フリー問題

問題文

An operator wants to make four separate traffic classes lossless on the same fabric. What is the practical limit on doing that?

選択肢

1. Only one class can be lossless per fabric, given that the mechanism has no way to identify more than one.
2. The limit is the number of physical queues, which is unrelated to buffer and is always large enough for any number of classes.
3. There is no practical limit, because the buffer required for a lossless class is proportional to the rate of the class rather than to the amount of traffic in flight, so dividing the same total rate among more classes does not increase the total requirement.
4. Each lossless class needs its own reserved buffer to hold the traffic already in flight when it pauses, so the finite buffer on each port has to be divided among them.