End-to-end multipathing through network having switching devices compatible with different protocols

A border switching device comprising:

• a first port configured for interfacing a first cluster of first switching devices compatible with a software-defined networking (SDN) protocol;
• a second port configured for interfacing a second cluster of second switching devices compatible with a protocol for an open systems interconnection (OSI) model layer, the second cluster within the first cluster;
• wherein the first port is configured for receiving data through the first cluster that is intended for a destination reachable only through the second cluster, the data formatted according to the SDN protocol;
• wherein the border switching device is configured for adding to the data a header formatted according to the protocol for the OSI model layer;
• wherein the border switching device is configured for routing the data, including the header, from the second port through the second cluster to another border switching device that is closest to the destination;
• and
• wherein the border switching device is one of a plurality of border switching devices located at a boundary between the first cluster and the second cluster that are compatible with the protocol for the OSI model layer, each second switching device directly connected to just a pair of the bordering switching devices and routing network traffic between the pair of the border switching devices through the second cluster of the network.

A method comprising

• receiving at first port data through a first cluster, the data being intended for a destination reachable only through a second cluster, the data formatted according to a first protocol;
• adding a header to the data, the header formatted according to a second protocol;
• at a second port routing the data, including the header, to another device that is closest to the destination;
• wherein the first cluster comprises first switching devices, each first switching device compatible with the first protocol;
• wherein the second cluster is within the first cluster, and comprises second switching devices, each second switching device is compatible with the second protocol, and
• wherein each second switching device is directly connected to just a pair of border switching devices, and just routes network traffic between the pair of the border switching devices through the second cluster of the network.