Final answer:
For max-min fair allocation of a 1 mb/s common link among three users, all users would get an equal share of 0.333 mb/s if x is less than or equal to 0.333 mb/s. If x is greater than that, fairness cannot be achieved with the given bandwidth constraint, and other allocation methods would need to be considered.
Step-by-step explanation:
When determining the max-min fair allocation for three users sharing a common link of 1 mb/s, we must consider the needs and limitations of each user. A max-min fair allocation looks to optimize the network resources fairly among all users.
User A's maximum limit is dictated by their access link at x mb/s, which means they cannot exceed this rate even if more bandwidth is available. User B requires at most x mb/s for their application, which means they will not use more bandwidth than x mb/s even if more is available. User C, on the other hand, will take as much bandwidth as possible for downloading a movie, with no specified upper limit. Thus, the max-min fair allocation would assign User A and User B x mb/s each, and whatever is left of the 1 mb/s would go to User C.
However, the scenario described implies that there's a combined bandwidth constraint of 1 mb/s for all three users. Therefore, if we assume that x is less than or equal to 0.333 mb/s, each user will get an equal share of the bandwidth, which is 0.333 mb/s, to achieve max-min fairness. If x is more than 0.333 mb/s, then max-min fairness is not achievable as the total required bandwidth would exceed the available bandwidth. In this case, alternative mechanisms for resource allocation might be considered to ensure fair distribution.