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Προσομοίωση Δικτύων 4η Άσκηση Σύνθετες τοπολογίες, διακοπή συνδέσεων, δυναμική δρομολόγηση
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Δημιουργία multihop τοπολογίας Based on already existing example create the following network All links are of 1Mb bandwidth, 10ms delay and DropTail One data flow from n(0) to n(3) CBR, 500byte packets, 0.005sec interval
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Δημιουργία multihop τοπολογίας Based on NAM application how many hops do the packets go through Evaluate performance using “4th_delay_1” awk script What is the main criteria of packet routing – Change receiver node to see the effect on routing What is the delay each hop adds to the aggregate delay measured – Set n(6) as the receiver at tcl script – Set node 6 as the receiver at awk script at line marked with # #EDO ALLAZETE TON RECEIVER Set n(3) as the receiver at tcl script – Identify a complete sequence of hops for a specific packet at trace file
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Δημιουργία Δυναμικής Τοπολογίας Indicate n(1)-n(2) link failure using the following commands – $ns rtmodel-at 1.0 down $n(1) $n(2) – $ns rtmodel-at 2.0 up $n(1) $n(2) See how link failure is presented at NAM application Use “4th_delay_1” to evaluate the effect at performance How many packets are successfully transmitted? – See how drop indications can be misleading Activate a routing protocol – $ns rtproto DV See how using a routing protocol mitigates the problem at NAM How many packets are “saved” due to DV routing protocol?
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Δημιουργία Δυναμικής Τοπολογίας DV routing is based on finding minimum weight routes – By default any link has a weight of “1” – You can control the weight of a link using the following command – $ns cost $n(1) $n(2) 10 Use the following command so that packet for flow 0->3 follow the long way around i.e. 0 6 5 4 3 Modify the script so that – For interval 0.5 – 3sec packets follow the short route – For interval 3 – 4.5sec packet follow the long route Check if “$ns cost $n(1) $n(2) 10” concerns only one direction or both of them
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