DCN_rpj10

DCN_rpj10 - NT503: Data Communication & Networking...

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1 NT503: Data Communication & Networking Switching technologies
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2 Switched networks ¾ Long distance transmission is typically done over a network of switched nodes ¾ Nodes not concerned with content of data ¾ End devices are stations ± Computer, terminal, phone, etc. ¾ A collection of nodes and connections is communication network ¾ Nodes may connect to other nodes or to stations ¾ Some redundant connections are desirable for reliability ¾ Switching techniques: ± Circuit-switching ± Packet switching ± Message switching
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3 A simple switched network
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4 Circuit switching ¾ Three phases - ± Connection establishment ± Transfer of data ± Connection termination ¾ Dedicated communication path between two stations is established first ¾ Must have switching capacity and channel capacity to establish connection ¾ Switching nodes must have intelligence to select paths depending on the type of data traffic ¾ No common format or protocol needs to be followed once the connection is established
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5 Circuit switching B A C D Source Destination
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6 Public circuit switched network
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7 Components of circuit switched network ¾ Subscriber ± Devices attached to network ¾ Local Loop ± Subscriber loop ± Connection to network ¾ Exchange ± Switching centers ¾ Trunks ± Branches between exchanges ± Multiplexed
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8 Circuit switching Advantages - ¾ Reliable message transfer once the connection is established ¾ Real time data transfer ¾ No chance of delay as the message flows through the network Disadvantages - ¾ Inefficient, since the path remains blocked (whether there is any data transfer or not) ¾ Poor utilization of network resources ¾ Entire message can be tapped by an intruder Application: telephone call, secure transactions
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