephone network </li></ul><ul><ul><li>Properties: </li></ul></ul><ul><ul><li>Point-to-point communication </li></ul></ul><ul><ul><li>Separate steps for circuit creation, use, and termination </li></ul></ul><ul><ul><li>Performance equivalent to an isolated physical path </li></ul></ul>
  45. 45. <ul><li>Message Switching: </li></ul><ul><li>Each message is addressed to a destination </li></ul><ul><li>When the entire message is received at a router, the next step in its journey is selected; if this selected channel is busy, the message waits in a queue until the channel becomes free </li></ul><ul><li>Thus, the message “travel (hope)” from node to node through a network while allocating only one channel at a time </li></ul><ul><li>Packet Switching: </li></ul><ul><li>Messages are split into smaller pieces called packets </li></ul><ul><li>These packets are numbered and addressed and sent through the network one at a time. </li></ul><ul><li>Allows Pipelining </li></ul>
  46. 46. Comparison of Switching Technologies: <ul><li>( Circuit switched ) </li></ul><ul><li>Advantages </li></ul><ul><ul><li>Only route once </li></ul></ul><ul><ul><li>Latency and bandwidth constant </li></ul></ul><ul><li>Disadvantages </li></ul><ul><ul><li>Idle resources unavailable for other connections </li></ul></ul><ul><ul><li>Large setup time </li></ul></ul><ul><ul><li>Single point of failure </li></ul></ul><ul><li>( Packet switched ) </li></ul><ul><li>Advantages </li></ul><ul><ul><li>Efficient use of wires </li></ul></ul><ul><ul><li>Small startup overhead </li></ul></ul><ul><li>Disadvantages </li></ul><ul><ul><li>Route each packet </li></ul></ul><ul><ul><li>Per packet overhead </li></ul></ul><ul><ul><li>Bursty </li></ul></ul>
  47. 47. Netiquette & Ethics
  48. 48. <ul><li>Etiquette: </li></ul><ul><li>Is the practice of good manners. </li></ul><ul><li>being polite and helpful. </li></ul><ul><li>being kind and not aggressive. </li></ul><ul><li>Being mindful of the fact that others may see things differently than oneself. </li></ul><ul><li>Netiquette: </li></ul><ul><li>Is etiquette for the Internet. </li></ul><ul><li>Being polite to others. </li></ul><ul><li>Important there are no facial clues or body-language to help us understand another person, as there is in face to face meetings. </li></ul>
  49. 49. <ul><li>Ten Commandments Of Computer Ethics: </li></ul><ul><li>Not Use A Computer To Harm Other People. </li></ul><ul><li>Not Interfere With Other People’s Computer Work. </li></ul><ul><li>Not Snoop Around In Other People’s Computer Files. </li></ul><ul><li>Not Use A Computer To Steal. </li></ul><ul><li>Not Use A Computer To Bear False Witness. </li></ul><ul><li>Not Copy Or Use Proprietary Software For Which You have Not Paid. </li></ul><ul><li>Not Use Other People’s Computer Resources Without Authorization </li></ul><ul><li>Not Appropriate Other People’s Intellectual Output. </li></ul><ul><li>You Shall Think About The Social Consequences Of The Program </li></ul><ul><li>You Shall Always Use A Computer to respect for your fellow humans. </li></ul>
  50. 50. <ul><li>Publishing and Browsing the Web </li></ul><ul><li>What is World Wide Web? </li></ul><ul><li>The World Wide Web (WWW) is a global interactive, dynamic, cross platform, graphical hypertext information system that runs on the Internet. </li></ul><ul><li>Internet Standard Domain Names: </li></ul><ul><ul><ul><ul><li>Edu: educational organizations </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Com: commercial organizations </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Gov: government institutions </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Mil: military groups </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Net: major network support centre's </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Org: organizations other than the above </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Int: international organizations </li></ul></ul></ul></ul>
  51. 51. <ul><li>Web Browser: </li></ul><ul><li>A Web Browser is special software such as Netscape, Mosaic or Internet Explorer. These browsers allow a user to view Web pages delivered from a client server (Web Site) situated at a particular URL on the World Wide Web </li></ul><ul><li>Search Engines on the WWW: </li></ul><ul><li>Tools on the WWW used to search and find web sites related to a particular topic. </li></ul><ul><li>provide for searching using keywords and boolean operators. </li></ul><ul><li>Popular ones are Alta Vista, Infoseek, HotBot,Web Crawler, Lycos and Yahoo. </li></ul><ul><li>Over 600 search engines working at present. </li></ul>
  52. 52. Web Page: A web Page is a single document written in HTML ( Hypertext Markup Language ) that includes the text of the document, its structure, any links to other documents and graphic images and other media. Homepage: Homepage is a Hypertext document a server will serve as default. URL: A URL is the space of a web browser where the address of a website is written
  53. 53. <ul><li>Web Protocol and Language: </li></ul><ul><li>HTTP (Hyper Text Transfer Protocol) </li></ul><ul><ul><li>The simple protocol used to transfer a World Wide Web page from one computer to another. </li></ul></ul><ul><ul><li>A web client opens up a connection to a web server and sends GET PAGENAME and then the web server sends back the page text (usually HTML) over the connection. </li></ul></ul><ul><li>HTML (Hyper Text Markup Language) </li></ul><ul><ul><li>The source form used for documents on the World Wide Web. HTML embeds commands that determine formatting along with the text to be displayed (e.g., to move to a new line or indent text). </li></ul></ul>
  54. 55. <ul><li>Uniform Resource Locator (URL): </li></ul><ul><li>Method of accessing Internet Resources. </li></ul><ul><li>URLs are used by web browsers to connect you directly to a specific document or homepage on </li></ul><ul><li>resource is physically located. </li></ul><ul><li>Example URL: </li></ul><ul><li>http://www.nic.in:80/nicnet.html </li></ul>Host Address Port Path/Document
  55. 56. <ul><li>Data Communication: </li></ul><ul><li>1) Coaxial cable </li></ul><ul><li>Widely installed for use in business and corporation Ethernet and other types of LANs. </li></ul><ul><li>Consists of inter copper insulator covered by cladding material, and then covered by an outer jacket </li></ul><ul><li>:Physical Descriptions: </li></ul> Covered by sheath material  Outer conductor is braided shielded (ground)  Separated by insulating material  Inner conductor is solid copper metal
  56. 57. <ul><li>Applications: </li></ul><ul><ul><li>TV distribution (cable TV); long distance telephone transmission; short run computer system links </li></ul></ul><ul><ul><li>Local area networks </li></ul></ul><ul><li>Transmission characteristics: </li></ul><ul><ul><li>Can transmit analog and digital signals </li></ul></ul><ul><ul><li>Usable spectrum for analog signaling is about 400 Mhz </li></ul></ul><ul><ul><li>Amplifier needed for analog signals for less than 1 Km and less distance for higher frequency </li></ul></ul><ul><ul><li>Operation of 100’s Mb/s over 1 Km. </li></ul></ul>
  57. 58. <ul><li>2) Twisted Pair Cables: </li></ul><ul><li>Physical description: </li></ul><ul><ul><li>Each wire with copper conductor </li></ul></ul><ul><ul><li>Separately insulated wires </li></ul></ul><ul><ul><li>Twisted together to reduce cross talk </li></ul></ul><ul><ul><li>Often bundled into cables of two or four twisted pairs </li></ul></ul><ul><ul><li>If enclosed in a sheath then is shielded twisted pair (STP) otherwise often for home usage unshielded twisted pair (UTP). Must be shield from voltage lines </li></ul></ul><ul><li>Application: </li></ul><ul><ul><li>Common in building for digital signaling used at speed of 10’s Mb/s (CAT3) and 100Mb/s (CAT5) over 100s meters. </li></ul></ul><ul><ul><li>Common for telephone interconnection at home and office buildings </li></ul></ul><ul><ul><li>Less expensive medium; limited in distance, bandwidth, and data rate. </li></ul></ul>
  58. 59. <ul><li>3) Optical Fibers: </li></ul><ul><li>Physical Description: </li></ul><ul><ul><li>Glass or plastic core of optical fiber = 2to125 µm </li></ul></ul><ul><ul><li>Cladding is an insulating material </li></ul></ul><ul><ul><li>Jacket is a protective cover </li></ul></ul><ul><ul><li>Laser or light emitting diode provides transmission light source </li></ul></ul><ul><li>Applications: </li></ul><ul><ul><li>Long distance telecommunication </li></ul></ul><ul><ul><li>Greater capacity (2 Gb/s over 10’s of Km) </li></ul></ul><ul><ul><li>Smaller size and lighter weight </li></ul></ul><ul><ul><li>Lower attenuation (reduction in strength of signal) </li></ul></ul><ul><ul><li>Electromagnetic isolation (not effected by external electromagnetic environment. </li></ul></ul><ul><ul><li>Greater repeater spacing (fewer repeaters, reduces line regeneration cost) </li></ul></ul>
  59. 60. <ul><li>4) Wireless Transmission: </li></ul><ul><li>Frequency range (line of sight): </li></ul><ul><ul><li>26 GHz to 40 GHz: for microwave with highly directional beam as possible </li></ul></ul><ul><ul><li>30 MHz to 1 GHz: for Omni directional applications </li></ul></ul><ul><ul><li>300MHz to 20000 GHz: for infrared spectrum; used for point to point and multiple point application (line of sight) </li></ul></ul><ul><li>Physical applications: </li></ul><ul><ul><li>Terrestrial microwave – long haul telecommunication service (alternative to coaxial or optical fiber) </li></ul></ul><ul><ul><li>Few amplifier and repeaters </li></ul></ul><ul><ul><li>Propagation via towers located without blockage from trees, etc (towers less than 60 miles apart) </li></ul></ul>
  60. 61. Data Security: Need for Security:
  61. 62. <ul><li>1. Network layer security </li></ul><ul><li>TCP/IP can be made secure with the help of cryptographic methods and protocols that have been developed for securing communications on the Internet. </li></ul><ul><li>Ex: Electronic mail security (E-mail) </li></ul><ul><li>2. Pretty Good Privacy (PGP) </li></ul><ul><li>PGP provides confidentiality by encrypting messages to be transmitted or data files to be stored using an encryption algorithm such 3DES or CAST-128 . </li></ul><ul><li>Email messages protection ways: </li></ul><ul><li>Signing an email message to ensure its integrity and confirm the identity of its sender. </li></ul><ul><li>Encrypting the body of an email message to ensure its confidentiality. </li></ul><ul><li>Encrypting the communications between mail servers to protect the confidentiality of both the message body and message header. </li></ul>
  62. 63. <ul><li>3. Multipurpose Internet Mail Extensions (MIME): </li></ul><ul><li>MIME transforms non-ASCII data at the sender's site to Network Virtual Terminal (NVT) ASCII data </li></ul><ul><li>It delivers it to client's Simple Mail Transfer Protocol (SMTP) to be sent through the Internet. </li></ul><ul><li>The server SMTP at the receiver's side receives the NVT ASCII data and delivers it to MIME to be transformed back to the original non ASCII data. </li></ul><ul><li>Example- </li></ul><ul><ul><li>Secure/Multipurpose Internet Mail Extensions (S/MIME) </li></ul></ul>
  63. 64. <ul><li>Firewalls: </li></ul><ul><li>A firewall controls access between networks. It generally consists of gateways and filters which vary from one firewall to another. Firewalls also screen network traffic and are able to block traffic that is dangerous. </li></ul><ul><li>Types of firewalls: </li></ul><ul><li>Packet filters </li></ul><ul><li>Packet filters are one of several different types of firewalls that process network traffic on a packet-by-packet basis. </li></ul><ul><li>Their main job is to filter traffic from a remote IP host, so a router is needed to connect the internal network to the Internet. </li></ul><ul><li>The router is known as a screening router, which screens packets leaving and entering the network. </li></ul>
  64. 65. <ul><li>2. Circuit-level gateways </li></ul><ul><li>The circuit-level gateway is a proxy server that statically defines what traffic will be allowed. </li></ul><ul><li>Circuit proxies always forward packets containing a given port number. </li></ul><ul><li>port number is permitted by the rules set </li></ul><ul><li>3. Application-level gateways </li></ul><ul><li>An application-level gateway is a proxy server operating at the TCP/IP application level. </li></ul><ul><li>A packet is forwarded only if a connection is established using a known protocol. </li></ul>
  65. 66. Malicious software and antivirus: 1. Malware Commonly, a computer user can be tricked or forced into downloading software onto a computer that is of malicious intent. Such programs are known as malware and come in many forms, such as viruses, Trojan horses, spyware, and worms. 2. Viruses Viruses are programs that can replicate their structures or effects by infecting other files or structures on a computer. The common use of a virus is to take over a computer to steal data. 3. Trojan horse A Trojan horse (commonly known as a Trojan ) is a general term for malicious software that pretends to be harmless so that a user willingly allows it to be downloaded onto the computer.
  66. 67. 4. Spyware The term spyware refers to programs that surreptitiously monitor activity on a computer system and report that information to others without the user's consent. 5. Worms Worms are programs that can replicate themselves thoughout a computer network, performing malicious tasks throughout. 6. Botnet A botnet is a network of &quot;zombie&quot; computers that have been taken over by a &quot;bot&quot; that performs large-scale malicious acts for the creator of the botnet.
  67. 68. <ul><li>Antivirus: </li></ul><ul><li>Antivirus programs and Internet security programs are useful in protecting a computer or programmable device from malware. </li></ul><ul><li>Such programs are used to detect and usually eliminate viruses. </li></ul><ul><li>A user would pay for antivirus software. </li></ul><ul><li>A computer users now can, and do, download from a host of free security applications on the Internet. </li></ul><ul><li>Buffer overflow attacks: </li></ul><ul><li>A buffer overflow is an attack that could be used by a cracker to get full system access through various methods. </li></ul><ul><li>By essentially cracking a computer using brute force. </li></ul><ul><li>Most security applications and suites are incapable of adequate defense against these kinds of attacks. </li></ul><ul><li>Ex- Through remote control process. </li></ul>
  68. 69. <ul><li>Client-Server Architecture: </li></ul><ul><li>A network architecture in which each computer or process on the network is either a client or a server . </li></ul><ul><li>Components of Client-Server Architecture: </li></ul><ul><li>Client </li></ul><ul><li>Server </li></ul><ul><li>Communication Network </li></ul>
  69. 70. Tier Architecture of Client Server model: 2-Tier Architecture : 2-tier architecture is used to describe client/server systems where the client requests resources and the server responds directly to the request, using its own resources. This means that the server does not call on another application in order to provide part of the service.
  70. 71. <ul><li>3-Tier Architecture : </li></ul><ul><li>In 3-tier architecture, there is an intermediary level, meaning the architecture is generally split up between: </li></ul><ul><li>A client, i.e. the computer , which requests the resources, equipped with a user interface (usually a web browser ) for presentation purposes </li></ul><ul><li>The application server (also called middleware ), whose task it is to provide the requested resources, but by calling on another server </li></ul><ul><li>The data server, which provides the application server with the data it requires </li></ul>
  71. 72. Multi-Tiered Architecture :
  72. 73. WWW Definition: All the resources and users on the Internet that are using the Hypertext Transfer Protocol (HTTP) History: 1969 - RFCs begun by S. Crocker 1972 - Email by Ray Tomlinson & Larry Roberts 1970’s - TCP by Vint Cerf & Bob Kahn 1980s – Hardware Explosion (LANs, PCs, and workstations) 1983 – Ethernet by Metcalfe 1985 – Internet used by researchers and developers
  73. 74. <ul><li>Development of Internet: </li></ul><ul><li>Internet evolved from ARPANET. It includes </li></ul><ul><ul><li>first operational packet network </li></ul></ul><ul><ul><li>applied to tactical radio & satellite nets also </li></ul></ul><ul><ul><li>had a need for interoperability </li></ul></ul><ul><ul><li>led to standardized TCP/IP protocols </li></ul></ul>
  74. 75. Model diagram of WWW: CGI User C L I E N T HTTP TCP/IP SERVER Docs

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