To Table of Contents To Bottom of Page To Next Chapter

CS458/558 -Introduction (The TCP/IP Protocol Family)

CS458/558 -Chapter 1 Open Systems, Standards, and Protocols

  1. Open Systems
    • What is an Open System? (non-proprietary)
      The description of the architecture has been published or is readily available to anyone who wants to build protocols for a hardware or software platform
      ex. UNIX
  2. Network Architectures
    network - collection of computers and peripherals connected by some medium
    • Local Area Networks (LAN) [network is localized to a single location (usually a building)]
      • bus [contains a single main communications pathway (backbone) with each device attached to the main cable(bus) through a transceiver or with a T-connector on a network interface card (NIC)] (usually Ethernet)
      • ring [uses a central control unit (Media Access Unit - MAU) with a ring circuit inside] (usually token ring)
      • star [requires a central computer with everything connected to it]
      • hub [uses a main cable (backplane) with hubs connected to it; computers are connected to the hubs or switches]
    • Wide Area Networks (WAN)
      composed of LANs joined together by high-speed links with gateways (routers / bridges) connecting the LAN to the WAN
  3. OSI Model (Layers)
    1. Physical (deals with the "mechanical, electrical, functional, and procedural means" required for transmission of data) [wiring: 10BaseT, 10Base2, etc.]
    2. Data Link ("provides for the control of the physical layer, and detects and possibly corrects errors that can occur") [handles data transmission errors] [Ethernet, Token-ring, etc.]
    3. Network (provides the physical routing of the data, determining the path between the machines)
    4. Transport (provides the "transparent transfer of data from a source end open system to a destination end open system") [establishes, maintains, and terminates communications between two machines; responsible for ensuring that data sent matches data received]
    5. Session (organizes and synchronizes the exchange of data between applications) [handles application errors]
    6. Presentation (converts applications' data (in ASCII or EBCDIC) into/from a common format)
    7. Application (end-user interface)
  4. Terminology and Notation
    1. packets uniform chunk of data with a header and a trailer
    2. Subsystem - collective of a particular layer across a network
    3. Entities - active routines that comprise a given layer
    4. N Notation - used to refer to a layer and the layers above/below it
    5. N-Functions - different things that the layer does
    6. N-Facilities - set of facilites provided to the layer above
    7. Services - entire set of facilities provided to the layer above
    8. Queues and Connections
      1. communication between two OSI applications in the same layer is through queues to the layer beneath them [Note that there is a queue for each direction]
      2. Data (service primitives) is put into/retrieved from the queue by the applications (service users)
        1. request primitive - service submits a service primitive to the queue requesting permission to communicate with another service in the same layer
        2. indication primitive - service provider in the layer beneath the sending application sends to the intended receiving application to let it know that communication is desired
        3. response primitive - sent by the receiving application to the layer beneath's service provider to acknowlege the granting of communications between the two service providers
        4. confirmation primitive sent from the service provider to the final application to indicate that both applications on the layer above can now communicate
      3. above is called confirmed service used by connection-oriented or connection mode communications
      4. if no response and confirmation - unconfirmed service used by connectionless mode uses data packets called datagrams
  5. Standards
    • Setting Standards
      1. International Standardization Organization (ISO)
        1. American National Standards Institute (ANSI)
        2. British Standards Institute (BSI)
        3. Deutsches Institut fur Normung (DIN)
        4. Association Francaise du Normalization (AFNOR)
    • Internet Standards
      1. Internet Configuration Control Board (ICCB) formed as part of DARPA in 1980
      2. renamed Internet Activities Board (IAB) in 1983
      3. task of developing Internet standards was assigned to the Internet Engineering Task Force (IEFT) in 1986
      4. now reports to the Internet Society formed in 1992
      5. open protocols first defined in the RFC 1310,2 (see list of RFCs in Appendix E)
  6. Protocols
    service data unit (SDU) - data sent between layers
    protocol data unit (PDU) - analogous data between two machines
    • Breaking Data Apart
      1. segmentation - process of breaking an N-service data unit(N-SDU) into several N-protocol data units (N-PDU)
      2. reassembly - process of combining several N-PDUs into an N-SDU
      3. blocking - combination of several SDUs (might be from different services) into a larger PDU within the SDUs' layer
      4. unblocking - breaking up a PDU into several SDUs in the same layer
      5. concatenation - process of one layer combining several N-PDUs from the next higher layer into one SDU
      6. separation - reverse of concatenation
      7. multiplexing - several connections are supported by a single connection in the next lower layer
      8. demultiplexing - connection is split into several connections for the layer above it
      9. splitting - single connection is supported by several connections in the layer below
      10. recombining - several connections are combined into a single one for the layer above
    • Protocol Headers - information attached to the front of data that describes the datagram it is attached to

To Table of Contents To top of page To Next Chapter