This paper deals with the problem of assuring strict QoS guarantees for the end to end connections that originate from Ethernet access network. It shows that despite high link capacities in some cases Ethernet network might be the reason of QoS deterioration. The primary reason is the lack of appropriate QoS differentiation and traffic isolation mechanisms. The shared buffers and priority schedulers available in most of Ethernet switches appear to be not sufficient to guarantee strict QoS. For these cases new solution is proposed which relies on additional traffic control mechanisms available in other network elements. Only additional mechanism supporting typical functionality of Ethernet switch can provide strict QoS guarantees what was verified in simulations studies.