Method and apparatus for preventing loops in a network topology

1. A method for preventing loops in a network topology comprising a plurality of switch devices, the method comprising:

assigning, to each switch device, a unique switch identification number, SW-ID;

exchanging each SW-ID between all switch devices;

building, for each switch device, a routing table based on said received SW-IDs, so that the switch devices can reach each other, each entry in the routing table associated with a switch device, and including an assigned SW-ID of the switch device, a dedicated port number, and a number of hops to reach the switch device, the number of hops corresponding to a shortest path to reach the switch device; and

receiving, at a first switch device, a data frame from a second switch device that includes a single switch identification number, namely a source switch identification number, SS-ID, assigned to the second switch device, the data frame is received at a port of the first switch device;

when, according to the routing table of the first switch device, the assigned SW-ID for the port of the first switch device is different from the SS-ID included in the data frame, discarding the data frame, and

when, according to the routing table of the first switch device, the assigned SW-ID for the port of the first switch device is not different from the SS-ID included in the data frame,

processing forwarding the data frame, wherein processing forwarding the data frame comprises:

when the data frame is a broadcast frame or an unknown-unicast frame,

flooding the data frame out from each port of the first switch device that is connected to other switch devices except from the port from which the data frame was received; and

removing the SS-ID from the data frame and flooding the data frame without the SS-ID frame out from each port of the first switch device that is directly connected to at least one host node, and

when the data frame is a known-unicast frame,

checking, using the routing table of the first switch device, if there is any SW-ID assigned to a port number that is associated with a MAC destination address in the data frame; and

when there is no SW-ID, removing the SS-ID from the data frame and forwarding the data frame out from said associated port to its destination MAC address; and

when there is a SW-ID, forwarding the data frame to the switch device having the SW-ID.

2. The method according to claim 1 , further comprising:

receiving, at a switch device, a data frame from a host device connected to the switch device;

when the data frame is a broadcast frame or a unknown-unicast frame,

adding or including, in the data frame, the SW-ID of the switch device as SS-ID and flooding the data frame including the SS-ID out from each port of the switch device that is connected to other switch devices except from the port from which the data frame was received; and

flooding the received data frame out from each port of the switch device that is directly connected to at least one host node except from the port from which the data frame was received;

when the data frame is a known-unicast frame,

checking, using the routing table, if there is any SW-ID assigned to a port number that is associated with a MAC destination address in the data frame; and

when there is a SW-ID, adding or including, in the data frame, the SW-ID of the switch device as SS-ID and forwarding the data frame including the SS-ID out from said port; and

when there is no SW-ID, forwarding the data frame out from said associated port, to its destination MAC address.

3. A switch device for preventing loops in a network topology comprising a plurality of switch devices, wherein each switch device is assigned a unique switch-identification number, SW-ID, the switch device comprising a processor and a memory, said memory containing instructions executable by the processor wherein the switch device is operative to:

exchange the assigned SW-ID with all switch devices;

receive from each switch device its assigned SW-ID;

build a routing table based on said received SW-IDs, each entry in the routing table associated with a switch device, and including an assigned SW-ID of the switch device, a dedicated port number, and a number of hops to reach the switch device, the number of hops corresponding to the shortest path to reach the switch device; and

receive a data frame from another switch device that includes a single switch identification number, namely a source switch identification number, SS-ID, assigned to said another switch device, the data frame being received at a port of the switch device;

when, according to the routing table of the switch device, the assigned SW-ID for this port is different from the SS-ID included in the data frame,

discard the data frame, and

when, according to the routing table of the switch device, the assigned SW-ID for this port is not different from the 55 -ID included in the data frame,

process forward the data frame, wherein process forward the data frame comprises:

when the data frame is a broadcast frame or an unknown-unicast frame,

flood the data frame out from each port of the switch device that is connected to other switch devices except from the port from which the data frame was received; and

remove the SS-ID from the data frame and flood the data frame without the SS-ID frame out from each port of the switch device that is directly connected to at least one host node, and

when the data frame is a known-unicast frame,

check, using the routing table of the switch device, if there is any SW-ID assigned to a port number that is associated with a MAC destination address in the data frame; and

when there is no SW-ID, remove the SS-ID from the data frame and forward the data frame out from said associated port to its destination MAC address; and

when there is a SW-ID, forward the data frame to the switch device having the SW-ID.

4. A switch device according to claim 3 , further operative to:

receive a data frame from a host device connected to the switch device;

when the data frame is a broadcast frame or a unknown-unicast frame,

add or include, in the data frame, the SW-ID of the switch device as SS-ID and flood the data frame including the SS-ID out from each port of the switch device that is connected to other switch devices except from the port from which the data frame was received; and

flood the received data frame out from each port of the switch device that is directly connected to at least one host node, except from the port from which the data frame was received; and

when the data frame is a known-unicast frame,

check, using the routing table, if there is any SW-ID assigned to a port number that is associated with a MAC destination address in the data frame; and

when there is a SW-ID, add or include, in the data frame, the SW-ID of the switch device as SS-ID and forward the data frame including the SS-ID, out from said port; and

when there is no SW-ID, forward the data frame out from said associated port, to its destination MAC address.

5. A method in a switch device for preventing loops in a network topology comprising a plurality of switch devices, wherein each switch device is assigned a unique switch-identification number, SW-ID, the method comprising:

exchanging the assigned SW-ID with all switch devices;

receiving from each switch device its assigned SW-ID;

building a routing table based on said received SW-IDs, each entry in the routing table associated with a switch device, and including an assigned SW-ID of the switch device, a dedicated port number, and a number of hops to reach the switch device, the number of hops corresponding to the shortest path to reach the switch device; and

receiving a data frame from another switch device that includes a single switch identification number, namely a source switch identification number, SS-ID, assigned to said another switch device, the data frame being received at a port of the switch device,

when, according to the routing table of the switch device, the assigned SW-ID for this port is different from the SS-ID included in the data frame,

discarding the data frame, and

when, according to the routing table of the switch device, the assigned SW-ID for this port is not different from the SS-ID included in the data frame,

processing forward the data frame, wherein processing forward the data frame comprises:

when the data frame is a broadcast frame or an unknown-unicast frame,

flooding the data frame out from each port of the switch device that is connected to other switch devices except from the port from which the data frame was received; and

removing the SS-ID from the data frame and flood the data frame without the SS-ID frame out from each port of the switch device that is directly connected to at least one host node, and

when the data frame is a known-unicast frame,

checking, using the routing table of the switch device, if there is any SW-ID assigned to a port number that is associated with a MAC destination address in the data frame; and

when there is no SW-ID, removing the SS-ID from the data frame and forward the data frame out from said associated port to its destination MAC address; and

when there is a SW-ID, forwarding the data frame to the switch device having the SW-ID.