There has been some good discussion around the subject of preemption. Looks like a majority of the active members on the reflector would prefer to leave it out. In this context, the MAC packet loss shall be zero under normal conditions.
Packet loss is also an important component of a service level agreement.
Service providers obviously want packet loss to be as close to zero as possible, and the MAC must do its part to help the overall system achieve this objective. Dropping packets or causing CRC errors to support pre-emption is not desirable. More comments on preemption William, You are right that the additional delay variation added by each additional node becomes lower as the number of nodes already taken into consideration increases. But the maximum delay variation will not decrease as the number of nodes increases. So the simulation shows the limit to the delay variation, under the noted assumptions.