Relay device

1. A relay device comprising:

an input buffer for receiving data units, each of which includes a header, to which multiple pieces of destination information have been added, and data associated with the header;

multiple virtual channels for storing data units, each of the multiple virtual channels storing a data unit in accordance with the destination information;

a destination comparing section for determining the order of allocation of virtual channels at a relay device on the receiving end with respect to the data units that are stored on the multiple virtual channels by seeing if their destinations are the same; and

an output section for outputting the stored data units preferentially through one of the virtual channels that has already allocated at the relay device on the receiving end.

2. The relay device of claim 1 , wherein the destination comparing section sorts the data units by the destination and determines the order of allocation so that if any data is going to be sent to a destination to which no virtual channel has been allocated yet at the relay device on the receiving end, some virtual channel is allocated to that data preferentially at the relay device on the receiving end.

3. The relay device of claim 2 , wherein if multiple data units are going to be sent to the same destination, the destination comparing section determines the order of allocation of the virtual channels to those data units at the relay device on the receiving end by reference to time information included in the header.

4. The relay device of claim 3 , wherein by using, as the time information, the amount of time that has passed since data was transmitted, the destination comparing section allocates one of the virtual channels at the relay device on the receiving end preferentially to data that was transmitted the longest time ago.

5. The relay device of claim 3 , wherein by using, as the time information, a deadline by which data should arrive at its destination, the destination comparing section allocates one of the virtual channels at the relay device on the receiving end preferentially to data that has the shortest time left until its deadline.

6. The relay device of claim 1 , further comprising multiple input ports, each of which receives data to be sent to a specified destination,

wherein the output section includes:

multiple output ports, each of which outputs data; and

a crossbar switch for outputting the data through the output ports according to the destinations of the data that are stored on the virtual channels by connecting one of the virtual channels that stores data, of which the time-information-based priority is higher than any other data, to one of the output ports that is connected to a bus leading to the destination of that data with the highest priority.

7. The relay device of claim 6 , wherein the longer the amount of time that passed since data stored on the virtual channel was transmitted, the higher its time-information-based priority.

8. The relay device of claim 6 , wherein the shorter the amount of time left until a deadline, by which data stored on the virtual channel should arrive at its destination, the higher its time-information-based priority.

9. The relay device of claim 6 , wherein each packet of the data is comprised of a number of flits and the data is transferred on a flit basis over the bus, and

wherein the relay device further includes a load measuring section for measuring the load of data that passes through the relay device itself, and

wherein if the load that has been measured by the load measuring section is greater than a predetermined threshold value, the crossbar switch changes connections between the virtual channels and the output ports every time one flit is transmitted, but

if the load is equal to or smaller than the threshold value, the crossbar switch changes connections between the virtual channels and the output ports every time a number of flits that form one packet are transmitted.

10. The relay device of claim 9 , wherein the load measuring section measures the number of flits that are stored on the virtual channels in its relay device as the load of the data that passes through the relay device.

11. The relay device of claim 9 , wherein every time one flit is transmitted, the crossbar switch changes connections between the virtual channels and the output ports.

12. The relay device of claim 1 , further comprising:

a transmission route analyzing section for finding transmission routes, respective parts of which are shared by multiple packets to be sent to mutually different destinations; and

an output channel selecting section for selecting, by reference to the time information and on a virtual channel's destination basis, an output channel to be connected to the virtual channel that stores the data with the highest time-information-based priority,

wherein by adopting the transmission routes that have been found by the transmission route analyzing section, the output channel selecting section allocates the virtual channels at the relay devices on the receiving end sequentially so that one of the relay devices that stores a packet that will arrive at its destination with the transmission route sharing minimized is given the virtual channel earlier than any other relay device.

13. The relay device of claim 1 , wherein the destination comparing section determines the order of allocation of the virtual channels at the relay devices on the receiving end to the data units that are stored on the multiple virtual channels by seeing if the same relay device is to pass on the routes leading to the destinations.

14. A relay device comprising

multiple virtual channels for storing data units, each of which includes a header, to which deadline information indicating a deadline by which data should arrive at its specified destination has been added, and data associated with the header, and

a destination comparing section for determining the order of allocation of virtual channels at a relay device on the receiving end with respect to the data units that are stored on the multiple virtual channels by reference to the time specified by the time information,

wherein once one of the virtual channels at the relay device on the receiving end has been allocated, the virtual channel begins to output the data unit stored and get that data unit relayed through an integrated circuit.