Positioning routing in the protocol stack (or `passing the bus-selection buck´)

It is proposed that the distributed queue dual bus (DQDB) medium access control (MAC) layer, which utilizes the services of dual unidirectional physical layer links, can be considered as providing access to dual unidirectional networks, rather than a single bidirectional network as alluded to in the IEEE 802.6 MAN standard. With the latter approach, the MAC layer may need to perform bus selection, whereas this is performed by higher layers in the former approach. The pros and cons of locating link selection in various positions of the protocol stack are examined