Outages on many packet switched nets classification

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Unformatted text preview: ive Routing Startegies Routing based on information sources local (isolated) • route to outgoing link with shortest queue • can include bias for each destination • Rarely used - does not make use of available info adjacent nodes • takes advantage on delay / outage info • distributed or centralized all nodes • like adjacent Isolated Adaptive Routing Isolated ARPANET Routing Strategies ARPANET 1st Generation 1969 distributed adaptive using estimated delay distributed queue length used as estimate of delay using Bellman-Ford algorithm using node exchanges delay vector with neighbors update routing table based on incoming info problems: doesn't consider line speed, just queue length queue length not a good measurement of delay responds slowly to congestion ARPANET Routing Strategies ARPANET 2nd Generation 1979 distributed adaptive using measured delay using timestamps of arrival, departure & ACK times recomputes average delays every 10secs any changes are flooded to all other nodes recompute routing using Dijkstra’s algorithm good under light and medium loads under heavy loads, little correlation between under reported delays and those experienced reported ARPANET Routing Strategies ARPANET 3rd Generation 1987 link cost calculations changed to damp routing oscillations and reduce routing overhead measure average delay over last 10 secs and measure transform into link utilization estimate transform normalize this based on current value and normalize prev...
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