Long distance transmission is typically done over a network of switched nodes Nodes not concerned with content of data End devices are stations Computer, terminal, phone, etc. A collection of nodes and connections is a communications network Data routed by being switched from node to node | William Stallings Data and Computer Communications Chapter 9 Circuit Switching Switching Networks Long distance transmission is typically done over a network of switched nodes Nodes not concerned with content of data End devices are stations Computer, terminal, phone, etc. A collection of nodes and connections is a communications network Data routed by being switched from node to node * Nodes Nodes may connect to other nodes only, or to stations and other nodes Node to node links usually multiplexed Network is usually partially connected Some redundant connections are desirable for reliability Two different switching technologies Circuit switching Packet switching * Simple Switched Network * Circuit Switching Dedicated communication path between two stations Three phases Establish Transfer Disconnect Must have switching capacity and channel capacity to establish connection Must have intelligence to work out routing * Circuit Switching - Applications Inefficient Channel capacity . | William Stallings Data and Computer Communications Chapter 9 Circuit Switching Switching Networks Long distance transmission is typically done over a network of switched nodes Nodes not concerned with content of data End devices are stations Computer, terminal, phone, etc. A collection of nodes and connections is a communications network Data routed by being switched from node to node * Nodes Nodes may connect to other nodes only, or to stations and other nodes Node to node links usually multiplexed Network is usually partially connected Some redundant connections are desirable for reliability Two different switching technologies Circuit switching Packet switching * Simple Switched Network * Circuit Switching Dedicated communication path between two stations Three phases Establish Transfer Disconnect Must have switching capacity and channel capacity to establish connection Must have intelligence to work out routing * Circuit Switching - Applications Inefficient Channel capacity dedicated for duration of connection If no data, capacity wasted Set up (connection) takes time Once connected, transfer is transparent Developed for voice traffic (phone) * Public Circuit Switched Network * Telecomms Components Subscriber Devices attached to network Local Loop Subscriber loop Connection to network Exchange Switching centers End office - supports subscribers Trunks Branches between exchanges Multiplexed * Circuit Switch Elements * Circuit Switching Concepts Digital Switch Provide transparent signal path between devices Network Interface Control Unit Establish connections Generally on demand Handle and acknowledge requests Determine if destination is free construct path Maintain connection Disconnect * Blocking or Non-blocking Blocking A network is unable to connect stations because all paths are in use A blocking network allows this Used on voice systems Short duration calls Non-blocking Permits all stations to connect (in pairs) at once Used for some data connections * .
