Lecture2_2up - ECE-547 Introduction to Computer...

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1 Purdue University ECE ECE -547 547 Introduction to Computer Introduction to Computer Communication Networks Communication Networks Instructor: Instructor: Xiaojun Xiaojun Lin Lin Lecture 2 Lecture 2 Purdue University Switching Switching ¾ Two main types of Telecommunication Networks ¾ Circuit Switched Networks (Telephone Networks) ¾ Packet Switched Networks (Telegraph Networks, and Computer Communication Networks, which we will discuss soon) M x N Switch Fabric M Inputs N Outputs Generic Switching Element
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2 Purdue University Circuit Switching Circuit Switching ¾ A wants to communicate with B ¾ Connection is established from A to B via the switching offices ¾ Time- or frequency-slots are reserved at each switch ¾ Connection is dedicated throughout the call duration ¾ More complex at connection-setup, but simpler operation during the call A B Switching offices Purdue University Packet Switching Packet Switching ¾ Users C and D are sending information to user E ¾ Information is packetized into packets/messages ¾ Packet switches read the header of each packet/message and route it to its destination. ¾ Paths are shared Switches or routers Multiplexing point C D E Information field header
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3 Purdue University Packet Switching Packet Switching ¾ Different paths can be used to get to the destination ¾ Congestion can take place at multiplexing points ¾ Simple operation, although it could also be complex if guarantees are required. Switches or routers Multiplexing point C D E Purdue University Packet Vs Circuit Switching Packet Vs Circuit Switching Packet Switching (e.g. Telegraph Networks) ¾ Easier to build (Intermediate routers do not maintain states). ¾ Physical routing or switching needs to be done at line speed. Little time for complex processing Circuit Switching (e.g. Telephone Networks) ¾ Intermediate routers must keep track of resources reserved ¾ Routing can be done over longer time durations (call arrival and departure times). More time for complex processing.
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4 Purdue University Packet Vs Circuit Switching Packet Vs Circuit Switching Packet Switching (e.g. Telegraph Networks) ¾ Network is used on demand. High network efficiency. ¾ Suitable for bursty traffic (e.g., file transfer). ¾ Packets may be dropped. Mechanisms must be in place to control congestion Circuit Switching (e.g. Telephone Networks) ¾ Connection is dedicated for the entire duration of the call. ¾ Inefficient but suitable for smooth traffic (e.g., voice). ¾ No need to control congestion during a call. However, calls may be blocked. Purdue University Packet Vs Circuit Switching Packet Vs Circuit Switching Packet Switching (e.g. Telegraph Networks) ¾ “Best Effort”: Good service quality when resources are plentiful.
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This note was uploaded on 01/06/2010 for the course ECE 547 taught by Professor Xiaojunlin during the Spring '09 term at Purdue University-West Lafayette.

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Lecture2_2up - ECE-547 Introduction to Computer...

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