What is the purpose of the network being designed?

Q: What is the purpose of the network being designed?

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This is the question that you should use to probe what kind of applications the client is going to be using on the network. By knowing the applications, you determine what speeds and other qualities you need in the network. Customers often don't know the exact amount of bandwidth they need, or other features, but bandwidth is usually the overriding one.

One should measure application requirements from real-world examples, so if you can spend time monitoring the network to determine average bandwidth used by certain applications, you're going to be able to do a much better job.

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Latency is another quality that you should investigate. Some applications require low-latency networking, like NFS, [which] really requires less than two milliseconds of latency, while other things, like FTP, can work on very high-latency networks.