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2 via B
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3 via C
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4 via D
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B
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1 via B
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2 via C
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3 via D
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C
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1 via C
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2 via D
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D
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3 via B
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1 via D
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E
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4 via B
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1 via E
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Distance vector protocols can operate in two different modes : `periodic updates` and `triggered updates`. `Periodic updates` is the default mode for a distance vector protocol. For example, each router could advertise its distance vector every thirty seconds. With the `triggered updates` a router sends its distance vector when its routing table changes (and periodically when there are no changes).
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Consider a distance vector protocol using split horizon and `periodic updates`. Assume that the link `B-C` fails. `B` and `C` update their local routing table but they will only advertise it at the end of their period. Select one ordering for the `periodic updates` and every time a router sends its distance vector, indicate the vector sent to each neighbor and update the table above. How many periods are required to allow the network to converge to a stable state ?
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Consider the same distance vector protocol, but now with `triggered updates`. When link `B-C` fails, assume that `B` updates its routing table immediately and sends its distance vector to `A` and `D`. Assume that both `A` and `D` process the received distance vector and that `A` sends its own distance vector, ... Indicate all the distance vectors that are exchanged and update the table above each time a distance vector is sent by a router (and received by other routers) until all routers have learned a new route to each destination. How many distance vector messages must be exchanged until the network converges to a stable state ?
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Consider again the network shown above. After some time, link state routing converges and all routers compute the same routing tables as above.
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