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Data Communication

Data Communication. What is Information Technology (IT)?. Information Technology (IT). Computer Technology. Communication Technology.

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Data Communication

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  1. Data Communication

  2. What is Information Technology (IT)? Information Technology (IT) Computer Technology Communication Technology To collect, store, process, search, retrieve, and present electronic information to meet the needs of various kinds of users, e.g., computer hardware & software, PDAs, printers, groupware, smart cards…. To deliver, disseminate, exchange, transmit, and receive electronic information in local, regional or global contexts, e.g., networks, fax machines, cell phones, email, satellites, GPS, Internet, telephony, ….

  3. What is Data Communication? • Communication of data between sources • Data formats – analog or digital or both • Data travels by a medium • Wires • Space

  4. Data Communication Applications (1) • Batch - bi-directional transfers of large amounts of data in concentrated groups • Data Entry - Lengthy inputs with short responses • Distributed - data and/or processing is handled by more than one processing unit • Inquiry/Response - Small inputs of data that may result in large responses

  5. Data Communication Applications (2) • Interactive - Short inputs and outputs. Real-time response with direct user interaction • Sensor-Based - Input derived from sensors instead of human operators • Combined - More than one of the above applications running at the same time

  6. Components of a Data Communication System • Transmitter • Receiver • Medium • Message • Protocol

  7. Components …. • The transmitter sends the message and the receiver receives the message. • The medium is the channel over which the message is sent • The protocol is the set of rules that guides how the data is transmitted from encoding to decoding. • The message is the data that is being communicated.

  8. Network Media • The channel over which a message travels

  9. Protocols • A set of predetermined rules • Protocol Suite A group of inter-related protocols that are necessary to perform a communication function • Implemented in software and hardware that is loaded on each host and network device • Individual protocols in a protocol suite may be vendor-specific and proprietary

  10. Function of Network Protocol • Network protocols are used to allow devices to communicate successfully

  11. Types of Messages Transaction summary for the day File Request ResponseYes, lots. Status The system is going down in 5 minutes ControlDon’t send me any more data, I’m currently busy Correspondence Any transaction for the acc. No. ? Memo Christmas party

  12. Rate of Data Transmission • The speed with which data can be transmitted from one device to another. • Data rates are often measured in megabits (million bits) or megabytes (million bytes) per second. (Mbps and MBps). • Another term for data transfer rate is throughput.

  13. What is a Computer Network? Two or more computers or communications devices connected by transmission media and channels and guided by a set of rules for communication purposes that allow users to communicate with each other and share applications and data. • Hardware: • Computer • Network card • Routers • Modem … • Media: • Cable • Wire • Microwave … Components of a Computer Network • Software: • Network OS • Utilities … • Network Design: • Logical layout • Physical layout …

  14. Network Essentials Models • Client/Server • Peer-to-Peer Technologies Types • Ethernet • Token Ring • Transmission Control Protocol/Internet Protocol (TCP/IP) • Wireless Application Protocol (WAP) • Local Area Network (LAN) • Metropolitan Area Network (MAN) • Wide Area Network (WAN) Network OS Topologies • Bus Topology • Ring Topology • Star Topology

  15. Network OS • An operating system that includes special functions for connecting computers and devices into a local-area network (LAN). Some operating systems, such as UNIX and the Mac OS, have networking functions built in. The term network operating system, however, is generally reserved for software that enhances a basic operating system by adding networking features. • Microsoft Windows Server 2003, Microsoft Windows Server 2008, UNIX, Linux, Mac OS X, and Novell NetWare

  16. Characteristics of NOS • Centrally manage network resources, such as programs, data and devices. • Secure access to a network. • Allow remote users to connect to a network. • Allow users to connect to other networks like the Internet. • Back up data and make sure it's always available. • Allow for simple additions of clients and resources. • Monitor the status and functionality of network elements. • Distribute programs and software updates to clients. • Ensure efficient use of a server's capabilities.

  17. Network Technologies • Based on bus topology; but can be used in star topology; • Higher speed: first Fast Ethernet, then Gigabit Ethernet; • Most popular: inexpensive, easy to install and maintain. Ethernet • Based on a ring topology; but can use a star topology; • Token-passing scheme to prevent collision of data; • The second most widely-used protocol after Ethernet. Token Ring • Based on client/server model of network computing; • Uses packet switching technique for data transmission; • Commonly used for Internet applications. TCP/IP • Uses client/server model of network computing; • Allows wireless devices to access the Internet and WWW; • Meets increasing demands for wireless Internet access. WAP

  18. Network Models • Peer to peer • Client Server

  19. Peer to peer

  20. Benefits of a Peer to Peer Network • A peer to peer network is inexpensive to set up. It uses the built in networking capabilities of Windows XP Professional (or Vista Business), so no special software is needed. It allows for file and printer sharing, and can be an adequate choice for a very small office.

  21. Limits of a Peer to Peer Network • Peer to peer networks are dependent upon the computer knowledge of each employee, as certain rules must be followed in order to minimize network interruptions. If a user shuts down his machine in the middle of the day, other users on the network lose access to the files in that machine's shared folder. • Network and data security are weak. • Files are not centralized, so getting a back up of all critical files is more difficult. • Ongoing tasks like anti-virus scanning and Windows updates are localized on each machine. Updating virus definitions and patches has to be done manually at each machine, which is time consuming.

  22. Client Server

  23. Limitations of a Client Server Computer Network • A server based computer network is more expensive to implement. Server computers are powerful machines with built-in redundancy and other hardware to provide data safety. Hence, they cost much more than a simple desktop computer. • The server network software is also much more powerful, complicated, and must be installed correctly to run all of the required tasks, and so the cost is higher for both the software and installation charges. • The server is a critical point of failure. If it goes down, the entire network comes to a halt. This drawback can be minimized with the installation of redundant drives in the server (so that if one fails, the others will still be working), and even a second server that can take over if the primary server fails completely. Cost then becomes the only issue.

  24. Benefits of a Client Server Network • The server stores all of the shared files for each user. • The server runs the file backups which can be scheduled in the middle of the night, minimizing network interruptions. • The server manages user security, and insures that all users who access the network are authorized to do so. • The server manages printer sharing and acts as a central repository for the printer drivers and settings. • The server manages other common tasks such as internet access, email routing, Windows updating and anti-virus definition management. • The server can also share software applications out to multiple users. • The server can also provide for an "Intranet", an internal website which holds shared company information such as news announcements, HR policies, training documents, and more.

  25. Network Types Networks infrastructures can vary greatly in terms of: • The size of the area covered • The number of users connected • The number and types of services available

  26. Network Types Local Area Networks (LANs) • An individual network usually spans a single geographical area, providing services and applications to people within a common organizational structure, such as a single business, campus or region • Administered by a single organization

  27. Network Types Wide Area Networks (WANs) • Networks that connect LANs in geographically separated locations

  28. Network Types The Internet • A global mesh of interconnected networks

  29. Network Types The Intranet • A private connection of LANs and WANs that belongs to an organization, and is designed to be accessible only by the organization's members, employees, or others with authorization.

  30. Network Topologies • The layout pattern of interconnections of the various elements (links, nodes, etc.) of a computer network

  31. Network Topologies • Physical topology - the physical design of a network including the devices, location and cable installation. • Logical topology - how data is actually transferred in a network as opposed to its physical design

  32. Network Topologies • Bus Topology • Ring Topology • Star Topology • Mesh Topology

  33. Bus Topology

  34. Advantages Disadvantages If the backbone fails, the entire bus network will be affected. Network speed decreases when the number of nodes increases. Troubleshooting is difficult when one of the nodes fails. • Easy implementation. New devices can be added to the backbone or to the existing nodes. • Failure of a node doesn't affect the entire LAN. • No disruptions to the network when connecting or removing devices. • Network can easily be extended, by adding new devices to the backbone or existing nodes.

  35. Ring Topology

  36. Advantages Disadvantages Implementation is difficult. Network administrator has to terminate the entire network to install a new node between existing nodes. A failing node will affect the entire LAN. Connecting or removing devices is difficult because network administrator needs to terminate the network in order to do it. Network speed decreases when the number of nodes increases.  • Troubleshooting is easy when one of the nodes fails. • Repair or remove the failing nodes and the network will continue to function.

  37. Star Topology

  38. Advantages Disadvantages If the host fails, the entire LAN will be affected.  Network speed decreases when the number of nodes increases. Troubleshooting is difficult when one of the nodes fails. A host must be installed to control the network. • It is easy to implement. You only add nodes to the host. • The failure of a node does not affect the entire LAN. • There are no disruptions to the network when connecting or removing devices. • The network can be extended by adding new devices to the host or nodes. • Troubleshooting is easy when the host fails. Simply repair or replace the host and the network will continue to function.

  39. Mesh Topology

  40. Advantages Disadvantages Requires more cable than the other LAN topologies. Complicated implementation. • Provides redundant paths between devices • The network can be expanded without disruption to current users.

  41. Layered Models • A protocol model provides a model that closely matches the structure of a particular protocol suite. • A reference model provides a common reference for maintaining consistency within all types of network protocols and services.

  42. IP Addresses and Host Names • Unique identifying number for each computer in the internet • 192.248.40.70 • 203.94.81.84 Information Technology Center, University of Peradeniya

  43. Network Classes Information Technology Center, University of Peradeniya

  44. IP Ranges Reserved for Private Use Information Technology Center, University of Peradeniya

  45. Domain Name Service (DNS) • Used to map human readable host names into corresponding IP addresses • www.google.com = 64.233.161.104 • www.hotmail.com = 210.158.219.56 Information Technology Center, University of Peradeniya

  46. How to find the IP Address of your Computer? • ipconfig Information Technology Center, University of Peradeniya

  47. ipconfig Information Technology Center, University of Peradeniya

  48. How to check the Network Connectivity? • ping Information Technology Center, University of Peradeniya

  49. ping Information Technology Center, University of Peradeniya

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