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Chapter3-Switch_Tchnology_Fundamentals
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
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