L25 - The Network Layer The network layer allows for...

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The Network Layer The network layer allows for numerous hops from source to destination. Multiple alternate routes are usually available. Finding the best route for packets in a packet switching network is an important and challenging problem. The choices in networks are: 1. Dedicated circuit switching, as in the telephone network. 2. Virtual circuit switching. 3. Datagram switching.
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Dedicated and virtual circuit switching The routing decision is made when the circuit is set up in these two cases.
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Datagram network Each packet or datagram finds its own route to destination Note that B.2 arrives before B.1 because it chose a faster route.
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Routing Algorithms Routing in packet switched networks Requirements of routing algorithms Correctness Simplicity Robustness - over a wide variation of conditions, failures and overloads. Stability - freedom from overreaction, unstable swings Optimality - maximize the average throughput, minimize delay Fairness - fairness and optimality can conflict.
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Sender n+1 needs n links, Senders 1to n need one link each. Each link has capacity = one unit/second.
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L25 - The Network Layer The network layer allows for...

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