| 摘要 |
A data network hub unit is stackable with other such units to constitute a hub in which each of the units can supply data packets to network data destinations and receive data packets from network data sources, and to form a closed data transmission ring which enables packets received at any unit to be transmitted from any other unit. The hub unit includes arbitration control means responsive to packet headers circulating on said ring. The arbitration control means is operative: (i) when the hub unit acts a master unit to supply data packets, to modify data packets to provide them each with an arbitration header which includes a grant field, a request priority field, capable of indicating various different level of priority, and a grant priority field; (ii) when the hub unit is acting as the master unit and has no more data packets to supply to the ring, to respond to an arbitration header which has a set priority field by setting the grant field and setting the grant priority field; (iii) when the hub unit is not the master unit but has data packets to place on the ring, to respond to arbitration headers by setting a priority field; and (iv) when the hub unit is not the master unit but has data packets to send, to respond to an arbitration header which has the grant field set and a grant priority field indicating a priority level corresponding to the priority requested by this unit to become the master unit.
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