12-Routing

12-Routing - William Stallings Data and Computer...

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William Stallings Data and Computer Communications 8 th Edition Chapter 12 Routing
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Routing
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Routing in Packet Switched Network Complex, crucial aspect of packet switched  networks Characteristics required Correctness Simplicity Robustness Stability Fairness Optimality Efficiency
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Performance Criteria Used for selection of route Minimum hop Costs may be assigned based on design criteria inverse data rate current delay number of hops Least cost See Stallings appendix 10A for routing algorithms
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Example Packet Switched Network
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Decision Time and Place Time Packet or virtual circuit basis Place Distributed Made by each node Centralized Source
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Network Information Source and Update Timing Routing decisions usually based on knowledge of  network (not always) Distributed routing Nodes use local knowledge May collect info from adjacent nodes May collect info from all nodes on a potential route Central routing Collect info from all nodes Update timing When is network info held by nodes updated Fixed - never updated Adaptive - regular updates
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Routing Strategies Fixed Flooding Random Adaptive
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Fixed Routing Single permanent route for each source to  destination pair Determine routes using a least cost algorithm  (appendix 10A) Route fixed, at least until a change in network  topology With fixed routing, there is no difference  between routing for datagrams and virtual  circuits. Simple, but inflexible
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Fixed Routing Tables
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Flooding No network info required Packet sent by node to every neighbor Incoming packets retransmitted on every link except  incoming link Eventually a number of copies will arrive at destination Each packet is uniquely numbered so duplicates can be  discarded Nodes can remember packets already forwarded to  keep network load in bounds Can include a hop count in packets
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Flooding Example
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Properties of Flooding
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This note was uploaded on 02/10/2012 for the course CSC 411 taught by Professor Simmons during the Spring '08 term at S. Alabama.

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12-Routing - William Stallings Data and Computer...

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