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Intro to Transmission Methods in Switched Networks

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• Some background information: congestion

  • Network congestion:

    Each data processing system has a certain maximum processing capacity So it is obvious that: Every computer network has a certain maximum transmission capacity When a system reaches/exceeds its maximum processing capacity, there will be backlogs in processing We call these "backlogs": congestion

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• Best route to the destination
  • Facts:

    When transmitting a message to the destination, we always try to use: The fastest (= best) route !!!!         The best route is dependent on the traffic situation in the network !!!!

  • Example:

    Best route at time 1: Best route at time 2: (Yes, computer networks can become congested too :))

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• Communication session
  • Fact:

    Computers rarely send a single message to other computers Multiple messages are usually exchanged in a single communication

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  • Session:

    Session = the serie of messages transmitted between 2 computers to complete a task

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• Route and routing decision
  • Route:

    Route = the path taken by a message that starts at the sender (computer) and ends at the receiver (computer)

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  • Routing decision:

    Routing decision = selecting the route

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• Timing to make routing decisions
  • Routing decision can be made in one of 2 ways:

    Circuit switching: The sender make the routing decision once at the start of of a communication session Result: All messages in the same session will use the same route to reach the destination !!!         Message/packet switching: The sender make a routing decision every time it sends a message/packet Result: Each message will use its own route to reach the destination !!!