Packet multicasting in a ring architecture

A network switch comprising:

• a plurality of media access control devices of which each includes ports for receiving and sending data packets, wherein each device examines media access control data of a received packet to determine whether a packet should be cast from a port or ports of any other device in the plurality;
• means for applying to a packet a field which has a plurality of segments, each segment corresponding to a respective one of said devices, wherein each such segment indicates whether said packet should traverse the respective one of said devices;
• and
• a respective connection from each device to the next so that the devices constitute a ring around which packets can be conveyed progressively from each device to the next,
• wherein each device on receipt of a packet having a said field:
• (a) modifies the respective field to indicate that the packet having said field has traversed the respective device;
• (b) places on the respective connection to the next device said packet having said field when said field indicates that said packet having said field should traverse at least one other of the devices;
• and
• (c) prevents further transmission of said packet having said field when said field indicates that the packet has no other device to traverse.

A network switch comprising:

• a plurality of media access control devices connected in a closed ring, each of said media access control devices including a plurality of ports for receiving and sending data packets;
• means for applying to a packet a field which has a segment corresponding to a respective one of each of said other devices, wherein at least one such segment comprises at least one bit of a particular binary value;
• and
• a respective connection from each device to the next so that packets can be conveyed progressively from each device to the next,
• wherein each device on receipt of a received packet having a field as aforesaid:
• (a) modifies said field by changing said at least one bit of the respective segment to the opposite binary value;
• (b) places said received packet on the respective connection to the next device when said field as thus modified has at least one bit of the said particular binary value;
• and
• (c) prevents further transmission of said received packet around said ring when all the bits in said field are of said opposite binary value.

A media access control device for use in a ring of devices and including a plurality of ports for receiving and sending data packets, wherein the media access control device:

• (a) receives a packet having a field which has a segment corresponding to a respective one of each of the devices in said ring, wherein each such segment indicates whether said packet should traverse said respective one of said devices;
• (b) modifies said field to indicate that said packet has traversed the media access control device;
• (c) sends said packet to a subsequent device in the ring when said field indicates that said packet should traverse at least one other of the devices;
• and
• (d) prevents further transmission of said packet when said field indicates that said packet has no other device to traverse.

A media access control device for use in a ring of devices, wherein the media access control device:

• (a) receives a packet having a field which has a segment corresponding to a respective one of each of the devices in said ring, wherein each such segment comprises at least one bit which indicates by a particular binary value whether said packet should traverse a respective one of said devices;
• (b) modifies said field by setting said at least one bit of the segment corresponding to the media access control device to an opposite binary value, whereby to indicate that said packet has traversed the media access control device;
• (c) sends said packet to a subsequent device in the ring when said field includes at least one bit of said particular binary value which indicates that the packet should traverse at least one other of the devices;
• and
• (d) prevents further transmission of said packet when said field comprises bits all of said opposite binary value.

A network switch comprising:

• a plurality of similar media access control devices each of which includes a plurality of ports for receiving and sending data packets and each including means for examining media access control data of a received packet to determine whether a packet should be cast from a port or ports of any other device in the plurality;
• means for applying to a packet a multi-bit field which identifies each of said other devices which contains a port from which the packets should be cast;
• and
• a respective connection from each device to the next so that the devices constitute a ring around which packets can be conveyed progressively from each device to the next,
• wherein each device includes:
• means for placing on the respective connection to the next device a packet when the said field identifies at least one other of the devices;
• and
• means for modifying said field to replace the identification of the respective device from a packet received by the device.