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Introduction to Data Communications

Introduction to Data Communications. In data communications, we transfer information in analog or digital form between two parties over a distance on networks The components of a given system are The message The sender The receiver The medium The protocol. Data Representation.

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Introduction to Data Communications

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  1. Introduction to Data Communications • In data communications, we transfer information in analog or digital form between two parties over a distance on networks • The components of a given system are • The message • The sender • The receiver • The medium • The protocol

  2. Data Representation • Information comes in many forms: • Text may be in ASCII, Extended ASCII, Unicode or ISO • Numbers: integers/fractions/exponentials • Images: GIF or JPEG or other • Audio: raw audio or compressed MP3 • Video: AVI, MPEG, Flash or other

  3. Structures and Topologies • Connection types may be: • Point-to-Point: 2 devices directly connected • Multipoint: multiple devices sharing links • Topologies may be: • Meshes, partly or fully meshed • Stars, buses or rings

  4. Network Categories • Personal Area Networks or PANs • Local Area Networks -LANs, usually private • Local (to a floor, a building or a campus) • Metropolitan Area Networks (MANs) • Town or city wide, public or private • Wide Area Networks (WANs) • National and International or Global

  5. Internetworks • When 2 or more networks are connected, they become an internetwork (small i) • When many networks are connected to the Global Internet, they become part of the Internet (capital I) • In AIT 235, we will increase our focus on transmission technologies and protocols

  6. Protocols and Standards • We will be studying many protocols in use in data communications. • Most of them are issued by Standards Organizations that publish open standards. • The standards documentation may be available on the Web or may be purchased for a fee.

  7. Many organizations play a part in telecommunications and usually have well-known acronyms associated with them. They include the following: ISO ITU-T ANSI IEEE EIA Frame Relay Forum ATM Forum ISOC IETF and others Standards Organizations

  8. Network Models • To give flexibility to networks, tasks are divided or “layered” in a hierarchy • One standard hierarchy is the 7 layer ISO model • A more common hierarchy is the 5 layer TCP/IP • In both models, each layer has a task and two interfaces, one up and one down • We will take a brief look and each layer and its tasks or responsibilities

  9. The ISO OSI Model

  10. The Internet or TCP/IP Model • Divides networking into five “layers”. • The layers from top to bottom are: • Application - what we actually want to do • Transport - end-to-end responsibility • Network - routing and switching • Data link - framing the bits • Physical - carrying the bits • Let’s look at each layer individually

  11. Physical Layer • This layer deals with the electrical and mechanical equipment needed to transmit information over the network • It is concerned with • Physical characteristics of interfaces and media • Representation and the transmission rate of bits • Bit Synchronization and Line Configuration • Physical Topology and Transmission Mode • It carries the Bits across each physical link

  12. Data Link Layer • Prepares the data into frames so that they can be transmitted across the network • Specific responsibilities include: • Framing and frame synchronization • Physical Addressing • Flow control and Error control • Access control • It aligns bits and contains them in Frames

  13. Network Layer • The network layer is responsible for the delivery of a packetized frame from its source to its destination • The network layer is responsible for • Logical or network-wide addressing • Routing or switching (more on that later) • It creates Packets to contain the frames

  14. Transport Layer • The transport layer is responsible for the end to end delivery of the packet from source to destination • The transport layer is responsible for • Service-point addressing • Segmentation and reassembly • Connection, flow and Error control • It creates Segments to contain the packets

  15. Application Layer • The application layer deals with interfaces and support for e-mail, remote file access and transfer and other services such as the World Wide Web. It is the interface to the user.

  16. Remembering the Layers • Transport Layer - Segments • Network Layer - Packets • Data Link Layer - Frames • Physical Layer - Bits • S, P, F, B = Swap Pizza For Beer

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