Full Bisection Bandwidth Network

1. A system comprising: a full bisection bandwidth network comprising: a plurality of nodes; a plurality of paths among the nodes; a plurality of Virtual Local Area Networks (“VLANs”) incorporating the plurality of nodes and the plurality of paths, wherein the plurality of VLANs comprises a first VLAN and a second VLAN and the plurality of paths comprises a first path, wherein the first path is between two nodes and does not pass through any intervening nodes; wherein the first path is assigned to the first VLAN and the second VLAN; wherein the first VLAN would not satisfy a spanning tree protocol if the first path is enabled in the first VLAN and the first VLAN satisfies the spanning tree protocol with the first path disabled in the first VLAN; and wherein the first path is enabled in the second VLAN and the second VLAN satisfies the spanning tree protocol with the first path enabled in the second VLAN; adding a node; adding paths to connect the added node to the full bisection bandwidth network; adjusting the assignments of the paths and the added paths to VLANs such that: each VLAN satisfies a spanning tree protocol; each of the plurality of paths is active in the full bisection bandwidth network; and the network remains a full bisection bandwidth network; wherein: the plurality of nodes comprises: a root layer of N Ethernet switches; a branch layer of M Ethernet switches, M>N; the plurality of paths among the nodes comprises: a path from branch layer switch BLS 1 to root layer switch RLS 1 assigned to a first VLAN; and a path from branch layer switch BLS 2 to root layer switch RLS 1 assigned to a second VLAN.

2. The system of claim 1 wherein: the full bisection bandwidth network comprises a path A connecting node X and node Y and a path B connecting node X and node Y, such that standard Ethernet protocol would treat path A and path B as redundant paths; and Path A and Path B are aggregated into a single trunk group such that Path A and Path B are active.

3. The system of claim 1 wherein: the full bisection bandwidth network has a fat tree topology.

4. The system of claim 1 further comprising: the full bisection bandwidth network has a fully connected mesh topology.

5. The system of claim 1 wherein: the plurality of paths among the nodes comprises: a path from each root layer switch to each branch layer switch; paths from a first root layer switch are assigned to a first set of VLANs; paths from a second root layer switch are assigned to a second set of VLANs; the first set of VLANs does not contain any VLANS belonging to the second set of VLANS; and the second set of VLANs does not contain any VLANs belonging to the first set of VLANs.

6. The system of claim 5 wherein M=2N.

7. The system of claim 1 wherein: the path from branch layer switch BLS 1 to root layer switch RLS 1 and a second path from branch layer switch BLS 1 to root layer switch RLS 1 are aggregated into a single trunk group.

8. The system of claim 1 further comprising: a plurality of servers coupled to the full bisection bandwidth network; and the plurality of paths among the nodes comprises a plurality of redundant paths from one of the plurality of servers to another of the plurality of servers.

9. The system of claim 1 further comprising: a plurality of servers coupled to the full bisection bandwidth network; and the plurality of paths among the nodes comprises a plurality of redundant paths from each of the plurality of servers to the others of the plurality of servers.

10. The system of claim 1 wherein: the plurality of paths among the nodes comprises: a second path redundant to the path from branch layer switch BLS 1 to root layer switch RLS 1 assigned to the first VLAN.

11. The system of claim 1 wherein: a plurality of servers is coupled to the branch layer of Ethernet servers; the plurality of paths among the nodes comprises: a first path from a first server to a second server; and a second path redundant to the first path from the first server to the second server.

12. The system of claim 1 wherein: a plurality of servers coupled to the branch layer of Ethernet servers; the plurality of paths among the nodes comprises: redundant paths from each of the plurality of servers through the branch layer of Ethernet switches and the root layer of Ethernet switches to the others of the plurality of servers.

13. A method comprising: providing a full bisection bandwidth network, having a plurality of nodes and a plurality of paths among the nodes, that is divided into a plurality of Virtual Local Area Networks (“VLANs”), wherein the plurality of VLANs comprises a first VLAN and a second VLAN and the plurality of paths comprises a first path, wherein the first path is between two nodes and does not pass through any intervening nodes, by assigning the first path to the first VLAN and to the second VLAN; disabling the first path in the first VLAN, wherein the first VLAN with the first path enabled in the first VLAN would not satisfy a spanning tree protocol and the first VLAN with the first path disabled in the first VLAN satisfies the spanning tree protocol; enabling the first path in the second VLAN, wherein the second VLAN satisfies the spanning tree protocol with the first path enabled in the second VLAN; the full bisection bandwidth network carrying a traffic load; balancing the traffic load among the paths; adding a node; adding paths to connect the added node to the full bisection bandwidth network; adjusting the assignments of the paths and the added paths to VLANs such that: each VLAN satisfies a spanning tree protocol; each of the plurality of paths is active in the full bisection bandwidth network; and the network remains a full bisection bandwidth network; wherein the plurality of nodes comprises a root layer of N Ethernet switches and a branch layer of M Ethernet switches, M>N, the plurality of paths comprises a path from each root layer switch to each branch layer switch, and wherein assigning the first path to the first VLAN and to the second VLAN comprises: assigning a path from branch layer switch BLS 1 to root layer switch RLS 1 to the first VLAN; and assigning a path from branch layer switch BLS 2 to root layer switch RLS 1 to the second VLAN.

14. A method comprising: providing a full bisection bandwidth network, having a plurality of nodes and a plurality of paths among the nodes, that is divided into a plurality of Virtual Local Area Networks (“VLANs”), wherein the plurality of VLANs comprises a first VLAN and a second VLAN and the plurality of paths comprises a first path, wherein the first path is between two nodes and does not pass through any intervening nodes, by assigning the first path to the first VLAN and to the second VLAN; disabling the first path in the first VLAN, wherein the first VLAN with the first path enabled in the first VLAN would not satisfy a spanning tree protocol and the first VLAN with the first path disabled in the first VLAN satisfies the spanning tree protocol; and enabling the first path in the second VLAN, wherein the second VLAN satisfies the spanning tree protocol with the first path enabled in the second VLAN; adding a node; adding added paths to connect the added node to the full bisection bandwidth network; adjusting the assignments of the paths and the added paths to VLANs such that: each VLAN satisfies a spanning tree protocol; each of the plurality of paths is active in the full bisection bandwidth network; and the network remains a full bisection bandwidth network; wherein the plurality of nodes comprises a root layer of N Ethernet switches and a branch layer of M Ethernet switches, M>N, the plurality of paths comprises a path from each root layer switch to each branch layer switch, and wherein assigning the first path to the first VLAN and to the second VLAN comprises: assigning a path from branch layer switch BLS 1 to root layer switch RLS 1 to the first VLAN; and assigning a path from branch layer switch BLS 2 to root layer switch RLS 1 to the second VLAN.

15. A method of claim 14 wherein adjusting the assignments comprises: adding a new VLAN.

16. A method of claim 14 wherein adjusting the assignments comprises: adding the added paths to the existing VLANs.

17. The method of claim 14 wherein the full bisection bandwidth network comprises a path A connecting node X and node Y and a path B connecting node X and node Y, such that standard Ethernet protocol would treat path A and path B as redundant paths, the method further comprising: aggregating Path A and Path B into a single trunk group so that Path A and Path B are active.

18. The method of claim 14 further comprising: constructing the full bisection bandwidth network to have a fat tree topology.

19. The method of claim 14 further comprising: constructing the full bisection bandwidth network to have a fully connected mesh topology.

20. The method of claim 14 further comprising: assigning paths from a first root layer switch to a first set of VLANs; assigning paths from a second root layer switch to a second set of VLANs; the first set of VLANs not containing any VLANS belonging to the second set of VLANS; and the second set of VLANs not containing any VLANs belonging to the first set of VLANs.

21. The method of claim 20 wherein M=2N.

22. The method of claim 14 further comprising: aggregating the path from the first branch layer switch BLS 1 to a first root layer switch RLS 1 with the path from the first branch layer switch BLS 1 to the first root layer switch RLS 1 into a single trunk group.

23. The method of claim 14 wherein a plurality of servers is coupled to the full bisection bandwidth network and the method further comprises: providing redundant paths from one of the plurality of servers to another of the plurality of servers.

24. The method of claim 14 wherein a plurality of servers is coupled to the full bisection bandwidth network and the method further comprises: providing redundant paths from each of the plurality of servers to the others of the plurality of servers.

25. The method of claim 14 further comprising: assigning a path redundant to the path from branch layer switch BLS 1 to root layer switch RLS 1 to the first VLAN.

26. The method of claim 14 further comprising: assigning a first path from a first server to a second server; and assigning a second path redundant to the first path from the first server to the second server.

27. The method of claim 14 further comprising: assigning redundant paths from each of the plurality of servers through the branch layer of Ethernet switches and the root layer of Ethernet switches to the others of the plurality of servers.