Ethernet recently begins to be used in backbone networks. To get better performance in there, many layer-2 spanning tree based Ethernet routing schemes have been proposed, such as spanning tree protocol(STP), multiple spanning tree protocol(MSTP), shortest path routing(SPB) and a special backbone routing scheme called ENDIST. We deal with analytic models that can analyze and compare these routing schemes. Previously an ideal model was proposed that calculate perfect scheduling and allows packet loss only at the source node to maximize the throughput. The analytic model in this paper practically assumes that packets are transmitted as much as possible and allows packet loss fairly during transfer at each node. We mathematically define this greedy analytic model and compare and analyze Ethernet backbone routings from the point of throughput.