Chapter3-Switch_Tchnology_Fundamentals.ppt

Chapter 3 Switch Technology Fundamentals 3.1 Circuit Switching 3.2 Message Switching 3.3 Packet Switching 3.4 Timing in Networks Switching Technology 3.1 Circuit Switching 3.2 Message Switching 3.3 Packet Switching 3.3.1 Virtual Circuit 3.3.2 Datagram 3.4 Timing in Networks Switching Technology §3.1 The Network Core mesh of interconnected routers the fundamental question: how is data transferred through net? circuit switching: dedicated circuit per call: telephone net packet-switching: data sent thru net in discrete “chunks” Virtual Circuit Datagram §3.1 Network Core: Circuit Switching End-end resources reserved for “call” link bandwidth, switch capacity dedicated resources: no sharing circuit-like (guaranteed) performance call setup required Network Core: Circuit Switching network resources (e.g., bandwidth) divided into “pieces” pieces allocated to calls resource piece idle if not used by owning call (no sharing) dividing link bandwidth into “pieces” frequency division time division Circuit Switching: FDM and TDM Circuit Switching: Multiplexing/Demultiplexing Time divided in frames and frames divided in slots Relative slot position inside a frame determines which conversation the data belongs to Needs synchronization between sender and receiver In case of non-permanent conversations needs to dynamically bind a slot to a conservation how to do this? If a conversation does not use its circuit the capacity is lost! Circuit Switching Delay Circuit Establishment Data  Transmission Circuit Termination DATA Numerical example How long does it take to send a file of 640,000 bits from host A to host B over a circuit-switched network? All links are 1.536 Mbps Each link uses TDM with 24 slots/sec 500 msec to establish end-to-end circuit Let’s work it out! §3.2 Message Switching each end-end data stream as messages user A B messages share network resources each message uses full link bandwidth resources used as needed, resource