EE450-U5-SwitchingTechnologies-Nazarian-Spring10

EE450-U5-SwitchingTechnologies-Nazarian-Spring10 -...

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University of Southern California Viterbi School of Engineering EE450 omputer Networks Computer Networks witching Technologies Switching Technologies Shahin Nazarian Spring 2010
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Switched (or Switching) Technologies Two main switching technologies are: Circuit Circuit-switched switched (used in PSTN) Packet Packet-switched switched (used in Internet) which is subcategorized as connectionless , e.g. IP, and connection connection-oriented oriented (aka the virtual virtual circuits circuits ) e.g., ATM (Asynchronous Transfer Mode,) and FR (Frame Relay) t: dn ’t nf nn ti nl UDP nd nn ti n Note: dont confuse connectionless UDP and connection- oriented TCP (layer 4) with connectionless or connection- oriented packet switching. Packet switching is related to layer and the IP rotocol CP and UDP both run over IP 3 and to the IP protocol. TCP and UDP both run over IP Both are typically not a fully-connected topology, e.g. a fully- connected MAN is not practical. They are partially connected, but ith redundant paths so multiple routes exist between two end Shahin Nazarian/EE450/Spring 2010 2 with redundant paths, so multiple routes exist between two end systems so that there are alternatives if one goes wrong
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Switched Network A switched network is a network that traffic goes from one switch to another (called switches in PSTN, but in Internet they are called routers) Suppose J wants to send a message to F. The message won’t be received by any other end system than F runks are not dedicated they are wide and shared using Trunks are not dedicated, they are wide and shared using FDM FDM, TDM TDM, or WDM WDM [Wavelength Division Multiplexing Wavelength Division Multiplexing] The only lines, dedicated are the end lines that are directly onnected to the end system connected to the end system Shahin Nazarian/EE450/Spring 2010 3
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Circuit-Switched Network Go back to our previous discussions on how for a phone call, a dedicated circuit (per demand for the duration f the call) is established Note that only a portion of of the call) is established. Note that only a portion of the trunks in the path of the dedicated circuit are used (either one frequency portion in FDM, or a time slot in TDM) Once the caller ends the phone call, all resources that ad been dedicated become free had been dedicated become free 64kbps is dedicated to each phone call (Question, how many calls can be carried through a 2Gbps shared trunk?) Traffic comes in the form of stream (such as voice, and video) or burst , i.e., data Shahin Nazarian/EE450/Spring 2010 4 Circuit-switched network is optimized for stream traffic (and real time applications) & not good for data
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Circuit-Switched Network (Cont.) In circuit-switched network as soon as the call is accepted and the circuit is dedicated there is no queuing or processing delay in nodes The total end-to-end delay in the circuit-switched network includes the setup time (aka connect time aka establish establish time) time) o ake the dedicated path between two end oints nd that
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EE450-U5-SwitchingTechnologies-Nazarian-Spring10 -...

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